Pipettes Three reference documents to calibrate a micropipette with air cushion

As presented in the article [P 1 331] , the use of pipettes to transfer liquids is a daily activity in most life science research laboratories. Modern quality assurance systems require periodic gravimetric control and, where necessary, pipette adjustment.

To achieve these objectives, the ISO/TR 20461 technical report was the first official document published in November 2000 to explain how to calibrate a piston-operated volumetric device (AVAP).

Considered a benchmark by many national accreditation bodies (e.g. COFRAC, DAKKS, UKAS, etc.), it has enabled many calibration laboratories applying for accreditation to demonstrate and/or maintain their competence in this field.

It is also used by in-house metrology departments working to ISO 17025 and ISO 15189 standards.

Since November 2000, several interlaboratory comparisons have been carried out, led by LNE in 2009, IPQ between July 2011 and June 2012 at the request of the BIPM, and DKD in 2009, showing significant discrepancies.

This article reviews the three main reference documents for the calibration of AVAPs:

• ISO/TR 20461:2000 – Technical report – Determination of uncertainty of measurement for volumetric measurements using the gravimetric method ;

• DKDR 8-1 – Guideline – Calibration of piston-operated pipettes with air cushion, issue 12/2011 ;

• COFRAC LAB GTA 90 – Accreditation Technical Guide – Calibration of volumetric piston instruments, June 2015