SIMPLE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC COLUMN-SWITCHING TECHNIQUE FOR THE ONLINE IMMUNOAFFINITY EXTRACTION AND ANALYSIS OF FLUNITRAZEPAM AND ITS MAIN METABOLITES IN URINE

A sensitive, simple and rapid method without sample pretreatment is pr esented for the simultaneous determination of flunitrazepam and its ma in metabolites (norflunitrazepam, 7-amino- and 7-acetamidoflunitrazepa m) in urine. The single-step procedure is based on a column-switching technique which uses an immobilized antibody in an extraction column f ollowing concentration on a precolumn and separation on an analytical column. UV detection was performed at 254 nm. The reusability of the a ntibody exceeds 88 runs and a complete analysis was performed in less than 40 min. The method shows coefficients of variation below 9.9% and rates of recovery greater than 92% tested at the level of 50 ng/ml ur ine. The limit of detection was below 2 ng/ml urine for the four compo unds. (C) 1997 Elsevier Science B.V.