Two simple, rapid and inexpensive spectrophotometric methods are described for the determination of albendazole (ALB) in bulk drug and in tablets. The methods are based on charge-transfer (CT) complexation reaction involving ALB as n-donor and iodine as σ-acceptor (method A) in dichloromethane or picric acid (PA) as π-acceptor (method B) in chloroform. The absorbance of CT complexes was measured at 380 nm for method A, and 415 nm for method B. The optimization of the experimental conditions is described. Under optimum conditions, Beer's law obeyed over the concentration ranges 8.0-240 and 2.4-42 μg mL-1 for method A and method B, respectively. The apparent molar absorptivity of CT complexes at the respective λmax are calculated to be 1.17×103 and 5.22×103 L mol-1cm-1 respectively, and the corresponding Sandell sensitivity values are 0.2273 and 0.0509 ng cm-2. The limits of detection (LOD) and quantification (LOQ) are calculated to be (0.69 and 2.08), and (0.10 and 0.30) μg mL-1 with method A, and method B, respectively. The intra-day and inter-day accuracy expressed as % RE and precision expressed as % RSD were less than 3%. The methods were applied to the determination of ALB in tablets.

Chloroquine Phosphate (CQP) is an antimalarial agent extensively used in the treatment of malaria. Two spectrophotometric methods, which are rapid, simple, selective and sensitive, are presented for the determination of CQP in bulk and dosage forms using two sulphonphthalein dyes: Bromocresol Green (BCG method) and Bromocresol Purple (BCP method). The methods are based on the formation of chloroform-soluble ion-pairs, when CQP is reacted with either dye, suitable for measurement at 420 nm in both the methods. The effects of reaction time, dye concentration and reaction medium were carefully studied and optimized. Under the optimum reaction conditions, Beer's law is obeyed overconcentration ranges 1-20 and 0.5-12 µg mL -1 CQP (base) for BCG method and BCP method respectively, with corresponding molar absorptivity values of 1.79 × 10 4 and 3.09 × 10 4 L mol -1 cm -1 . The calculated limits of detection (LOD) and quantification (LOQ) are 0.27 and 0.82 µg mL -1 (BCG method); 0.15 and 0.46 µg mL -1 (BCP method). Intra-day and inter-day %RSD values were ≤1.56% and ≤1.83% whereas the respective %RE values were better than 2%. Robustness of the methods was determined by performing analysis with slightly altered optimum conditions while ruggedness was tested by inter-personnel as well as inter-equipment variations; the %RSD values were within the accepted limits in both instances. Method selectivity was as ascertained by placebo blank and synthetic mixture analysis with no detectable interference from co-formulated substances in the assays. The methods were applied to the determination of CQP in tablets, suspension and injections with satisfactory results. Accuracy was also confirmed by recovery test via standard-addition procedure.

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 9.56·10 3 l·mol -1 · cm -1 and 0.031 μg/cm 2 , respectively. The limits of detection and quantifi cation 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.Introduction. Mebendazole (MBD), chemically known as methyl-5-benzoyl-2-benzimidazole carbamate, is an anthelmintic and antiinfestive used against hookworm, pinworm, roundworm, tapeworm, threadworm, and mixed infestations. It is available in tablet and suspension form. Depending on the type of worm to be treated, the dosage varies in adults and children [1]. MBD in bulk drug and tablet dosage form are both included in the USP 23 monographs [2], while the oral suspension is listed in the second supplement [3] of USP 23. The drug is also offi cial in Indian pharmacopoeia [4] and European pharmacopoeia [5], and the latter describes a potentiometric titration of 250 mg of MBD in formic acid-acetic acid and methyl ethyl ketone mixture with acetic HClO 4 . Different analytical methods are found in the literature for the assay of MBD in pharmaceuticals and include titrimetry [6-9], UV-spectrophotometry [9-12], phosphorimetry [13], proton nuclear magnetic resonance spectrometry [14], fl uorimetry [15,16], thermogravimetry [17,18], membrane-sensor based potentiometry [19], DC polarography [20], differential pulse polarography [21,22], high-performance liquid chromatography [23][24][25], and high-performance thin layer chromatography [26,27]. Most of these methods are complicated and need sophisticated instruments.The literature survey reveals several visible spectrophotometric methods. When MBD was hydrolyzed with KOH, a yellow colored substance (2-amino-5-benzoylbenzimidazole) was formed, which was measured at 420 nm [28]. MBD on treatment with hydroxylamine, dicyclohexylcarbodiimide, and FeCl 3 produced a red colored product measurable at 520 nm that served as a basis for an assay [29]. Kar [30] has described a method based on a 2:1 complex formed by MBD with potassium bismuth(III) iodide....

A rapid, simple, cost effective, accurate and precise direct titrmetric method for the determina tion of isoniazid (INH) in pharmaceutical preparations has been developed and validated. The method is based on the titration of INH with 0.02 M acetous perchloric acid in glacial acetic acid using crystal violet as indicator. The method is applicable over the range of 1.5-15.0 mg INH. The validation of the method yielded good results that included precision (RSD < 3% for intra and inter day precision), and accuracy (relative error ≤2.6%). It was also found that the excipients in the commercial tablet preparation did not interfere with the assay and the results were comparable with the official method.

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 6.48×10 3 L mol -1 cm -1 and 0.0604 µg cm -2 , respectively, for method B, and their respective values for method C are 9.96×10 3 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.Uniterms: Diethylcarbamazine citrate/determination. Titrimetry/quantitative analysis. Spectrophotometry/ quantitative analysis. Pharmaceutical formulations/analysis. 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 6.48×10 3 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 9.96×10 3 L ...

Two spectrophotometric methods are described for the determination of isoniazid (INH) in pharmaceuticals. In the first method (FCR method), INH is reacted with Folin-Ciocalteu reagent in Na2CO3 medium and the resulting blue colored chromogen measured at 760 nm. Iron(II), formed as a result of reaction between INH and iron(III), is made to react with ferricyanide, and the resulting Prussian blue is measured at 760 nm, basing the second method (FFC method). The conditions for better performance are optimized. Beer’s law is obeyed in the concentration ranges 0.5–10 and 0.2–3.0 μg mL−1 for FCR method and FFC methods, respectively, with corresponding molar absorptivity values of 1.12×104 and 4.55×104 L mol−1 cm−1. The methods are validated for accuracy, precision, LOD, LOQ, robustness, and ruggedness as per the current ICH guidelines. The validated methods were successfully applied to quantify INH in its commercial formulation with satisfactory results; hence the methods are suitable for isoniazid determination in bulk drugs and pharmaceuticals.

No abstract

Albendazole (ALB) is a potent benzimidazole anthelmintic used in the treatment of human intestinal helmintiasis as well as of hytatid cysts and neurocysticercosis. Two rapid, simple, sensitive, and selective spectrophotometric methods are presented for the determination of ALB in pharmaceuticals. The methods are based on the formation of dichloromethane soluble 1 : 1 ion-pair complexes (ALB : dye) formed between ALB and sulfonphthalein dyes, bromophenol blue BPB, (method A) and bromothymol blue BTB, (method B). The complexes formed were measured directly (without extraction) at 445 nm (method A) and 460 nm (method B). The experimental conditions were optimized and the systems obey Beer’s law for 1.5–21.0 and 2.0–32.0 μg mL−1 ALB for method A and method B respectively. The molar absorptivity and Sandell's sensitivity were calculated to be  L mol−1 cm−1 and 0.0209 ng cm−2, and  L mol−1 cm−1 and 0.0350 ng cm−2 using BPB and BTB, respectively. The limits of detection and quantification were calculated to be 0.01 and 0.03, and 0.16, and 0.49 μg mL−1 using BPB and BTB, respectively. The relative standard values for intra-day and inter-day precision were less than 3%, and the accuracy was better than 3% for both methods.