No abstract

Three simple and sensitive spectrophotometric methods are proposed for the determination of atenolol (ATN) in bulk drug and tablets. The methods are based on the bromination of ATN by the bromine generatedin situby the action of the acid on the bromate–bromide mixture followed by the determination of unreacted bromine by reacting with a fixed amount of either meta-cresol purple (MCP) and measuring the absorbance at 540 nm (method A) and 445 nm (method B) or erioglaucine (EGC) and measuring the absorbance at 630 nm (method C). Beer's law is valid within the concentration ranges of 1.0–20.0, 2.0–40.0 and 1.0–8.0 μg/mL for method A, method B and method C, respectively. The calculated molar absorptivities were found to be 1.20×104, 4.51×103and3.46×104  L/mol⋅cmfor method A, method B and method C, respectively. Sandell’s sensitivity values, correlation coefficients, limits of detection and quantification are also reported. Recovery results were statistically compared with those of a reference method by applying Student’st- andF-test. The novelty of the present study is the measurement of two different colors using MCP, that is, red-pink color of MCP in acid medium at 540 nm and yellowish-orange color of brominated MCP at 445 nm.

No abstract

One titrimetric and two spectrophotometric methods which are simple, sensitive, and economic are described for the determination of sumatriptan succinate (STS) in bulk drug and in tablet dosage form using N-bromosuccinimide (NBS) as a brominating agent. In titrimetry, aqueous solution of STS is treated with a measured excess of NBS in acetic acid medium, and after the bromination of STS is judged to be complete, the unreacted NBS is determined iodometrically (method A). Spectrophotometric methods entail addition of a known excess of NBS in acid medium followed by the determination of residual NBS by its reaction with excess iodide, and the liberated iodine (I3 −) is either measured at 370 nm (method B) or liberated iodine is reacted with starch followed by the measurement of the blue colored starch-iodine complex at 570 nm (method C). Titrimetric method is applicable over range 1.0–10.0 mg STS (method A), and the reaction stoichiometry is found to be 1 : 3 (STS : NBS). The spectrophotometric methods obey Beer's law for concentration range 0.6–15.0 μg mL−1 (method B) and 0.2–4.0 μg mL−1 (method C). The calculated apparent molar absorptivity values were found to be 2.10 × 104 and 7.44 × 104 L mol−1 cm−1, for method B and method C, respectively.

Two new simple and sensitive extraction-free spectrophotometric methods have been established for the determination of ofloxacin (OFX). The methods are based on ion-pair complex formation reaction between OFX and acidic sulphonphthalein dyes, bromocresol purple (method A), and bromocresol green (method B) in dichloromethane. The experimental variables such as reaction medium, reaction time, and reagent concentration have been carefully optimized to achieve the highest sensitivity. Both dyes react spontaneously with OFX to give yellow-colored complexes. Beer's law is obeyed over the concentration ranges of 1.0-16 g ml . The limits of detection (LOD) and quantification (LOQ) are also reported. A Job's plot of the absorbance versus the molar ratio of OFX to each of dyes under consideration indicated (1 : 1) ratio and the conditional stability constant ( ) of the complexes have been calculated. The proposed methods were applied successfully to the determination of OFX in tablets with good accuracy and precision and without interference from common additives. The results obtained by the proposed methods were compared favorably with those of the reference method.

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....

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 ...

An accurate and precise spectrophotometric method is presented for the determination of zolmitriptan (ZMT) based on the formation of a red color product with vanillin in presence of concentrated H 2 SO 4 , with the chromogen being measured at 580 nm. The reaction proceeds quantitatively at room temperature in 10 min. The calibration curve is linear over the range 5.0-90.0 g mL and described by the regression equation = (−)0.0101+0.0117 with a regression coefficient ( ) of 0.9994 ( = 7). The calculated molar absorptivity and Sandell sensitivity values are 3.3 × 10 3 L mol −1 cm −1 and 0.0872 g cm −2 , respectively. The limits of detection (LOD) and quantification (LOQ) calculated as per ICH guidelines are 1.26 and 3.81 g mL −1 , respectively. The within-day accuracy expressed as relative error was better than 1.78% with precision (RSD) ranging from 0.83 to 1.45%. The between-day accuracy ranged from 1.21 to 1.84% with a precision less than 1.66%. The method was successfully applied to the analysis of one brand of tablet containing zolmitriptan. The results obtained were in agreement with those obtained by published reference method. The accuracy was also checked by placebo blank and synthetic mixture analyses besides recovery study via standard addition procedure.