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The voltammetric behaviour of quetiapine (QTP) was studied using direct current (DC t ), differential pulse (DPP) and alternating current (AC t ) polarography. The drug manifests cathodic waves over the pH range of 6 -11.8. The waves were characterized as being irreversible, diffusion-controlled with limited adsorption properties. At pH 8, the diffusion current-concentration relationship was rectilinear over the range of 8 -44 µg/mL and 4 -44 µg/mL using DC t and DPP modes, respectively, with minimum detection limits (LOD) of 0.06 µg/mL and 0.04 µg/mL using the DC t and DPP modes, respectively. The diffusion-current constant (I d ) is 1.36 ± 0.04 (n = 10). The proposed method was successfully applied to the determination of the studied compound both in pure form and in formulations. The results obtained were favourably compared with those obtained using a reference method. A pathway for the electrode reaction was postulated.

A simple, economic, selective, and stability indicating spectrofluorimetric method was developed for the determination of famotidine (FMT); is based on its reaction with 9, 10-phenanthraquinone in alkaline medium to give a highly fluorescent derivative measured at 560 nm after excitation at 283 nm. The fluorescence intensity-concentration plot was rectilinear over the concentration range of 50-600 ng/ml with minimum quantification limit (LOQ) of 13.0 ng/ml and minimum detection limit (LOD) of 4.3 ng/ml. The factors affecting the development of the fluorescence intensity of the reaction product were carefully studied and optimized. The method was applied for the determination of FMT in its dosage forms. The stability of the compound was studied, and the proposed method was found to be stability indicating one. The results obtained were in good agreement with those obtained by the official method. Furthermore, the method was applied for the determination of FMT in spiked and real human plasma. The mean % recovery (n = 4) was found to be 99.94 +/- 0.24, and 105.13 +/- 0.64 for spiked and real human plasma, respectively. The composition of the reaction product as well as its stability constant was also investigated. Moreover, the method was utilized to investigate the kinetics of both alkaline and oxidative induced degradation of the drug. The apparent first order rate constant and half life time of the degradation product was calculated. A proposal of the reaction pathway was postulated.

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