Drug screening in biological fluids. The need for a systematic approach

In this paper the key steps towards drug screening in biological fluids are considered: (i) sample work up-isolation-concentration; (ii) differentiation-detection; (iii) identification. For (i) solid-phase extraction has very good potential; for (ii) thin-layer chromatography, gas chromatography and high-performance liquid chromatography, in combination with their respective detection modes, each have their particular advantages and disadvantages; for (iii) extensive computerized data bases are essential. It is emphasized that each step must be approached and carried out in a systematic way, not only to make sure that all substances of interest can be detected, but also for their correct identification. To this end all analytical procedures and techniques used require extensive validation of their detection and identification properties.