Laboratory Pipettes – Types, Accuracy & Usage Guide
A pipette is a calibrated instrument designed to aspirate and dispense precise volumes of liquid. From 0.1 µL micropipettes to 100 mL volumetric models, pipettes are fundamental to quantitative work in molecular biology, chemistry, and clinical diagnostics.
This guide covers pipette types, accuracy principles, ISO standards, usage techniques, and contamination control protocols for laboratory professionals.
12+ Pipette Types
Volumetric, graduated, micropipettes, multichannel, repeat dispensers
ISO 8655:2022 Compliant
Tolerance limits, calibration protocols, accuracy testing
Manual & Electronic
Air-displacement, positive-displacement, automated dispensing
Clinical to Research
PCR, ELISA, cell culture, drug formulation, titration
📑 Table of Contents
What Is a Pipette? Anatomy & Fundamentals
A pipette is a precision liquid-handling instrument used in laboratories to measure and transfer specific volumes of liquids. Unlike pouring or estimating, pipettes provide quantitative control over volume transfer — essential for reproducible experiments, serial dilutions, and quantitative assays.
Pipettes range from simple glass tubes (Pasteur pipettes) to sophisticated electronic micropipettes capable of dispensing 0.1 µL with sub-microliter accuracy. They are classified by mechanism (air-displacement vs. positive-displacement), operation (manual vs. electronic), and volume capacity.
Pipette Anatomy: Core Components
Barrel
The main cylindrical body that holds the piston mechanism and volume adjustment controls. Typically made of autoclavable plastic or glass.
Plunger
The depressible button that controls aspiration and dispensing. Has two stopping points: first stop for aspiration, second stop for complete dispensing.
Tip Cone
The attachment point for disposable tips. Ensures airtight seal critical for accurate volume displacement.
Volume Adjustment
Mechanical dial or digital display for setting the desired volume. Variable pipettes allow adjustment; fixed pipettes have a single predetermined volume.
Ejector Button
Releases the disposable tip after use, preventing cross-contamination and allowing hands-free tip disposal.
Piston/Air Cushion
In air-displacement pipettes, the air cushion between piston and liquid enables volume control. Positive-displacement uses direct contact.
Pipette vs. Pipettor vs. Burette
| Instrument | Volume Range | Accuracy | Primary Use |
|---|---|---|---|
| Volumetric Pipette | 1–100 mL (fixed) | ±0.01 mL | High-precision fixed volume transfers |
| Micropipette (Pipettor) | 0.1 µL–10 mL (variable) | ±1–3% | Flexible micro-volume work |
| Serological Pipette | 1–50 mL (graduated) | ±2% | Cell culture, routine transfers |
| Burette | 10–100 mL (continuous) | ±0.05 mL | Titration, continuous dispensing |
Types of Pipettes
Pipettes are classified by mechanism (air vs. positive displacement), volume capacity (fixed vs. variable), and delivery method (manual vs. electronic). Understanding the differences ensures optimal selection for your application.
Operational Principle
Glass tube with a single calibrated bulb designed to deliver one fixed volume (e.g., 5.00 mL, 10.00 mL, 25.00 mL). The pipette is filled to the etched calibration line using a pipette filler or bulb—never by mouth pipetting due to contamination and safety risks. Liquid drains by gravity to deliver the precise volume.
Accuracy
Class A volumetric pipettes:±0.01 mL tolerance for a 10 mL pipette (0.1% error). Individually calibrated and serialized with certificates traceable to NIST standards. This represents the highest accuracy achievable with manual glassware.
Applications
- Preparing standard solutions:Creating reference standards for analytical chemistry where exact concentrations are critical for calibration curves and quality control
- Analytical chemistry:Quantitative analysis, titrations, and spectrophotometric assays requiring maximum accuracy (±0.1%)
- Pharmaceutical manufacturing QC:Validating drug potency and ensuring compliance with USP/FDA specifications
Limitations
Fixed volume only (no flexibility); slower workflow compared to adjustable micropipettes; requires manual pipette filler for safety; cleaning and drying between uses adds time; fragile glass construction.
Best for:When highest accuracy is non-negotiable and volume is known in advance. Preferred in analytical labs where ISO 17025 accreditation requires traceable measurement standards.
Operational Principle
Glass or disposable plastic tube with graduated markings along its length, allowing measurement of variable volumes.Mohr pipetteshave markings that stop before the tip (measure to an intermediate mark).Serological pipettesare calibrated to the tip for complete drainage. Used with pipette controllers or manual bulbs.
Accuracy
±1–2% typical accuracy. For example, a 10 mL serological pipette has ±0.1–0.2 mL tolerance. Less accurate than volumetric pipettes but more flexible. Glass serological pipettes can be Class A (±1%) or Class B (±2%).
Applications
- Cell culture media preparation:Adding variable volumes of serum, antibiotics, or growth factors to culture flasks where ±2% accuracy is sufficient
- Routine liquid transfers:General lab work including buffer preparation, dilutions, and reagent additions where high throughput matters more than sub-percent accuracy
- Educational laboratories:Teaching proper pipetting technique and volume measurement in undergraduate chemistry and biology courses
Best for:Cell culture, microbiology, and routine lab work where speed and volume flexibility outweigh the need for highest accuracy. Disposable plastic serological pipettes eliminate cross-contamination risk.
Operational Principle
Piston-driven instrument using an air cushion between the piston and liquid to aspirate and dispense micro-volumes (0.1 µL to 10 mL). Disposable plastic tips attach to the tip cone, providing a sterile barrier. Variable-volume models allow adjustment across a range (e.g., 20–200 µL); fixed-volume models deliver only one preset volume with higher precision.
Accuracy
±1–3% for ISO 8655:2022 compliant models. For example, a 100 µL setting on a 20–200 µL pipette: ±1 µL accuracy, ±0.5 µL precision (CV <0.5%). Single-channel electronic pipettes can achieve ±0.6% accuracy at optimal volumes.
Applications
- PCR and qPCR setup:Dispensing primers, probes, polymerase, and template DNA with sub-microliter precision critical for reproducible Ct values
- ELISA and immunoassays:Adding antibodies, antigens, substrates, and stop solutions to 96/384-well plates
- DNA/RNA quantification:Preparing samples for spectrophotometry (NanoDrop) or fluorometry (Qubit) where 1–2 µL samples are typical
- General molecular biology:Restriction digests, ligations, protein assays, and any application requiring 0.5–1000 µL volumes
Best for:The workhorse of modern molecular biology labs. Offers excellent balance of accuracy, speed, and flexibility. Filter tips recommended for PCR to prevent aerosol contamination.
Operational Principle
Piston directly contacts the liquid inside a disposable capillary piston (Wiretrol-type or Eppendorf Repeater tips). No air cushion exists, eliminating vapor pressure effects. The piston travels inside the tip itself, creating a positive seal. Each tip contains its own integrated piston assembly.
When to Use
- Viscous liquids:Glycerol (50–80%), serum, honey, oils, and high-concentration protein solutions (>10 mg/mL) where air-displacement pipettes under-aspirate due to liquid clinging to tip walls
- Volatile solvents:Acetone, methanol, ethanol, chloroform, and other organic solvents that evaporate in the air gap of standard pipettes, causing volume loss (up to 5–10% error)
- High-density liquids:Cesium chloride (CsCl) gradient solutions, Percoll, Ficoll, and other dense media used in density gradient centrifugation
- Foaming solutions:Detergent-containing buffers, SDS solutions, and lysates that create bubbles with air-displacement pipettes
Trade-offs
Higher accuracy for difficult liquids (±0.5–1% for viscous samples) but slower operation. Tips cost 3–5× more than standard tips because they include the piston mechanism. Less commonly used than air-displacement for routine aqueous work.
Best for:Specialized applications where air-displacement fails. Essential in organic chemistry, lipid biochemistry, and any work with non-aqueous or high-viscosity samples.
Operational Principle
8-channel or 12-channel pipette head allowing simultaneous aspiration and dispensing into microplate rows. Each channel operates as an independent air-displacement pipette, synchronized mechanically (manual) or electronically (electronic models). Channel spacing matches standard 96-well (9 mm) or 384-well (4.5 mm) plate dimensions.
Applications
- 96/384-well ELISA plate filling:Dispensing samples, standards, antibodies, and substrates across entire rows in a single action—reducing time from 96 individual dispenses to 12 (8-channel) or 8 (12-channel)
- High-throughput screening (HTS):Drug discovery, compound libraries, and enzyme assays requiring thousands of individual wells to be filled rapidly
- Serial dilutions across plates:Creating concentration gradients by transferring from one row to the next, ideal for IC50 determinations and dose-response curves
- PCR plate setup:Filling 96-well PCR plates for qPCR, genotyping, or high-throughput sequencing library prep
Best for:Any microplate-based assay. Electronic multichannel pipettes offer programmable protocols (multiple dispenses, mixing cycles) and reduce hand strain. Essential for labs running >10 plates per week.
Operational Principle
Syringe-based dispensing system that attaches directly to a reagent bottle. The pipette aspirates a large volume (e.g., 50 mL) once, then dispenses multiple identical aliquots (e.g., 100× 500 µL dispenses) without re-aspiration. Volume is set mechanically or digitally. Stepper motor advances the plunger in precise increments.
Applications
- Dispensing identical volumes repeatedly:Adding the same volume of buffer, reagent, or substrate to 50–200 tubes or wells. Example: dispensing 1 mL of culture medium into 100 tubes for bacterial cultures
- Buffer preparation:Creating large batches of working solutions by dispensing fixed volumes of stock solutions into multiple vessels
- Reagent addition in batch processes:Pharmaceutical manufacturing, diagnostic kit production, and any production environment requiring thousands of identical dispenses per day
Accuracy
±0.5–2% depending on volume and viscosity. More accurate for larger volumes (>500 µL). Digital repeat dispensers track cumulative error and alert when recalibration is needed.
Best for:High-volume, repetitive dispensing where a single reagent is added to many samples. Saves time (10–20× faster than single-channel pipetting) and reduces repetitive strain injury (RSI) risk.
Manual vs Electronic Pipettes
Manual Pipettes
- Mechanism:Thumb-operated plunger controls piston movement
- Cost:$150–$500 per pipette
- Precision:User-dependent; requires consistent technique
- Maintenance:Annual calibration; minimal electronics
- Ergonomics:Can cause thumb strain with prolonged use
- Best for:General lab work, teaching, budget-conscious labs
Electronic Pipettes
- Mechanism:Motor-driven piston; electronic controls
- Cost:$800–$3,000+ per pipette
- Precision:Consistent dispensing speed → higher reproducibility
- Features:Programmable protocols, multi-dispense, automatic tip ejection
- Ergonomics:Reduced hand strain (ideal for high-throughput)
- Best for:High-throughput labs, repetitive workflows
Multichannel (8/12 Tips)
- Mechanism:8 or 12 parallel channels for microplate work
- Efficiency:8–12× faster than single-channel
- Applications:ELISA, qPCR plate setup, serial dilutions
- Limitation:Requires aligned tip racks and microplates
- Types:Available in manual and electronic versions
Repeat Dispensers
- Mechanism:Syringe-based; one aspiration, multiple dispenses
- Use case:Dispensing 50–100+ identical aliquots
- Accuracy:±0.5–2% for repetitive volumes
- Sterilization:Autoclavable syringes for sterile work
- Best for:Bulk reagent dispensing, buffer preparation
Accuracy vs Precision
Accuracy
Definition:How close the dispensed volume is to the intended volume.
Example:Setting 100 µL and dispensing 99.8 µL = high accuracy (0.2% error)
Formula:Accuracy (%) = [(Measured Volume – Set Volume) / Set Volume] × 100
Precision
Definition:Reproducibility of repeated measurements (low variation).
Example:10 dispenses yielding 99.8, 99.9, 99.7, 100.0, 99.8… = high precision (CV < 1%)
Formula:Coefficient of Variation (CV) = (Standard Deviation / Mean) × 100
High Accuracy
High Precision
🎯 Ideal: Hits bullseye consistently
High Accuracy
Low Precision
📊 Centered but scattered
Low Accuracy
High Precision
⚠️ Consistent but offset
Low Accuracy
Low Precision
❌ Random errors
Factors Affecting Accuracy
Temperature
Liquids expand/contract with temperature. Air cushion in air-displacement pipettes is also temperature-sensitive. ISO 8655 specifies 20°C ± 2°C for calibration.
Liquid Properties
Viscosity:High-viscosity liquids (glycerol) require slower aspiration/dispensing speeds.
Density:Calibration is typically for water (1.00 g/mL).
Volatility:Volatile solvents evaporate in the tip.
Tip Fit & Quality
Loose tips cause air leaks → volume loss. Use manufacturer-matched or ISO-certified tips. Pre-wetting the tip reduces surface tension effects (especially for <10 µL volumes).
Pipetting Technique
Plunger speed:Too fast = air bubbles.
Angle:Hold pipette vertically (10–20° max deviation).
Immersion depth:2–3 mm for micropipettes.
Calibration Drift
Pipettes lose accuracy over time due to piston seal wear, spring fatigue, or mechanical drift. Annual calibration is standard; high-use labs may calibrate quarterly.
Environmental Factors
Humidity:Affects air-displacement pipettes.
Atmospheric pressure:Altitude changes affect air cushion behavior.
Static electricity:Can cause droplets to cling to tip.
ISO 8655:2022 Standards
Tolerance Limits (µL)
| Volume Range | 10% Volume | 50% Volume | 100% Volume |
|---|---|---|---|
| 0.1–2 µL | ±8.0% | ±3.0% | ±2.5% |
| 2–10 µL | ±5.0% | ±1.5% | ±1.0% |
| 10–100 µL | ±3.0% | ±1.0% | ±0.8% |
| 100–1000 µL | ±1.5% | ±0.8% | ±0.6% |
| 1000–10,000 µL | ±1.0% | ±0.6% | ±0.6% |
Key Points:
- Lower volumes have higher % error tolerancesdue to inherent difficulty in micro-volume precision. Sub-microliter volumes are physically harder to control with mechanical pistons.
- Pipettes should be tested at 10%, 50%, and 100% of their nominal volumeto verify accuracy across the entire working range. This ensures the pipette performs correctly at both ends of its capacity.
- Calibration uses gravimetric method:weigh dispensed water using an analytical balance, then calculate volume based on water density at 20°C (1 mg H₂O ≈ 1 µL). This is the ISO-specified gold standard for pipette verification.
Note:Pipettes meeting ISO 8655:2022 standards display compliance certification on their packaging. Annual calibration is recommended to maintain accuracy within these tolerances.
How to Use Pipettes: Step-by-Step Protocol
1. Visual Inspection
Check pipette body for damage, ensure volume display is clear, verify tip ejector functions.
2. Tip Fitting
Insert pipette into tip with firm, twisting motion. Check for airtight seal (no gaps). Avoid hammering (damages piston).
3. Calibration Check
If critical work, perform quick check: dispense into weighing boat, confirm volume matches setting.
4. Aspiration
Pre-wet:Aspirate and dispense the liquid 2–3 times to equilibrate tip.
Immersion depth:2–3 mm for micropipettes, deeper for serological.
Plunger action:Press to first stop, slowly release plunger to aspirate.
5. Dispensing
Touch tip to vessel wall at 10–45° angle. Press plunger to first stop (wait 1 second), then to second stop to expel residual liquid. Withdraw while pressing second stop.
6. Disposal
Eject tip into waste container. Never re-use tips (contamination risk).
Reverse Pipetting Technique
When to Use
Reverse pipetting is the preferred technique for:
- Viscous liquidssuch as glycerol, serum, or high-concentration protein solutions that resist complete dispensing
- Volatile solventsincluding acetone, ethanol, or methanol where evaporation risk during pipetting can cause volume loss
- Foaming solutionslike detergent-containing buffers or cell lysates that create bubbles during standard pipetting
- Small volumes (<5 µL)where surface tension effects become significant and standard technique may leave residual liquid in the tip
Core Principle:Aspirate more liquid than needed by pressing to the second stop, then dispense only the target volume by pressing to the first stop. The excess liquid remains in the tip and is discarded with it, ensuring complete and accurate delivery.
Step-by-Step Protocol
1. Over-aspiration
Press plunger all the way to the second stop (not just the first stop). Immerse tip 2-3 mm into liquid and slowly release plunger. This draws extra volume into the tip beyond your target amount.
2. Pre-wetting (Optional)
Dispense the entire volume back into the source vessel. Re-aspirate again to the second stop. This pre-wetting step equilibrates the tip interior and improves accuracy for viscous or volatile liquids.
3. Partial Dispense
Touch tip to the receiving vessel wall at a 30-45° angle. Press plunger down only to the first stop and hold for 1 second. Your target volume is now delivered, while excess liquid remains safely in the tip.
4. Final Blow-out
Withdraw the pipette while keeping plunger at first stop position. Eject the tip with excess liquid still inside. Do NOT press to second stop during dispensing—this would expel the extra volume.
Ergonomics & RSI Prevention
Best Practices
- Use Electronic Pipettes for High-Throughput:Eliminates thumb force requirement.
- Alternate Hands:Switch pipetting hand every 30–60 minutes if possible.
- Lightweight Pipettes:Choose models with ergonomic grips and minimal weight.
- Proper Posture:Keep wrist neutral (avoid bending). Adjust chair height so arms are at 90°.
- Take Breaks:5-minute break every hour of continuous pipetting. Perform hand stretches.
Contamination Control
Contamination is the primary concern in molecular biology, clinical diagnostics, and analytical chemistry. Pipettes can transfer contaminants in three directions:
Pipette → Sample Contamination
Risk:Residue from previous samples, reagents, or external contaminants on the pipette transfers to the new sample, compromising experimental integrity.
- Always use new, sterile tips for each sample transfer.Never reuse tips between samples, even for the same reagent. Cross-contamination at nanogram levels can invalidate PCR and qPCR results.
- Never touch the tip to non-sterile surfacesincluding benchtops, gloves, or tube exteriors. Even brief contact can introduce bacterial, fungal, or nucleic acid contamination.
- Use filter tips for PCR, qPCR, and molecular biology work.The hydrophobic filter barrier prevents aerosols from entering the pipette body, eliminating a major route of cross-contamination in DNA/RNA work.
- Decontaminate pipette exterior regularlyusing 70% ethanol wipes or UV decontamination chambers (for DNA work). UV exposure (254 nm) for 15-30 minutes destroys surface nucleic acids.
Sample → Pipette Contamination
Risk:Liquid or aerosols enter the pipette body through the tip cone, contaminating internal components (piston, seals) and creating a reservoir of contamination for future samples.
- Never overfill tips or aspirate too quickly.Keep liquid level well below the filter barrier (if using filter tips). Overfilling bypasses the filter and allows direct liquid contact with the piston assembly.
- Release plunger slowly and steadily during aspiration.Fast plunger release creates negative pressure that can suck liquid or aerosols into the pipette shaft. Use 2-3 second release time for volumes >100 µL.
- Use positive-displacement pipettes for hazardous, infectious, or radioactive materials.The disposable capillary piston creates a physical barrier, preventing any sample contact with the pipette body.
- If liquid enters pipette body: immediately stop work and decontaminate.Disassemble the lower barrel, clean all components with appropriate decontaminant (10% bleach for biologics, RNase Away for RNA work), rinse, dry, and recalibrate before returning to service.
Sample → Sample Cross-Contamination
Risk:Trace amounts of one sample carry over to subsequent samples through aerosols, residual liquid in tips, or pipette body contamination. Critical concern in qPCR, forensics, and clinical diagnostics.
- Change tips between every single sample without exception.Even “identical” samples can have different amplification efficiencies or unknown variables. In forensics and diagnostics, tip reuse is grounds for invalidating results.
- Use barrier/filter tips to prevent aerosol-mediated transfer.Pipetting volatile or foaming solutions generates aerosols that can contaminate the pipette shaft and subsequent samples. Filter tips block these aerosols at the tip level.
- Run negative controls (no-template controls) to detect contamination.Include water-only controls in every PCR plate. Amplification in negative controls indicates contamination somewhere in the workflow—often pipettes or reagents.
- For ultra-sensitive work, use dedicated pipettes for different steps.Designate separate pipettes for master mix preparation vs. template addition. Never use a pipette that touched amplicons (post-PCR) for pre-PCR steps. Color-code pipettes to enforce separation.
Selecting the Right Pipette
| Application | Recommended Pipette | Key Features |
|---|---|---|
| PCR Setup | Air-displacement micropipette (0.5–10 µL, 10–100 µL) | Filter tips, high precision, calibrated |
| ELISA/Plate Assays | Multichannel (8/12-channel, 50–300 µL) | Speeds up plate filling, electronic preferred |
| Viscous Liquids (Glycerol) | Positive-displacement | Direct piston contact, unaffected by viscosity |
| Organic Solvents | Positive-displacement or glass pipettes | Solvent-resistant materials |
| Cell Culture (Sterile Work) | Serological pipettes (5–25 mL) with pipette controller | Sterile, individually wrapped, easy media addition |
| Analytical Chemistry (Titration) | Burette or volumetric pipette | Highest accuracy for fixed/continuous volumes |
Industry Use Cases
Pipettes are essential across diverse industries, each with specific accuracy requirements, regulatory standards, and contamination control protocols. Here are three major applications:
Clinical Laboratories
- Blood chemistry panels:Measuring glucose, electrolytes, liver enzymes, and kidney function markers from patient serum samples with sub-microliter precision.
- Immunoassays (ELISA, CLIA):Enzyme-linked and chemiluminescent immunoassays for detecting antibodies, hormones, tumor markers, and infectious disease antigens in clinical specimens.
- Hematology applications:Cell counting, blood smear preparation, and hemoglobin quantification requiring accurate dilutions for automated analyzers and manual microscopy.
- Coagulation studies:Prothrombin time (PT), activated partial thromboplastin time (aPTT), and D-dimer testing requiring precise plasma-to-reagent ratios for clotting cascade analysis.
Critical Requirement:CAP (College of American Pathologists) and CLIA (Clinical Laboratory Improvement Amendments) compliance mandates use of calibrated, traceable pipettes with documented maintenance records. Annual calibration certificates are required for inspection.
PCR & Molecular Biology
- DNA/RNA extraction:Isolating nucleic acids from tissue, blood, or cell cultures using phenol-chloroform or column-based methods requiring precise buffer and elution volumes.
- qPCR master mix preparation:Real-time PCR setup demands accurate pipetting of primers, probes, polymerase, and template DNA. A 1 µL error can shift Ct values by multiple cycles.
- Next-generation sequencing library prep:NGS workflows (Illumina, PacBio) require sub-microliter accuracy for adapter ligation, size selection, and quantification steps critical for sequencing quality.
- CRISPR reagent handling:Gene editing experiments require precise delivery of guide RNA, Cas9 protein, and donor DNA templates—errors compromise editing efficiency and specificity.
Critical Requirement:Filter tips are mandatory for all PCR and molecular biology work to prevent nucleic acid contamination. Even nanogram-level carryover of amplicons can produce false-positive results. Use dedicated pre- and post-PCR pipettes.
Pharmaceutical QC
- Drug formulation and dosing:Measuring active pharmaceutical ingredients (APIs) at microgram-to-milligram levels for tablet, capsule, and injectable formulations. Accuracy directly impacts therapeutic efficacy and safety.
- Dissolution testing:USP-compliant dissolution studies measure drug release rates from solid dosage forms. Requires precise sampling at defined time points (5, 10, 15, 30, 60 min) for HPLC analysis.
- HPLC sample preparation:High-performance liquid chromatography sample prep demands accurate dilutions, internal standard addition, and mobile phase preparation for quantitative drug analysis.
- Stability studies:ICH-guideline stability testing tracks drug degradation over time under controlled conditions (25°C/60% RH, 40°C/75% RH). Pipetting errors compromise shelf-life determinations.
Critical Requirement:GMP (Good Manufacturing Practice) compliance demands quarterly pipette calibration, full traceability to NIST standards, and validated cleaning procedures. All calibrations must be documented in laboratory notebooks and audit trails.
Frequently Asked Questions
Common questions about pipette calibration, usage, maintenance, and best practices answered by laboratory professionals.
General laboratories:Annual calibration is the standard minimum requirement. This applies to academic research labs, hospital laboratories, and most quality control environments where pipettes are used daily but not under GMP/GLP regulatory oversight.
High-use laboratories:Quarterly or semi-annual calibration is recommended when pipettes are used intensively (>100 cycles per day) or in critical applications like clinical diagnostics, pharmaceutical QC, or molecular diagnostics where accuracy directly impacts results.
GMP/GLP environments:Calibration frequency is defined in Standard Operating Procedures (SOPs) and typically requires quarterly verification plus immediate recalibration after any event that could affect accuracy (dropped pipette, liquid intrusion, mechanical damage, or observed drift in performance).
ISO 8655:2022 recommendation:Calibrate at least once per year, or after 5,000–10,000 pipetting cycles, whichever comes first. Many manufacturers embed cycle counters in electronic pipettes to track usage and trigger maintenance alerts.
Entire pipette body:Most modern micropipettes are NOT fully autoclavable. The high temperature (121°C) and pressure of autoclaving can damage electronic components, degrade rubber O-rings and seals, warp plastic barrels, and compromise calibration. Always check the manufacturer’s specifications before attempting to autoclave.
Lower barrel section:Some pipette models (e.g., Eppendorf Research Plus, Gilson Pipetman) have detachable lower barrels that are autoclavable. These can be sterilized at 121°C for 20 minutes and reassembled after cooling. Verify compatibility in your pipette’s user manual.
Pipette tips:Yes, disposable tips can be autoclaved if they are made of autoclavable polypropylene and labeled as such. Use autoclave-safe tip racks, loosely arranged to allow steam penetration. Typical cycle: 121°C for 20 minutes with dry cycle. Filter tips require extra care as the filter material may be damaged by excessive moisture.
Alternative decontamination methods:For the pipette body, use UV decontamination (254 nm wavelength for 15-30 minutes) to destroy surface DNA/RNA, or wipe with 70% ethanol for bacterial decontamination. For molecular biology work, specialized decontaminants like RNaseZap or DNA-ExitusPlus are effective.
Classification applies to glass volumetric pipettes only:Class A and Class B are ASTM designations for graduated glass pipettes, not micropipettes. Micropipettes follow ISO 8655 standards instead.
Class A (Grade A):Highest accuracy glass pipettes, individually calibrated and certified. Tolerance: ±0.01 mL for a 10 mL pipette. Each pipette is serialized and comes with a calibration certificate traceable to national standards. Used for analytical chemistry, pharmaceutical QC, and any work requiring maximum accuracy. Typically 2-3× more expensive than Class B.
Class B (Grade B):Standard accuracy for routine laboratory work. Tolerance: ±0.02 mL for a 10 mL pipette. Not individually calibrated; manufactured to batch specifications. Suitable for educational labs, routine transfers, and applications where slight volumetric variance is acceptable. More economical option.
Note on micropipettes:Micropipettes (adjustable volume, piston-driven) are classified under ISO 8655:2022, which defines tolerance limits based on volume range (e.g., ±1% for 100-1000 µL range). They don’t use Class A/B terminology.
Contamination barrier function:Filter tips contain a hydrophobic barrier (typically PTFE or polyethylene membrane) at the proximal end that prevents aerosols, liquid droplets, and vapors from entering the pipette body. This eliminates cross-contamination between samples and protects the piston assembly from corrosive or infectious materials.
When filter tips are mandatory:PCR and qPCR work (prevents amplicon contamination), radioactive material handling, infectious sample processing (BSL-2 and higher), work with volatile or corrosive solvents, any ultra-sensitive molecular biology application where nanogram-level cross-contamination invalidates results, and forensic DNA analysis.
Cost considerations:Filter tips cost approximately 2–3× more than standard tips due to the filter membrane manufacturing. A box of 96 standard 200 µL tips costs $8-12; filter tips cost $20-30. However, this is negligible compared to the cost of failed experiments, contaminated reagents, or invalidated clinical samples.
Performance note:Filter tips may require slightly different aspiration technique (slower plunger release) to avoid compressing the filter. Some users report 1-2% lower dispensing accuracy with certain filter tip brands, though high-quality filter tips (Rainin, Eppendorf) show no significant accuracy difference.
First stop (primary stop):The initial point of resistance when pressing the plunger down. This stop corresponds to the calibrated volume setting on your pipette. All aspiration and standard dispensing uses the first stop. When you press to the first stop and release, the piston moves through a displacement equal to your set volume.
Second stop (blow-out stop):Pushing past the first stop requires additional force (you’ll feel increased resistance). This extra travel expels residual liquid clinging to the tip interior, ensuring complete dispensing. The second stop displaces approximately 10-15% more volume than the first stop, depending on pipette model.
Standard (forward) pipetting technique:Press plunger to first stop before immersing tip → aspirate by slowly releasing to rest position → touch tip to receiving vessel wall → dispense by pressing to first stop → pause 1 second → press to second stop to clear tip → withdraw while holding second stop.
Reverse pipetting technique:Press plunger all the way to second stop before aspiration → aspirate extra volume → dispense by pressing only to first stop (leaving excess in tip) → discard tip with excess liquid. Used for viscous, volatile, or foaming liquids where standard technique causes inaccuracy.
Conversion formula: 1 mL = 1,000 µL
To convert microliters to milliliters, divide by 1,000.
To convert milliliters to microliters, multiply by 1,000.
Common conversions:
• 1 µL = 0.001 mL
• 10 µL = 0.01 mL
• 100 µL = 0.1 mL
• 250 µL = 0.25 mL
• 500 µL = 0.5 mL
• 1,000 µL = 1 mL
• 1,500 µL = 1.5 mL
• 5,000 µL = 5 mL
Practical tip:When working with recipes or protocols, always double-check the units. A common error is confusing µL with mL, leading to 1,000× dosing errors. For example, adding 100 µL when 100 mL was required (or vice versa) can ruin experiments or create safety hazards.
Relationship to other units:1 µL is also equal to 1 microliter = 0.001 cubic centimeters (cc) = 0.001 milliliters. For water at 20°C, 1 µL weighs approximately 1 milligram (mg), making gravimetric calibration straightforward: 1 mg H₂O ≈ 1 µL.