DEVELOPMENT AND ANALYTICAL APPLICATIONS OF COCAINE MEMBRANE ELECTRODE

New membrane electrodes based on polyvinylchloride films consisting of cocaine-dipicrylaminate, cocaine-tetraphenylborate and cocaine-Reineckate ion-association complexes were developed. The performance characteristics of cocaine-dipicrylaminate membrane electrode were found to the best. This electrode showed Nernstian response over the range of 5×10^-2 to 2×10^-5 mol/L with cationic slope of 59 mV/concentration decade with the limit of detection at 8×10^-6 tool/L, The responses were not affected by pH in the range of 4 to 7. The coefficients of selectivity relative to many substances and some other alkaloids were small, only chloropromazine, papaverine, tetracaine and quinidine showed interference. Potentiometric titration with sodium tetraphenylborate of cocaine hydrochloride samples showed an average recovery of 99.6% and coefficients of variation of 0.66%, while the determination of 4% cocaine hydrochloride solution with direct potentiometric method showed an average recovery of 99.6% and coefficients of variation of 1.3%. The results obtained by the proposed method agreed well with those by volumetric methods. In contrast to volumetric methods, which are timeconsuming and require large samples, the proposed method is simple, fast and sensitive.