Evaluation of reproducibility uncertainty in micropipette calibrations for non-nominal volumes through an interlaboratory study

The nominal volume of a variable volume micropipette is the maximum volume of the range specified by the micropipette manufacturer. The purpose of the present study is to quantify the reproducibility standard uncertainty for non-nominal volume micropipette calibrations for variable volume micropipettes. An interlaboratory study was implemented for this purpose, using variable volume micropipettes with nominal volumes of 10 μL, 200 μL, and 1000 μL and setting the measurement volumes as 10 %, 50 %, and 100 % of the nominal volumes. In our previous paper (Accredit Qual Assur 19:377, 2014), we quantified the uncertainty due to reproducibility using only data obtained for nominal volume calibrations. From the results obtained, we found that the reproducibility uncertainties quantified for nominal volumes are too small to cover interlaboratory variations for non-nominal volume calibrations. For calibrations of 10 % and 50 % of the nominal volumes, the reproducibility uncertainties must be increased by the factors of 2.7 and 1.4, respectively, for micropipettes with nominal volumes of 10 μL to 1 000 μL, based on the results of this study.