Influence of biological matrix on chromatographic behavior and detection of selected acidic, neutral, and basic drugs examined by means of a standardized HPLC-DAD system.

Human serum, autopsy blood, and liver samples were extracted by means of liquid-liquid extraction at acidic and at basic pH and at basic pH following acid hydrolysis. Six selected basic and six selected acidic or neutral drugs were added to the extracts. The spiked and blank samples were examined by means of reversed-phase high-performance liquid chromatography (HPLC) under standardized conditions using diode array detection. The retention index (RI) values of drugs were determined using a 1-nitroalkane scale and secondary standards. The RI values were virtually unaffected by biological matrix. On the other hand, the detection of some substances may be impaired by matrix peaks occurring regularly in biological extracts. The retention index values and UV spectra of three identified (phenethylamine, tryptamine, and indole) and nine unidentified substances were included in an HPLC database.