GIFSQ Tools · Module 15 — Metrology, Validation & Laboratory Accreditation · Tool 298 of 500
Verify a piston pipette by the gravimetric method of ISO 8655: mean delivered volume, systematic error and random error (CV) against your maximum permissible errors.
Try sample values — fills the form with the worked example below.
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Mean volume
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Systematic error (%)
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Random error, CV (%)
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Result
Equation: Mean volume = ΣV ÷ n. Systematic error (%) = (mean − nominal) ÷ nominal × 100. Random error CV (%) = SD ÷ mean × 100 (sample SD, n − 1). Pass when |systematic error| ≤ maximum systematic error and CV ≤ maximum random error.
Method: Gravimetric pipette verification per ISO 8655-6: weigh replicate deliveries of distilled water, convert mass to volume with the water density at the test temperature, and compare the systematic and random errors with the maximum permissible errors of ISO 8655-2.
Assumptions: the volumes entered are already converted from mass using the water density at the test temperature; the replicates are independent deliveries at the same setting.
Limitations: the density correction matters — at 20 °C water is 0.9982 g/mL, and the value changes with temperature; evaporation during weighing biases small volumes low.
Rounding: mean volume to 2 decimal places; systematic error and CV to 2 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Method: Gravimetric pipette verification per ISO 8655-6: weigh replicate deliveries of distilled water, convert mass to volume with the water density at the test temperature, and compare the systematic and random errors with the maximum permissible errors of ISO 8655-2.
Assumptions: the volumes entered are already converted from mass using the water density at the test temperature; the replicates are independent deliveries at the same setting.
Limitations: the density correction matters — at 20 °C water is 0.9982 g/mL, and the value changes with temperature; evaporation during weighing biases small volumes low.
Rounding: mean volume to 2 decimal places; systematic error and CV to 2 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: Nominal 1000 µL, ten deliveries 998, 1001, 999, 1002, 1000, 1001, 999, 1000, 1002, 1001 µL, limits 0.8% and 0.4%: mean = 1000.30 µL, systematic error = 0.03%, CV = 0.13% — pass.
Enter values above to see results.
ISO 8655-2 maximum permissible errors for a 1000 µL pipette are 0.8% systematic and 0.4% random — use the limits for your own pipette size and class. Tool 298 of 500 — GIFSQ
