Part 6 follows the gravimetric method, considered one of the best methods for pipette calibration according
to ISO’s 2022 standard, whereas Part 7 provides several alternative methods. Also, Part 6 includes the following requirements and, unlike the 2002 standard, does not allow for deviations:
• Number of measurements
A minimum of 3x10 measurements is required (the 2002 standard allowed testers to claim conformity with less than 10 measurements). The three volumes tested must be 10%, 50% and 100%. If a pipette’s minimum volume range is greater than 10%, that volume can be tested.
• Room temperature
The testing room temperature may only vary by ±0.5 °C while testing, and the equipment must be given time to equilibrate.
• Water temperature
The difference in temperature between water and air must not exceed ±0.5 °C. The water temperature must be recorded at the beginning and end of calibration and printed on the certificate.
• Tip changes
Tips must be changed after five dispenses. For example, in a 3x10 calibration for a single-channel pipette, a technician must use six tips (two for each test volume).
Part 7 provides several alternative methods, including a modified gravimetric method that has less strict environmental control requirements, thus making it easier to perform calibrations onsite. Rainin Service lists specific requirements in our standard method document, PS-125. For laboratories who desire ISO/IEC 17025-accredited work that is not strictly ISO 8655 Part 6 compliant, we recommend calibrating according to Part 7.