Fluorometric determination of propoxyphene.

With 4-chloro-7-nitrobenzo-2, 1,3-oxadiazole (I), fluorescent derivatives of propoxyphene can be prepared, thus enabling quantitation of the drug in biological samples. This technique offers an acceptable alternative to gas chromatographic (1-5) or ultraviolet spectrophotometric (6, 7) procedures. Favorable aspects of the fluorometric technique are high sensitivity, specificity, potential for rapid analysis of large numbers of samples, and ease of confirming positive results-even at low concentrations-by thin-layer chromatography of the highly fluorescent products. While (I) has been applied to the analysis of carbamates (8) and primary and secondary amines (9), this paper reports the first application of the reaction of (I) with a tertiary amine. This anomalous reaction of (I) does not represent a new reaction category. Rather, it is based on the peculiar chemistry of propoxyphene. Our hypothesis is that propoxyphene is probably N-demethylated under the reaction conditions and that the resulting secondary amine, norpropoxyphene, undergoes nucleophilic aromatic substitution with (I). Data to substantiate this mechanism are presented in the Discussion.