Liquid Handling

Monitoring ofMeasuring InstrumentsTechnical InformationCalculationsMonitoring of measuring instrumentsMeasuring values obtained in the course of a monitoringprocedure are to be evaluated as follows:Example: Transferpette ® adjustable volume, 20-200 µl1. Calculation of the mean volumeThe weighing parameters obtained using the gravimetrictest are simply the mass values corresponding to thepipetted volume. In order to obtain the actual volume,a correction must be calculated.A mean volume ( x _ ) of the weighing values is then calculatedby dividing the sum of the weighings by the numberof weighings made. This mean mass is then multiplied bya correction _ factor (Z, units of µl/mg) to give the meanvolume ( V ) delivered. The factor Z combines density ofwater, testing temperature and atmospheric pressure.For a typical temperature of 21.5 °C and air pressureof 1013 mbar (hPa), Z=1.0032 µl/mg.Gravimetric testing values at21.5 °C (Z = 1.0032)Tested volume (µl): 200.0000Specified value (mg): 199.3620x 1 200.2000x 2 199.6000x 3 199.4900x 4 199.7000x 5 199.7000x 6 199.2900x 7 199.3500x 8 199.4100x 9 199.2000x 10 199.1900V – = x – · ZV – = x 1 + x 2 + x 3 +... + x nn· ZV – 200.2 +199.6 +199.49 + ... + 199.19=10V – = 199.513 · 1.0032V – = 200.1514· 1.00322. Calculation of accuracyA [%] = V– - V spec.· 100 A [%] =V spec.200.1514 - 200· 100200A [%] = 0.076Extract from the table "Factor Z for Liquid Handling Instruments"Temperature°CFactor Zml/gTemperature°CFactor Zml/g18 1.0024518.5 1.0025519 1.0026419.5 1.0027420 1.0028420.5 1.0029421 1.0030521.5 1.0031622 1.0032722.5 1.0033823 1.0035023.5 1.0036224 1.0037424.5 1.0038625 1.0039925.5 1.0041226 1.00425322info@brand.de