Direct colorimetric method for determination of organophosphates in human urine

A simple and sensitive method for determination of organophosphorus pestici des in human urine was developed by detecting the color complexes which res ulted from reactions of organophosphorus pesticides and 4-(4-nitrobenzyl)py ridine (NBP) in urine. Based on studies of reaction conditions, e.g. reacti on temperature and time, and reagent concentration, a colorimetric method w as established. A 0.1-ml volume of NBP (45% in acetone) was added to a 1.0- ml volume of a urine sample, and the mixture was heated at 100 degrees C fo r 20 min. After cooling, 0.1 ml of tetraethylenepentamine was added. The or ganophosphorus pesticides showed a characteristic purplish blue color and t he coloring complexes which were produced were stable for several hours. Fu rthermore, these complexes could be determined spectrophotometrically. The detection limits were 0.10-10 mu g/ml in urine. The required time for analy sis was approximately 30 min for one sample. Comparing the result of the pr oposed method with those of the GC-MS method, the results were similar for the 12 poisoning cases studied. Thus, the proposed method is useful for det ection of these pesticides in critical care practices. (C) 2000 Elsevier Sc ience B.V. All rights reserved.