Quantitative determination of glycine in commercial dosage forms by kinetic spectrophotometry

A kinetic method for the determination of nanogram quantities of amino acid glycine (Gly) is described. The catalytic activity of cobalt in the reaction of oxidation of purpurin (1,2,4-trihydroxyantraquinone, PP) by hydrogen peroxide in alkaline buffer solution decreases in the presence of micro quantities of glycine. Operating conditions for the successful determination of glycine were optimized and yielded a theoretical detection limit of 6.5 ng/mL. Kinetic equations are proposed for the investigated process. The interference effects of certain foreign ions and amino acids upon the reaction rate were studied in order to assess the selectivity of the method. The procedure was successfully applied to the determination of glycine in various pharmaceutical samples. The unique features of this procedure are that the determination can be carried out rapidly at room temperature and analysis time is short. The procedure is simple, inexpensive and efficient for use in the analysis of a large number of samples. The article is published in the original.     

Quantitative analysis of rabeprazole sodium in commercial dosage forms by spectrophotometry

The main aim of this work is to develop and validate two spectrophotometric methods for the quantitative analysis of rabeprazole sodium in commercial dosage forms. Method A is based on the reaction of drug with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in the presence of ammonium cerium(IV) nitrate in acetic acid medium at room temperature to form red-brown product which absorbs maximally at 470 nm. Method B utilizes the reaction of rabeprazole sodium with 1-chloro-2,4-dinitrobenzene (CDNB) in dimethyl sulfoxide (DMSO) at 45+/-1 degrees C to form yellow colored Meisenheimer complex. The colored complex has a characteristic band peaking at 420 nm. Under the optimized reaction conditions, proposed methods are validated as per ICH guidelines. Beer's law is obeyed in the concentration ranges of 14-140 and 7.5-165 microg ml(-1) with linear regression equations of A=6.041 x 10(-4)+1.07 x 10(-2)C and A=1.020 x 10(-3)+5.0 x 10(-3)C for methods A and B, respectively. The limits of detection for methods A and B are 1.38 and 0.75 microg ml(-1), respectively. Both methods have been applied successfully for the estimation of rabeprazole sodium in commercial dosage forms. The results are compared with the reference UV spectrophotometric method.     

Quantitative analysis of mebeverine in dosage forms by HPLC

Summary A simple and rapid, high performance liquid chromatographic (HPLC) procedure for determination of mebeverine in dosage forms (tablet and liquid) is described. Reversed-Phase chromatography was carried out using a mobile phase containing 0.05 M ammonium acetate buffer and acetonitrile, [(45%, v/v) pH 5.2] with UV-detection (263 nm). Replicate regression analyses of three standard plots in the concentration range of 0.5–10 mcg mL⁻¹ obtained on three different days gave a correlation coefficient >0.9995 and the coefficient of variation of the slopes <2.2%. The assay was precise within day and between days as indicated by ANOVA test. The recoveries from 10 replicate tablets of two commercial mebeverine brands and liquid were in order 99.3, 100.5 and 100.1% of the label amount and their coefficient of variations were 1.41, 0.89 and 0.69%, respectively. The limit of quantitation of mebeverine was 5 ng mL⁻¹.     

Kinetic spectrophotometric analysis of pantoprazole in commercial dosage forms.

A kinetic spectrophotometric method has been developed which is based on the oxidation of pantoprazole with Fe(III) in sulfuric acid medium. Fe(III) subsequently reduces to Fe(II), which is coupled with potassium ferricyanide to form Prussian blue. The reaction is followed spectrophotometrically by measuring the increase in absorbance with time (1-8 min) at 725 nm. The initial rate method is adopted for constructing the calibration graph, which is linear in the concentration range of 5-90 microg ml(-1). The regression analysis yields the calibration equation, nu = 3.467 x 10(-6) + 4.356 x 10(-5)C. The limits of detection and quantitation are 1.46 and 4.43 microg ml(-1), respectively. The proposed method was optimized and validated both statistically and through recovery studies. The experimental true bias of all samples is < +/-2.0%. The method has been successfully applied to the determination of pantoprazole in pharmaceutical preparations.     

Determination of 1,4-benzodiazepines in drug dosage forms by difference spectrophotometry

A spectrophotometric method has been developed for the determination of seven 1,4-benzodiazepines, namely: chlordiazepoxide, diazepam, nitrazepam, oxazepam, lorazepam, temazepam and cinolazepam. The method involves reduction of the target compounds using Zn/HCl and measuring the difference in the absorbance before and after reduction. The quantities of zinc and acid required for efficient reduction were carefully studied. 1–20 g ml^–1 of the compounds could be determined with < 1% error. The method was applied successfully to the determination of these compounds in pharmaceutical dosage forms. The results were sufficiently accurate and precise and comparable to those from the official methods.     

Determination of amlodipine in pharmaceutical dosage forms by liquid chromatography and ultraviolet spectrophotometry

A liquid chromatography (LC) method and an ultraviolet (UV) spectrophotometric method were developed and validated for quantitative determination of amlodipine in tablets and compounded capsules. The isocratic LC analyses were performed on an RP18 column using a mobile phase composed of 0.1% (v/v) ortho-phosphoric acid (pH 3.0) -acetonitrile (60 + 40, v/v) at a flow rate of 1.0 mL/min. The UV spectrophotometric method was performed at 238 nm. The analytical methods were validated according to International Conference on Harmonization Guidelines. The calibration graphs were linear [correlation coefficient (r) > 0.999] in the studied concentration range of 10-30 microg/mL for LC and 10-35 microg/mL for UV spectrophotometry. The relative standard deviation values for intraday and interday precision studies were less than 2%, and the accuracy was greater than 98% for both methods. The specificity of the LC method was proved using forced degradation. Statistical analyses showed no significant difference between the results obtained by the 2 methods. The proposed methods are precise and accurate and can be applied directly and easily to the oral pharmaceutical preparations of amlodipine.     

Kinetic spectrophotometric determination of famotidine in commercial dosage forms.

A simple kinetic spectrophotometric method is described for the determination of famotidine. The method is based on the oxidation of the drug with alkaline potassium permanganate. The reaction is followed spectrometrically by measuring the rate of change of the absorbance at 610 nm. The initial-rate and fixed-time (at 12 min) methods are adopted for determining the drug concentration. The calibration graphs are linear in the ranges of 2-10 microg mL(-1) and 1-8 microg mL(-1) using the initial-rate and fixed-time methods, respectively. The method has been applied to the determination of famotidine in tablet formulations. The obtained results are compared statistically with those given by a reference spectrophotometric method.     

UV spectrophotometry and nonaqueous determination of terbinafine hydrochloride in dosage forms.

An ultraviolet spectrophotometric and a nonaqueous volumetric method for determining terbinafine hydrochloride (TH) in pharmaceutical formulations are presented. The UV spectrophotometric procedure was developed for assay of TH in raw materials, tablets, and creams. The method was tested for linearity (0.8-2.8 micrograms/mL, r = 0.9997), recovery (102.00% for creams and 99.90% for tablets) and precision (101.3%, CV = 0.96%, n = 9, for creams; 100.25%, CV = 1.08%, n = 9, for tablets). The volumetric method involves titration of TH with 0.05M perchloric acid with crystal violet as indicator. This method was used for quantitative determination of TH in raw materials and tablets. Mean recovery and precision were, respectively, 100.41 and 101.18% (CV = 1.64%, n = 9) for TH tablets. There were no significant differences between the proposed methods and a previously described high-performance liquid chromatographic method. The UV spectrophotometric and titrimetric methods are potentially useful for a routine laboratory because of their simplicity, rapidity, and accuracy.     

Quantitative determination of oxybutynin hydrochloride by spectrophotometry, chemometry and HPTLC in presence of its degradation product and additives in different pharmaceutical dosage forms

Simple, accurate, sensitive and validated UV spectrophotometric, chemometric and HPTLC-densitometric methods were developed for determination of oxybutynin hydrochloride (OX) in presence of its degradation product and additives in its pharmaceutical formulations. Method A is the first derivative of ratio spectra (DD¹) which allows the determination of OX in presence of its degradate in pure form and tablets by measuring the peaks amplitude at 216 nm. Method B and C are principal component regression (PCR) and partial least-squares (PLS) for determination of OX in presence of its degradate in pure form, tablets and syrup. While, the developed high performance thin layer chromatography HPTLC-densitometric method was based on the separation of OX from its degradation product, methylparaben and propylparaben followed by densitometric measurement at 220 nm which allows the determination of OX in pure form, tablets and syrup. The separation was achieved using HPTLC silica gel F₂₅₄ plates and chloroform:methanol:ammonia solution:triethylamine (100:3:0.5:0.2, v/v/v/v) as the developing system. The accuracy, precision and linearity ranges of the developed methods were determined. The results obtained were statistically compared with each other and to that of a reported HPLC method, and there was no significant difference between the proposed methods and the reported method regarding both accuracy and precision.     

Quantitative determination of vitamin b12 by cyan dosage,with infrared absorption spectrophotometry

Microchimica Acta - Vitamin B12 has been determined by measurement of the infrared absorption of the cyano-group band at 2137 cm?1, the samples being pelleted with KBr. The error is within...     

Determination of chlorine in atmosphere by kinetic spectrophotometry

A kinetic method for determination of chlorine in air was described in the present work. The method based on fading of methyl orange (MO) containing solution in air absorption process. A determination limit of 2.64 microg L(-1) was found. With the present method, chlorine concentration could be determined in several minutes with convenient manipulation. As concentration variation of methyl orange in the absorption solution did not affect the experimental results, fabrication and preservation of the stock absorption is also convenient. The present method is promising in monitoring chlorine concentration in atmosphere.     

Comparative study on the determination of cephalexin in its dosage forms by spectrophotometry and HPLC with UV-vis detection

This paper discusses the spectrophotometric determination of cephalexin as the intact cephalexin or as its acid-induced degradation product. Cephalexin can be determined in the range 1 × 10^–5–18 × 10^–5 M with relative standard deviations of 5-1%. The limits of quantitation and detection were 10^–5 and 0.3 × 10^–5 M, respectively. These procedures were compared with reversed-phase HPLC determination. No interference was observed in the presence of common pharmaceutical adjuvants. The H-point standard additions method was applied in order to correct for the possible presence of the cephalexin precursor, 7-aminocephalosporanic acid; this improves the selectivity of the UV-vis spectrophotometric method.     

阻抑动力学光度法测定芦丁的研究

在稀硫酸介质中,微量芦丁对高碘酸钾氧化玫瑰桃红R褪色反应有明显的阻抑作用,据此建立了测定微量芦丁的动力学光度新方法。选定了最佳条件并测定了反应动力学参数,方法的线性范围为0.02～0.4μg mL,检出限为5.0×10-9g mL。方法已用于槐米和芦丁片剂中芦丁的测定。     

阻抑动力学光度法测定痕量尿素

研究了在酸性介质中,痕量尿素对NO2-催化KBrO3氧化维多利亚绿G的阻抑作用,通过测量617 nm处吸光度的变化,建立了测定痕量尿素的阻抑动力学光度分析的新方法。在最佳实验条件下,测定尿素的线性范围为0.0~0.14mg/L,检出限为5.0×10-6g/L。对2.0μg/25 mL进行10次平行测定的相对标准偏差为2.8%。并试验了共存离子对催化反应的影响,常见的离子均不干扰测定。方法可用于废水中痕量尿素的测定。     

催化动力学测定痕量对苯二酚

研究了在pH7.3的KH2PO4 Na2HPO4缓冲介质中,痕量对苯二酚催化高碘酸钾氧化靛红褪色的新指示反应及其动力学条件,建立了动力学光度法测定痕量对苯二酚的新方法。该方法检出限为6.8×10-6g L,线性范围是0.04～0 18μg mL和0.28～0.54μg mL。可用于显影废液中对苯二酚的测定。     

阻抑动力学光度法测定痕量邻苯二甲酸二辛酯

在HAc-NaAc缓冲介质中,邻苯二甲酸二辛酯对H2O2氧化中性红褪色反应有明显的抑制作用,据此建立了测定痕量邻苯二甲酸二辛酯的阻抑动力学光度法。测定的线性范围为0．26～4．10μg/mL,检出限为0．038μg／mL,回收率在98％～102％之间。该方法已用于一次性塑料袋、塑料拖鞋、河泥中邻苯二甲酸二辛酯的测定。     

阻抑动力学光度法测定水中痕量苯胺

基于KH2PO4-Na2HPO4缓冲介质中,痕量苯胺对高碘酸钾氧化维多利亚绿反应有阻抑作用,建立了一种测定痕量苯胺的催化动力学的新方法。该方法的线性范围为0~100μg/L,检出限为2.0×10-6g/L。已用于废水中苯胺的测定。     

阻抑动力学光度法测定痕量铜

在pH 4.5的HAc-NaAc缓冲溶液中, 痕量铜对KBrO3氧化亮绿SF的褪色反应有明显的阻抑作用, 据此建立了测定痕量铜的新方法. 方法的线性范围为0.004～0.048 μg/mL, 检出限为8.63×10-4 μg/mL, 已用于人发中铜的测定.     

Rapid analysis of dosage forms of some pharmaceuticals by nonaqueous thermometric titrimetry

The use of the technique of solution thermochemistry is proposed for the rapid assay for quality control and quality assurance of dosage amounts of some ethical formulations of some antimalarial drugs. The active ingredients are chloroquine, hydroxychloroquine, dapsone, proguanil hydrochloride, and pyrimethamine.Assay is done without the separation of the excipients and without isolation or derivatisation of the analytes. The titrations are done in glacial acetic acid and utilise the catalysed hydrolysis of acetic anhydride by perchloric acid to indicate the endpoint of the reactions.The time taken for a typical assay, of a typical dosage amount is about 3–5 minutes. The reproducibility is of the order of 1% for the milligramme amounts of analyte present in the dosage amounts of the drugs.

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Zusammenfassung Es wird die Anwendung eines lösungsthermochemischen Verfahrens zu Schnellbestimmungen bei der Qualitätskontrolle und — sicherung von Wirkstoffeinsatzmengen einiger rezeptpflichtiger Präparate von einigen antimalarischen Arzneimitteln empfohlen. Die aktiven Bestandteile sind Chloroquin, Hydroxychloroquin, Dapson, Proguanilhydrochlorid und Pyrimethamin.Die Bestimmungen werden ohne jegliche Abtrennung der Bindestoffe und ohne Isolierung oder Derivatisierung der zu bestimmenden Substanzen durchgeführt. Die Titrierungen werden in Eisessig durchgeführt und bedienen sich der katalytischen Hydrolyse von Essigsäureanhydrid durch Perchlorsäure als Endpunktindikation der Reaktion.Die Dauer für eine typische Probe bei einer typischen Wirkstoffmenge beträgt etwa 3–5 Minuten. Die Reproduzierbarkeit liegt in der Größenordnung von 1% für Milligrammengen der zu analysierenden Stoffe im Arzneimittel.

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We acknowledge the Nigerian Government for the provision of a grant to one of us (S.I.A.). We acknowledge the following for the gifts of samples of the authentic drugs and the tablets assayed in this work: Imperial Chemical Industries plc; May and Baker plc; Winthrop Laboratories plc; Wellcome Foundation (Medical Division).