[Metabolite isolation for mass spectrometrical determination of new drugs (author's transl)].

Only very minute concentrations of metabolites of highly effective and consequently low dosed drugs can be detected in urine. In order to identify the structure of these compounds they must be concentrated by a factor up to 1:10(6). Isolation of metabolites, especially when present as conjugates, becomes more complicated the greater the polarity. In this paper some methods for isolation are presented using column- and thin-layer chromatography as well as extraction and dialysis, finally their practical application and their most effective combination are described. Priority must be given to solving two problems: firstly, a rough pre-purification is necessary to eliminate physiological components from the urine such as salts, urea, etc., and secondly, the mixture of metabolites has to be separated into single metabolites. Examples are given to demonstrate the practicability of these methods for the isolation and structural identification of metabolites belonging to varying structural classes.