Learn more about critical aspects of ISO standards related to precision volumetry.
Guidelines on how to correctly use and calibrate volumetric instrument with plunger are given by the ISO 8655 standard. Among other elements, the standard describes pipetting techniques and calibration parameters such as number of measurements for each volume (minimum, intermediate and maximum), admissible ambient temperature and humidity level, etc. However, ISO 8655 standard does not take the measurement uncertainties into consideration. They are regulated by the ISO 17025 standard, which goes a big step ahead of ISO 8655.
Several instruments such as analytical balances, thermometers, hygrometers, barometers are involved in pipette and dispenser calibration. Parameters such as water evaporation, ambient temperature, barometric pressure, and pipette construction are of utmost importance. Human factors such as operator technique are critical. Each single element has its uncertainty factor that should be considered during calibration. For example, using analytical balance with the incorrect resolution, an inaccurate thermometer, or working with a high water evaporation rate (humidity below 50%) while calibrating, versus results obtained with quality measurement devices and stabilized conditions will all lead to increased measurement uncertainty. However, operator skills and test procedures belong to the most critical uncertainty parameters in the pipette calibration process. For the highest level of calibration, an accredited certificate under the ISO 17025 standard provides details on the measurement uncertainties for each volume calibrated.
When taking those factors into account, ISO 17025 accredited calibrations represents a level above the ISO 8655 standard and guarantees the “best measurement uncertainties” for a given volume. All uncertainty values within a given organization are published by governmental bodies of the member countries and remain available from the International Laboratory Accreditation Corporation (known as ILAC, www.ilac.org).
Socorex maintains an excellent uncertainty level in its calibration laboratories. The reasons are our highly qualified operators, reliable measuring devices, and respect of strict standard conditions while performing pipette and dispenser calibration of all brands. The Socorex Service Center can provide accredited laboratories the required ISO 17025 certificate for each of their measurement instruments. This certificate must be kept carefully as part of the laboratory quality documents and may be requested during a quality audit.