Titrimetric and spectrophotometric assay of diethylcarbamazine citrate in formulations using iodate and iodide mixture as reagents

One titrimetric and two spectrophotometric methods are proposed for the determination of diethylcarbamazine citrate (DEC) in bulk drug and in formulations using potassium iodate and potassium iodide as reagent. The methods employ the well-known analytical reaction between iodate and iodide in the presence of acid. In titrimetry (method A), the drug was treated with a measured excess of thiosulfate in the presence of unmeasured excess of iodate-iodide mixture and after a standing time of 10 min, the surplus thiosulfate was determined by back titration with iodine towards starch end point. Titrimetric assay is based on a 1:3 reaction stoichiometry between DEC and iodine and the method is applicable over 2.0-10.0 mg range. The liberated iodine is measured spectrophotometrically at 370 nm (method B) or the iodine-starch complex measured at 570 nm (method C). In both methods, the absorbance is found to be linearly dependent on the concentration of iodine, which in turn is related to DEC concentration. The calibration curves are linear over 2.5-50 and 2.5-30 µg mL-1 DEC for method B and method C, respectively. The calculated molar absorptivity and Sandell sensitivity values were 6.48×103 L mol-1 cm-1 and 0.0604 µg cm-2, respectively, for method B, and their respective values for method C are 9.96×103 L mol-1 cm-1 and 0.0393 µg cm-2. The intra-day and inter-day accuracy and precision studies were carried out according to the ICH guidelines. The methods were successfully applied to the analysis of DEC formulations.Propõem-se titulação e dois métodos espectrofotométricos para a determinação de citrato de dietilcarbamazina (DEC) a granel e em suas formulações, usando iodato de potássio e iodeto de potássio como reagente. Os métodos utilizam a reação analítica conhecida entre iodato e iodeto, na presença de ácido. Na titulometria (Método A), o fármaco foi tratado com excesso medido de tiossulfato, na presença de excesso não medido de mistura iodato-iodeto e, depois de um tempo de repouso de 10 min, o excesso de tiossulfato foi determinado por titulação de retorno com iodo até o ponto final com amido. A titulação é baseada em reação com estequiometria 1:3 entre DEC e iodo e o método é aplicável na faixa de 2.0-10.0 mg. O iodo liberado é medido espectrofotometricamente a 370 nm (método B) ou o complexo de iodo-amido medido a 570 nm (método C). Em ambos os métodos, a absorvância é considerada linearmente dependente da concentração de iodo, a qual, por sua vez, está relacionada à concentração de DEC. As curvas de calibração são lineares para concentrações de DEC de 2.5-50 e 2.5-30 mg mL- 1 para o método B e para o método C, respectivamente. A absortividade molar calculada e os valores de sensibilidade Sandel foram 6.48×103 L mol-1 cm- 1 e 0.0604 ug cm-2, respectivamente, para o método B, e os seus respectivos valores para o método C são 9.96×103 L mol-1 cm-1 e 0.0393 mg cm-2. Os estudos de exatidão e precisão intra-dia e inter-dia foram realizados de acordo com as diretrizes da ICH. Os métodos foram aplicados com sucesso na análise de formulações de DEC

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Development and validation of stability-indicating uv-spectrophotometric methods for the determination of flunarazine dihydrochloride in dosage form

Two sensitive, precise and cost-effective UV-spectrophotometric methods are described for the determination of flunarazine dihydrchloride (FNH) in bulk drug and tablets. The proposed methods are based on the measurement of the absorbance of FNH either in 0.1 M HCl (method A) or in acetonitrile (method B) at 253 nm. As per the International Conference on Harmonization (ICH) guidelines, the methods were validated for linearity, accuracy, precision, limits of detection (LOD) and quantification (LOQ) and robustness and ruggedness. Beers law is obeyed over the concentration ranges of 2.5-30.0 µg mL-1 in method A and 1.0-20.0 µg mL-1 in method B. The calculated molar absorptivity values are 2.12104 and 2.47104 L mol-1 cm-1 for method A and method B, respectively. The proposed methods were applied successfully to the determination of FNH in tablets with good accuracy and precision without any detectable interference from common excipients. The accuracy of the proposed methods was further assessed by the recovery studies via a standard addition method. In addition, forced degradation of FNH was conducted in accordance with the ICH guidelines. Acidic and basic hydrolysis, thermal stress, peroxide and photolytic degradation were used to assess the degradation behavior of the drug. Substantial degradation was observed during oxidative degradation and no degradation was observed under other stress conditions

Titrimetric assay of zolmitriptan in non-aqueous medium

Based on the nitrogenous base or tertiary amine moiety in zolmitriptan (ZMT), an anti-migraine drug, two highly accurate and selective titrimetric methods are proposed for the determination of ZMT in bulk drug and pharmaceuticals. In these methods, the drug dissolved in glacial acetic acid, was titrated with acetous perchloric acid and end point determined either visually by using crystal violet indicator (method A) or potentiometrically by using combined glass-SCE electrode (method B). Both the methods are applicable over the concentration range of 1.0-10.0 mg of ZMT. Calculations are based on 1:1 molar ratio i.e., ZMT: HClO4, owing to the presence of one tertiary nitrogen atom. The procedures were applied to determine ZMT in its tablets and the results were found to be in good agreement with those obtained by the reference method. Associated pharmaceutical materials did not interfere. The precision results, expressed by inter-day and intra-day relative standard deviation values, were satisfactory (= 1.77). Accuracy was satisfactory as well. The accuracy and reliability of the methods were further ascertained by recovery studies via standard addition technique with percent recoveries in the range 98.00 - 102.0 with standard deviation of less than 0.15

Extractive spectrophotometric methods for the determination of zolmitriptan in bulk drug and pharmaceutical formulation using bromocresol green

Considering the basic property of zolmitriptan (ZMT) to generate ion-pairs with sulfonephthalein dyes two methods have been developed for its assay in bulk drug and dosage form. The fi rst method (method A) is based on the formation of a colored ion-pair complex (1:1 drug:dye) of ZMT with bromocresol green (BCG) at pH 4.20 ± 0.01 and extraction of the complex into chloroform followed by measurement of the yellow ion-pair complex at 435 nm. In the second method (method B), the drug-dye ion-pair complex was treated with ethanolic potassium hydroxide in ethanolic medium and the resulting base form of the dye was measured at 630 nm. Beer’s law was obeyed in the concentration range of 0.8–18.0 and 0.08–1.4 μg/ml for method A and B, respectively, and the corresponding molar absorptivity values were 1.50⋅104 and 1.52⋅105 l/(mol⋅cm). The Sandell sensitivity values were 0.0191 and 0.0019 μg/cm2 for method A and method B, respectively. The stoichiometry of the ion-pair complex formed between the drug and dye (1:1) was determined by Job’s continuous variation method and the stability constant of the complex was also calculated. The proposed method was successfully extended to dosage form (tablets)

Extraction-free ion-pair methods for the assay of trifluoperazine dihydrochloride in bulk drug, tablets, and spiked human urine using three sulfonphthalein dyes

Three simple and sensitive extraction-free spectrophotometric methods are described for the determination of trifl uoperazine dihydrochloride (TFH). The methods are based on ion pair complex formation between the nitrogenous compound trifl uoperazine (TFP) converted from trifl uoperazine dihydrochloride and sulfonphthalein dyes, namely, bromocresol green (BCG), bromothymol blue (BTB), and bromophenol blue (BPB) in dichloromethane medium in which all the above experimental variables were circumvented. The colored products are measured at 425 nm in the BCG method, 415 nm in the BTB method, and 420 nm in the BPB method. The stoichiometry of the ion-pair complexes formed between the drug and dye (1:1) was determined by Job’s continuous variations method, and the stability constants of the complexes were also calculated. These methods quantify TFP over the concentration ranges of 1.25–20.0 μg/ml in the BCG method, 1.5–21.0 μg/ml in the BTB method, and 1.5–18.0 μg/ml in the BPB method. The molar absorptivity (l•mol–1•cm –1) and Sandell sensitivity (ng/cm2 ) were calculated to be 2.06•104 and 0.0197; 1.82•104 and 0.0224; and 2.22•104 and 0.0183 for the BCG, BTB, and BPB methods, respectively. The methods were successfully applied to the determination of TFP in pure drug, pharmaceuticals, and in spiked human urine with good accuracy and precision

Spectrophotometric assay of mebendazole in dosage forms using sodium hypochlorite

A simple, selective and sensitive spectrophotometric method is described for the determination of mebendazole (MBD) in bulk drug and dosage forms. The method is based on the reaction of MBD with hypochlorite in the presence of sodium bicarbonate to form the chloro derivative of MBD, followed by the destruction of the excess hypochlorite by nitrite ion. The color was formed by the oxidation of iodide with the chloro derivative of MBD to iodine in the presence of starch and forming the blue colored product, which was measured at 570 nm. The optimum conditions that affect the reaction were ascertained and, under these conditions, a linear relationship was obtained in the concentration range of 1.25-25.0·g/ml MBD. The calculated molar absorptivity and Sandell sensitivity values are 9.56·103 l·mol-1·cm-1 and 0.031 μg/cm2, respectively. The limits of detection and quantification are 0.11 and 0.33 μg/ml, respectively. The proposed method was applied successfully to the determination of MBD in bulk drug and dosage forms, and no interference was observed from excipients present in the dosage forms. The reliability of the proposed method was further checked by parallel determination by the reference method and also by recovery studies