Analyses in hanging drops — A modern variant of feigl's spot tests

Summary

Different steps of analytical procedures, i.e. preconcentration, extraction and detection, were performed with isolated drops hanging at loops, in order to reduce changes in the analyte content, which may result from interactions between the sample and the surfaces of container walls. Detection of analytes in the drops were based on either photometry with a fiber optic or conductometry with miniaturized conductometric cells and determinations were carried out by volumetry or using calibration curves. The recovery of sample pretreatment within the drop was determined by using fluorescein as a less volatile compound. The experiments serve as simulations for later studies with acoustically levitated drops placed in the nodal points of standing ultrasonic waves.