Milligram mass metrology for quantitative deposition of liquid samples

Abstract

Quantitative dispensing of liquids by mass becomes increasingly difficult as sample volume decreases. Whereas ml quantities of liquid can be directly weighed as dispensed on an analytical balance or using pycnometer methods, μl samples are more challenging due to their milligram-scale mass and rapid evaporation. Here, a method for quantitative determination of the mass of μl liquid droplets is proposed. The weighing of a microcapillary pycnometer combined with traceable calibration masses and corrections for sample evaporation allows determination of the droplet mass on the order of 1 mg with relative combined expanded uncertainty of 0.3%.