Professor Kalvoda commented that with very low concentrations of drugs or of their metabolites, where — according to the lecture — the sensitivity of DPP does not suffice, the so-called adsorptive stripping polarography (vide supra in the introduction) could be very advantageous. With respect to this new, promising method it will be necessary, however, to solve the problem of presence of other, interfering surface active substances by developing simple separation processes, e.g. by means of molecular exclusion chromatography. Only then it may be used in practical pharmaceutical or environmental analysis (e.g. urine or serum analysis). Further he asked whether a combination of TLC separation with DPP determination would be possible in a similar manner as that of TLC with DCP in some papers published by Oelschläger and co-workers.