[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fI8QCKcdVKhApakNHUA8cBGwS2vbp37G9vFT_TCfZqtM":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":39,"author":40,"createdDate":41,"lastUpdatedDate":42,"draft":43,"category":44,"image":45,"body":46,"faq":47,"tags":63,"related":65},"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.","Ashma Shrestha","2022-07-29","2026-07-08",false,"lab-equipment",null,"In a microbiology practical, a student is performing a tube agglutination test. She needs to transfer exactly 1 mL of patient serum to each tube in a serial dilution series. She picks up a serological pipette, fills it to the 1 mL graduation mark, and dispenses — then moves through the dilution series. At the end, the results are inconsistent: the agglutination pattern doesn't follow the expected gradient. The problem surfaces during review. She had been using a serological pipette correctly — blowing out the last drop — but she had read the meniscus from the top of the curve rather than the bottom. Each \"1 mL\" delivery was actually 1.05–1.1 mL. Across eight tubes, the dilution factor drifted. The test had to be repeated.\n\nGlass pipette technique comes down to two things that seem minor until they aren't: knowing which type of pipette you are holding (drain-out or blow-out), and reading the meniscus from the correct reference point. Both errors are invisible at the time they happen and only appear in the results.\n\nPipettes are the calibrated laboratory equipment used to handle liquids. Many kinds of pipettes are used in the laboratory, like micropipette, glass pipette, automated pipette, etc.\n\nAmong those, glass pipettes are one of the liquid handling instruments carrying utmost significance due to their precision. These are useful in handling samples with volume in milliliter (ml).\n\nGlass pipettes are of different types, and handling of glass pipettes requires an attached filler (pipette bulb or pipette filler) at the top for filling the liquids. They have uses in various sectors like chemical laboratories, biochemistry laboratories, forensic science, microbiology laboratories, etc.\n\n## Why Glass Pipettes Matter in Microbiology\n\nThe [micropipette](https:\u002F\u002Fmicrobeonline.com\u002Fmicropipette-parts-types-and-uses\u002F) has replaced glass pipettes for most microliter-scale work. But glass pipettes remain the instrument of choice whenever volumes in the milliliter range need to be transferred — and in microbiology, this is more common than students expect.\n\nPreparing liquid culture media requires transferring 5 mL, 10 mL, or 25 mL volumes of reagents and supplements with accuracy. Serological tests — tube agglutination, Widal test, VDRL, complement fixation — require serial dilutions in mL volumes where a volumetric pipette delivers the precision needed. Blood culture bottles are inoculated with defined volumes of blood (8–10 mL for adult bottles). Antimicrobial stock solutions are prepared in mL volumes before being diluted to µL-scale working concentrations.\n\nIn each of these contexts, choosing the wrong glass pipette type — or using the right type incorrectly — introduces a volume error that propagates through every subsequent step.\n\n## Types of Glass Pipettes\n\n![Types of glass pipette - Types of glass pipette](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FTypes-of-Glass-Pipettes.png)Figure: Types of glass pipette\n\nThe glass pipettes generally used have three types;**graduated**,**non-graduated, and Pasteur pipettes.**\n\n### Graduated pipettes\n\nGraduated glass pipettes are the type of pipettes that has increments marked along the straight glass tube. Its another name is **measuring pipette**. It is further classified into two types based on the graduation mark and nominal volume it can pipet;**Mohr’s and serological pipette.**\n\n- **Mohr’s pipette:** A Mohr’s pipette is used as a drain-out pipette. It is a straight tube having a graduation mark at each 0.1 ml interval. The first graduation mark begins well past the bottom of the tip. The broken tip can disrupt the precision of handling the liquid.\n- **Serological pipette:** A serological pipette is used as a blow-out pipette. It is a straight tube with a graduation mark near the tip. A slight pressing of the bulb is necessary at the end of dispensation for accuracy.\n\n### Mohr's vs. Serological Pipette: The Distinction That Matters Most\n\nThese two pipettes look almost identical. The difference is in how the last drop is handled — and confusing them introduces a consistent delivery error.\n\n| Feature | Mohr's Pipette | Serological Pipette |\n| --- | --- | --- |\n| Delivery type | Drain-out | Blow-out |\n| Graduation mark position | Stops above the tip — last section ungraduated | Extends to the tip |\n| Last drop | Left in the tip — do NOT blow out | Must be blown out to deliver full volume |\n| Identification | No graduation near tip | Blow-out ring at top (near suction end); graduation near tip |\n| Risk of confusion | Blowing out a Mohr's over-delivers; not blowing out a serological under-delivers | Same — opposite error |\n| Best used for | Partial volume delivery from a measured range | Full nominal volume delivery |\n\n**The practical rule:** Before using any graduated glass pipette, check the tip. If the graduation marks stop before the tip, it is a Mohr's — do not blow out. If the marks extend to the tip and there is a ring near the top, it is serological — blow out completely.\n\nLikewise, based on construction, pipettes are of three types; **type 1, type 2, and type 3.**\n\n- **Type 1:** These have nominal values at the bottom and can deliver liquid samples partially only for all the values.\n- **Type 2:** These have nominal values at the top of the pipette and the highest value below.\n- **Type 3:** These are like type 1 in construction, but they can deliver fluids completely only in nominal value.\n\nSimilarly, based on the accuracy, the graduated pipettes are of \\*\\*class A, class As, and class B. Class A and As are very accurate because they have specified error ranges. In contrast, class B is less accurate because it has double the general error limits.\n\n### Non-graduated pipettes\n\nNon-graduated pipettes are the pipettes that lack the increment of graduation mark in the tube. The other denotation of a non-graduated pipette can also be a volumetric pipette, a bulb pipette, or a **transfer pipette**.\n\n### Pasteur pipettes\n\nPasteur pipettes are called an eye dropper or a dropper. Its construction is either with glass or plastic material. The tip end tapers to a narrow opening in the Pasteur pipette. There is a bulb at the top of the pipette in the case of plastic and glass Pasteur pipette needs a rubber bulb for withdrawing liquid. A teat pipette is the combination of a glass pipette and a rubber bulb.\n\n## Parts of Glass Pipettes\n\n![Parts of glass pipette - Parts of glass pipette](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FParts-of-Glass-pipette.png)Figure: Parts of glass pipette\n\nThe parts of glass pipettes are as follows:\n\n- **Orifice of the tip:** It is the pointed end of the pipette and comes in direct contact with the liquid.\n- **Calibration details:** It is an area in the pipette above the graduation mark. It has the imprinted details about the manufacturer, volume range (measuring) or nominal volume (bulb pipette), tolerance volume, calibration temperature, standard applied for calibration, and waiting time.\n- **Color rings: Color rings or color bands is a code to identify the nominal volume of the pipette by some companies.**\n- **Suction end:** It is the top part of the pipette, where the pipette filler or bulb can attach for aspirating and dispensing the liquids.\n- **Additional parts:** The **bulb pipette** has **a volume mark** for pipetting or transferring the correct amount of liquid volume. The **blow-out or serological pipette** has a **blow-out ring**near the topmost or suction part of the pipette.\n\n## Handling of Glass Pipettes\n\nWhile handling glass pipettes, one should never aspirate fluids in the laboratory from the mouth. A pipette bulb, rubber bulb, or filler is used for aspirating.\n\n### Reading the Meniscus\n\nThe meniscus is the curved surface of liquid at the graduation mark. Reading it incorrectly produces a consistent volume error on every pipetting step.\n\n**For colourless and light-coloured liquids (water, saline, most reagents):** Read from the **bottom** of the meniscus curve — the lowest point of the concave surface — with the eye level with the graduation mark. Reading from the top of the meniscus over-reads the volume.\n\n**For coloured or opaque liquids (iodine, some dye solutions, mercury):** These form a convex meniscus. Read from the **top** of the curve.\n\n**Parallax error:** If the eye is above or below the level of the graduation mark when reading, the mark appears to intersect the meniscus at the wrong point. Always position the eye exactly level with the graduation mark — not above, not below.\n\nA simple habit eliminates both errors: before every pipetting step, lower your head until your eye is level with the graduation mark, then read. This takes two seconds and prevents the most common volume error in glass pipette technique.\n\n### Pipette Bulb\n\n![pipette filler - Pipette filler or pipette bulbImage source: Paweena.S, CC BY-SA 4.0https:\u002F\u002Fcreativecommons.org\u002Flicenses\u002Fby-sa\u002F4.0, via Wikimedia Commons](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FBulb_for_graduated_pipettes.jpg)Figure: Pipette filler or pipette bulbImage source: Paweena.S, CC BY-SA 4.0https:\u002F\u002Fcreativecommons.org\u002Flicenses\u002Fby-sa\u002F4.0, via Wikimedia Commons\n\nA pipette bulb is made up of rubber, so it is also called a **rubber bulb**. It is used to safely fill the pipette with liquid in the laboratory, hence named pipette filler. The generally used pipette filler are general purpose bulbs, three-valve bulbs, and thumb wheel type fillers (made of plastic).\n\nSteps for using three valve pipette bulb:\n\n### Filling the Liquid\n\n1. Fill the pipette with pipette filler approximately above 5 mm of the mark.\n2. Then, adjust and bring the liquid to the graduated mark.\n3. Set the meniscus at the mark (for colorless liquid, the upper meniscus, and the colorful fluid lower meniscus).\n4. Remove excess liquid from the tip for precise delivery.\n\n### Dispensing the Liquid\n\n1. Place the tip of the pipette into the container.\n2. Press the filler to dispense all the liquid.\n3. Wait for a few seconds when the liquid reaches the tip (based on the company’s guidelines).\n4. After the wait time, draw the pipette upwards by touching the wall to dispense the remaining liquid. Do not blow out the remaining liquid.\n\n## Common Errors in Glass Pipette Use\n\n| Error | Consequence | Prevention |\n| --- | --- | --- |\n| Blowing out a Mohr's pipette | Over-delivery — the ungraduated tip section adds volume beyond the set amount | Check for blow-out ring; if absent, it is a Mohr's — drain only |\n| Not blowing out a serological pipette | Under-delivery — the last drop (which is part of the nominal volume) remains in the tip | Confirm blow-out ring is present; give a final press of the bulb after dispensing |\n| Reading meniscus from the top (colourless liquid) | Consistent over-reading — each volume is larger than intended | Read from the bottom of the meniscus, eye level with the mark |\n| Parallax error | Volume appears correct but is actually over or under | Eye must be exactly level with the graduation mark, not above or below |\n| Mouth pipetting | Ingestion or inhalation of hazardous liquids; biological hazard | Always use a pipette bulb, filler, or mechanical pipetting aid — no exceptions |\n| Filling above the mark then over-draining | Imprecise final volume | Fill approximately 5 mm above the mark, then adjust down slowly to the graduation mark |\n| Broken tip on Mohr's pipette | Volume delivery is undefined — the ungraduated section is now missing | Discard immediately; a broken-tip Mohr's pipette cannot be used accurately |\n| Touching pipette tip to container wall during Mohr's drainage | Drainage stops prematurely; tip contact creates surface tension that holds liquid back | Drain freely into the container; touch the wall only at the end to remove the hanging drop |\n\n## Uses of Glass Pipettes\n\nThe glass pipette has broad utility in almost all science laboratories. Some fields with the use of glass pipettes are as follows:\n\n- **Chemistry laboratory:** It is used in transferring liquids during various processes. The volumetric pipette is helpful in different tests relating to volumetric analysis.\n- **Pharmaceutical industry:** Glass pipettes in the pharmaceutical industry have utility in drug production. It is used to transfer measured volume in during quality control as well.\n- **Microbiology laboratory:** Like droppers, glass pipettes transfer different chemicals in milliliter (ml) in various experiments.\n- **Biochemistry laboratory**: The primary uses of glass pipettes in the biochemistry laboratory are as follows:\n  - For preparing buffer solution.\n  - To transfer the solution for conducting different biochemical tests.\n  - For accurate measurements of the chemicals.\n\nFor a comparison of all pipette types used in the microbiology laboratory, see [Types of Pipettes in the Microbiology Laboratory](https:\u002F\u002Fmicrobeonline.com\u002Ftypes-of-pipettes-in-microbiology\u002F)\n\n## How to Remember\n\n**Mohr's drains; serological blows — the easiest distinction in pipetting.** Mohr's = drain out (like a drain pipe — liquid flows and stops). Serological = blow out (like blowing the last drop out of a straw). If you remember nothing else about glass pipettes, remember this one distinction — it prevents the most common delivery error.\n\n**The meniscus rule: \"Colourless = bottom; coloured = top.\"** For transparent liquids, read the bottom of the curve. For opaque or coloured liquids, read the top. And always — always — get your eye level with the mark before reading.\n\n**Glass pipettes think in mL; micropipettes think in µL.** If your volume has a decimal point and the unit is µL, you need a micropipette. If your volume is a whole number in mL (1 mL, 5 mL, 10 mL), glass pipettes are the right instrument. Crossing this boundary — using a glass pipette for µL work — introduces errors large enough to invalidate the result.\n\n**Volumetric pipette = one volume, highest accuracy.** It has one mark, delivers one volume, and is the most accurate glass pipette for that volume. When precision matters more than flexibility, reach for the volumetric (bulb) pipette.\n\n## Key exam facts in one table\n\n| Topic | Key fact |\n| --- | --- |\n| Glass pipette volume range | mL scale — not suitable for µL work |\n| Graduated pipette synonym | Measuring pipette |\n| Mohr's pipette | Drain-out; graduation stops above tip; do NOT blow out last drop |\n| Serological pipette | Blow-out; graduation extends to tip; identified by blow-out ring at top; must blow out for full volume |\n| Volumetric (bulb) pipette | Non-graduated; one fixed exact volume; highest accuracy; also called transfer pipette or bulb pipette |\n| Pasteur pipette | Dropper; approximate transfer only; no graduation; not for accurate volume measurement |\n| Class A vs. Class B accuracy | Class A: tighter specified error tolerances; Class B: double the error limits of Class A |\n| Meniscus reading — colourless liquid | Read from the BOTTOM of the concave curve, eye level with mark |\n| Meniscus reading — coloured\u002Fopaque liquid | Read from the TOP of the convex curve |\n| Parallax error | Eye above or below mark level causes false high or false low reading |\n| Mouth pipetting | Strictly prohibited in all laboratory settings |\n| Pipette filler types | General purpose bulb, three-valve bulb, thumb wheel filler |\n| Three-valve bulb — fill | Fill \\~5 mm above mark, then drain to mark; set meniscus before dispensing |\n| Broken tip on Mohr's | Discard — volume is undefined without the intact drain-out tip |\n\n**References**\n\n- Cheesbrough, M. (2006). *District Laboratory Practice in Tropical Countries, Part 2* (2nd ed.). Cambridge University Press.\n- ISO 835:2007. *Laboratory glassware — Graduated pipettes*. International Organization for Standardization.\n- Clinical and Laboratory Standards Institute (CLSI). (2016). *Clinical Microbiology Procedures Handbook* (4th ed.). American Society of Microbiology. \u003Chttps:\u002F\u002Fdoi.org\u002F10.1128\u002F9781555818814>\n- Harvey, D. (2016). *Analytical Chemistry 2.1*. Community College of DuPage. \u003Chttps:\u002F\u002Fchem.libretexts.org\u002FBookshelves\u002FAnalytical_Chemistry\u002FAnalytical_Chemistry_2.1\\_(Harvey)>\n- Mahon, C. R., Lehman, D. C., & Manuselis, G. (2018). *Textbook of Diagnostic Microbiology* (6th ed.). Elsevier.",[48,51,54,57,60],{"question":49,"answer":50},"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":52,"answer":53},"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":55,"answer":56},"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":58,"answer":59},"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":61,"answer":62},"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.",[64],"pipette",[66,89,114,139,161],{"slug":67,"title":68,"description":69,"seoTitle":45,"seoDescription":45,"author":40,"createdDate":70,"lastUpdatedDate":71,"draft":43,"category":44,"image":45,"faq":72,"tags":88},"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","2026-07-19",[73,76,79,82,85],{"question":74,"answer":75},"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":77,"answer":78},"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":80,"answer":81},"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":83,"answer":84},"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":86,"answer":87},"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.",[64],{"slug":90,"title":91,"description":92,"seoTitle":45,"seoDescription":45,"author":40,"createdDate":93,"lastUpdatedDate":71,"draft":43,"category":44,"image":45,"faq":94,"tags":113},"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.","2022-07-19",[95,98,101,104,107,110],{"question":96,"answer":97},"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":99,"answer":100},"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":102,"answer":103},"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":105,"answer":106},"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":108,"answer":109},"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":111,"answer":112},"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.",[64],{"slug":115,"title":116,"description":117,"seoTitle":45,"seoDescription":45,"author":40,"createdDate":118,"lastUpdatedDate":42,"draft":43,"category":44,"image":45,"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.",[64],{"slug":140,"title":141,"description":142,"seoTitle":45,"seoDescription":45,"author":40,"createdDate":143,"lastUpdatedDate":42,"draft":43,"category":44,"image":45,"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.",[64],{"slug":162,"title":163,"description":164,"seoTitle":165,"seoDescription":166,"author":167,"createdDate":168,"lastUpdatedDate":169,"draft":43,"category":44,"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.",[64],[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.*",432,{"slug":196,"name":40,"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":45,"body":45,"postCount":205},"sushmita-baniya","Sushmita Baniya","Author \u002F Contributor",32,{"slug":207,"name":208,"description":204,"image":45,"body":45,"postCount":209},"samikshya-acharya","Samikshya Acharya",20,{"slug":211,"name":212,"description":204,"image":45,"body":45,"postCount":213},"alisha-tripathi","Alisha Tripathi",6,{"slug":215,"name":216,"description":217,"image":45,"body":45,"postCount":218},"aastha-shrestha","Aastha Shrestha"," Author \u002F Contributor",10,{"slug":220,"name":221,"description":222,"image":45,"body":45,"postCount":223},"guest-author","Guest Author","Guest Author \u002F Contributor",2,{"slug":225,"name":226,"description":204,"image":45,"body":45,"postCount":227},"srijana-khanal","Srijana Khanal",18,{"slug":229,"name":230,"description":222,"image":45,"body":45,"postCount":231},"dr-poonam-acharya","Dr. Poonam Acharya",1,{"slug":233,"name":234,"description":204,"image":45,"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]