Bromatometric assay of simvastatin in pharmaceuticals

Titrimetric and spectrophotometric methods are proposed for the determination of simvastatin (SMT) in bulk drug and in tablets. The methods employ bromate-bromide mixture in acid medium as the brominating agent and iron (III) and thiocyanate as auxiliary regents. In titrimetry, SMT is treated with a measured excess of bromate-bromide mixture in HCl medium, and after a definite time, the unreacted bromine is determined iodometrically. In spectrophotometric method, the residual bromine is reduced by iron (II) and the resulting iron (III) is complexed with thiocyanate, and the absorbance is measured at 470 nm. In both methods, the amount of in situ generated bromine corresponds to the SMT content. The experimental conditions are optimized. Titrimetry is applicable over 1-10 mg range and the calculations are based on the molar ratio of 1: 0.666 (SMT: KBrO3). In spectrophotometric method, Beer's law is obeyed over the concentration range 1-10 A mu g/mL. The calculated molar absorptivity is 3.02 x 10(4) L/mol cm and the corresponding sandel sensitivity being 0.0081 A mu g/cm(2). The limit of detection (LOD) and limit of quantification (LOQ) are calculated to be 0.10 and 0.31 A mu g/mL, respectively. The intra-day and inter-day precision calculated from the analysis of pure SMT were less than 2 and 2.7%, respectively. The methods were satisfactorily applied to the determination of SMT in tablets, and no interferences from common tablet excipients were observed. The validity of the methods was further ascertained by parallel assay by an established technique and by recovery studies

Use of a diazocoupling reaction for sensitive and selective spectrophotometeric determination of furosemide in spiked human urine and pharmaceuticals

Two simple, sensitive, and selective spectrophotometric methods for the determination of 5-(aminosulfonyl)-4-chloro-2-((2-furanylmethyl)amino)benzoic acid (furosemide, FUR) are described. The methods are based on acid hydrolysis of FUR to free primary aromatic amine and diazotization followed by coupling with N-1-napthylethylene diamine (NEDA) (method A) or 4,5-dihydroxynaphthalene-2,7-disulfonic acid (chromotropic acid, CTA) (method B). The colored reaction product can be measured spectrophotometrically at 520 nm (method A) or 500 nm (method B). Beer's law is obeyed over the ranges of 1.75-21.0 mu g mL(-1) and 2.5-30.0 mu g mL(-1), for method A and method B, respectively. Apparent molar absorptivities and Sandell's sensitivities (in L mol(-1) cm(-1) and mu g cm(-2) per 0.001 absorbance unit, respectively) were 1.34 x 10(4) and 0.0253 using NEDA as the coupling agent, and 8.5 x 10(3) and 0.0389 using CTA for the same purpose. Analysis of solutions containing seven different concentrations of FUR gave a correlation coefficient of 0.9979 using NEDA and 0.9984 using CTA, while the slope and the correlation coefficient of the regression equation were calculated. The reaction stoichiometry in both methods was evaluated by the limiting logarithmic method and was found to be 1: 1 (diazotized FUR: NEDA or diazotized FUR: CTA). The methods were successfully applied to the determination of FUR in spiked human urine and in pharmaceutical formulations. The recovery of FUR from spiked urine was satisfactory resulting in the values of (109.4 +/- 4.37) % using NEDA and (113.0 +/- 4.74) % using CTA. Results of the analysis of pharmaceuticals demonstrated that the proposed procedures are at least as accurate and precise as the official method while a statistical analysis indicated that there was no significant difference between the results obtained by the proposed methods and those of the official method

Investigation and optimisation of the use of spectrophotometry for the assay of simvastatin with in situ bromine and three dyes as reagents

Three simple and sensitive spectrophotometric methods are described for the determination of simvastatin (SMT) in bulk drug and in tablets using bromate–bromide as the bromination reagent in acid medium, and three dyes as subsidiary reagents. All the three methods are based on the bromination of SMT by a known excess of in situ generated bromine followed by determination of unreacted bromine by reacting with a fixed amount of methyl orange (method A), indigo carmine (method B) or meta–cresol purple (method C) and measuring the absorbance at 510, 610 or 540 nm. In all the methods, the amount of bromine reacted corresponds to the amount of SMT. The experimental conditions for the assay have been optimized. In all the methods, the absorbance is found to increase linearly with the concentration of SMT at the respective wavelengths. Beer's law is obeyed over the ranges 0.5–3.0, 2.5–15.0 and 2.5–15.0 |ig mL–1 for method A, method B and method C, respectively and the respective molar absorptivity values are 1.0 ×10 5, 2.3 ×104 and 2.1 ×104 l mol–1 cm–1. The limits of detection and quantification are reported for all the methods. The performance of the methods was validated according to the present ICH guidelines. The methods gave similar results in terms of precision and accuracy. The repeatability and intermediate precision, expressed by the RSD was better than 2%. The accuracy of the methods expressed as relative error was satisfactory. The proposed methods were applied to the analysis of tablet form of SMT and the results tallied well with the label claim. No interference was observed from the concomitant substances normally added to tablets. The results were statistically compared with those of a literature method by applying the Student's t–test and F–test. The accuracy and validity of the methods were further ascertained by performing recovery studies via spike method and standard–addition method

The development and validation of visible spectrophotometric methods for simvastatin determination in pure and the tablet dosage forms

Two simple and sensitive spectrophotometric methods have been developed for the determination of simvastatin (SMT) in pure form and in tablets using insitu generated bromine, and p-phenylenediamine (PPDA) or o-dianisidine (ODA) as reagents. The methods are based on the bromination of SMT by a measured excess of in situ bromine in acid medium followed by the determination of unreacted bromine by reacting with PPDA and measuring the resulting red color at 510 nm (method A) or reacting with ODA and measuring the absorbance at 470 nm (method B). The conditions for the assay have been optimized. Beer's law is obeyed over the concentration ranges 20-120 and 2-12 µg/ml for method A and method B, respectively. The calculated molar absorbtivities are 2.24×103 and 1.91×104 dm3 mol-1 cm-1 for the method A and the method B, respectively; 0.1868 and 0.0115 µg/cm2 being the corresponding Sandell sensitivities. The LOD and LOQ for method A are found to be 2.96 and 8.97 µg/ml, and the respective values for method B are 0.14 and 0.42 µg/ml. The intra-day and inter-day precision and accuracies were checked. The assay precision was less than 5 % CV and the accuracy was 97.38-103.4 %. The methods were used for the determination of SMT in tablets. No interference from the excipients added to tablets was found. The accuracy and validity of the methods were further ascertained by recovery studies via the standard addition technique

Spectrophotometric determination of isoxsuprine hydrochloride as base form in pharmaceutical formulation through charge transfer complexation

Two simple and selective spectrophotometric methods are described for the determination of isoxsuprine hydrochloride (ISX·HCl) as base form in bulk drug and in injections and tablets. The methods are based on the molecular charge-transfer complexation of ISX base (ISX) with either p-chloranilic acid (PCA) or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The intense colored radical anions formed on dissociation, are quantitated at 520 nm (PCA method) or 600 nm (DDQ method). The optimum assay conditions were optimized. Beer's law is obeyed in the concentration ranges 5.28 × 10–5 to 42.2 × 10–5 mol dm–3 in PCA method and 0.79 × 10–5 to 10.6 × 10–5 mol dm–3 in DDQ method, with respective molar absorptivity values of 1.32 × 103 and 6.55 × 103 dm3 mol–1 cm–1. The reaction stoichiometry in both methods was evaluated by either Job’s method or limiting logarithmic method and was found to be 1:1 (ISX: PCA, ISX: DDQ). Developed methods were validated according to ICH guidelines and found to be accurate and precis

Determination of raloxifene hydrochloride in human urine by LC-MS-MS

A sensitive and selective liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method was developed to determine raloxifene hydrochloride (RLX) in human urine. After a solid-phase extraction with SPE cartridge, the urine sample was analyzed on a C18 column (Symmetry 3.5μm; 50 mm4.6 mm i.d) interfaced with a triple quadruple tandem mass spectrometer. A positive electrospray ionization was employed as the ionization source. The mobile phase consisted of ammonium acetate (pH 4.0)–acetonitrile (60:40, v/v).The method was linear over a concentration range of 20–1000 ng mL-1. The lower limit of quantitation was 20 ng mL-1. The intra-day and inter-day relative standard deviation across three validation runs over the entire concentration range was <10.5%. The accuracy determined at three concentrations (50, 500 and 850 ng mL-1 RLX) was within ±0.84% in terms of relative errors

Spectrophotometric Determination of isoxsuprine yydrochloride as base form in pharmaceutical formulation through charge transfer complexation

Two simple and selective spectrophotometric methods are described for the determination of isoxsuprine hydrochloride (ISX.HCl) as base form in bulk drug and in injections and tablets. The methods are based on the molecular charge-transfer complexation of ISX base (ISX) with either p-chloranilic acid (PCA) or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The intense colored radical anions formed on dissociation, are quantitated at 520 nm (PCA method) or 600 nm (DDQ method). The optimum assay conditions were optimized. Beer's law is obeyed in the concentration ranges 5.28 x 10(-5) to 42.2 x 10(-5) mol dm(-3) in PCA method and 0.79 x 10(-5) to 10.6 x 10(-5) mol dm(-3) in DDQ method, with respective molar absorptivity values of 1.32 x 10(3) and 6.55 x 10(3) dm(3) mol(-1) cm(-1). The reaction stoichiometry in both methods was evaluated by either Job's method or limiting logarithmic method and was found to be I:I (ISX: PCA, ISX: DDQ). Developed methods were validated according to ICH guidelines and found to be accurate and precise

Non-aqueous and two-phase titrimetric assay of isoxsuprine hydrochloride in pharmaceuticals

Based on the nitrogenous base or quaternary ammonium moiety in isoxsuprine hydrochloride (ISX), two highly accurate and selective titrimetric methods are proposed f or the determination of ISX in spiked human urine, injection and tablets. Non-aqueous titration (Method A) involves removal of protonated amine using mercuric acetate for enhanced basic nitrogen prior to titration with perchloric acid in an acetic acid medium using crystal violet as indicator. Two-phase titration (Method B) is based on ion association complex formation between sodium lauryl sulphate (SLS) and protonated amine of ISX at pH 2.5 in aqueous phase, end point being detected by change in dimethyl yellow color in chloroform layer. The methods are applicable over the concentration range 2.0--20.0 mg and 1.0--10.0 mg for method A and method B, respectively. Calculations are based on 1: 1 molar ratio, i.e., JSX: HClO4 for method A and ISX: SLS for method B, owing to the presence of one nitrogen atom. Method A is applicable to the determination of ISX in tablets whereas method B is applicable to spiked human urine, injection and tablets. The methods are validated statistically by comparing the results with those of the reference method by applying the Student's t-test and F-test. The accuracy was further ascertained by recovery studies via standard addition technique

Bromatomatric assay of gatifloxacin in pharmaceuticals

Three new, simple, and cost-effective visible spectrophotometric methods are proposed for determination of gatifloxacin (GTF) using bromate-bromide mixture, and three dyes, methyl orange, indigocarmine and thymol blue, as reagents.The methods engross the addition of a known excess of bromate-bromide mixture to GTF in hydrochloric acid medium followed by determination of residual bromine by reacting with a fixed amount of either methyl orange andmeasuring the absorbance at 520 nm (method A) or indigo carmine and measuring the absorbance at 610 nm (method B) or thymol blue and measuring the absorbance at 550 nm (method C). In all the methods, the amount of brominereacted corresponds to the amount of GTF, and the absorbance is found to increase linearly with the concentration of GTF. Under the optimum conditions, GTF could be assayed in the concentration range 0.25-1.5, 0.5-6.0, and 0.5-10μg/mL by method A, method B and method C, respectively. The apparent molar absorptivities are calculated to be 1.6x105, 4.0x104 and 3.2x104 L mol-1 cm-1 for the method A, method B and method C, respectively, and the corresponding Sandell sensitivity values are 0.0025, 0.010 and 0.012 μg/cm2. The intra-day and inter-day precision, and the accuracy of the methods were evaluated as per the current ICH guidelines. The methods were successfully applied to the determination of GTF in pharmaceutical preparations without the interference from any of the pharmaceutical adjuvants