Purification and analysis of drug residues in urine samples by on-line immunoaffinity chromatography/high-performance liquid chromatography/continuous-flow fast atom bombardment mass spectrometry

An automatic system for the on-line extraction and analysis of diethylstilbestrol in the urine of rats and calves is described. Extraction was done by injecting samples directly into an immunoaffinity column containing antidiethylstilbestrol antibodies bound to a Sepharose matrix, and analysis was done by on-line high-performance liquid chromatography with ultraviolet and continuous-flow fast atom bombardment mass spectrometry detectors. The system, consisting of one injector, two switching valves, and three pumps, was operated under computer control and allowed to perform a complete analysis of a sample in 28 min. An accurate quantitation by isotope dilution was also possible, by the use of deuterated diethylstilbestrol as internal standard. The sensitivity of the method, using selected-ion monitoring of the molecular ion of diethylstilbestrol, was 2 ng/mL, injecting 1 mL of urine sample. Results obtained from analyzing the urine of rats and calves treated with diethylstilbestrol are presented.