Cell membranes are usually impermeable to foreign materials, which means materials like proteins and nucleic acid cannot enter the cells. The phenomenon of using an electric pulse helps in creating temporary pores in the cell membrane. This phenomenon is called electroporation. 

The instrument used to create these pores is termed an electroporator. The electroporator is widely used in molecular biology, genetic engineering, and biotechnology. The basic principle of an electroporator is creating transient pores in the cell membrane by sending a brief electrical pulse. 

The transient pores formed during this method allow entry of foreign genetic material inside the cell, which incorporates itself into the cell’s genome. The instrument has various designs and capacities, from small benchtops to larger-scale automated systems. 

Principle of Electroporator

An electroporator follows the principle of electroporation, where the use of electric pulses or electricity assist in forming pores in the membranes. These pores help in introducing foreign genetic material and proteins into the cells. 

Electroporation has five fundamental principles: cell membrane permeabilization, electrical pulses, pore formation, uptake of genetic material, and cellular recovery. 

1. Cell Membrane Permeabilization: The cell membrane is primarily impermeable to large molecules like RNA, DNA, and proteins. The electrical pulses used by this instrument temporarily disrupt the cell membrane’s integrity. The temporary disruption creates temporary pores in the cell membrane, allowing the entry of the materials inside the cell. 
2. Electrical Pulses: The electroporation method applies short, high-voltage electrical pulses in the cells. The vibrations generate an electric field throughout the cell membrane. The electric field disrupts the lipid bilayer, forming temporary pores. 
3. Pore Formation: When the electric field is provided in the cell, the cell membrane goes through a process called dielectric breakdown. The dielectric breakdown causes lipid molecules of the cell membrane to reorient and create temporary openings and pores in the membrane. 
4. Uptake of Genetic Material: Once pore formation occurs, the size is large enough to enter genetic materials and proteins in the cell. DNA is drawn into the cell through these pores due to electrostatic forces. 
5. Cellular Recovery: The cell membrane reseals itself once the electrical pulse is withdrawn. Usually, the cells can recover in a growth medium that helps repair the membrane and resume their normal cellular functions. 

However, the successful completion of electroporation depends on factors like electrical pulse voltage, durage, number, types of cells used, and the introduced genetic material’s size and type. The optimization of these parameters is critical to achieve efficient electroporation and ensure cell viability. 

Parts of Electroporator

An electroporator is a complex laboratory instrument that performs electroporation to introduce foreign materials into the cells by forming temporary pores. Based on different companies, the parts of the electroporator can vary widely. 

However, some of the common parts of an electroporator include a control panel, electrical pulse generator, cuvette chamber, electrodes, pulse controller, high-voltage supply, safety features, cooling systems, and adapters. 

Control Panel

The control panel is the area in the laboratory instrument where the user inserts instructions for the electroporation process. It is also referred to as an interface. This part helps in controlling voltage, pulse duration, and pulse number. It may have a display screen for viewing the progress of the procedure.  

Electrical Pulse Generator

This part of the laboratory instrument generates electrical pulses required for electroporation. It produces high-voltage pulses, which are delivered to the cell. 

Cuvette Chamber

This is where the cell sample is added for electroporation. It usually has two electrodes where the cells are exposed to electrical pulses. The size of cuvettes vary widely to fit the different volume of the samples. 

Electrodes

The instrument has two electrodes, one at each end of the cuvette chamber. The electrodes provide electrical pulses to the cell sample. The electrodes are of different types: plate, cuvette, and specialized. The specialized electrodes are specific to certain cell types. 

High-voltage Supply

The high-voltage power supply sends off the necessary electrical energy for generating high-voltage pulses for electroporation. Its role is ensuring that electrical pulses are delivered at specified voltage levels.  

Safety Features

Electrical isolation and interlocks are the safety features of electroporators. The electrical isolation protects the user from electrical shocks and overcurrent protection. Likewise, interlocks prevent the instrument from operating when not correctly configured. 

User Manual and software

The electroporators come with a user manual that provides instructions on operation and maintenance. Modern electroporator has software for programming and controlling the instrument. 

Miscellaneous Parts

1. Adapters: Some electroporators may include holders or adapters. These adapters ensure the cuvettes or samples are appropriately placed for electroporation.  
2. Pulse Controller: Some electroporators have a separate component or module for controlling the different parameters of electrical pulse like duration, number, and voltage. This part helps in obtaining precise control of the electroporation conditions. 
3. Cooling Systems: Various electroporators have a cooling system for dissipating generated heat. It is crucial when dealing with multiple samples or high-throughput applications. 
4. Data Logging and Concetivity: New generation electroporators may have data recording capabilities for recording the parameters and outcomes of each electroporation test. Some models of electroporators may also have connectivity options like USB ports or data transferring software for data retrieval and analysis. 
5. Trigger: Some electroporators consist of trigger or footswitch mechanisms. This mechanism allows the user to initiate the electrical pulse delivery manually.  

Although these are some of the commonly present parts of an electroporator, the specific features and details can vary between different models and brands. So, studying the user manual is vital before operating the electroporator. 

Uses of Electroporator

Electroporators are widely useful laboratory instruments in various molecular biology, genetic engineering, and biotechnology fields. Whatever the field of biology, the primary use of the device is to incorporate genetic material into cells. 

1. Electroporators help in gene therapy research, functional genomics, and gene expression studies in mammalian cells by the process called transfection. It is also helpful in producing viral vectors by introducing viral genomes into producer cells for gene therapy and gene delivery applications.   
2. It is also used to introduce plasmid DNA or other genetic material in bacterial and yeast cells or transform, essential in molecular biology biotechnological applications. 
3. This equipment is also helpful in generating genetically modified organisms by introducing specific mutations into the genomes of these organisms. 
4. Likewise, this technique has successfully developed recombinant proteins by introducing targeted genetic components into the genome. This introduction helps in expressing the desired proteins. 
5. Electroporators are also helpful in gene editing technologies like CRISPR-Cas9 for delivering CRISPR components into the cells for editing specific genomes. 
6. In some cases, electroporation is useful in fusing cells, which applies to hybridoma technology producing monoclonal antibodies. It also applies to drug delivery mechanisms in pharmacology research and drug discovery. 
7. Electroporation is helpful in cancer research for drug screening, gene therapy, and delivery of therapeutic agents in cancer cells. Similarly, this technique is also applicable in vaccine development by enhancing the delivery of DNA-based vaccines to cells, which helps in improving immune response. 
8. The instrument helps introduce genes into stem cells, essential in stem cell research. In plant biotechnology, this instrument helps introduce foreign genes into plant cells for improving crops, disease resistance, and developing genetically modified crops.  

Types of Electroporator

Electroporators are different types with slight variations in features, pulse parameters, voltage ranges, and other specifications. The choice of this instrument depends on the specific needs of the researchers and the types of cells and organisms used for the research. Some common types of electroporators, with brief descriptions of each.

Yeast and Bacterial Electroporators

These instruments transform yeast and bacterial cells. The bacterial electroporators are used in molecular biology research for cloning, genetic engineering, and protein expression of bacteria. These electroporators also have specialized cuvettes and parameters optimized for bacterial cells. 

Plant and Mammalian Cell Electroporators

The mammalian electroporators provide the necessary flexibility and control to work on mammal cells. These instruments are helpful in transfecting mammalian cells with DNA, RNA, or other nucleic acids. These are significant in gene expression studies, gene therapy research, and gene editing. Plant electroporators are crucial for genetically modifying plant cells and tissues and can accommodate larger volumes and use specialized electrodes or cuvettes suitable for plant materials. 

High-throughput electroporators

These can process multiple samples simultaneously, making the output through and at a high rate. These are applicable in drug screening or large-scale protein expression studies. 

Desktop Benchtop Electroporators

These are compact instruments suitable for small-scale experiments and individual laboratories. Although close, they are versatile and commonly used for various electroporation applications. 

Automated Electroporators

Various other processes within electroporation get automated in this type of electroporator, like cell handling, dispensing, and data collection. These help in high-throughput and automation of laboratories like drug discovery and genomics.  

Flow Electroporators

These help enable continuous and efficient cell electroporation in a fluid stream. These are highly efficient in cell therapy and other applications requiring high cell throughputs.  

Clinical and Portable Electroporators

These are used in clinical trials and potentially therapeutic purposes for gene delivery to patient’s cells during gene therapy. Some electroporators are small, portable, and designed for field applications like point-of-care diagnostics and on-site genetic modification experiments in remote locations.  

References

1. Electroporation. Bio. https://www.bio-rad.com/en-np/category/electroporation  
2. Fisher Scientific. https://www.fishersci.com/us/en/browse/90222047/electroporators
3. Schmitt, M. A., Friedrich, O., & Gilbert, D. F. (2019). Portoporator©: A portable low-cost electroporation device for gene transfer to cultured cells in biotechnology, biomedical research and education. Biosensors & bioelectronics, 131, 95–103. https://doi.org/10.1016/j.bios.2019.02.024 

Histology studies biological tissues that are preserved carefully, usually by embedding them in paraffin wax. These methods of careful preservation maintain relationships between cells and their various components and also helps in passing illuminating radiation through them. 

Since most biological tissues are optically dense, these require thin slicing so that the microscopic details of each cell can be easily studied. The mechanical device, microtome, helps achieve the thin slicing of the tissues for studying under a microscope. 

Micro means small, and tome means cut in Greek. The instrument has sharp blades or a microtome knife for making the thin slice. Traditionally, the microtomes helped in free-hand sectioning of the tissues using a sharp razor. 

Whereas modern microtomes are precise instruments for cutting thin sections uniformly. With time one can cut fragile and translucent areas using the device. Generally, a microtome has a knife, base, and sample holder. 

It has many different types based on operating mode and knife material; manual, automated, semi-automated microtome with steel, diamond, glass, tungsten carbide, or sapphire knife. The instrument is mainly used in histological and pathological studies and analyses.     

Parts of Microtome

The instrument has mainly three parts; the base/body of the microtome, the knife in the knife holder, and the tissues/material holder. 

1. Base/body: The body/base of the microtome helps to keep the instrument upright. It has a part for the attachment of the knife holder. It has a scale where the distance for movement of the material holder is set. 
2. Knife and knife holder: The knife holder holds the knife fixed on the body. The knife/blade can be made up of diamonds, glass, or metals. It is of different types. 
3. Tissue/material holder: The material holder holds the specimen. Unlike any other cutting appliance, it is the movable part of the microtome. The cutting action can be vertical or horizontal, and the holder moves at a pre-selected distance in the body. 

Types of Knife and Its Angle

The materials used in making of the knife are either stainless steel, diamond, tungsten, sapphire, or glass. Likewise, its profile also decides the types of a knife; plano-concave, biconcave, wedge, and tool edge knives. 

Based on the material used for construction

1. Steel knife: The material used for this kind of knife is from high-quality carbon or tool-grade steel. The steel should be rust-resistant and heated to harden the edge. The hardening of the edge of the steel determines its sharpness.
2. Tungsten knife: These knives are made of tungsten carbide. These are non-magnetic and 100 times harder than that steel. These types are highly brittle. It is resistant to wear and can make up to 30,000 serial sections of undecalcified bone embedded in methacrylate after each sharpening.
3. Diamond knife: The knife is made of gen quality diamonds. The blades are expensive but very durable due to their hardness. The knife is used for cutting very thin sections. 
4. Sapphire knife: The knife is produced from a single piece of sapphire created artificially from alumina monocrystal under computer-controlled thermal conditions. It is harder than glass and tungsten, which ensures its durability. The knife can only cut smaller-sized blocks, and the edge is limited to 11 mm.  
5. Glass knife: It is used in ultramicrotomy. Its cutting edge is placed against/across the thickness of the glass. It is also called the Ralph knife, and different profiles of the knife are used for cutting sections from various embedded materials. The knives are hard but brittle. However, the knife is susceptible to storage for an extended period. So, it should be treated before use. 
6. Disposable knife: The knife is made of stainless steel and has replaced conventional knives. Teflon coating is preferred for cryostats. 
7. Non-corrosive knife: The non-corrosive blade is used for cryo-microtome and is made of heat-treated stainless steel, free from all impurities. It has 12-15% chromium. 

Based on the profile

1. Plano-concave knife: The knife has one plane surface, and another surface is concave. The biconcave side has two hollow ground surfaces, and both surfaces are incredibly sharp. The blade is used for cutting soft, celloidin-embedded material or foam compounds. The knife does not apply to hard substances. The knife should be placed obliquely to the object when cutting sections. 
2. Biconcave knife: It is similar to the plano-concave knife, only with a thicker back. It is used for cutting hard materials. The blade is placed obliquely to the material being sectioned. The degrees of concavity vary highly. 
3. Wedge knife: This knife is more rigid than plano-concave and biconcave knives. It is used for cutting rigid materials. It has an extra thick wedge at the tip; it cannot grind as sharp as a plano-concave and biconcave knife. It helps cut thin specimens of the cryostat, frozen, and paraffin-embedded specimens. The cutting plane should be placed transverse to the object. 
4. Tool edge knife: It helps cut hard material because its stability is excellent. The blade has the least sharpness of all the types. The knife’s cutting edge is made by grinding a bevel on each side of plano-concave, biconcave, and wedge knives or the angled surface of a tool edge knife. The face of the bevel encloses a sharper angle than the main surfaces of the blade.   

Types of Microtome

Microtomes are available in different types depending on the manufacturing companies used. Based on the operating mode, there are three types; manual, semi-automatic, and automatic microtome. 

Manual microtome

The microtome that requires human intervention for operation is the manual microtome. All stages of this kind of microtome are manual. 

There are different types of manual microtomes; rocking, rotary, freezing, vibrating, sledge, sliding, cryostat, saw, hand, and ultra microtomes. It is simple to use and has three moving parts;

Rocking microtome

It has the oldest design and is relatively cheaper than other types of the microtome. It is named due to its rocking action due to cross-arm presence and is exclusively applicable in slicing paraffin blocks. Here the tissue moves through the arc as the material holder moves towards the knife (Heiffor knife) that is rigidly attached to the holder. The thinly cut section comes out curved due to the presence of a slightly biconcave knife. 

Since the tissue section comes out as curved, it may lack flat surfaces for viewing. Although highly reliable, lightweight, and low maintenance, their lightweight might lead to unstableness and vibration while operating it. Nowadays, the rotary microtome significantly replaces the rocking microtome.  

Rotary microtome

It is the most commonly used instrument in routine laboratories, and the blade is kept horizontally. The paraffin block with tissue moves up and down with the help of a rotatory handle in the microtome. One rotation of the handle moves the block down; another moves it down. This action helps in cutting the tissue as thin as a ribbon. The rotary microtome can be automated or semi-automated by adjusting and controlling the block’s movement and the knife’s angle. 

The section comes out very thin (2-3 μm) with suitable quality ribbons. The microtome is highly stable and can easily cut various types of tissue. However, the microtome is not ideal for cutting large blocks of tissue. Likewise, it is expensive and leads to accidents as the knife faces up. 

Hand microtome

This kind of microtome is only applicable in sectioning rigid botanical material. Although thin tissue sections can be obtained from plant cells, thin sections from animal tissues are difficult to obtain.  

Vibrating microtome

This microtome is applicable for producing thin slices from unfixed, unprocessed, or not frozen tissue samples from animal and botanical sources. It is assumed to replace the hand microtome. Its name is derived front he high-speed vibration used by the safety blade, which can increase the cutting speed. The vibration speed is adjusted by altering the electrical voltage applied to the knife. The fresh tissue sample is immersed in the fluid to prevent the tearing of the material and dissipate heat produced during vibration.   

Sledge microtome

This instrument is used to cut sections of large blocks of tissue. Here the block is fixed in a static position within a steel carriage. The carriage slides backward and forward against a fixed horizontal knife. The knife is large (usually 24 cm long) and wedge-shaped, reducing the vibration and requiring less sharpening. The knife holders are adjustable and tiltable to the desired angle of the knife to the block. The whole instrument is heavy and hence very stable. The only disadvantage of this microtome is; it is relatably slow than the rocking or rotary microtome.  

Cryostat

In this type of microtome, cutting occurs by placing it in a deep freeze cabinet. The cabinet has a double glass window and a door for passing the samples in and out. The inside of the cabinet has a fluorescent light and a fan. The fan helps to provide proper cool air circulation. The temperature inside the cabinet is kept between -10ºC to -40ºC using liquid nitrogen. It is used as an alternative for freezing microtomes. It became popular after developing fluorescent antibody staining techniques for making thin sections of fresh frozen tissue free of ice crystals.  

Ultramicrotome

This instrument obtains ultrathin (40-100 nano micron) tissue sections for the transmission electron microscope. This microtome uses a diamond, sapphire, or glass knife. The extensive tissue sections are cut into small blocks (1×1 mm size) and then cut using an ultramicrotome under an optical microscope. After the cut, each section is floated to a water bath adjacent to the knife edge. 

The advanced mechanisms used in this type of microtome are thermal and mechanical. In the thermal mechanism, the tissue sample is heated in a bifurcated metal strip to induce expansion. In mechanical advancement, a microprocessor couples with a precise stepping motor. The motor helps provide even cutting of the sections and for constant reproducibility.  

Sliding microtome

In this instrument, the knife moves horizontally against a fixed block. The movement progresses in an inclined plane. It was designed for cutting celloidin-embedded sections and paraffin-embedded sections.  

Freezing microtome

This type of microtome is applicable for cutting thin slices of frozen tissue samples. The instrument is connected to the CO2 by a flexible metal tube and attached to one of the working tables. This microtome differs from another type because the knife/blade moves, and the tissue holder stays static. The tissue block moves slightly in a pre-set amount at the end of each cut. 

Although this microtome helps cut thin sections of frozen specimens, it cannot generate consistent, high-quality thin sections of tissues. 

The instrument does not require solid CO2 or liquid nitrogen to provide the cooling effects; It has two different kinds of metals in opposite directions. When electric current flows through them, one metal helps to generate heat, and the other benefits in losing the generated heat.    

Automatic microtome

Much human intervention is not required to operate this type of microtome. One must feed the information about size and direction to a computer for cutting thin slices of tissues.

Ultra-thin, computerized, and laser microtomes are some kinds of the commercially available automatic microtome.

Computerized microtome

This type of microtome has an advanced thermostatic switch, cyro-scalpel, cyroplate, and semiconductor freezing. It cuts slices in the range of 1-25 μm. It can carry out both freezing and routine paraffin sectioning. The microtome operates once the technical staff feeds data (the required size and the number of sections needed). The cryo-scalpel and cyroplate temperatures range from 0ºC to -18ºC and -10ºC to -40ºC, respectively.  

Laser microtome

This kind of microtome helps in cutting biological specimens using a laser. This type helps obtain non-contact sectioning without thermal damage and gets precise slices. An infrared laser beam with a short pulse duration is used because there is almost no heat generation. Depending on its type, the processed tissue is sliced in about 5-100 μm before processing.  

Uses of Microtome

Microtome is used in different laboratories to study other tissues’ histopathology (animal and plant). Different types of microtomes are used in various laboratories for different purposes. 

1. In ophthalmology, sledge microtome helps study tissue sections of the eyes. 
2. Sliding microtome helps in sectioning brain tissues better by this type of microtome. 
3. Cryomicrotome is used in nerve biopsy.
4. Rocking, rotary, hand, and vibrating microtome is helpful in general biological laboratories for studying tissue sections embedded in paraffin. It is also used in performing a small biopsy. 
5. Sledge microtome is also helpful in the study of tissues embedded in celloidin. 
6. Electron microscopy requires slices as thin as ten nano micrometers, so the ultramicrotome helps achieve pieces as thin as 5-10 nano microns. 

Advantages

Sectioning of tissue using blades and knives may prove to be difficult because of the preservation methods used. Some tissues are preserved in paraffin blocks, which can be hard to cut into thin pieces. Likewise, frozen specimens prove to be very difficult to cut. The use of microtomes may help in achieving thin slices of biological samples. 

Besides helping cut thin slices of biological specimens, its different types carry different advantages. The advantages of different kinds of microtomes are as follows:

1. Laser microtome helps obtain non-contact processing of the tissue and cut the tissue in its native forms without thermal damage. It also enables secure sub-micrometer precision, is less time-consuming, and has fewer artifacts.     
2. Rocking microtome is easy to operate, requires low maintenance, and is relatively inexpensive. 
3. Sledge microtome helps in cutting hard and large tissue. 
4. Like sledge microtome, sliding microtome helps in cutting large tissues. It is easy to operate and inexpensive. It is also applicable for tissue embedded in celloidin.  
5. Ultramicrotome helps obtain ultra-thin slices of the tissue specimens for observation under an electron microscope.    
6. Cryomicrotome and freezing microtome help obtain a thin slice of the freshly frozen specimens.  

Disadvantages of Microtome

Although the microtome is a handy instrument, microtome has some disadvantages depending on the type of microtome used. Some of them are:

1. Some microtomes are expensive. Cryostat, Ultramicrotome, and laser microtome are some of the expensive instruments. One must be mindful of purchasing the right kind of microtome. 
2. Some are lightweight so that they can be unsteady. The rocking microtome is one of the lightest microtomes, which can cause vibration, which leads to uneven tissue sectioning. 
3. Most of them require a skilled workforce. Since many commonly used microtomes are manually operated, the technical staff managing these must be experienced to obtain even thin sections.  
4. Without much care, the blades of the microtome may lead to accidents. Sharpening and fixing of edges may lead to accidents in the laboratory. The accidents can be avoided if the procedure of tissue sectioning is done carefully. 

 References

1. Dey, P. (2018). Tissue Microtomy: Principle and Procedure. In: Basic and Advanced Laboratory Techniques in Histopathology and Cytology. Springer, Singapore. https://doi.org/10.1007/978-981-10-8252-8_5
2. Mohammed, Faraz & Thapasum Fairozekhan, Arishiya & Mohamed, Shamaz. (2012). Microtomes and microtome knives. Annals of Dentistry. 19. 62-65. 10.22452/adum.vol19no2.4. 
3. Donald B. McMillan, Richard J. Harris, Introduction, Editor(s): Donald B. McMillan, Richard J. Harris, An Atlas of Comparative Vertebrate Histology, Academic Press, 2018, Pages ix-xxix, ISBN 9780124104242, https://doi.org/10.1016/B978-0-12-410424-2.00018-4. (https://www.sciencedirect.com/science/article/pii/B9780124104242000184) 

Working in various laboratories requires familiarizing oneself with laboratory equipment. Chemistry laboratory perform tests that help determine the chemical properties of different elements and compounds. The equipment required for the chemistry laboratory can be for both general purposes and particular purposes. 

The general-purpose equipment required in the chemistry laboratory includes a bunsen burner, crucible, weighing balance, litmus paper, and glassware like test tubes, beakers, and funnels.

Particular purposes like gas preparation and titration require different laboratory equipment, including a gas jar, Wolff’s bottle, burettes, and pipettes. Other equipment used in the chemistry laboratory correlates to safety concerns, like gloves and goggles.  

General Purpose Equipment Used in Chemistry Laboratory

Every chemistry laboratory requires some equipment, no matter the tests being performed in the laboratory. The general-purpose equipment used in the chemistry laboratory includes a bunsen burner, tongs, test tube holder and rack, spatula, and droppers. 

Bunsen burner 

It is the laboratory equipment useful for heating materials. The burner produces a single open flame with the use of gas. The gas is either natural, like methane, or petroleum, like propane and butane. In chemistry laboratories, it helps to perform heating experiments like evaporation. 

Read more about Bunsen burner here

Tripod Stand

The material used for its construction is iron. Its purpose is to hold glassware during heating. The top part of the equipment can either be triangular or circle shaped. It is the part that holds the wire mesh gauge and glassware for heating. As the name suggests, the base of this laboratory equipment has three legs. 

Wire mesh gauge

The material of the gauge is metal wires like iron, nichrome, or steel. The gauge is placed on top of a tripod for using a bunsen burner. It helps provide even heating while using glassware with a flat bottom surface. Some wire mesh gauge has a ceramic center, which helps in protecting the glass from breakage due to heat and provides much more heating.   

Tongs

These hold hot equipment like beakers, flasks, and crucibles after or during experiments. The shape of this equipment is like scissors. There are different types of tongs based on their purpose. Beaker tongs have rubber for easy gripping. Flask tongs have rounded ends for easy holding. 

Test tube holder and rack

The holder helps in handling test tubes while heating or using harmful chemicals. One should only use test tubes with holders if they are dealing with acids and bases to avoid accidents in the laboratory. 

The purpose of a test tube rack is to place the test tube upright. The stand helps in storing and transferring multiple test tubes at a time. The materials used for construction of the rack are metal, plastic, or wood. It comes in various sizes and shapes. The stand commonly used in chemistry laboratories is the classic type with 8-10 holes for test tubes.   

Desiccator 

The use of laboratory equipment is for drying wet substances. It is also applicable for storing moisture-sensitive substances. The equipment is used under vacuum pressure. There are various types of desiccators. It can be either manual or automated.  

In chemistry laboratories, desiccators help store some chemicals and compounds sensitive to water, like sodium.

Read more about desiccators here.

Centrifuge 

It is a piece of laboratory equipment useful to separate components of a mixture based on size, density, viscosity, and motor speed. The separation occurs due to the centrifugal force in the rotor where a sample is placed. There are different types of centrifuges benchtops, ultracentrifuges, high-speed, low-speed, and refrigerated centrifuges. 

Read more about centrifuges here.   

Blotting and filter paper 

These are absorbent paper that helps in absorbing moisture from different objects. The use of a sheet of blotting paper in separation techniques like western blotting and chromatographic techniques. The material used for its construction is cotton cellulose instead of nitrocellulose. The filter paper is a round-shaped paper used for filtering purposes. 

Spatula

The use of a spatula in chemistry laboratories is to transfer solid materials or powder, mix materials, and scrap materials from surfaces. The material used for the construction of reusable spatulas is stainless steel. There are different styles of stainless steel spatulas; micro, double-ended, and trough-shaped spatulas are some types. 

Laboratory thermometer

The thermometer measures different chemicals and substances’ room temperature, freezing, and boiling points. The room temperature measuring thermometer is glass and contains a long stem with alcohol or mercury. Freezing and boiling point measuring thermometers are infrared thermometers.  

Forceps

These are hinged tools that help to grasp and hold objects. Their main use is when hands and fingers are too big for things. There are various forceps like a thumb, locking, and kelly forceps. 

Thumb forceps or tweezers are useful in chemistry laboratories. In chemistry laboratories, forceps help to hold chemicals and solids that should not be handled with bare hands, like sodium metal. The thumb forceps are held like pen style between the thumb and index finger. 

Litmus paper

The use of litmus paper or pH strips is to check the solution’s pH or acidity and alkalinity. The litmus paper determines the acidity and alkalinity of the solution, whereas pH strips determine the pH of the solution. Litmus paper changes to red when the solution is acidic and blue when the solution is basic or alkaline.  

Analytical balance

This laboratory equipment helps in weighing the mass of chemicals and objects. It can measure up to 0.01 mg. The balance is very precise equipment for measurement and comes in different varieties like single pan, double pan, electronic, and microbalance. In chemistry laboratories, this equipment makes solutions by weighing the right amount of substances (generally solid).  

Read more about analytical balance here.

Droppers 

This equipment dispenses liquid substances from one container to another for various experiments. The droppers are plastic or glass and may or may not have graduation marks. The plastic droppers are for one-time use, and glass droppers are reusable. One end of the dropper has a bulb that helps dispense the perfect drop of solution.  

Mortar and pestle

These are two pieces of laboratory equipment that aid in crushing and grinding objects. The shape of the mortar is like a bowl. Its construction is from durable materials like ceramic or stones. The pestle is a club-shaped grinding piece of equipment made of the same material as mortar. Mortar and pestle help grind various grains and food materials in daily life. Their use is in grinding massive solid particles into small sizes in chemistry laboratories.  

Glassware used in Chemistry Laboratory

Although many pieces of equipment required in chemistry laboratories are made of glass, this section comprises general purposes laboratory equipment constructed of glass. These include test tubes, flasks, stirrers, etc.

Test tubes

These are used to perform various laboratory tests. In the chemistry laboratory, test tubes assist in testing different properties of organic and inorganic compounds. It is also helpful to study various properties of gases after laboratory preparation. 

The tube has a cylindrical shape with closed rounded bottoms and open at the top. There may or may not be the presence of rims at the top. These come in various sizes and are the most common laboratory equipment.

Read more about test tubes here.

Round bottom flask

The flask has a round bottom or base and is applicable in various experiments, especially gas preparation and distillation. RB flask is made of borosilicate glass and is available in multiple sizes, and the number of necks also varies. 

Beaker

The use of laboratory equipment is to hold chemicals or liquids in laboratories. It has a beak-like spout on the top of the flask, which helps quickly pour fluids, decreasing the risk of spilling. It is available in various sizes, like common form and tall form. Graduations marks are present in some beakers. However, these could be more precise. 

Read more about beakers here.

Glass rod

It is applicable in stirring and mixing liquids. The equipment is made of borosilicate glass and does not have any openings. The rod comprises a single glass piece, and its length is 10-40 cm with a diameter of 0.5 cm.  

Glass tube

Like glass rods, these are also made of single glass pieces that are cylindrical and hollow from both sides. Its use is for liquid dispensing tubes for transferring solutions from one place to another or delivery tubes for gas production. 

Funnel

This piece of laboratory equipment is helpful in the filtration and pouring of liquids or fine-graded materials from one container to another. Its neck is narrow, which allows only a certain amount of fluids to pass through. The use of funnels is also in other separation methods, like evaporation and condensation. 

Watch glass

This piece of laboratory equipment is concave in shape and useful in evaporating liquid by placing it on top of a beaker with boiling water. It is also known as clock glass. It also holds solid substances and covers beakers.

Reagent bottle

The use of these bottles are to preserve and store chemicals and prepare solutions. These are generally made of borosilicate glass and have a stopper. Like beakers, these also have graduation marks, but the marks could be more precise.

Read more about laboratory glassware here. 

Special Purpose Laboratory Equipment

Some equipment in the chemistry laboratory is essential only during experiments like gas preparation and distillation. The laboratory equipment required in chemistry laboratories for different purposes is as follows:

Titration Equipment

Titration is the method of slowly adding a solution of known concentration into another solution of unknown concentration until it reaches the neutralization indicated by the change in color. Specific equipment is used in titration: pipette, burette, cylinder, volumetric flask, etc.

Pipette

This equipment has graduation marks for precise measurements. It helps in transferring liquids and drawing up chemicals. These are cylindrical tube-like structures. Some pipettes have bulbs in between with graduation marks at the top of the pipette. 

Read more about glass pipettes here. 

Pipette bulb

The pipette bulb draws up liquid and attaches it to the pipette. The material used for its construction is rubber, and gentle pressure helps draw the liquid from the container. 

Graduated cylinder

The use of this laboratory equipment is to measure the volume of the liquids precisely. The shape of the equipment is cylinder and tall with a precise graduation mark at the 0.1 to 1 ml interval. The other term used for this equipment is measuring cylinder. Its top part is hollow with a spout for easy pouring, and the base is suitable for flat surfaces.

Read more about graduated cylinders here. 

Burette

This laboratory equipment has a long cylindrical tube-like body with a slightly pointed bottom. The tube has graduation markings, and the bottom part has a stock clock that controls the liquid flow. It holds the solution and allows the control flow of the solutions for titration.  

Conical flask

The other name of this flask is Erlenmeyer’s flask. Its shape is cone-like, with a flat bottom and a cylindrical neck. Its use is as a reaction flask. These also have graduation marks, just like beakers which could be more precise. It is available in various sizes or can hold different volumes. The flask is placed below the burette in the ring stand. It receives the solution from the burette. The flask is usually made of borosilicate glass.

Read more about conical flask here.

Burette clamp and ring stand

Like all clamps, burette clamps secure the burette in the ring stand during titration. It has an adjustable cork for changing the width of the clamp. One should be careful not to break the glass burette while tightening the cork. 

A ring stand is a metal stand with a long rod to attach different clamps. The base of the stand is suitable for placing a conical flask during titration. 

Volumetric flask

This equipment helps measure/prepare precise solutions at a specific temperature. Its bottom is flat and pear-shaped. The equipment’s neck is long and cylindrical with calibrated markings. Its use is in preparing molar solutions and is available in different volumes. However, it lacks graduation marks.   

Gas Preparation Equipment

The reason for gas preparation in the laboratory can vary. The type of gas prepared can vary greatly. Some specific laboratory equipment, like Woulfe’s bottle, beehive shelf, and gas jar, are designed for gas preparation.  

Woulfe’s bottle 

Named after the scientist Peter Woulfe, this bottle prepares gases in the laboratory. Its shape is cylindrical with 2-3 mouths. The use of a double-mouthed bottle is common where one mouth is shut airtight with a thistle funnel attached to the cork, and the other is shut airtight with a cork with an attached delivery tube.  

Beehive shelf

It is a porcelain or ceramic piece of laboratory equipment. It helps in collecting gas under the water. One end of the delivery tube is placed inside the opening present at the base of the shelf. Its top part has a circular opening from which the gas passes to the gas jar placed on top of it. 

Gas jar

As the name suggests, the jar collects gas after preparation. Its shape is a cylinder with an end hollow, and another end closed. It is usually made up of glass. The jar has a lid to protect the gas from escaping. 

Thistle funnel

It is glassware that is a cylinder shape with an end with a bulb. The blub has flared rims. It is placed inside Woulfe’s bottle with the help of a cork. Liquid materials like hydrochloric acid in case of hydrogen preparation, are poured through it. It helps in the slow pouring of fluids and prevents the liquid’s backflow during gas preparation. Its one end should be dipped inside the fluid to avoid escaping of prepared gas.

Kipp’s Apparatus

This apparatus aids in preparing gases in small volumes. A Dutch pharmacist, Petrus Jacobus Kipp, designed it. It helps in generating a continuous supply of gas during laboratory experiments. Nowadays, it is highly applicable in preparing hydrogen sulfide gas. It has three bulbs; bulbs A, B, and C. 

The placement of the bulbs needs should be in the correct order. The base bulb is A, the middle bulb is B, and the final bulb C is placed at the top of bulb B. The C bulb has an inlet and long stem that reaches bulb A. Solution is poured through the inlet in bulb C, and gas passes out from the outlet present in bulb B. The outlet has a stopper that can control the passing of air.   

Cork

It is made of rubber. Drilling a hole in the cork similar to the delivery tube and thistle funnel helps create an airtight seal while preparing gases. It is placed on the opening of Woulfe’s bottle and round bottom flask. It comes in various sizes depending on the gas produced and the apparatus used. 

Water trough

This piece of equipment is a container that holds water. It is an important piece of equipment for gas collection. A beehive shelf is placed inside it above the gas jar. It is also applicable in distillation to hold the conical flask and cool down the heated and separated liquid.   

Distillation Equipment

Distillation is the method of separating liquid components in a mixture by selective evaporation and condensation. Some pieces of equipment used in distillation are common, like a Bunsen burner, tripod stand, and wire gauge. Others, like glass retort and condenser, are uncommon. 

Glass retort

This equipment aids in dry distillation. It has a spherical vessel where the substance to be separated is placed and a long neck that acts as a condenser. There is also an inlet in the cylindrical container for pouring the substance. Heat is provided in the vessel. Its use is in purifying water from dissolved minerals and substances. 

Distillation flask

This piece of laboratory equipment aids to separate two different liquids with varying boiling points. The bottom of the flask is round for even heating. It has a long neck and side arm for condensation. 

Equipment for Lassaigne’s Test

Lassaigne’s test helps to detect foreign elements present in the organic compound. It requires some equipment that is not used generally, which are ignition tubes and crucible. Other pieces of equipment are common, like test tubes, burners, and beakers.

Ignition tube

It is a glass tube similar in structure to generally used test tubes. However, the ignition tube is small in size. Its use is for heating sodium metal and an organic compound. 

Crucible

The use of this equipment is for crushing the heated ignition tube and making a solution for testing specific to particular foreign elements. The material used for its construction is porcelain or ceramic. It may or may not come with a cover. 

Safety Equipment Required in Chemistry Laboratory

Safety should be of utmost priority in any laboratory. Chemistry laboratory deals with different chemicals and compounds that can cause harm to laboratory technicians and people dealing with these chemicals. The safety equipment includes:

Goggles

Using goggles helps protect the eyes from the splashes of chemicals. These goggles are generally tight-fitting, with clear glass. Experts recommend the use of certified goggles.  

Apron

Acids used in chemistry labs can damage clothes. Likewise, colored compounds like potassium dichromate leave permanent stains on clothes. So, safety protocols recommend the use of an apron in the chemistry laboratory.

Gloves

Chemicals generally irritate the skin when frequently handled, so gloves can protect hands from being chemicals and heat related burns. Likewise, experiments relating to heating are also frequent in chemistry laboratories, so the use of gloves while handling hot equipment is necessary for one conducting the experiments.  

References

1. Laboratory glassware & glass lab equipment: Biomall.in India [Internet]. Biomall. [cited 2023Jan8]. Available from: https://www.biomall.in/category/laboratory-glassware?or=1
2. What is the difference between class A and as graduated pipettes? [Internet]. BRAND. [cited 2023Jan18]. Available from: https://shop.brand.de/en/volumetric-instruments/graduated-pipettes.html
3. Flasks [Internet]. Scilabware. Available from: https://www.obrnutafaza.hr/pdf/scilabware/Flasks.pdf
4. Desiccators [Internet]. Duran. Available from: https://www.obrnutafaza.hr/pdf/duran/Dessicators.pdf
5. Fisher Scientific. [cited 2023Jan18]. Available from: https://www.fishersci.co.uk/gb/en/browse/90111060/distilling-flasks
6. Fisher Scientific. [cited 2023Jan18]. Available from: https://www.fishersci.com/us/en/browse/90094123/specific-gravity-bottles?page=1
7. Laboratory glassware cleaning [Internet]. University of Wisconsin-Madison; [cited 2023Jan18]. Available from: https://ehs.wisc.edu/wp-content/uploads/sites/25/2017/01/GlasswareCleaning.pdf
8. Watch Glasses Information [Internet]. Watch Glasses Selection Guide: Types, Features, Applications | Engineering360. [cited 2023 March 31]. Available from: https://www.globalspec.com/learnmore/labware_scientific_instruments/labware_consumables/watch_glasses
9. The bunsen burner – eastern illinois university [Internet]. [cited 2023Mar31]. Available from: https://www.eiu.edu/eiuchem/forms/burner.pdf
10. Fisher Scientific. [cited 2023Mar31]. Available from: https://www.fishersci.com/us/en/browse/90227061/laboratory-spatulas

A hot plate is a portable tabletop machine that uniformly heats solutions and materials. They are safer than the bunsen burner because they do not consist of open flame but instead consist of the hot plate only. 

The maximum temperature range of this device is 350℃, which is high enough to ignite a wide range of low-boiling solvents such as pentane, hexane, diethyl ether, acetone, and low-boiling petroleum ether. Further, some hot plates are available with stirrers to enhance the automatic mixing of liquids during heating.

Parts of Hot Plate

A hot plate is a simple device consisting of a flat surface with a heating element. It consists of various parts to function that includes;

Controls and indicators

1. Power indicator: It illuminates continuously after turning on the switch.
2. Heat control knob: It helps to adjust the desired temperature by turning clockwise and counter-clockwise as per requirement.
3. Stir control knob: It helps adjust the stir bar’s rotation speed.
4. Stirring speed display: It is generally present in a hot plate stirrer that helps to display the stirring speed.
5. Heating temperature display: It is in a digital type that helps display the temperature.
6. Hot top indicator: It illuminates when the top of the plate is too hot to touch (hotter than 60℃).
7. Temperature probe in use indicator: When the external temperature probe attaches to the unit, this indicator illuminates

Connections

1. External temperature control input: An optional external temperature control input plugs into the connector.
2. Power cord input: The power connector of the hot plate attaches to this connector.
3. Top plate: The top plate can comprise various materials, i.e., aluminum, ceramic, stainless steel, etc. The central part of the hot plate holds the vessel containing the solutions. It provides the surface to heat the solution uniformly. The type of it that we use depends on the nature of the material to be heated.

Accessories 

Hot plates are available with various accessories to conduct multiple experiments. These include; the vertical support rod, holding rod, external temperature controller, and thermometer holder.

Vertical support rod and holding rod help to provide support to the glassware used in conducting experiments. Similarly, an external temperature controller helps to adjust the temperature and a thermometer helps to hold the thermometer.

Principle of the Hot Plate

The main principle of a hot plate is based on heating through conduction. When you place the sample on a hot plate, heat transfers from the container to the sample through direct contact.

In a hot plate, the temperature control connects to a heating element that encloses inside a plate. When the instrument reaches the desired temperature, the heating element activates, and the plate begins to heat up. The sample is then placed at the top of the plate, transferring heat from the plate to the sample.

Whereas, in the case of a hot plate stirrer, along with a heating element, there is an electromagnet that fits in the internal structure of the hot plate. In this hot plate type, a magnetic bar known as a ‘stir bar’ is placed in a solution containing a beaker that helps to mix the solution by spinning. Two knobs of heat control and rotation control, respectively, fits in a hot plate to control heat and rotation. When the hot plate switch is turned on, a heating knob helps to adjust the temperature. In comparison, the rotation control knob is used to adjust the rotation of the stir bar.

Types of Hot Plate

Hot plates are of various types, but we have to choose based on the material we heat, which are as follows;

Based on Display:

Hot plates are of two types based on display;

1. Analog-type hot plates: These are the most simple and cost-effective type. They consist of a knob to adjust temperature and rotation speed. These types of hot plates lack a readout screen to report the exact temperature and speed. However, they consist of an indicator light that helps to know the heating element and operating stirring mechanism.
2. Digital type hot plates: This type consists of a temperature and speed control knob and a readout screen. This type of hot plate helps to achieve exact temperature and speed.

Based on Design:

Hot plates are of three types based on the designs;

1. Standard hot plates: These types of hot plates are only used to heat the sample. These do not have a stirring function. Further, such types of hot plates require less maintenance and re-calibration routines.
2. Magnetic stirrer with hot plates: This type of hot plate consists of a heating system and an electromagnet placed under its surface. The heating system helps to heat the solution, whereas the electromagnet helps to move the electromagnet immersed in a solution to move in a circular motion.
3. Stirring hot plates: Heating and stirring elements are installed at the flat top surface in this hotplate type. It is the most expensive type of hot plate that provides uniform heating of high-volume or viscous samples.

Based on materials used:

These instruments are of four types based on the material used to make hot plate surfaces;

1. Ceramic hot plates: These plates can endure temperatures up to 350℃ and resist corrosion. These types of hot plates are suitable for glass beakers.
2. Polypropylene hot plates: These types of plates cannot withstand high temperatures like ceramic and aluminum plates but has a high tolerance to chemicals, acids, and solvents. These types of hot plates are primarily used in the wet chemistry lab for various purposes.
3. Stainless steel hot plates: These plates are highly resistant to corrosion, ether, and alcohol. They are suitable for ISO-grade cGMP spaces.
4. Aluminum hot plates: The aluminum plate provides more uniform heat and is tough to crack. It is appropriate for high-throughput lab operations.  

Procedure for Operating Hot Plate

The procedure involved in operating hot plates is as follows;

1. Place the hot plate on a clean and flat surface.
2. Then, switch on the plug connected to the instrument.
3. After that, fill the solution on a vessel. Then, place it on top of the intrument (plate where heating occurs), and wait for heating.
4. To adjust the temperature, turn the heat control knob clockwise or anticlockwise as per requirement.
5. Similarly, in the case of a hot plate stirrer, place the stir bar into the vessel containing the solution and adjust temperature and rotation by turning the temperature control knob and rotation control knob, respectively, into clockwise or anticlockwise directions.
6. After the completion of heating, switch off the device.
7. Lastly, clean up the device and working area.

Applications of Hot Plate

The hot plate is commonly used in chemistry, zoology, microbiology, physics lab, and also in other areas for the following purposes;

1. Laboratory hot plates heat specimens for histological, pathological, and cytological investigations.
2. In the microbiology laboratory, hot plates are used to prepare media and reagents.
3. In mining industries, hot plates are used to heat hazardous chemicals by using a protective coating.
4. These instruments are used to prepare meals in some places where kitchen stoves are unavailable.
5. It is used for testing the potency of analgesics by observing the response to heat-produced pain.
6. In a chemistry laboratory, hot plates are used to melt solid material, boil liquids, conduct reactions, and also for drying purposes.

Advantages

Hot plates have a wide range of advantages, which are as follows;

1. They are very cost-effective.
2. Hot plates are portable devices.
3. They are simple to use.
4. This laboratory equipment is an essential device in various laboratory procedures.
5. They do not require any other source to operate except electricity.
6. They are easy to clean and maintain.

Limitations

Some of the limitations of a hot plate are given below;

1. They can produce burns, fires, and electric shocks, resulting in accidents.
2. They have a limited temperature range to operate compared to Bunsen burners.

Precautions While Handling

Some precautions that we need to follow while handling hot plates are as follows;

1. Always unplug the device when not in use.
2. Regularly check the cords and plugs of the device to see if they are damaged or worn out. Similarly, make sure to keep any electrical cord away from the heat.
3. Never keep flammable or combustible material near the instrument.
4. Always use glassware made up of heat-resistant material, and check its crack before use.
5. Make sure to check the thermostat that might have been corrupted by long-term use.
6. Do not heat a metal pan or foil on the instrument at 200℃. It can damage the device.
7. Use thermal gloves or tongs to remove a hot object from the instrument.

References

1. Hot plate use. UC San Diego. Retrieved on 23rd March 2023. Retrieved from; https://blink.ucsd.edu/safety/fire/requirements/hot-plates.html
2. Differences between hot plates and hot plates magnetic stirrer: Pros, cons, and limitations. Retrieved on 22nd March 2023. Retrieved from; https://labproinc.com/blogs/laboratory-equipment/differences-between-hot-plates-and-magnetic-stirrers-pros-and-cons-and-limitations

Laboratory glassware is the most used laboratory equipment in various laboratories. Among many glasswares, test tube is applicable in biological as well as chemical laboratories.  

The test tube is a long cylindrical handheld tube shaped like a finger that has been used in various experiments. It has different types depending on the material and purpose of the experiment. 

Depending on the laboratory, test tubes also have different functions; in the chemistry laboratory, the test tube helps to test the properties of various chemicals and gasses. Likewise, the microbiology laboratory uses it to prepare culture media, collect samples, and hold fluids.

Test tubes are closed at the bottom and open at the top. The bottom of most test tubes is slightly curved/spherical. The length and diameter of the test tubes vary significantly from small (Durham) tubes to large culture tubes. 

Sizes of Test Tubes

Test tubes are available in variable sizes; ranging from 10 to 20 mm wide and 50 to 200 mm in length. The standard test tube size used in laboratories is 18 mm✕150 mm. 

1. Extra small (Durham) tube: comes in two dimensions; 5 mm✕35 mm or 4 mm✕40 mm. It is applicable for detecting gas produced by microorganisms. These are placed upside down in order to trap the gas. 
2. Small tube: The dimension of the small tube is 13 mm✕100 mm, and it can hold 9 ml of materials. It is helpful in performing different types of experiments.  
3. Medium tube: The medium-sized tube is 16 mm✕150 mm in dimensions. It can hold approximately 22 ml of material. 
4. Large tube: The dimension of a large-sized tube is 20 mm✕200 mm. It can hold 28 ml of material. 

Types of Test Tubes

This laboratory glassware are classified on different types on two basis; based on the material used for constructing them and based on the purpose. 

Based on the material

Depending on the material used, test tubes are of two types; disposable and reusable.

1. Disposable test tubes: The disposable test tubes are made of various kinds of plastics like nylon, polyethylene, polypropylene, polyurethane, polyvinyl chloride, and polytetrafluoroethylene. Surprisingly, plastic test tubes are resistant to UV light like neoprene tubes, and different temperature ranges, like test tubes made up of nitrile operable in -30℉ to 275℉. The plastic tubes made up of polyethylene are resistant to high pressure.   
2. Reusable test tubes: These are made of glass; borosilicate, fused silica, or quartz glass are some of the types of glass used for the test tubes. These tubes are highly resistant to temperature so autoclavable and tolerate chemicals. Although these tubes are transparent, they are more costly than disposable ones. 

Other materials used in the construction of test tubes are metal and ceramic. However, using test tubes made of these materials is relatively uncommon. 

Based on Purpose 

Depending on the purpose, test tubes are of various types. Like thin-walled, medium-walled, thick-walled, rimmed, screw top, ground glass tops, plain tops, graduated test tubes, and some come with stoppers, push caps, and screwtops are some of the types of test tubes.

1. Thin-walled test tube: It is used for storage, holding, and mixing purposes but not heating due to the risk of easy breakage. The wall thickness in the tube is generally 0.5-0.6 mm. 
2. Thick-walled test tube: It is used for strong heating of chemicals as the glass wall is thick. Its wall thickness is 1.5 mm.
3. Rimmed test tube: The rim of the test tube helps in providing extra mechanical strength in the test tube. It helps in easy holding using a test tube holder. 
4. Screw top test tube: The screw top helps secure the materials inside the tube. It is usually helpful in sample collection, culture media preparation, and blood collection.  
5. Plain top test tube: There is no rim or screw at the top of the test tube. It is useful for holding the chemicals before and during the experiment. 
6. Medium-walled test tube: These tubes have a 1-1.2 mm wall thickness. It has usage in performing exothermic chemical reactions and gentle heating of materials. 
7. Test tube with ground glass stopper: The tube is generally useful for storing chemicals and has a ground glass top to attach the stopper.  
8. Graduated test tube: Like a graduated cylinder, it precisely measures samples before performing experiments. Usually, the tube has a thick wall and an interchangeable glass stopper. 

Uses of Test Tubes

Test tubes have a wide range of functions depending on the laboratories. In chemical laboratories, these tubes test the substances’ properties and perform experiments in different forms between two or more chemicals. The various functions of test tubes are as follows:

1. Sample collection in clinical laboratories: The collection of samples like bodily fluids (saliva, pus, and sputum) occur in clean, sterilized test tubes. It helps to efficiently transfer samples from one place to another to confirm disease diagnosis. 
2. Blood collection in phlebotomy: Blood collection tubes are test tubes with color-coded caps that helps in identifying the purpose of blood collection and preservatives added to the tube. Phlebotomy is a procedure of withdrawing blood from the veins placed in the blood collection tube. 
3. Culture media preparation in microbiological laboratories: The preparation of broth or liquid medium usually occurs in the test tube. Other biochemical mediums are also prepared in the test tube. It helps in the identification of microorganisms. 
4. Analysis of chemicals: In the chemistry laboratory, a test tube is useful to study chemicals. The physical and chemical properties of chemicals in various physical states (solid, liquid, and gas) are analyzed by multiple tests using the test tube. 
5. Disease diagnosis: The use of test tube in clinical and microbiological laboratories not only help in collecting samples and blood but also helps in disease diagnosis by performing various test, especially in culturing cancer cells and biochemistry tests. 
6. Holding or storing samples/chemicals: The use of some samples and chemicals may be frequent, so saving and keeping these chemicals and samples for the test and future tests is another usage of test tubes. 
7. Heating experiments: Different experiment requires heating of the material for mixing or accurate result like Benedict’s tests, Fehling test, etc., and the material involved is small in amount. So, using a test tube helps in performing these experiments.        

Importance of Test Tubes 

Test tubes, although small, are an essential piece of laboratory glassware. It is paramount in laboratories that handle risky, hazardous chemical materials, contagious samples, and growing microbial cultures. Brief description of some of the importance of test tubes are as follow:

1. Helps in handling hazardous chemicals: Chemicals like acids and bases can create hazards if not handled with care. Likewise, laboratories use different chemicals that can threaten human and environmental health, so using safety measurements with safer equipment is a must. Hence, using test tubes can decrease the risk of causing accidents in the laboratory. 
2. Helpful in safely performing experiments: As discussed earlier, some experiments require handling hazardous material. In contrast, some may require heating, so using the test tube helps perform experiments safely. Sometimes mixing chemicals and samples in a wide-mouthed container may increase the chance of spillage, so safety guidelines suggests using smaller mouthed test tube. 
3. Storage and holding of samples: Some cases demand long-term storage of samples, so using test tubes for storing and holding samples is helpful. 

References

1. Fisher Scientific. [cited 2023Mar22]. Available from: https://www.fishersci.com/us/en/browse/90168062/test-tubes?page=1
2. Test tubes information [Internet]. GlobalSpec. [cited 2023Mar22]. Available from: https://www.globalspec.com/learnmore/labware_scientific_instruments/clinical_research_labware/test_tubes
3. Dimeski G, Yow KS, Brown NN. What is the most suitable blood collection tube for glucose estimation? Ann Clin Biochem. 2015 Mar;52(Pt 2):270-5. doi: 10.1177/0004563214544708. Epub 2014 Jul 7. PMID: 25002707.
4. Bayot ML, Tadi P. Laboratory Tube Collection. 2022 Aug 8. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–. PMID: 32310451.

Beaker is a deep, wide-mouthed, thin-walled, flat-bottom container with a tiny spout at the top that aids pouring. They are used for heating, mixing, or storing purposes in scientific laboratories. Although beakers have been used since the Neolithic era (the past 10,000 years), John Joseph Griffin is credited with inventing the most common kind.

The beakers are commonly made of glass. However, beakers made of plastic and metals are the most widely used nowadays.

Features of Beaker

Although there are different types of beakers, some features of all the types are similar, which are as follows:

1. Shape: Beakers are cylindrical that have a wide mouth and flat bottom.
2. Spout: Beaker consists of a thin lip-like structure (spout) at the uppermost region that helps in easy and smooth pouring.
3. Sizes of beaker: Beakers are available in various sizes. Therefore, they are used according to the requirement.
4. Heat resistant: Beakers are made of glass, plastic, or steel that are heat tolerant.
5. Graduation marker: Most of the beakers have clear and marked graduation.

Types of Beakers

Laboratory beakers come in a variety of shape, sizes, and materials which is broadly classified into the following types;

Based on their Height and Shape

Beakers are categorized into four types based on their height and shape;

1. Tall form beaker: It is also known as Berzelius beaker, which is used in the titration. This type of beaker is thin, and its height is double the diameter. This type of beaker may also have a handle for easy pouring.
2. Small form beaker: It is also known as a Griffin beaker. Their height is about 40% of the diameter. Due to the wide, flat bottom, glass beakers are ideal for heating on a hot plate.
3. Flat beaker: It is also known as a crystallizer, which is used to perform crystallization. Unlike other beakers, these types do not have flat scales on their wall.
4. Phillips beaker: Philips beakers mostly lookalike like a Griffin beaker, but under closer observation, it has been found that the wall of the beaker is sliding and graduating towards the mouth of the beaker. 

Based on the Raw Material Used

1. Glass beakers: They are usually made of borosilicate glass that can tolerate temperatures up to 400℃ and are chemical resistant.
2. Plastic beakers: These beakers are made of many plastic types. Choosing the right one for the application depends on the chemical and heat resistance required. For example, LDPE (low-density polyethylene) and Polypropylene beakers can be used for weak chemical reactions and low heat up to 80℃. Whereas, PTFE (polytetrafluoroethylene) plastic types are compatible with all chemical reactions as well as heat up to 360℃.
3. Metal beakers: Such types of beakers are made of aluminum or stainless steel. Metal beakers are lightweight and more durable than glass beakers. On the other hand, the metal beaker is opaque. So, seeing the contents within it is not easy. Alumunium beakers can withstand temperatures up to 340℃ while stainless steel beakers can withstand up to 550 ℃. 

Available Sizes of Beakers

Beakers are available in various types. Each type is available in multiple sizes, that includes;

1. Low High beaker: It includes 5 ml, 10 ml, 25 ml, 50 ml, 100 ml, 150 ml, 250 ml, 400 ml, 500 ml, 600 ml, 800 ml, 1000 ml, 2000 ml, 3000 ml, 5000 ml, and 10000 ml.
2. High beaker: It includes 50 ml, 100 ml, 150 ml, 250 ml, 400 ml, 500 ml, 600 ml, 800 ml, 1000 ml, 2000 ml, 3000 ml, and 5000 ml.
3. Thick wall type: It includes; 150 ml, 400 ml, 600 ml, 1000 ml, 2000 ml, and 5000 ml.

Applications of Beaker

Beakers have a wide range of applications in scientific laboratories, including;

1. Beakers are used to hold solid or liquid samples as reaction containers.
2. Beakers are used for stirring liquids to prepare reagents or chemicals.
3. Berzelius beakers are used for titration experiments where solutions are mixed to generate many outcomes.
4. Flat-form beakers are used for hot bath heating in scientific laboratories.
5. Plastic beakers are used to carry out gamma spectral analysis and similar experiments.

Advantages of a Beaker

Beaker is multi-purpose glassware used in the laboratory that has the following benefits;

1. It is the most commonly available glassware.
2. It is available in various volumes, sizes, and shapes.
3. It also can calculate liquid volume when strict accuracy is not necessary.
4. It is easier to use in the heating and mixing process.
5. The spout helps in easy pouring.

Limitations of a Beaker

Despite having benefits, beaker glassware also has some limitations such as;

1. Beaker consists of a spout at the topmost part. Therefore, it does not consist lid to cover it tightly.
2. Because of the straight surface with a wide mouth, it has a high chance of spillage during swirling.
3. Measuring the exact volume of solution in a beaker is not so accurate. Therefore, a separate measuring cylinder should be used.
4. The wider mouth of a beaker leads to fast evaporation and vaporization.

Precautions

While using a beaker, the following precautions should be taken;

1. After usage, always clean the beaker to prevent contamination.
2. To prevent splashing, slowly pour the liquid into the beaker.
3. Always use a spoon or stirrer inside the beaker in order to mix the solutions.
4. Do not fill the beaker more than ⅓ when heating.
5. Always use safety tongs while handling the hot beaker.
6. The beaker should always be placed at the center or over an open flame.

References

1. Beakers. Retrieved from https://www.borosil.com/site/assets/files/1112/beaker.pdf. Retrieved on 28th January 2023.
2. Laboratory Beakers and their many Uses. Retrieved from https://www.labpeople.com/blog/laboratory-beakers-and-their-many-uses/. Retrieved on 27 January 2023.

Different tests and biochemical assays require varying types of sample collection tubes. In-vitro analysis of blood samples can be performed in clinical laboratories using serum or plasma. 

Blood is collected in test tubes or blood collection tubes (BCTs) with air-tight closures, color-coded for practical and easy identification. These are also called Vacutainer® or evacuated tubes. 

These are either made up of plastic or glass and have rubber stopper at the top. The rubber top creates a vacuum seal that helps in drawing a pre-determined volume of blood. These tubes are used in various diagnostic fields like chemical/biochemical, hematological, molecular, and serological testing.

Color of the tubes determine the types of additives added in the tubes. Thorough mixing of tubes with additives is must. All tubes with anticoagulants should be mixed gently 10-12 times to mix the additive with the blood and prevent clotting. When blood is not mixed thoroughly with the additives may result in errors in the test.

Performing more than one test is possible from one tube. You may check with the laboratory for the minimum amount of needed blood.

Components of Blood Collection Tube

The blood collection tubes are similar to the test tube in shape and size. However, these have stoppers and can be made from either plastic or glass. The following are the components of blood collection tube:

1. Tube wall: The blood collection tube is of 50-150 mm in length and 10-20 mm in diameter. The glass used is borosilicate or soda-lime and the plastic used is of polyethylene terephthalate or polyethylene and polypropylene. The plastic tubes are more durable and carry less risk of cross contamination.    
2. Rubber stopper: The rubber stopper is colorful and easily penetrable by needle and self seal after removing the needle. Butyl rubber and halogenated butyl rubber are common materials for stopper. 
3. Stopper lubricant: Lubricants like silicone oils, glycerol, and fluids are applied in the stopper. These lubricants help in easy removal and insertion of stopper. 
4. Tube surfactant: Tube surfactant should chosen wisely as these might interfere with antibodies and disrupt the reactions required. The surfactant helps reducing non-specific adsorption, improve blood flow, and preventing absorbing of proteins, RBCs, and platelets to the tube wall. 

Additional components

Besides the general components, additional components are present in different color caps, which are as follows:  

1. Separating gel: These are present in SST (serum separating tubes) and used to separate serum from clotted or whole blood. The gel used is thixotropic gel which is lodged between the packed cells and serum. 
2. Anticoagulants: Potassium EDTA, trisodium citrate, potassium oxalate, sodium fluoride, and heparin salts act as anticoagulants and chelating agents in blood collection tubes. 
3. Clot activator particles: These are present in plastic tubes and the particles activate clot either intrinsically or extrinsically. Ellagic acid, thrombin, snake venoms, and thromboplastin are activate clot extrinsically. Silica, glass, bentonite, kaolin, and diatomaceous earth activate clot intrinsically.  
4. Protease inhibitors: EDTA and citrate also acts protease inhibitors by limiting the activation of proteases. Aprotinin and sulfonyl halides are other protease inhibitors used in Vacutainer® tubes.  

Order of Draw

Blood collection in tubes follows a principle known as “order of draw”. A specific order for transferring the drawn blood is necessary for avoiding cross-contamination of additives. The recommended order of draw for blood collection tubes are:

1. First draw in blood culture bottle or tube (yellow or yellow-back top) 
2. Second draw in a coagulation tube (light blue color). Concern of contamination by tissue, fluids, or thromboplastins may arise, so one can draw in non-additive tube first followed by the light blue top.  
3. Third draw is on a non-additive tube (red top).
4. Final draw in additive tube in following order:

1. SST (red-gray or gold top) which contains gel separator and clot activator.
2. PST (light green top) with lithium heparin anticoagulant and a gel separator.
3. Sodium heparin (dark green top)
4. EDTA (lavender top)
5. ACDA or ACDB (pale yellow top) that hs acid citrate dextrose.
6. Oxalate/ fluoride (light gray top)

Do not transfer a sample from one collection tube to another or mix blood from different collection tubes. 

Color of the Cap and Its Purpose

As mentioned earlier, the color of the top of the tube signifies the purpose and anticoagulant added to the tube. The color of the tube also determines the clotting time required as well as the number of necessary inversions after the blood is transferred into the tubes. Standard laboratory practices use yellow, pink, blue, lavender/purple, red, green, and light blue color tubes. 

The color of the tube with anticoagulant and their area of use are as follows: 

Marble or Gold (SST)

• Additive: Plastic tubes with clot activator and gel for serum separation.
• Tube Inversions: 5 tube inversions required to ensure the mixing of clot activator with blood. 
• Clotting Time Required: 30 minutes 
• Commonly Associated Tests: Chemistry profiles, electrolytes, lipid panel, hepatic panel, hepatitis panel, thyroid studies, iron studies, cancer markers, lithium, alcohol, vitamin B12, vitamin D, hormone studies, cardiac markers, lidocaine, folate, therapeutic drugs (except carbamazepine), tricyclic antidepressants, salicylate, and homocysteine (ON ICE).

Plain Red

• Additive: Silicone coated made of glass.
• Tube Inversions: No tube inversions required.
• Clotting Time Required: 60 minutes 
• Commonly Associated Tests : Rheumatoid factor (RF), RPR (rapid plasma reagin test), uric acid, PTH (parathyroid hormone), insulin, prealbumin, magnesium, BhCG (beta-human chorionic gonadotropin) test, FT3/FT4 (free triiodothyronine and free thyroxine), digoxin, amylase, lipase, cortisol, CRP (C-reactive protein) test, and C-peptide.

Green

• Additive and tube Inversions: Lithium heparin (light green tube tubes containing lithium heparin and gel for plasma separation) is the additive. Eight tube inversions to ensure mixing the anticoagulant with blood to prevent clotting.
• Clotting Time Required: No clotting time required. 
• Commonly Associated Tests: Green and light green Vacutainer tubes are preferable for all STAT general chemistry requests. 
  1. Chemistry profiles
  2. Ionized calcium
  3. Lipid panel
  4. Hepatic panel
  5. Cardiac markers 
  6. Rheumatoid factor (RF) test
  7. Ammonia (ON ICE)
  8. Therapeutic drugs (except for VANC and lithium). 
  9. BhCG Quant

Gray

• Additive: Sodium Fluoride/Potassium Oxalate
• Tube Inversions: 8 tube inversions ensure proper mixing of additives with blood. 
• Clotting Time Required: No clotting time required. 
• Commonly Associated Tests: Lactic acid (ON ICE). Gray top tubes can be used when checking Glucose levels only. These tubes preserve glucose and are helpful when drawing blood samples a long distance from the hospital. 

Purple/Lavender

• Additive: Spray-coated K2 EDTA added in a plastic tube. So, also called as EDTA tube. 
• Tube Inversions: 8 tube inversions required to ensure the mixing of the anticoagulant with the blood. 
• Clotting Time Required: No 
• Commonly Associated Tests: CBC (Complete blood count)/PLT Count, H&H (hemoglobin and hematocrit), SED Rate (ESR- eosinophil sedimentation rate), BNP (B-type natriuretic peptide) test, HgbA1C, Cyclosporin, Sickle cell, RETIC (reticulocyte count), Path Review, Intra op PTH, Vancomycin, HIV, Direct Coombs, RBC Folate, PROGRAF, CD3/CD4.

Pink

• Additive: Spray-coated K2 EDTA added in plastic tubes. 
• Tube Inversions: 8 tube inversions prevent clotting. 
• Clotting Time Required: No
• Commonly Associated Tests: Blood typing and RH, Blood typing and Screening, Antibody Screen, Crossmatch, RHOGAM Workup 

Blue

• Additive: Buffered sodium citrate 0.1-5 M (3.2%) glass and 0.109 M (3.2%) plastic. It is also called as PT tube.
• Tube Inversions: 3-4 tube inversions ensure proper mixing of the anticoagulant with the blood.
• Clotting Time Required: No
• Commonly Associated Tests 
  1. PT/INR (Prothrombin time/International normalized ratio) test
  2. PTT (partial thromboplastin time) test
  3. Fibrinogen
  4. D’DIMER
  5. Special Coag and Factor Assays call the lab before collection

Royal Blue

• Additive: Plastic tubes is sprayed with K2 EDTA. K2 EDTA increases the MCV (mean corpuscular volume) of RBC in higher concentrations.  
• Tube Inversions: 8 tube inversions ensure proper mixing of the anticoagulant with the blood.
• Clotting Time Required: No
• Commonly Associated Tests: Toxicology testing determines the trace amount of metals like aluminum, cadmium, copper, lead, mercury, selenium, zinc, etc.

The Gold Top (SST-Serum Separator Tube) and Plain Red Top Tube should be mixed 5-6 times because they contain a clot activator. The Green Top (PST-Plasma Separator Tube) is preferred if listed.

In summary

The color of the tube and the anticoagulant added to it is as follows:

Color of the Tube	Anticoagulant
Yellow, Pink, and Blue	Sodium polyanethole sulfonate (SPS)
Light Blue “citrate tube”	Sodium citrate (3.2%)
Red	No anticoagulant or additive inside the tube
Green	Heparin (sodium heparin, lithium heparin, or ammonium heparin)
Lavender/Purple “EDTA tubes”	Ethylene-diamine-tetra-acetic-acid
Gray	Potassium oxalate and sodium fluoride

References and further readings 

1. MD ECK. Phlebotomy [Internet]. WebPath. [cited 2023Jan24]. Available from: https://webpath.med.utah.edu/TUTORIAL/PHLEB/PHLEB.html 
2. Bayot ML, Tadi P. Laboratory Tube Collection. [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK555991/
3. BD Vacutainer Venous Blood Collection Tube Guide – Hopkins Medicine [Internet]. www.bd.com/vacutainer. BD Diagnostics; [cited 2023Jan24]. Available from: https://www.hopkinsmedicine.org/immunogenetics/_docs/Tubes_chart.pdf
4. Bowen RAR, Remaley AT. Interferences from blood collection tube components on clinical chemistry assays. Biochemia Medica. 2014Feb15;24(1):31–44.  
5. https://www.bd.com/en-us/products-and-solutions/products/product-families/bd-vacutainer-blood-collection-tubes