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The construction and electrochemical response characteristics of poly(vinyl chloride) matrix ion-selective electrodes (ISEs) for dextromethorphan (DXM) hydrobromide are described. The membranes incorporate ion-association complexes of DXM with reineckate salt {[Cr(NH3)2(SCN)4]NH4} or phosphomolybdic acid [H3(PMo12O40)], as electroactive materials and dioctylphthalate or dibutylsebacate as a plasticizing solvent mediator. The sensors display a fast, stable and linear response with slopes of 54.4 to 59.5 mV/decade at pH 2.5 -6.5 and a detection limit of 1.0 ¥ 10 -6 M. Moreover, the sensors exhibit very good selectivity for DXM over opiate alkaloids, as well as organic and inorganic cations. The sensors proved to be useful for the determination of 5.0 ¥ 10 -5 -1.0 ¥ 10 -3 M DXM hydrobromide in pure as well as in dosage forms by direct potentiometry and standard addition methods. Determination of 5.0 ¥ 10 -4 M DXM using the standard addition method and a sensor based on phosphomolybdate and dioctylphthalate shows an average recovery of 99.8% and a relative standard deviation (RSD) of 0.4%.

Abstract.A simple, accurate and selective method is described for the determination of morphine in illicit powders, based on monitoring the initial rate of fluoride ion liberation from the reaction of morphine with 1-fluoro-2,4-dinitrobenzene at pH 9 and 35 ~ using a solid-state fluoride ion-selective electrode. Under optimized reaction conditions, as little as 15 btg/ml of morphine is ,determined with an average recovery of 99.5% and a mean relative standard deviation of 1.2%. Determination of morphine in real illicit powders containing 6-18 % morphine gives results comparing favorably with those obtained from isocratic reverse-phase high-performance liquid chromatography. No interferences are caused by many structurally related and associated compounds such as codeine, acetylcodeine, ethylmorphine, acetylmorphine and diacetylmorphine (heroin). A gravimetric method for determining morphine based on a reaction with 1-chloro-2,4-dinitrobenzene to form dinitrophenyl morphine precipitate was described by Mannich in 1935 [-12]. In 1951 Dann and Wippern investigated and recommended the use of 1-fluoro-2,4-dinitrobenzene for precipitation of morphine

1-(3-chlorophenyl)piperazine (mCPP) is a wide spread new psychoactive substance produces stimulant and hallucinogenic effects similar to those sought from ecstasy. Hence, in the recent years, mCPP has been introduced by the organized crime through the darknet as a part of the illicit ecstasy market with a variable complex profile of pharmacologically active substances that pose problematic risk patterns among people who take these seized products. Accordingly, the design of selective sensors for the determination of mCPP is a very important demand. In this respect, a supramolecular architecture; [Na(15-crown-5)][BPh4] from the assembly of 15-crown-5 and sodium tetraphenylboron has been utilized as an ionophore, for the first time in the selective recognition of mCPP in conjunction with potassium tetrakis(p-chlorophenyl)borate and dioctylphthalate through polymeric membrane ion sensors. The ionophore exhibited a strong binding affinity that resulted in a high sensitivity with a slope closed to the ideal Nernstian value; 58.9 ± 0.43 mV/decade, a larger dynamic range from 10−6 to 10−2 M, a lower limit of detection down to 5.0 × 10−7 M and a fast response time of 5 s. Very important also is it was afforded excellent selectivity towards mCPP over psychoactive substances of major concern, providing a potentially useful system for the determination of mCPP in the illicit market. On comparison with the natural β-cyclodextrin as an ionophore, it exhibited more sensitivity and selectivity estimated to be the superior.

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