[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fGyZXARlg7-zC34qPJBWX0ID8wjoWCzkXHFThbyjgJtk":32,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":188},[4,8,12,16,20,24,28],{"title":5,"slug":6,"path":7},"About Microbeonline.com","about-microbeonline-com","\u002Fabout-microbeonline-com\u002F",{"title":9,"slug":10,"path":11},"About Me","about-me","\u002Fabout-microbeonline-com\u002Fabout-me\u002F",{"title":13,"slug":14,"path":15},"Advertise with Us","advertise-us","\u002Fadvertise-us\u002F",{"title":17,"slug":18,"path":19},"Privacy Policy","privacy-policy","\u002Fprivacy-policy\u002F",{"title":21,"slug":22,"path":23},"Abbreviations","abbreviations","\u002Fabbreviations\u002F",{"title":25,"slug":26,"path":27},"Microbes","microbes","\u002Fmicrobes\u002F",{"title":29,"slug":30,"path":31},"Books","recommended-books","\u002Frecommended-books\u002F",{"type":33,"data":34},"blog",{"slug":35,"title":36,"description":37,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":40,"lastUpdatedDate":41,"draft":42,"category":43,"image":38,"body":44,"faq":45,"tags":64,"related":66},"micropipette-parts-types-and-uses","Micropipette: Parts, Types, and Uses","Learn the parts, types, and uses of micropipettes — including air vs. positive displacement, pre-wetting technique, reverse pipetting for viscous samples, and common errors that affect diagnostic accuracy.",null,"Ashma Shrestha","2022-07-19","2026-07-19",false,"lab-equipment","In a molecular diagnostics laboratory, a junior technician is preparing a PCR master mix. She needs to add 2 µL of DNA template to each reaction tube. She reaches for the P200 micropipette — the only one on the bench — sets it to 2 µL, and proceeds. The PCR runs overnight. The next morning, every reaction shows either no amplification or inconsistent bands. The problem: a P200 set to 2 µL operates at 1% of its working range. At that scale, a small variation in plunger pressure, tip seating, or angle produces a 50–100% error in actual volume delivered. Some tubes got 1 µL of template; others got 3 µL. The master mix was never at fault. The micropipette selection was.\n\nThe micropipette is the most precise liquid transfer instrument in the microbiology laboratory — but only when the right model is selected for the target volume, the technique is correct, and the instrument is calibrated. Understanding all three is what separates a reliable result from a failed run.\n\nA pipette is an equipment ideal for pipetting or transferring liquid samples in the laboratory. Generally, glass or regular pipette can only transfer sample volume in a milliliter. For laboratories handling small volumes of samples (volumes in microliters), the ideal choice is a micropipette.\n\n**A micropipette is the laboratory equipment used for aspirating and dispensing small volumes (as small as 0.2 µl) of liquid.  These are used in pharmaceutical, molecular, forensic, and diagnostic laboratories. It is of different types based on its principle (air and positive displacement), capacity (P20-P10,000), channels (single and multi), and working mechanics (manual and automatic).**\n\n> microliter=µl\n\n## Why Micropipette Technique Matters in Clinical Microbiology\n\nA microliter is one-thousandth of a milliliter — a volume invisible to the naked eye. At this scale, small errors in technique become large proportional errors in the final result.\n\nConsider antibiotic susceptibility testing by broth microdilution. Each well in the microtiter plate receives a defined volume of antimicrobial at a specific concentration. A 10% volume error in one well shifts the antimicrobial concentration by 10% — enough to push a result from susceptible to resistant, or vice versa. A patient may receive the wrong antibiotic based on a pipetting error that took less than a second to make.\n\nIn [PCR](https:\u002F\u002Fmicrobeonline.com\u002Fpolymerase-chain-reaction-pcr-steps-types-applications\u002F), the consequences are equally significant. Template DNA is added in volumes of 1–5 µL. An error of even 1 µL — invisible, undetectable at the time — changes the template concentration enough to cause non-specific amplification, failed amplification, or false-negative results in diagnostic assays.\n\nThis is why micropipette technique is not a minor procedural detail. It is a pre-analytical variable that directly affects diagnostic accuracy.\n\n## Parts of Micropipette\n\n![Parts of micropipette - Parts of Micropipette](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FParts-of-Micropipette.png)Figure: Parts of Micropipette\n\n1. **Plunger:** The plunger is the topmost part of the micropipette. Pushing down the plunger helps in the aspiration and dispensation of the desired amount of liquids. It consists of two stops, the first stop is for aspiration and the second stop is for dispensation.\n2. **Tip ejector button:** A button beside the plunger helps in the ejection\u002Fremoval of pipette tips without using hands. \\\n   Read more: [Pipette Tips: Types, Uses, and Criteria to Choose It](https:\u002F\u002Fmicrobeonline.com\u002Fpipette-tips-types-uses-and-criteria-to-choose-it\u002F)\n3. **Volume adjustment knob:** It is a knob attached to the plunger. Turning it helps in adjusting the desired volume in the adjustable volume micropipette. It cannot be turned\u002Frotated in a fixed volume micropipette.\n4. **Digital volume display window:** It displays the volume that the micropipette can withdraw.\n5. **Plastic shaft:** A plastic shaft is a tube-like structure filled with air in an air displacement micropipette. Once you press the piston, some amount of air from the shaft releases, helping in the aspiration of liquid. In contrast, releasing the piston helps dispense liquid, and the air again fills up the shaft.\n6. **Ejector arm:** It is an extension of the tip ejector button. It puts pressure on the pipette cone once the ejector button is pressed.\n7. **Tip cone:** It is the place where the pipette tip is attached.\n8. **Pipette tip:** It is equipment made up of virgin polypropylene or molded plastics that come in direct contact with the liquid.\n\n## How to Use a Micropipette?\n\nThe correct way of using a micropipette affects its durability. The procedure for operating it is as follows:\n\n1. **Select the right micropipette:** Any micropipette has a fixed volume range. P1000 is an adjustable volume micropipette measuring liquid from 100 to 1000 µl. Likewise, P20 can aspirate fluid from 2 to 20 µl. So select the pipette based on the volume of liquid.\n2. **Adjust pipette to the right volume:** After choosing the correct pipette, adjust the micropipette to the desired volume with the help of a volume adjustment knob. Do not turn the knob above the range of the micropipette. It will damage the micropipette.\n3. **Attach the pipette tip:** Select the pipette tip based on micropipette use. Avoid touching the tip with your hands; instead, place the micropipette above the tip and press down to attach the tip to the tip cone. Make sure the tip is firmly attached to the micropipette.\n4. **Aspiration of liquid:** The plunger of the micropipette has two stops. For aspirating, press the plunger to the first stop and dip the end tip into the fluid to be aspirated. Release the plunger but make sure the tip is inside the liquid until the plunger regains its original position.\n5. **Dispensation of liquid:** Insert the tip into the container where you want to dispense the sample. Firstly, press the plunger to the first stop and pause. Then, press the plunger to the second stop to completely expel the liquid. Hold the plunger until you pull the tip entirely out of the tube to avoid re-aspiration.\n6. **Removing tip:** Firstly, place the micropipette above the disposing container. Then, press the tip ejector button to remove the tip. Avoid using your hands to remove the tip.\n\n### Pre-wetting the Tip (Critical for Accurate Volume Delivery)\n\nThe first aspiration with a new, dry tip consistently delivers less volume than intended. This happens because the dry polypropylene surface of the tip absorbs a small amount of liquid, reducing the actual volume dispensed.\n\n**When to pre-wet:** Before any measurement where accuracy is critical — PCR setup, serial dilutions, ELISA, any assay where the first pipetting step matters.\n\n**How to pre-wet:**\n\n1. Attach a new tip to the micropipette.\n2. Aspirate the target liquid to the first stop and dispense it back into the source container.\n3. Repeat 2–3 times.\n4. The tip surface is now conditioned — proceed with the actual transfer.\n\nPre-wetting takes 10 seconds and prevents a systematic low-volume error on every first aspiration.\n\n### Reverse Pipetting (For Viscous or Volatile Samples)\n\nStandard (forward) pipetting — press to stop 1, aspirate, press to stop 1 again to dispense — works well for aqueous solutions. For viscous samples (glycerol, serum, concentrated protein solutions) or volatile liquids (ethanol, chloroform), it introduces errors because viscous liquids resist the air cushion, and volatile liquids evaporate into the air cushion and are under-delivered.\n\n**Reverse pipetting technique:**\n\n1. Press the plunger all the way to the **second stop** before dipping into the liquid.\n2. Release the plunger slowly — this aspirates more than the set volume (overfill).\n3. Withdraw the tip from the liquid and touch it to the container wall to remove the hanging drop.\n4. Dispense by pressing only to the **first stop** — this delivers the exact set volume, leaving the excess in the tip.\n5. Discard the tip with the remaining liquid still inside.\n\nThe excess liquid in the tip acts as a buffer that compensates for the resistance of viscous flow. Never press to the second stop when dispensing in reverse pipetting — this expels the excess and over-delivers.\n\n## Common Micropipette Errors and How to Avoid Them\n\n| Error | What goes wrong | Prevention |\n| --- | --- | --- |\n| Using wrong pipette size | P1000 set to 2 µL = 1% of range; ±50% volume error is common | Always use the smallest pipette whose range covers your target volume |\n| Not pre-wetting the tip | First aspiration delivers less than intended; systematic low-volume error | Pre-wet 2–3 times before critical transfers |\n| Pipetting at wrong angle | Tilting >20° during aspiration creates hydrostatic pressure that over-aspirates | Hold micropipette vertically or at ≤20° tilt during aspiration |\n| Immersing tip too deeply | Liquid wets the outer tip surface; excess carried into next container | Immerse only 2–3 mm below the liquid surface |\n| Pressing to second stop during aspiration | Over-aspiration — more than the set volume enters the tip | Press only to first stop for aspiration in forward pipetting |\n| Withdrawing tip before plunger fully releases | Air bubble aspirated with sample; volume short | Keep tip submerged until plunger has fully returned to rest position |\n| Using standard tip for PCR | Aerosols enter the barrel; PCR product contaminates future reactions | Use filter tips for all PCR work and infectious specimens |\n| Touching tip to container bottom during dispensing | Tip blocks, liquid backs up; volume not fully delivered | Touch the container wall at a 45° angle; do not press tip flat to bottom |\n| Ignoring calibration schedule | Volume drift undetected — all results systematically off | Calibrate every 3–6 months per laboratory SOP; document each calibration |\n\n## Types of Micropipettes\n\n![Types of micropipette - Types of micropipette](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FTypes-of-micropipette.png)Figure: Types of micropipette\n\nMicropipettes are classified on different basis. The basis for the classification of micropipettes are; **the principle, the number of channels, pipetting mechanism, and volume.**\n\n### Based on the Principle\u002FDisplacement Method\n\nAir displacement micropipette\n\nThe piston is inside the pipette. There is an air cushion between liquid and piston. During aspirating liquid, the piston displaces an equal volume of air to the volume adjusted in the micropipette. The temperature and viscosity of the liquid greatly influence the precision of the air displacement micropipette. Likewise, calibration of the micropipette from time to time is also necessary.\n\nPositive displacement micropipette\n\nThe piston is not inside the pipette shaft but inside the pipette tip. There is no air cushion between piston and liquid. The piston contacts the liquid directly, and no air is replaced during aspiration. No external factors like temperature and viscosity influence these kinds of pipettes due to the absence of the air cushion. It is also accurate for samples that are viscous and volatile sample.\n\n### Based on the Number of Channels\n\nSingle channel\n\nOnly a shaft is present in a single channel micropipette that can transfer one liquid at a time. They are available in various capacities and provide excellent accuracy. The capacity available ranges from 0.2 to 10,000 µl.\n\nMultichannel\n\nMultiple shafts are present in a multichannel micropipette that can transfer various liquids simultaneously. Common multichannel micropipette has 8-12 channels, but 4, 6, 16, and 18 channels are also available. It is best for tests involving multiple wells like ELISA, DNA amplification tests, etc. The capacity of multichannel micropipettes ranges from 0.2 to 1200 µl.\n\n### Based on the Pipetting Mechanism\n\nMechanical\u002FManual\n\nIn the mechanical\u002Fmanual micropipette, personnel has to apply pressure to press the plunger for aspiration and dispensation. The piston has a spring.\n\nElectronic\n\nAn electronic button replaces the mechanical plunger. It is also called an [automated pipette](\u002Fautomated-pipette-liquid-handling-system\u002F) and replaces manual labor. These have customizable programs to adjust to any requirement of the pipetting.\n\n### Based on the Volume\n\nFixed volume micropipette\n\nThese do not have an adjustment knob for chaining the volumes. These pipettes transfer an equal volume of samples every time. It is ideal for transferring viscous liquids in laboratories with a limited budget. It decreases the chance of error due to mistakenly changing the volume.\n\nAdjustable volume micropipette\n\nThese have volume adjusting knobs for changing the volume. The volume of these pipettes comes in a range like P20 can transfer a volume of 0.2 to 20 µl. The available volume ranges are as follows:\n\n| Volume range | Name\u002Ftitle |\n| --- | --- |\n| 0.2-2 µl | P2 |\n| 0.5-10 µl | P10 |\n| 2-20 µl | P20 |\n| 5-50 µl | P50 |\n| 10-100 µl | P100 |\n| 20-200 µl | P200 |\n| 100-1000 µl | P1000 |\n| 500-5000 µl | P5000 |\n| 1000-100000 µl | P10000 |\n\n> 1000 µl= 1 ml10000 µl= 10 ml\n\n## How to Remember\n\n**The P-number rule: \"P tells you the maximum, not the ideal.\"** A P1000 can measure up to 1000 µL but is most accurate between 100–1000 µL. A P20 is most accurate between 2–20 µL. The P-number is the ceiling of the working range, not the sweet spot. Never use a micropipette at the very bottom of its range for a critical measurement.\n\n**Air displacement vs. positive displacement — the cushion analogy:** Air displacement pipettes have an air cushion between the piston and the liquid — like a syringe with an air gap before the plunger reaches the fluid. This cushion means temperature and viscosity affect the volume. Positive displacement pipettes have no cushion — the piston directly contacts the liquid, like a syringe plunger touching the fluid directly. No air, no temperature effect, no viscosity problem. Positive displacement = direct contact = best for difficult samples.\n\n**Two stops, two actions:** Stop 1 = aspirate (and first phase of dispense). Stop 2 = expel completely. In forward pipetting: aspirate at stop 1, dispense to stop 1, push to stop 2 only to blow out. In reverse pipetting: aspirate at stop 2, dispense only to stop 1. The second stop is always the \"extra push\" — use it intentionally, never accidentally.\n\n**The size selection rule — \"Match the pipette to the volume, not the other way around.\"** If the volume is 5 µL, use the P20 (range 2–20 µL), not the P200 or P1000. If two pipettes both cover your volume, choose the one whose range makes your target volume fall in the upper half of its scale.\n\n## Uses of Micropipette\n\nMicropipettes are suitable in the laboratory that handles minute (0.1 to 1000 µl) volumes of samples. Some areas that use micropipettes are as follows:\n\n1. **Clinical and microbiological laboratory:** It is used for different tests used in diagnosing diseases. Serological tests (antibody\u002Fantigen detection using rapid test kits, [ELISA tests](https:\u002F\u002Fmicrobeonline.com\u002Felisa-principle-types-and-applications\u002F), etc.), molecular tests (sequencing, PCR, blotting techniques, electrophoresis, etc.), and virus culture in cell lines use it for transferring reagents\u002Fsamples.\n2. **Chemical laboratory:** These laboratories use micropipettes to handle viscous and volatile liquids for various experiments.\n3. **Forensic laboratory:** These laboratories use micropipettes to analyze blood, tissues, and fibers. Micropipettes are also helpful tests that determine the genetics of victims or analysis of DNA materials and fingerprints found at the crime scene.\n4. **Pharmaceutical laboratory:** These laboratories use micropipettes for medicine\u002Fdrug production. These also use micropipettes for the produced drugs’ QC (quality control) testing.\n5. **Food and beverage industry:** Primarily, micropipettes function as liquid handling devices in these industries, and quality assurance tests are another area of micropipettes’ application.\n\nFor a comparison of all pipette types used in microbiology, see [Types of Pipettes in the Microbiology Laboratory](https:\u002F\u002Fmicrobeonline.com\u002Ftypes-of-pipettes-in-microbiology\u002F)\n\n## Key exam facts in one table\n\n| Topic | Key fact |\n| --- | --- |\n| Definition | Aspirates and dispenses volumes from 0.2 µL to 10,000 µL |\n| Working principle | Air displacement — piston displaces air; liquid enters the tip only |\n| Liquid contacts | Tip only — never the barrel\u002Fshaft |\n| Two plunger stops | Stop 1 = aspiration and first-phase dispensing; Stop 2 = blow-out\u002Fcomplete expulsion |\n| Air displacement limitation | Affected by temperature, viscosity, and altitude |\n| Positive displacement advantage | Direct piston-liquid contact; unaffected by viscosity or volatility; used for special samples |\n| P1000 working range | 100–1000 µL (not 0–1000 µL — avoid the lowest 10% of range) |\n| P20 working range | 2–20 µL |\n| Pre-wetting | Condition tip 2–3 times before critical first aspiration to prevent short-delivery |\n| Reverse pipetting | Used for viscous\u002Fvolatile samples; aspirate to stop 2, dispense to stop 1 only |\n| Filter tips — when mandatory | PCR, RNA\u002FDNA work, infectious specimens |\n| Calibration frequency | Every 3–6 months; ISO 8655 standard governs piston-operated volumetric apparatus |\n| Most common selection error | Using too large a pipette for the target volume (e.g., P1000 for 5 µL work) |\n| Multichannel micropipette | 8–384 channels; simultaneous transfer into multiple wells; used for ELISA, MIC plates |\n| Spanish terminology | Micropipeta; partes de la micropipeta — article receives significant traffic from Spanish-speaking students |\n\n**References**\n\n1. Clinical and Laboratory Standards Institute (CLSI). (2016). *Clinical Microbiology Procedures Handbook* (4th ed.). American Society of Microbiology. \u003Chttps:\u002F\u002Fdoi.org\u002F10.1128\u002F9781555818814>\n2. ISO 8655-1:2022. *Piston-operated volumetric apparatus — Part 1: Terminology, general requirements and user recommendations*. International Organization for Standardization.\n3. Eppendorf AG. (2019). *The Lab Pipetting Guide*. Eppendorf. \u003Chttps:\u002F\u002Fwww.eppendorf.com\u002Fpipetting-guide>\n4. Sanders, E. R. (2012). Aseptic laboratory techniques: Plating methods. *Journal of Visualized Experiments*, (63), e3064. \u003Chttps:\u002F\u002Fdoi.org\u002F10.3791\u002F3064>\n5. Mahon, C. R., Lehman, D. C., & Manuselis, G. (2018). *Textbook of Diagnostic Microbiology* (6th ed.). Elsevier.",[46,49,52,55,58,61],{"question":47,"answer":48},"What is the difference between air displacement and positive displacement micropipettes?","In air displacement micropipettes, a cushion of air separates the piston from the liquid inside the tip. The piston displaces air, which draws liquid into the tip. This method is accurate for standard aqueous samples but is affected by temperature, viscosity, and altitude. In positive displacement micropipettes, the piston contacts the liquid directly inside a specialised tip — there is no air cushion. This makes positive displacement pipettes accurate for viscous, volatile, and high-density samples that would compress or expand an air cushion and produce volume errors.",{"question":50,"answer":51},"How do I select the correct micropipette size for my volume?","Always select the smallest micropipette whose range covers the target volume. For example, to transfer 5 µL, use a P20 (range 2–20 µL) rather than a P200 or P1000. Using a pipette at the extreme low end of its range introduces proportionally large errors — a P1000 set to 5 µL operates at 0.5% of its working range, where small variations in technique produce large percentage errors in actual volume delivered.",{"question":53,"answer":54},"What is pre-wetting a micropipette tip and why is it necessary?","Pre-wetting involves aspirating the target liquid into a new tip and dispensing it back into the source container, repeating 2–3 times before the actual transfer. A dry tip surface absorbs a small amount of liquid on first contact, causing the first aspiration to deliver slightly less than the set volume. Pre-wetting saturates the tip surface, eliminating this short-delivery error. It is especially important for critical measurements in PCR setup, serial dilutions, and ELISA.",{"question":56,"answer":57},"When should reverse pipetting be used instead of forward pipetting?","Reverse pipetting is used for viscous samples (glycerol, serum, concentrated protein solutions) and volatile liquids (ethanol, chloroform). In forward pipetting, the air cushion compresses under the resistance of viscous flow, causing under-delivery. Reverse pipetting overcomes this by aspirating more than the target volume (press to stop 2), then dispensing only to stop 1 — the excess in the tip acts as a buffer that compensates for the resistance of viscous flow. Never press to the second stop when dispensing in reverse pipetting.",{"question":59,"answer":60},"What are the most common micropipette errors in the laboratory?","The most common errors are: using too large a pipette for the target volume (e.g., P1000 for 5 µL work); not pre-wetting the tip before critical first aspirations; pipetting at an angle greater than 20° during aspiration; immersing the tip too deeply into the liquid; and using standard tips for PCR work where filter tips are mandatory. Each error produces a different type of volume inaccuracy or contamination event.",{"question":62,"answer":63},"How often should micropipettes be calibrated?","Micropipettes should be calibrated every 3–6 months under normal laboratory use, or more frequently if used heavily or after being dropped or repaired. Calibration uses the gravimetric method — weighing dispensed distilled water at a known temperature and converting weight to volume using a density conversion factor. Accuracy should fall between 99% and 101% of the nominal volume. ISO 8655 is the governing standard for piston-operated volumetric apparatus.",[65],"pipette",[67,92,114,139,161],{"slug":68,"title":69,"description":70,"seoTitle":71,"seoDescription":72,"author":39,"createdDate":73,"lastUpdatedDate":74,"draft":42,"category":43,"image":38,"faq":75,"tags":91},"glass-pipettes-types-handling-and-uses","Glass Pipettes: Types, Handling, and Uses","Glass pipettes transfer mL-scale volumes in microbiology labs. Learn the types (Mohr's, serological, volumetric, Pasteur), how to read the meniscus correctly, and the drain-out vs. blow-out distinction students most often confuse.","Glass Pipettes: Types, Meniscus Reading, Blow-Out Rules, and Uses","Compare Mohr, serological, volumetric, and Pasteur pipettes, read the meniscus correctly, and apply drain-out and blow-out rules for accurate transfers.","2022-07-29","2026-07-08",[76,79,82,85,88],{"question":77,"answer":78},"What is the difference between a Mohr's pipette and a serological pipette?","A Mohr's pipette is a drain-out type: the graduation marks stop above the tip, and the liquid in the ungraduated section below the last mark is not delivered. Never blow out a Mohr's pipette. A serological pipette is a blow-out type: the graduation marks extend to the tip, and the last drop must be expelled by pressing the bulb at the end of dispensing. Serological pipettes are identified by a blow-out ring near the suction end at the top. Confusing the two introduces a systematic delivery error — blowing out a Mohr's over-delivers; not blowing out a serological under-delivers.",{"question":80,"answer":81},"How do you read the meniscus correctly in a glass pipette?","For colourless and light-coloured liquids, read from the bottom of the concave meniscus curve, with your eye exactly level with the graduation mark. Reading from the top of the curve over-reads the volume. For coloured or opaque liquids that form a convex meniscus, read from the top of the curve. Parallax error — caused by positioning your eye above or below the graduation mark — produces false high or false low readings and is eliminated by always levelling your eye with the mark before reading.",{"question":83,"answer":84},"What is a volumetric pipette and when is it used?","A volumetric pipette (also called a bulb pipette or transfer pipette) is a non-graduated pipette designed to deliver one specific fixed volume with the highest accuracy of any glass pipette type. It has a single volume mark on the bulb section and no graduation marks along the stem. It is used when one exact volume is needed repeatedly — for example, in titrations, standard solution preparation, or media preparation steps requiring a precise defined volume. It is not suitable when partial volumes or flexible delivery amounts are needed.",{"question":86,"answer":87},"Why is mouth pipetting prohibited in the laboratory?","Mouth pipetting creates a direct route for laboratory liquids — including infectious specimens, toxic chemicals, and corrosive reagents — to enter the mouth, be inhaled, or be swallowed. It has caused laboratory-acquired infections, chemical poisonings, and deaths. All aspirating in the laboratory must be done with a pipette bulb, three-valve filler, or mechanical pipetting aid. Mouth pipetting is prohibited by laboratory safety regulations in all clinical and research settings globally.",{"question":89,"answer":90},"What are the different accuracy classes of glass pipettes?","Graduated glass pipettes are classified as Class A, Class As, and Class B based on accuracy. Class A and Class As pipettes have tightly specified error tolerances and are suitable for analytical and clinical work requiring high accuracy. Class B pipettes have double the error limits of Class A and are used for general laboratory work where a lower level of precision is acceptable. For any work where volume accuracy affects clinical results — serological titrations, media preparation to precise concentrations — Class A pipettes should be used.",[65],{"slug":93,"title":94,"description":95,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":96,"lastUpdatedDate":41,"draft":42,"category":43,"image":38,"faq":97,"tags":113},"multichannel-pipettes-parts-and-calibration","Multichannel Pipettes: Parts and Calibration","Multichannel pipettes aspirate and dispense into multiple wells simultaneously. Learn their parts, forward and backward pipetting technique, calibration procedure, and when to use them in ELISA and MIC testing.","2022-07-23",[98,101,104,107,110],{"question":99,"answer":100},"What is a multichannel pipette used for in clinical microbiology?","Multichannel pipettes are used for any procedure that uses a microtiter plate format — 96-well or 384-well. The most common clinical microbiology applications are ELISA (loading patient samples and reagents across the plate), broth microdilution MIC testing (preparing serial antibiotic dilutions across a row of wells), and serological titrations. The multichannel pipette delivers identical volumes into multiple wells simultaneously, improving reproducibility compared to repetitive single-channel pipetting.",{"question":102,"answer":103},"What is the difference between an 8-channel and a 12-channel multichannel pipette?","A standard 96-well microtiter plate has 8 rows (labelled A to H) and 12 columns (labelled 1 to 12). An 8-channel pipette fills one entire column at a time, requiring 12 pipetting steps to fill a full plate. A 12-channel pipette fills one entire row at a time, requiring 8 pipetting steps to fill a full plate. The choice between them depends on whether the procedure is organised by column or by row — for example, if each row contains one patient's serial dilutions, a 12-channel pipette processes one patient per step.",{"question":105,"answer":106},"What is the difference between forward and backward pipetting with a multichannel pipette?","Forward pipetting (also called exact pipetting) is the standard method: press the plunger to stop 1 before aspiration, release to fill, then press to stop 1 to dispense and stop 2 to blow out. It is used for standard aqueous liquids. Backward pipetting (overfilling technique) presses the plunger to stop 2 before aspiration, aspirating more than the target volume, then dispenses only to stop 1 — the excess remains in the tip and is discarded. Backward pipetting is used for foamy or viscous liquids where forward technique causes inconsistent fill across channels.",{"question":108,"answer":109},"Why must a trough (reagent reservoir) be used with a multichannel pipette?","A multichannel pipette has 8 or more tip cones spread across a fixed distance that matches the spacing of a microtiter plate. Individual test tubes are too narrow and spaced too far apart for all channels to reach the liquid simultaneously. A reagent trough provides a wide, shallow source of liquid where all channels can immerse to equal depth at the same time, ensuring each channel aspirates the same volume. Unequal immersion depth is one of the most common causes of inconsistent volume delivery across channels.",{"question":111,"answer":112},"How is a multichannel pipette calibrated?","Multichannel pipettes are calibrated using the gravimetric method: dispensed distilled water is weighed on an analytical balance, and volume is calculated using the formula V = w × Z, where w is the average weight of water dispensed and Z is a conversion factor based on water density at the measured temperature. Each channel must be calibrated individually, which makes multichannel calibration more time-consuming than single-channel calibration. Target accuracy is 99–101% of nominal volume. Because of the complexity, many laboratories use specialist calibration service providers for multichannel pipettes.",[65],{"slug":115,"title":116,"description":117,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":118,"lastUpdatedDate":74,"draft":42,"category":43,"image":38,"faq":119,"tags":138},"pipette-tips-types-uses-and-criteria-to-choose-it","Pipette Tips: Types, Uses, and Criteria to Choose It","Pipette tips are the aseptic barrier between specimen and pipette. Learn tip types — filter, low-retention, wide-bore — and when each is clinically mandatory vs. optional.","2022-07-15",[120,123,126,129,132,135],{"question":121,"answer":122},"Why are filter tips mandatory for PCR work?","During pipetting, aerosols are generated — fine droplets that can travel upward through the tip and into the pipette barrel. In PCR, even nanogram quantities of contaminating DNA or PCR product entering the barrel are enough to cause false-positive results in subsequent runs. Filter tips contain a hydrophobic polyethylene filter inside the tip shaft that physically blocks aerosols and liquid from travelling beyond the tip. Filter tips are mandatory for all PCR setup, RT-PCR, sequencing, and RNA handling. Standard non-sterile tips are not acceptable substitutes for this work.",{"question":124,"answer":125},"What is the difference between low-retention tips and standard tips?","Standard polypropylene tips allow a thin film of liquid to adhere to the inner tip surface, which is not significant for most aqueous samples. Low-retention tips have a modified hydrophobic inner surface that minimises this adhesion, resulting in more complete liquid delivery and better volume accuracy. They are used for viscous samples, concentrated protein solutions, expensive or scarce reagents, and any situation where even a small residual volume left in the tip represents a meaningful loss or accuracy problem.",{"question":127,"answer":128},"When should wide-bore pipette tips be used?","Wide-bore tips have an enlarged orifice compared to standard tips. They are used when the sample contains intact cells, blood, dense cell suspensions, or any particulate material that would be sheared or clogged by the narrow opening of a standard tip. Shearing cells through a narrow tip orifice damages cell membranes, affects cell viability, and produces inaccurate counts in haemocytometer or flow cytometry applications. Wide-bore tips allow these samples to pass through without mechanical damage.",{"question":130,"answer":131},"Can non-sterile autoclavable tips be used for RNA work?","No. Autoclaving kills microorganisms but does not reliably eliminate RNase activity. RNases are extremely heat-stable enzymes that can survive autoclaving and degrade RNA samples on contact. For RNA extraction, RT-PCR, and any procedure involving RNA, only certified RNase-free pre-sterile tips should be used — these are manufactured and packaged under conditions that confirm absence of RNase, DNase, ATP, and endotoxins, and come with a sterilization certificate.",{"question":133,"answer":134},"What does tip colour indicate?","Tip colour is a size indicator, not a sterility indicator. Yellow tips typically correspond to the 200 µL volume range; blue tips to the 1000 µL range; white or clear tips to the 10 µL range. Colour coding is largely standardised across major manufacturers but can vary — always confirm the volume range on the packaging label. Sterility status is stated on the packaging, not indicated by colour.",{"question":136,"answer":137},"Why should tips never be touched by hand before use?","Human skin carries RNases, DNases, and microorganisms that transfer to the tip on contact. For molecular work, skin RNases degrade RNA samples; for microbiology culture work, skin commensals introduced on a tip can appear as contaminants in culture results. Tips should always be attached using the pipette's tip ejector mechanism pressing into the tip rack, and removed using the tip ejector button — hands should never contact the tip body or orifice.",[65],{"slug":140,"title":141,"description":142,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":143,"lastUpdatedDate":74,"draft":42,"category":43,"image":38,"faq":144,"tags":160},"automated-pipette-liquid-handling-system","Automated Pipette: Liquid Handling System","Automated pipettes use software-controlled robotic arms for precise high-throughput liquid handling. Learn their working principles, parts, benefits, and limitations in microbiology.","2022-07-10",[145,148,151,154,157],{"question":146,"answer":147},"What is an automated pipette and how does it differ from a manual micropipette?","An automated pipette (also called a liquid handling robot or automated liquid handling system) is a software-controlled instrument where robotic arms aspirate and dispense defined volumes without continuous human intervention. A manual micropipette requires the operator to perform every aspiration, dispensation, tip change, and plate movement individually. Automated systems process more than 100 samples per hour with coefficient of variation values typically below 1%, eliminating fatigue-related error and throughput limitations of manual pipetting.",{"question":149,"answer":150},"What is the difference between semi-automatic and fully automatic pipetting systems?","Semi-automatic pipetting systems handle aspiration and dispensation mechanically but require human intervention for moving plates or tubes between steps and for changing tips. They process 10–100 samples at a time. Fully automatic (robotic) systems use robotic arms to move plates, change tips, and manage all physical steps — the only human input required is programming the run parameters at the start. Fully automatic systems provide a walk-away facility, allowing the technician to perform other tasks while the system processes samples.",{"question":152,"answer":153},"What is acoustic droplet ejection (ADE) and how is it different from standard pipetting?","Acoustic droplet ejection (ADE) is a contactless pipetting method that uses focused sound energy (acoustic waves) to eject precise droplets of liquid from a source well directly into a target well — no tip, no physical contact, no contamination risk from tip-to-liquid contact. The volume of each droplet is controlled by the frequency of the acoustic pulse. ADE achieves the highest precision and lowest contamination risk of any liquid transfer method but is also the most expensive and is used primarily in high-throughput drug discovery and genomics applications.",{"question":155,"answer":156},"What are the main advantages of automated liquid handling in clinical microbiology?","The main advantages are: higher throughput (>100 samples per hour versus 48–96 by a manual technician), improved reproducibility (identical volume and timing across all samples), reduced fatigue-related error (no drift in technique over long processing sessions), reduced contamination risk (fewer human touchpoints during the run), and walk-away operation (technician time is freed for other tasks). These advantages were demonstrated clearly during the COVID-19 pandemic, when reference laboratories used robotic extraction systems to process hundreds of PCR samples per day.",{"question":158,"answer":159},"Why are automated pipetting systems not commonly used in district-level laboratories in low- and middle-income countries?","The primary barriers are cost and maintenance. Entry-level automated liquid handling systems cost from approximately $10,000; fully integrated high-throughput platforms cost $150,000 or more. Ongoing maintenance requires trained service engineers, regular calibration, and replacement parts — all of which are difficult to access and expensive in resource-limited settings. Most district-level diagnostic laboratories in Nepal, Nigeria, the Philippines, and similar settings rely on manual micropipettes and glass pipettes for routine work, with automation limited to national reference laboratories or large urban hospital laboratories.",[65],{"slug":162,"title":163,"description":164,"seoTitle":165,"seoDescription":166,"author":167,"createdDate":168,"lastUpdatedDate":169,"draft":42,"category":43,"image":170,"faq":171,"tags":187},"types-of-pipettes-used-in-the-microbiology-laboratory","Types of Pipettes Used in the Microbiology Laboratory","Learn the types of pipettes used in microbiology — glass, micropipette, multichannel, automated, and calibrated — with a guide on choosing the right pipette for your procedure.","Laboratory Pipettes: Choose the Right Type and Avoid Volume Errors","Choose among glass, micropipette, multichannel, and automated pipettes by volume and task, with calibration, handling, and error-prevention guidance.","Acharya Tankeshwar","2026-06-28","2026-07-10","https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002Fcolorful-pipette-for-microbeonline.png",[172,175,178,181,184],{"question":173,"answer":174},"What are the main types of pipettes used in a microbiology laboratory?","Five main types are used: glass pipettes (graduated, volumetric, and Pasteur) for mL-scale transfers; micropipettes for µL-scale precision work; multichannel pipettes for simultaneous transfer into multiple wells of a microtiter plate; automated liquid handling systems for high-throughput processing; and pipette tips, the disposable consumables that serve as the aseptic barrier in all micropipette-based work.",{"question":176,"answer":177},"What is the difference between a pipette and a micropipette?","A glass pipette measures and transfers volumes in the milliliter range (0.1 mL to 25 mL) and requires a pipette bulb or filler for aspiration. A micropipette measures and transfers volumes in the microliter range (0.2 µL to 10,000 µL) using an air displacement mechanism — liquid enters only the disposable tip and never contacts the pipette barrel. The key distinction is scale: glass pipettes work in mL, micropipettes work in µL.",{"question":179,"answer":180},"How do I choose the right pipette for a procedure?","Three questions guide selection. First, what volume do you need? If the volume is in mL, use a glass pipette; if in µL, use a micropipette — and select the smallest micropipette model whose range covers your target volume. Second, how many simultaneous transfers are needed? If filling a microtiter plate, use a multichannel pipette. Third, what is the contamination risk? For PCR, RNA work, or infectious specimens, use filter tips with any micropipette.",{"question":182,"answer":183},"When is a multichannel pipette used instead of a single-channel micropipette?","A multichannel pipette is used whenever the target container is a microtiter plate — 96-well or 384-well format. Clinical applications include ELISA, broth microdilution MIC testing, and serological titrations. The multichannel pipette delivers identical volumes into multiple wells simultaneously from a single plunger depression, improving reproducibility compared to repetitive single-channel pipetting.",{"question":185,"answer":186},"What is a calibrated loop and how does it differ from a pipette?","A calibrated inoculating loop delivers a defined volume (1 µL or 10 µL) of specimen onto a culture plate — functioning as a volume measurement device without needing a pipette or tip. It is used specifically for semi-quantitative urine culture in microbiology. A pipette, by contrast, aspirates and dispenses liquid between containers using a mechanical aspiration mechanism. The calibrated loop is a low-cost, practical alternative to pipettes for a specific clinical purpose in resource-limited settings.",[65],[189,195,201,206,210,214,219,224,228,232],{"slug":190,"name":167,"description":191,"image":192,"body":193,"postCount":194},"acharya-tankeshwar","Editor-in-chief","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Ftankeshwar-acharya-author-microbeonline.jpg","***Tankeshwar Acharya, MSc (Medical Microbiology)***\n\n*Tankeshwar Acharya is an Assistant Professor in the Department of Microbiology at Patan Academy of Health Sciences (PAHS), Nepal, where he has been teaching and practicing clinical microbiology for over 14 years. He is the founder of Microbe Online, one of the leading free microbiology education resources on the web, covering bacteriology, mycology, parasitology, immunology, and clinical laboratory diagnostics written from direct experience in both the classroom and the diagnostic laboratory.*",433,{"slug":196,"name":39,"description":197,"image":198,"body":199,"postCount":200},"ashma-shrestha","SEO Copywriter and Science Communicator\nKathmandu, Nepal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fashma-shrestha.png","Ashma Shrestha holds a Master of Science in Medical Microbiology from the Institute of Science and Technology (IOST), Tribhuvan University, Nepal, where she developed a strong foundation in virology, molecular biology, and diagnostic microbiology.\n\nShe now works as an SEO Copywriter at Resolution Digital, where she combines her scientific training with research-driven content strategy. She is certified in Google Analytics and Google Business Profile (GBP), and brings a data-informed approach to science communication writing content that is not only accurate but structured to reach and serve the students who need it most.\n\nAt microbeonline, Ashma contributes articles primarily in virology and molecular biology, areas she finds most compelling for their mechanistic depth and their growing clinical relevance. Her writing reflects the same standard the site is built on: factual rigor, clear explanation of the *why* behind microbiology concepts, and content that helps students move from memorization to genuine understanding.\n\nShe is passionate about making complex microbiological concepts accessible without sacrificing accuracy; a skill that sits at the intersection of her scientific training and her professional work in content and SEO.",81,{"slug":202,"name":203,"description":204,"image":38,"body":38,"postCount":205},"sushmita-baniya","Sushmita Baniya","Author \u002F Contributor",32,{"slug":207,"name":208,"description":204,"image":38,"body":38,"postCount":209},"samikshya-acharya","Samikshya Acharya",20,{"slug":211,"name":212,"description":204,"image":38,"body":38,"postCount":213},"alisha-tripathi","Alisha Tripathi",6,{"slug":215,"name":216,"description":217,"image":38,"body":38,"postCount":218},"aastha-shrestha","Aastha Shrestha"," Author \u002F Contributor",10,{"slug":220,"name":221,"description":222,"image":38,"body":38,"postCount":223},"guest-author","Guest Author","Guest Author \u002F Contributor",2,{"slug":225,"name":226,"description":204,"image":38,"body":38,"postCount":227},"srijana-khanal","Srijana Khanal",18,{"slug":229,"name":230,"description":222,"image":38,"body":38,"postCount":231},"dr-poonam-acharya","Dr. Poonam Acharya",1,{"slug":233,"name":234,"description":204,"image":38,"body":235,"postCount":236},"nisha-rijal","Nisha Rijal","**Nisha Rijal** is a microbiologist and quality assurance specialist. She served for nearly 12 years as a microbiologist at the National Public Health Laboratory (NPHL), Nepal's national reference laboratory, and continues to work as a consultant microbiologist in international public health organization. ",51]