# Pipette Calibration Records: What to Document and How to Maintain Them By the end of this article you will be able to build a pipette calibration record that survives an audit, run a gravimetric calibration on an air displacement pipette, convert the weighings into accuracy and precision numbers, decide pass or fail against defined limits, and set up a system that keeps those records organized, signed, and retrievable for years. Before you start, have the following on hand: - The pipette, with its unique lab asset number and serial number visible - An analytical balance with readability of at least 0.1 mg for volumes of 100 µL and above (a 0.01 mg or better balance for smaller volumes), with a current calibration certificate - Distilled or deionized water equilibrated to room temperature - A thermometer for the water and the room - The tip lot you use routinely with that pipette - A log sheet, spreadsheet, or [laboratory information management system](/knowledge/bioinformatics/lims-explained-lab-information-management-systems) (LIMS) entry set up with the field structure described below - Your laboratory's standard operating procedure (SOP) for pipette calibration and the manufacturer's specification sheet for the pipette model A brief note on terms. Calibration is the comparison of a pipette's delivered volume against a reference value, in this case mass measured on a balance. A calibration record is the document that captures what was measured, how, when, by whom, and what was decided. Record keeping is the discipline of creating, storing, and maintaining those documents so that any reviewer can reconstruct the calibration years later. This article covers all three. ## Why Pipette Calibration Records Matter Pipettes drift. Springs relax, seals wear, vapor builds in the shaft, and a pipette that delivered 1000.0 µL in January may deliver 993 µL by summer. In [molecular biology](/blog/careers/molecular-biology), a 2 percent volume error in a 25 µL qPCR master mix component can shift Ct values and change the interpretation of an assay. The gravimetric procedure in ISO 8655, the international standard for piston-operated volumetric apparatus, is the recognized reference method for detecting that drift. The measurement itself, however, is only half of the system. An unrecorded calibration does not exist as far as an auditor, a collaborator, or a reviewer of a published dataset is concerned. Records matter for four practical reasons: 1. **Traceability.** A record links each result to a specific instrument, balance, operator, tip lot, and date. If a batch of data is questioned, you can determine whether the pipette was in tolerance on the day the data were generated. 2. **Trend detection.** A series of records shows drift between service events. A pipette whose systematic error moves from -0.1 percent to -0.6 percent over two cycles is telling you a seal is failing, even though both readings might individually pass. 3. **Compliance.** Good laboratory practice (GLP), ISO/IEC 17025 testing and calibration laboratories, and clinical laboratory accreditation programs all require documented evidence of measuring equipment calibration, defined acceptance criteria, and signed records. The specific retention periods and formats come from your own quality manual and the accreditation program that applies to your laboratory. 4. **Repair decisions.** A record that separates as-found data (the pipette's condition when it arrived for calibration) from as-left data (its condition after any adjustment) tells you whether a pipette is stable after service or needs more frequent attention. ## What a Complete Calibration Record Must Contain A calibration record has one job. It must let a competent stranger reconstruct exactly what happened. To do that, it needs fields in five groups: instrument identity, measurement conditions, raw results, calculations, and decisions. **Instrument identity.** The record must identify the physical object unambiguously. That means the lab asset number, the manufacturer and model, the serial number engraved on the instrument, the pipette type (single channel, multichannel, air displacement, positive displacement), and the nominal volume range, for example 100 to 1000 µL. **Measurement conditions.** The record must state how the numbers were produced. That includes the calibration method (gravimetric, per ISO 8655), the balance used and its identification, the balance readability, the balance's own calibration due date, the test volumes, the number of replicate deliveries at each volume, the tip manufacturer and lot number, the water grade, the water temperature, the ambient temperature, and the operator's name. If your procedure applies a z factor for buoyancy and evaporation corrections, record which z value was used and how it was selected. **Raw results.** The individual masses for every replicate delivery, not just the summary. Raw data are what an auditor wants to see, and they are what allow a recalculation if a formula is ever questioned. **Calculations.** The mean mass, the mean converted volume, the standard deviation, the [coefficient of variation](/blog/research-skills/how-to-calculate-coefficient-of-variation), the systematic error as a percentage, and the acceptance limits applied, with a statement of where those limits came from (the manufacturer's specification sheet or an internal SOP limit). **Decisions and signatures.** A pass or fail statement, any corrective action taken, the as-found and as-left data if the pipette was adjusted or repaired, the date of the next calibration, the operator's signature, and a reviewer's or supervisor's signature. An unsigned record is an incomplete record. ## Pipette Calibration Record Keeping Template The template below is a field structure you can copy directly into a spreadsheet, a printable form, or a LIMS instrument record. Each row lists a field, what belongs in it, and a filled example. | Field | What to enter | Example entry | |--|--|--| | Record ID | Unique identifier for the record itself | CAL-2026-0347 | | Pipette asset ID | Your lab's internal asset tag | P-0042 | | Manufacturer, model | Make and exact model | Brand X, Model 1000XL | | Serial number | From the instrument body | AX-778214 | | Pipette type | Channel count and mechanism | Single channel, air displacement | | Nominal range | Full adjustable range | 100 to 1000 µL | | Calibration method | Reference method used | Gravimetric, ISO 8655 basis | | Test volumes | Every volume tested | 1000 µL and 100 µL | | Replicates per volume | Number of deliveries weighed | 10 | | Balance ID and readability | Asset number and smallest digit | BAL-01, 0.1 mg | | Balance calibration due | Date from the balance certificate | 2026-09-30 | | Tip manufacturer and lot | What was actually used | Brand Y, lot 4471A | | Water grade and temperature | Type of water and measured temperature | Type II DI, 21.5 °C | | Ambient conditions | Room temperature (and pressure if your z table needs it) | 22.0 °C, 1012 hPa | | Calibration date | Date the measurements were taken | 2026-03-12 | | Operator | Person who ran the weighings | J. Rivera | | Raw masses | Every replicate, in mg | See example section | | Mean volume | Converted from mean mass | 998.28 µL | | Systematic error | Accuracy as a percentage | -0.17% | | Repeatability | CV as a percentage | 0.079% | | Acceptance criteria | Limits and their source | ±0.5% error, ≤0.5% CV, per manufacturer spec sheet rev. C | | Decision | Pass or fail | Pass | | As-found status | Condition before any action | In tolerance | | Action taken | None, adjustment, repair, or service | None required | | As-left status | Condition after any action | Same as as-found | | Next calibration due | Scheduled date | 2027-03-12 | | Service certificate reference | Attached external certificate number, if any | SVC-2026-118 | | Operator signature and date | Signed on the day of measurement | Signed 2026-03-12 | | Reviewer signature and date | Second person confirming the calculation | Signed 2026-03-13 | Two design rules make this template work in practice. First, never allow a field to be left blank. If a field does not apply, enter "N/A" with a reason, because an empty cell is indistinguishable from an oversight. Second, keep the acceptance criteria in the record itself. A pass or fail statement without the limits it was judged against cannot be defended in an audit. ## Generating the Data: The Gravimetric Calibration Walkthrough This walkthrough calibrates a single channel 100 to 1000 µL air displacement pipette at its maximum volume of 1000 µL, using the gravimetric method. Ten replicate deliveries are weighed on a 0.1 mg analytical balance. All numbers in the example are illustrative and rounded for clarity. Your acceptance limits always come from the manufacturer's specification sheet or your SOP, not from this article. ### Step 1. Prepare and document the environment Set the pipette, the water, and the tips on the bench at least an hour in advance so everything reaches room temperature. Record the room temperature and the water temperature. A temperature mismatch between the water and the pipette changes the delivered volume and is one of the most common causes of a pipette "failing" a check that it would otherwise pass. ### Step 2. Confirm the balance Verify the balance level bubble is centered, the door closes fully, the display zeroes, and the balance's external calibration certificate is current. Record the balance asset number, readability, and certificate due date in the record. A calibration of a pipette on an uncalibrated balance is invalid and must not be recorded as a pass. ### Step 3. Set up the weighing vessel and tare Place a small evaporation-resistant vessel, such as a weigh boat inside a wider container, on the pan, close the door, wait for the stability indicator, and tare. Do this before every weighing. For a 1000 µL delivery the mass is about 1 g, which sits comfortably within the capacity of any analytical balance. ### Step 4. Pre-wet the tip Attach a fresh tip from the routine lot. Aspirate and dispense the full test volume three times against the wall of the vessel or a waste tube without weighing. Pre-wetting saturates the dead air volume inside the tip and shaft with water vapor. Skipping it biases the first delivery low and widens your spread. ### Step 5. Perform ten replicate deliveries For each replicate: 1. Press the plunger to the first stop smoothly. 2. Immerse the tip 2 to 3 mm below the water surface, held vertically. 3. Aspirate at a consistent, moderate speed. 4. Touch the tip against the vessel wall to remove clinging droplets. 5. Dispense into the tared vessel with the tip against the inner wall, pause, then blow out to the second stop. 6. Close the balance door, wait for the stability indicator, and record the mass to full readability. Record every individual mass. Ten readings at 1000 µL might look like this: ``` Replicate Mass (mg) 1 993.9 2 995.6 3 994.5 4 996.0 5 994.8 6 995.7 7 994.2 8 995.9 9 994.6 10 995.8 ``` ### Step 6. Repeat at the second test volume For a variable volume pipette, ISO 8655 specifies testing at the top of the range and at a low volume, commonly 10 percent of nominal. Repeat steps 3 through 5 at 100 µL using a 0.01 mg or better balance, because 0.1 mg readability is too coarse when a 100 µL delivery weighs only about 100 mg and a single 0.1 mg digit represents roughly 0.1 percent of the reading on its own. ### Step 7. Convert mass to volume Mass in milligrams converts to volume in microliters through the z factor, which folds in the density of water at the measured temperature plus corrections for air buoyancy and evaporation. Near 20 to 22 °C the z factor is about 1.003 µL per mg. Take the exact value from the reference tables in ISO 8655 or your pipette manufacturer's documentation for the temperature you measured, and record which value you used. ### Step 8. Run the calculations ![Calculation card showing mean mass 995.10 mg times z 1.0032 giving 998.28 microliters and a systematic error of -0.17 percent.](/article-images/illustrations/pipette-calibration-record-keeping-systematic-error-calc.webp) Here is a spreadsheet layout and the formulas that produce the record's summary numbers. The masses occupy cells B8 through B17 and the z factor sits in cell B5. ``` Cell B19 =AVERAGE(B8:B17) Cell B20 =STDEV.S(B8:B17) Cell B21 =B19*B5 Cell B22 =(B21-1000)/1000*100 Cell B23 =B20/B19*100 ``` The expected output for the data above: ``` Mean mass (mg): 995.10 Standard deviation (mg): 0.78 Mean volume (µL): 998.28 Systematic error (%): -0.17 CV (%): 0.079 ``` Worked by hand: the ten masses sum to 9951.0 mg, so the mean is 995.10 mg. Multiplying by the z factor, 995.10 × 1.0032 = 998.28 µL. The systematic error against the 1000 µL set point is (998.28 - 1000.00) / 1000.00 × 100 = -0.17 percent. The sample standard deviation of the masses is 0.78 mg, giving a coefficient of variation of 0.78 / 995.10 × 100 = 0.079 percent. ### Step 9. Decide pass or fail ![Decision card walking from the measured systematic error and CV through the acceptance limits to quarantine, service and an as-left pass.](/article-images/illustrations/pipette-calibration-record-keeping-pass-fail-triage.webp) Suppose the manufacturer's specification sheet for this model at 1000 µL states a systematic error limit of ±0.5 percent and a repeatability limit of 0.5 percent CV. Both calculated values sit inside those limits, so the record states Pass, and the as-found status is "in tolerance, no adjustment required." Now consider a second pipette whose ten weighings at 1000 µL produce a mean mass of 990.0 mg. The mean volume is 990.0 × 1.0032 = 993.17 µL, a systematic error of -0.68 percent. Against the same ±0.5 percent limit that is a fail. The record must then show three things: the as-found data proving the fail, the corrective action (the pipette is removed from service, tagged, and sent for adjustment or repair), and the as-left data from a repeat calibration after the adjustment proving the pipette now passes. Only the as-left pass returns the pipette to the bench. If the pipette cannot be adjusted in house, the record notes it was quarantined and references the external service certificate. ### Step 10. Sign, date, and schedule The operator signs and dates the record on the day of measurement. A second qualified person reviews the raw data and the arithmetic and signs as reviewer. Enter the next calibration due date. Many laboratories set recalibration intervals of 6 or 12 months and shorten them for pipettes with a history of drifting out of tolerance or for pipettes used in regulated assays. The interval itself is your laboratory's choice, justified by the trend in your records. ## The Parameters That Matter Every number in a pipette calibration record reduces to a small set of parameters. The table below collects the formulas you will use and the worked values from the example above. | Parameter | Symbol or name | Formula | Example value | |--|--|--|--| | Mass to volume conversion | V | V = m × z | 995.10 mg × 1.0032 = 998.28 µL | | Mean volume | V̄ | Average of converted replicate volumes | 998.28 µL | | Systematic error (accuracy) | e | (V̄ - V_set) / V_set × 100 | -0.17% | | Repeatability (precision) | CV | SD / V̄ × 100 | 0.079% | | Standard deviation of replicates | SD | Sample SD of the replicate volumes or masses | 0.78 mg | | Uncertainty of the mean | u | SD / √n | 0.78 / √10 = 0.25 mg | | Expanded uncertainty | U | 2 × u (k = 2, approximately 95% coverage) | 0.50 mg | | z factor | z | Buoyancy and evaporation corrected reciprocal of water density | ≈ 1.003 µL/mg near 20 °C | Three clarifications prevent most confusion here. **Accuracy and precision are separate lines in the record.** Systematic error describes how far the average delivery sits from the set volume. Repeatability describes how tightly the deliveries cluster. A pipette can be precise but inaccurate (tight cluster, wrong center), accurate on average but sloppy (correct center, wide cluster), or both. Acceptance criteria therefore always have two limits, and a pipette must clear both. **The z factor is not optional decoration.** A milligram of water does not occupy exactly one microliter at room temperature once buoyancy of the weighing vessel in air and surface evaporation are considered. Dividing by 1.000 instead of applying the correct z factor introduces a systematic bias of roughly 0.3 percent, which is comparable to the entire tolerance of many pipettes at the top of their range. **As-found and as-left are two different records of the same instrument.** As-found is the truth about what your bench was using before anyone touched the pipette. As-left is the truth about what will be used going forward. Auditors specifically look for both when a pipette failed and was adjusted, because an as-left pass with no as-found data hides the period during which out-of-tolerance results were being generated. ## Common Spreadsheet and LIMS Errors With Fixes Most calibration record problems show up as spreadsheet errors or as complaints during audits. Here are the ones seen most often, with the exact behavior you will see and the fix. **#DIV/0! in the CV cell.** The coefficient of variation divides by the mean, and the standard deviation function divides by the count of values. If you dragged the formulas down before all ten masses were entered, or if the range was pasted over an empty column, Excel shows #DIV/0!. Fix: confirm the range points at exactly ten filled cells. The function requires at least two numeric values. **#VALUE! in every calculation cell.** This almost always means a mass was typed with its unit attached, for example "995.1 mg" instead of 995.1. Excel stores that as text, and arithmetic on text returns #VALUE!. Fix: enter numbers only and put the unit in the column header. Find the offending cell by selecting the mass range and checking which cells are left aligned, the visual signature of text rather than a number. **#NAME? when using modern functions.** STDEV.S was introduced in Excel 2010. Opening a legacy workbook in an older version returns #NAME? for every cell that uses it. Fix: use the legacy STDEV function in files that must remain compatible with older software, or upgrade the file format. **Formulas that silently shift after inserting rows.** If someone inserts a row to add an eleventh weighing, the range B8:B17 in copied formulas becomes B9:B18 and quietly drops the first mass from the mean. The result is a plausible-looking number built on nine of ten points. Fix: lock ranges with absolute references, written as $B$8:$B$17, or convert the data block to a defined table so ranges expand automatically. After any structural edit, spot check one formula by hand. **A mean entered directly against a percentage limit.** A record that states "mean 995.10, limit 1000 ±0.5" mixes units and invites a false pass, because 995.10 µL is a 0.49 percent error that happens to fall inside a ±0.5 percent limit only by coincidence of the nominal volume. Fix: always calculate the systematic error as a percentage (or in µL) and compare it against the limit expressed the same way, exactly as the manufacturer's sheet expresses it. **LIMS rejection flags.** Modern LIMS platforms block calibration sign-off when required fields are empty, when the balance's own calibration due date has passed, when the operator lacks training authorization for the method, or when the pipette's asset record shows a status of quarantined. These are not software faults. The fix is procedural: complete training assignments, keep balance certificates current in the system, and clear quarantine status only through the documented as-left pass. **A stability indicator that never settles on the balance.** If the drift is downward over seconds, the vessel is losing water to evaporation or the air currents in the draft shield have not settled. If it never stabilizes at all, check for a static charge on plastic vessels, a door not fully closed, or a vibration source such as a centrifuge on the same bench. Never record a mass while the stability indicator is active. ## How to Verify a Calibration Result Before you sign the record, run these checks. Each one catches a specific class of error. 1. **Recompute one replicate by hand.** Convert replicate 1 from mg to µL using the z factor and confirm the arithmetic matches the spreadsheet. 2. **Sanity check the spread.** If the coefficient of variation comes out near zero, below what the balance's readability could physically resolve, suspect that a row was pasted twice or that values were transcribed from a previous record. Real replicate data always show some variation consistent with the balance resolution. 3. **Check the sign of the error.** A delivered mass below the nominal mass means a low volume and a negative error. Sign errors are among the most common transcription mistakes and flip a failing pipette into an apparent pass. 4. **Compare against history.** Pull the previous record for the same asset ID. If the pipette drifted by more than a few tenths of a percent since the last calibration, note the trend even if the current result passes. A control chart, a simple plot of systematic error versus calibration date for each pipette, is the standard visual tool for this and flags drift long before a failure. 5. **Confirm both test volumes pass.** A pipette that passes at 1000 µL but fails at 100 µL is common, because absolute errors grow proportionally larger at the low end of the range. Both points belong in the record with their own statistics and decisions. 6. **Verify the z factor against the recorded water temperature.** If the water was 24 °C and the z value in the formula came from the 20 °C row of the table, the converted volume carries a small but real bias. The fix is to use the value matched to the measured temperature and note it in the record. ## Maintaining Records Over Time A record that cannot be found five years later has failed at its only real job. Maintenance covers storage, retrieval, retention, and change control. **Choose a system and stay in it.** Paper logbooks, controlled spreadsheets on a shared drive, and LIMS records all work. What fails is a mixture, where some pipettes live in the binder, some in a personal spreadsheet, and some only in the service vendor's portal. Pick one primary system, and if you use paper as the raw capture, scan or transcribe into the primary system within a defined period written into your SOP. **Use a consistent naming and indexing convention.** A useful convention for file names or record IDs is the asset ID plus the calibration date, for example P-0042_2026-03-12. Index the master list by asset ID, serial number, location, and due date. When an auditor asks for the record for a specific pipette, you should be able to produce it in under a minute. **Control the template itself.** The blank form or spreadsheet is a controlled document. Give it a document number and version, for example FORM-QC-014 rev. 2, and reference that version in every completed record. When you revise the template, note what changed and why. This is what allows an auditor to confirm that the record you produced in 2023 was made on the form that was current in 2023. **Back up electronic records.** Spreadsheets on a shared drive need scheduled backups and access control, meaning operators can write but not silently alter signed records. If your system allows editing after sign-off, the record must show the edit, who made it, when, and why. That audit trail requirement is a core expectation in ISO/IEC 17025 and in regulated clinical environments. **Set the retention period in writing.** How long you keep pipette calibration records is defined by your quality manual and by the accreditation or regulatory program your laboratory operates under. What is universally expected is that the period is written down, that destruction after the period is itself documented, and that records remain retrievable and legible for the full period, including through any software migration. **Keep the physical loop closed.** Every pipette on the bench should carry a calibration label with the asset ID, the calibration date, and the next due date. A pipette past its due date is removed from service, tagged, and recalibrated before use. The record for that event then shows the pipette was used past due if it was, which is exactly the kind of gap a reviewer will find and which is far better surfaced and documented internally than discovered externally. ## Pipetting Technique and Its Effect on Calibration Records Calibration records measure the pipette, but the pipette is operated by people, and the same instrument can deliver different volumes under different hands. Two implications follow. First, the calibration itself must be performed with standardized technique so the record describes the instrument rather than the operator. That means consistent plunger speed, vertical aspiration, shallow immersion depth, brief wall contact after aspiration, controlled dispensing against the vessel wall, and pre-wetting as described in the walkthrough. An operator who aspirates briskly on one replicate and slowly on the next will inflate the standard deviation and record a precision problem that belongs to the method, not the pipette. Second, daily technique on the bench affects whether the calibrated performance holds in practice. Forward pipetting, plunger to the first stop, aspirate, then dispense to the first stop with a blow-out, is the default for aqueous solutions. Reverse pipetting, aspirating to the second stop and dispensing only to the first, leaves a residual volume in the tip and is used for viscous or foaming liquids because it improves accuracy with those fluids, at the cost of needing a setting offset. Positive displacement pipettes, which have the piston in direct contact with the liquid, are the correct choice for volatile solvents and viscous solutions where an air column compresses unpredictably. If a pipette is routinely used under conditions that differ from the calibration conditions, the record should note the intended use, because a calibration performed with water does not by itself guarantee performance with glycerol-heavy master mixes. Training matters here too. When an operator's technique changes, the recorded repeatability of the next calibration can change with it. Reviewers comparing current records to the control chart should ask whether a shift in CV tracks an instrument change or a personnel change before ordering a service. ## Common Mistakes and Limitations These are the errors that appear repeatedly in real calibration programs. Each one is specific and fixable. - **Recording only the summary, never the raw data.** A record with a mean and a pass statement cannot be independently recomputed. Enter all ten masses. - **Calibrating at a single volume.** A pipette tested only at its maximum can be badly out of tolerance at 10 percent of range, which is where most low volume work happens. Test both points. - **Using an uncalibrated or unverified balance.** The pipette result inherits the balance's error. Check the certificate date every time and record it. - **Skipping pre-wetting.** The first delivery after a dry tip runs low, inflating both the error and the spread. Pre-wet three times. - **Skipping thermal equilibration.** Cold water on a warm bench, or a pipette carried in from a cold room, produces a bias that looks like instrument failure. - **Applying the wrong z factor.** Using 1.000 µL/mg or a z value for the wrong temperature adds a systematic bias on the order of a few tenths of a percent, which can flip a marginal result in either direction. - **No as-found data after repair.** If a vendor services a pipette, the record must still capture the pre-service as-found check. Otherwise nobody knows how long the pipette was out of tolerance. - **Acceptance limits pulled from memory.** Limits change between specification sheet revisions. Record the revision you used. - **Unsigned or retrospectively signed records.** Signatures dated weeks after the measurement undermine the entire document. Sign on the day. - **Treating the sticker as the record.** The calibration sticker proves a due date. The record proves the evidence behind it. Auditors ask for the record. Two limitations frame everything above. Gravimetric calibration with water characterizes the pipette under aqueous, room temperature conditions. Performance with viscous, volatile, or cold samples requires method-specific verification, and for those matrices a positive displacement pipette is often the right instrument choice. Second, the acceptance limits, recalibration intervals, and retention periods described here in qualitative terms are set by your own quality system, the manufacturer's current specification sheet, and the accreditation program that governs your laboratory. Individual decisions about a specific pipette that failed calibration, particularly whether out-of-tolerance data were generated for regulated samples, should be reviewed with your quality assurance unit under your SOP. ## Frequently Asked Questions ### How often should pipettes be calibrated? Most laboratories recalibrate every 6 to 12 months, and shorten the interval for pipettes with a drift history or heavy regulated use. Your SOP defines the interval, and the trend in your own records is the evidence that justifies it. ### What is the difference between as-found and as-left data? As-found data show the pipette's performance before any adjustment, documenting what the bench was actually using. As-left data show performance after any adjustment or repair, documenting what returns to service. ### Can I calibrate my own pipettes or must a service technician do it? You can perform in-house gravimetric calibration if you have a suitable analytical balance, trained operators, and an SOP. Many laboratories verify in house on a defined schedule and send pipettes for professional service and adjustment annually or when they fail. ### What is the difference between a calibration certificate and a calibration record? A certificate is issued by a calibration provider and summarizes their measurement of your instrument. A calibration record is your laboratory's complete document, including raw data, calculations, limits, decisions, and signatures, whether the calibration was internal or external. ### How long should calibration records be kept? Retention periods are set by your quality manual and the accreditation or regulatory program that applies to your laboratory. Whatever period applies, it must be written in your SOP and records must stay retrievable for the full term. ### What acceptance limits should I use for pipette calibration? Use the systematic error and repeatability limits from the pipette manufacturer's specification sheet, or tighter internal limits if your applications demand them. Always record the limits and their source in the record itself. ### Does pipetting technique change calibration results? Yes. Inconsistent plunger speed, skipped pre-wetting, a non-vertical hold, and uneven dispensing all inflate measured error and spread. Calibration must use standardized technique so the record reflects the instrument. ### What should I do when a pipette fails calibration? Remove it from service immediately, tag it, record the as-found failure, and send it for adjustment or repair. After service, run a new gravimetric calibration, record the as-left data, and return it to use only after an as-left pass.