Determination of glafenine in dosage forms and serum by thin layer densitometry and high performance liquid chromatography.

New thin layer densitometry and high performance liquid chromatography (HPLC) methods are described for quantitative determination of glafenine in dosage forms in the presence of its photo-degradation products and in serum in the presence of its metabolites. Mobile phases consisting of toluene-isopropyl alcohol-dimethylformamide-water (18:3:1:0.5) and methanol-water-phosphoric acid (80:120:0.5) are found to be efficient for reasonable separation and adequate resolution of glafenine from associated substances by thin layer chromatography (TLC) and HPLC techniques, respectively. The methods are used for the study of glafenine purity, stability, bioavailability, bioequivalence and tablet dissolution rate. The results obtained by TLC and HPLC techniques are in good agreement and offer the advantages of reproducibility and accuracy.

Liquid and poly (vinyl chloride) matrix membrane electrodes for the selective determination of cocaine in illicit powders.

The construction of liquid membrane and PVC matrix-type cocainium ion selective electrodes and their use for direct potentiometry and potentiometric titration of cocaine are described. The ion-pair complexes of cocaine cation with reineckate and tetraphenylborate anions are either dissolved in nitrobenzene solvent or dispersed in a PVC matrix, with DOP or DBS plasticizer, and used as the ion-exchange membranes. The electrochemical response characteristics of electrodes incorporating these types of membranes are evaluated with regard to the effect of pH, foreign basic compounds, temperature and gamma-radiation. The electrodes display a stable fast Nernstian response for 10(-2)-10(-5)M cocainium cation over the pH range 3-7, the lower limit of detection being 1 mug/ml. Determination of as low as 20 mug/ml cocaine hydrochloride shows an average recovery of 98% and a mean standard deviation of +/-0.6%. The electrodes exhibit useful analytical characteristics for determining cocaine in some illicit powders. The results agree fairly well with those obtained by gas-liquid chromatography.

Nitron tetrachloroaurate(III) electrodes with poly(vinyl chloride) and liquid membranes for the selective determination of gold.

PVC matrix and liquid membrane electrodes have been developed for direct potentiometric determination of gold(III). The membranes incorporate nitron tetrachloroaurate(III) as electroactive material. Fast response for gold(III) over the concentration range 10(-5)-0.1M, with response slopes of 52.8-55.2 mV/decade is obtained. The electrodes show good selectivity for gold(III) at pH 2-5 in the presence of many anions and cations. The PVC membrane electrode offers the advantages of greater selectivity (except for Cr(3+), Mn(2+) and ClO(-)(4)) and higher thermal stability. The liquid membrane electrode gives a higher response slope and faster time of response than the PVC membrane electrode. Determination of AuCl(-)(4) over the range 2 mug/ml-2 mg/ml shows an average recovery of 98.5% and a mean standard deviation of 1.0%. Determination of gold in some gold alloys (58.3-99.9% Au) and pharmaceutical preparations gave an average recovery of 99.4% and a mean standard deviation of 0.7%, which are comparable with the performance obtained with the spectrophotometric Malachite Green and gravimetric U.S. Pharmacopeia methods.

Liquid membrane electrodes for the selective determination of nicotine in cigarette smoke.

Five liquid membrane electrode systems responsive to the nicotinium cation are described. These electrodes are based on the use of the ion-association complexes of the nicotinium cation with tetraphenylborate, 5-nitrobarbiturate, flavianate, reineckate and picrolonate counter anions in nitrobenzene solvent as ion-exchange sites. The performance characteristics of these electrodes, evaluated according to IUPAC recommendations, reveal fast, stable and near-Nernstian responses for 10(-2)-10(-5) M nicotine over the pH range 3.5-7. Many inorganic and organic cations do not interfere. The direct potentiometric determination of 3 micrograms ml-1-1.6 mg ml-1 of nicotine in aqueous solutions showed an an average recovery of 99.5% and a mean standard deviation of 1.2%. The electrodes were also used for monitoring the titration of nicotine with sodium tetraphenylborate, measuring the pK of nicotine and determining nicotine in the smoke from different cigarettes. The results compare favourably with those obtained by the standard gas chromatographic method.