A new spectrophotometric method is proposed for the assay of ranitidine hydrochloride (RNH) in bulk drug and in its dosage forms using ceric ammonium sulphate (CAS) and two dyes, malachite (MAG) green and crystal violet (CV) as reagents. The method involves the addition of a known excess of ceric ammonium sulphate to ranitidine hydrochloride in acid medium, followed by the determination of unreacted CAS by reacting with a fixed amount of malachite green or crystal violet and measuring the absorbance at 615 or 582 nm respectively against the reagent blank. The Beer's law is obeyed in the concentration range of 0.4-8.0 µg/ ml of ranitidine hydrochloride (RNH) for RNH-MAG system and 0.2-1.6µg/ml of ranitidine hydrochloride for RNH-CV system. The molar Absorptivity, Sandell's sensitivity for each system were calculated. The method has been successfully applied to the determination of ranitidine hydrochloride in pure and dosage forms.

A simple and rapid spectrophotometric method for the determination of nevirapine is described. The method is based on the reaction of nevirapine with tetrathiocyanatocobalt(II) ion in buffer of pH 4 to form the corresponding complex. Beer's law is obeyed in the range of 0.2 - 2.0 µg mL-1 for nevirapine. The optical parameters such as molar absorptivity, Sandell's sensitivity, detection limit and quantitation limit were found to be 1.16× 10(4) Lmol-1cm-1, 2.09 X 10-3 µg cm-2, 0.073 µg mL-1 and 0.222 µg mL-1 respectively. The optimum reaction conditions and other analytical parameters were evaluated. The statistical evaluation of the method was examined by determining intra-day and inter-day precision. The proposed method has been successfully applied for the determination of nevirapine in pharmaceutical formulations.

A simple spectrophotometric method for the determination of cefotaxime, ceftriaxone, cefadroxil and cephalexin with variamine blue is presented. The determination is based on the hydrolysis of β-lactam ring of cephalosporins with sodium hydroxide which subsequently reacts with iodate to liberate iodine in acidic medium. The liberated iodine oxidizes variamine blue to violet colored species of maximum absorption at 556 nm. The absorbance is measured within the pH range of 4.0-4.2. Beer's law is obeyed in the range of 0.5-5.8 µg mL-1, 0.2-7.0 µg mL-1, 0.2-5.0 µg mL-1 and 0.5-8.5 µg mL-1 for cefotaxime, ceftriaxone, cefadroxil and cephalexin respectively. The analytical parameters were optimized and the method is successfully applied for the determination of cefotaxime, ceftriaxone, cefadroxil and cephalexin in pharmaceuticals.

Um método espectrofotométrico simples, rápido e sensível foi desenvolvido para a determinação de hipoclorito usando Rodamina B. O método proposto considera a reação de hipoclorito com iodeto de potássio em meio ácido, com liberação de iodo. O iodo liberado descora a solução vermelho-rosada de Rodamina B que pode ser medida em 553 nm. Este decréscimo na absorbância é diretamente proporcional à concentração de hipoclorito e obedece a lei de Beer no intervalo de 0,1 a 4,0 mg µL-1 de hipoclorito. A absortividade molar, sensitividade de Sandell, limite de detecção e de quantificação do método são 2,57×10(5) L mol-1 cm-1, 2,01×10-3 µg cm-2, 0,070 µg mL-1 e 0,212 µg mL-1, respectivamente. As condições ótimas de reação e outros parâmetros analíticos foram avaliados. O efeito dos íons interferentes na determinação é descrito. O método proposto foi aplicado com sucesso na determinação de hipoclorito em várias amostras de água de torneira, água mineral e leite.

A simple, rapid and sensitive spectrophotometric method has been developed for the determination of hypochlorite using Rhodamine B. The proposed method reports the reaction of hypochlorite with potassium iodide in an acid medium with iodine liberation. The liberated iodine bleaches the pinkish red color of the Rhodamine B and can be measured at 553 nm. This decrease in absorbance is directly proportional to the hypochlorite concentration and obeys Beer's law in the range of 0.1 - 4.0 µg mL-1of hypochlorite. The molar absorptivity, Sandell's sensitivity, detection limit and quantitation limit of the method were found to be 2.57×10(5) L mol-1 cm-¹, 2.01×10-3 µg cm-2, 0.070 µg mL-1 and 0.212 µg mL-1 respectively. The optimum reaction conditions and other analytical parameters were evaluated. The effect of interfering ions on the determination is described. The proposed method has been successfully applied to the determination of the hypochlorite in various samples of tap water, natural water and milk.

Foi desenvolvido um método simples, rápido e sensível para a determinação de periodato em amostras de água de rio e em solução. O método é baseado na reação do periodato com iodeto em meio ácido, com liberação de iodo. O iodo liberado diminui a intensidade da cor violeta do azure B, medida em 644 nm. O decaimento da absorbância é diretamente proporcional a concentração de periodato e obedece a lei de Beer na faixa de 0,2 - 5,5 µg mL-1. A absortividade molar, a sensibilidade de Sandell e os limites de detecção e de quantificação encontrados foram 1,09x10(5) L mol-1 cm-1, 1,75x10-3 µg cm-2, 0,07 µg mL-1 and 0,20 µg mL-1, respectivamente. As condições ótimas de reação e os parâmetros analíticos foram avaliados. O efeito de íons interferentes é descrito. O método proposto foi aplicado com sucesso na determinação de periodato em amostras de águas de rio e em solução.

A simple, rapid and sensitive spectrophotometric method has been developed for the determination of periodate in solution and river water samples. The method is based on the reaction of periodate with iodide in an acid medium to liberate iodine. This liberated iodine bleaches the violet color of the azure B and is measured at 644 nm. This decrease in absorbance is directly proportional to the periodate concentration and obeys Beer's law in the range of 0.2 - 5.5 µg mL-1. The molar absorptivity, Sandell's sensitivity, detection limit and quantitation limit of the method were found to be 1.09 X 10(5) L mol-1 cm-1 , 1.75 X10-3 µg cm-2, 0.07 µg mL-1 and 0.20 µg mL-1 respectively. The optimum reaction conditions and other analytical parameters were evaluated. The effect of interfering ions on the determination is described. The proposed method has been successfully applied to the determination of periodate in solutions and river water samples.

Um método espectrofotométrico simples, rápido e sensível foi desenvolvido para a determinação traço de cromo usando azul de Variamina como reagente cromogenico. O método proposto consiste na reação de cromo(VI) com iodeto de potássio, em meio ácido, liberando iodeto que então oxida o azul de Variamina formando um composto de cor violeta com o máximo de absorção em 556 nm. A lei de Beer é obedecida na faixa de 2-12 mig mL-1 para Cr(VI). A absortividade molar, a sensibilidade de Sandell, o limite de detecção e de quantificação do método foram encontrados como sendo 0,911×10(4) L mol-1 cm-1, 1,14×10-2 mig cm-2, 0,02 mig mL-1 e 0,07 mig mL-1 respectivamente. As condições analíticas e ótimas da reação foram avaliadas. O efeito de íons interferentes na determinação é descrita. O cromo(III) pode ser determinado depois da oxidação à cromo (VI), com brometo em solução aquosa alcalina. O método desenvolvido foi aplicado com sucesso na análise de cromo em ligas de aço, efluentes industrias, águas naturais e amostras de solo.

A simple, rapid and sensitive spectrophotometric method has been developed for the determination of trace amounts of chromium using variamine blue as a chromogenic reagent. The proposed method is based on the reaction of chromium(VI) with potassium iodide in acid medium to liberate iodine, which oxidizes variamine blue to form a violet colored species having an absorption maximum 556 nm. Beer's law is obeyed in the range 2-12 mug mL-1 of Cr(VI). The molar absorptivity, Sandell's sensitivity, detection limit and quantitation limit of the method were found to be 0.911×10(4) L mol-1 cm-1, 1.14×10-2 mug cm-2, 0.02 mug mL-1 and 0.07 mug mL-1 respectively. The optimum reaction conditions and other analytical conditions were evaluated. The effect of interfering ions on the determination is described. The chromium(III) can be determined after it is oxidized with bromine water in alkaline medium to chromium(VI). The developed method has been successfully applied to the analysis of the chromium in alloy steels, industrial effluents, natural water samples and soil samples.