Spectrophotometric and spectrofluorimetric methods for the determination of pregabalin in bulk and pharmaceutical preparation

Two new, sensitive and selective spectrofluorimetric and spectrophotometric methods have been developed for the determination of the gamma-amino-n-butyric acid derivative pregabalin (PGB) in bulk drug and capsule. Pregabalin, as a primary amine compound, reacts with 7-chloro-4-nitrobenzofurazon (NBD-Cl) which is a highly sensitive fluorogenic and chromogenic reagent used in many investigations. According to this fact, spectrophotometric and spectrofluorimetric methods for the determination of pregabalin in capsules were developed for the first time. The relation between the absorbance at 460 nm and the concentration is rectilinear over the range 0.5-7.0 microg mL(-1). The reaction product was also measured spectrofluorimetrically at 558 nm after excitation at 460 nm. The fluorescence intensity was directly proportional to the concentration over the range 40-400 ng mL(-1). The method was applied successfully to the determination of this drug in pharmaceutical dosage form. The mean recovery for the commercial capsules was 99.93% and 99.96% for spectrophotometric and spectrofluorimetric study, respectively. The suggested procedures could be used for the determination of PGB in pure and capsules being sensitive, simple and selective.     

Application of ternary and multicomponent complexes to spectrophotometric and spectrofluorimetric analysis of inorganics

The application of ternary and multicomponent complexes in spectrophotometric and spectrofluorimetric determination of trace elements is reviewed. Newer types of colour systems employing mixed ligand, surfactant sensitized, ion-association, flotation, derivative and FIA systems are described. Separate sections are devoted to advances in both spectrophotometric and spectrofluorimetric determination of individual elements. Future trends in spectrophotometric and spectrofluorimetric analysis are discussed.     

Spectrophotometric and spectrofluorimetric methods for analysis of tramadol, acebutolol and dothiepin in pharmaceutical preparations

Sensitive spectrophotometric and spectrofluorimetric methods are described for the determination of tramadol, acebutolol and dothiepin (dosulepin) hydrochlorides. The two methods are based on the condensation of the cited drugs with the mixed anhydrides of malonic and acetic acids at 60 degrees C for 25-40 min. The coloured condensation products are suitable for the spectrophotometric and spectrofluorimetric determination at 329-333 and 431-434 nm (excitation at 389 nm), respectively. For the spectrophotometric method, Beer's law was obeyed from 0.5 to 2.5 microg ml(-1) for tramadol, dothiepin and 5-25 microg ml(-1) for acebutolol. Using the spectrofluorimetric method linearity ranged from 0.25 to 1.25 microg ml(-1) for tramadol, dothiepin and 1-5 microg ml(-1) for acebutolol. Mean percentage recoveries for the spectrophotometric method were 99.68+/-1.00, 99.95+/-1.11 and 99.72+/-1.01 for tramadol, acebutolol and dothiepin, respectively and for the spectrofluorimetric method, recoveries were 99.5+/-0.844, 100.32+/-0.969 and 99.82+/-1.15 for the three drugs, respectively. The optimum experimental parameters for the reaction has been studied. The validity of the described procedures was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The proposed methods were successfully applied for the determination of the selected drugs in their pharmaceutical preparations with good recoveries. The procedures were accurate, simple and suitable for quality control application.     

New spectrophotometric and spectrofluorimetric methods for the determination of angiotensin II receptor antagonists in tablets and plasma

Spectrophotometric and spectrofluorimetric methods for the determination of five Angiotensin II type 1 receptor antagonists in tablets and plasma have been developed and optimized. The spectrophotometric method involves the addition of a measured excess of bromate-bromide in HCl medium and subsequent estimation of the residual bromine by reacting with a fixed amount of methyl orange. The spectrofluorimetric method depends on the oxidation of the drugs with cerium(IV) and subsequent monitoring of the fluorescence of the induced cerium(III) at 365 nm with excitation at 255 nm. Both of the proposed methods were successfully applied to the determination of the investigated drugs in their pure forms and pharmaceutical preparations. Besides, the spectrofluorimetric method was applied to the determination of irbesartan and telmisartan in biological fluids with good accuracy and precision.     

Spectrophotometric and spectrofluorimetric methods for analysis of acyclovir and acebutolol hydrochloride

Simple and sensitive spectrophotometric and spectrofluorimetric methods are described for analysis of acyclovir and acebutolol hydrochloride. The proposed methods are based on oxidation of the selected drugs with cerium(IV) ion in acidic medium with subsequent measurement of either the decrease in absorbance at 320nm or the fluorescence intensity of the produced cerous(III) ion at 361-363nm (excitation at 250nm). Beer's law obeyed from 2 to 8, 0.25 to 2.5microgcm-1 acyclovir, 1 to 7 and 0.25 to 2.5microgml-1 acebutolol hydrochloride, using the spectrophotometric and spectrofluorimetric method, respectively. The proposed method were successfully applied for determination of the selected drugs in their pharmaceutical preparations with good recoveries.     

Net analyte signal standard addition method (NASSAM) as a novel spectrofluorimetric and spectrophotometric technique for simultaneous determination,application to assay of melatonin and pyridoxine

In this work a new modification of the standard addition method called “net analyte signal standard addition method (NASSAM)” is presented for the simultaneous spectrofluorimetric and spectrophotometric analysis. The proposed method combines the advantages of standard addition method with those of net analyte signal concept. The method can be applied for the determination of analyte in the presence of known interferents. The accuracy of the predictions against H-point standard addition method is not dependent on the shape of the analyte and interferent spectra. The method was successfully applied to simultaneous spectrofluorimetric and spectrophotometric determination of pyridoxine (PY) and melatonin (MT) in synthetic mixtures and in a pharmaceutical formulation.     

Spectrophotometric and spectrofluorimetric methods for analysis of acyclovir and acebutolol hydrochloride

Simple and sensitive spectrophotometric and spectrofluorimetric methods are described for analysis of acebutolol hydrochloride. The proposed methods are based on oxidation of the selected drug with cerium(IV) ion in acidic medium with subsequent measurement of either the decrease in absorbance at 320 nm or the fluorescence intensity of the produced cerous(III) ion at 363 nm (excitation at 250 nm). Beer's law obeyed from 1.0-7.0 microg ml(-1) and 0.25-2.5 microg ml(-1) acebutolol hydrochloride, using the spectrophotometric and spectrofluorimetric method, respectively. The proposed methods were successfully applied for determination of the selected drug in its pharmaceutical preparation with good recoveries.     

Spectrophotometric and fluorimetric determination of nomifensine maleate

Three methods have been developed for the determination of nomifensine maleate alone and in capsules: a spectrophotometric, an iodine charge-transfer, and a spectrofluorimetric method. All three give linear calibration graphs, over the ranges 20-100, 1-5 and 0.1-0.5 microg/ml, respectively, with coefficients of variation of 0.8, 1.3 and 1.3%, respectively.     

Spectrophotometric and spectrofluorimetric methods for the determination of ramipril in its pure and dosage form

This paper describes three sensitive spectrophotometric and spectrofluorimetric methods for determination of ramipril in its pure form and pharmaceutical tablets. The first method is based on the oxidation of the drug with 1-chlorobenzotriazole reagent (CBT) in strong alkaline medium followed by measuring the absorbance at 350 nm. The method obeys Beer's law over concentration range 15-50 microg ml(-1). For the second and third, both are non-extractive methods based on the formation of ternary complex between copper (II), eosin and ramipril in the presence of methylcellulose as surfactant. Spectrophotometrically, under the optimum condition, the ternary complex showed an absorption maximum at 543 nm. The method obeys Beer's law over concentration range of 20-80 microg ml(-1). A fluorescence quenching method for the determination of ramipril by forming this ternary complex was also investigated for the propose of enhance the sensitivity of the determination. The methods are simple, sensitive, and accurate. The results obtained are reproducible with a coefficient of variation less than 2%. The proposed have been successfully applied to the assay of ramipril in tablets. The results compare favorably with official method.     

Determination of palladium with thiocyanate and rhodamine b by a solvent-extraction method

Sensitive spectrophotometric and spectrofluorimetric procedures for the determination of palladium have been developed, based on solvent-extraction of the ion-pair formed between Rhodamine B and the anionic complex of Pd(II) with thiocyanate. With an organic to aqueous phase-volume ratio of 1:5, the molar absorptivity is 9.0 x 10(4) l.mole(-1).cm(-1) and the absorbance of the reagent blank is 0.026. Spectrophotometrically, palladium can be determined in the range 0.1-8.8 mug. Spectrofluorimetrically, it can be determined over the range 0.04-1.5 mug. The spectrophotometric procedure has been applied to the determination of palladium in dental alloys, organopalladium compounds and hydrogenation catalysts.     

A spectrophotometric assay for solid phase primary amino groups

A rapid, sensitive, and convenient spectrophotometric assay was developed for the measurement of amino groups on solid supports. This method is based on the reaction of amino groups of solids with an excess ofo-phthaldialdehyde (OPA) and subsequent quantitative determination of unreacted OPA by reaction with glycine. Four solids possessing variable quantities of amino groups were examined. Results indicate that about 70% of the total surface amino concentration (determined by the microKjeldahl method) are available for ligand attachment. Unlike the spectrophotometric 2,4,6-trinitrobenzenesulfonic acid method, the OPA spectrophotometric assay is more rapid, sensitive, and convenient, and unlike the spectrofluorimetric OPA, it does not require sophisticated instrumentation.     

Isolation and purification of a vertebral hemoglobin,the chicken hemoglobin,and its interaction with copperglutathione complex

Hemoglobin was isolated from chicken blood and purified by biochemical methods.This hemoglobin was allowed to interact with copperglutathione (CuGSH) and the interaction pattern was monitored by spectrophotometric and spectrofluorimetric techniques. The interaction ratio was found to be 1:0.7 in both the cases. The equilibrium constant data suggested associative binding and a fluorimetric study revealed that such association occurred around tryptophan residues of hemoglobin.     

Estimation of Performance Characteristics of an Analytical Method Using the Data Set Of The Calibration Experiment

Abstract

A model to calculate the analytical sensitivity, limit of detection, limit of determination and precision of a method of instrumental analysis through a data set obtained by calibration experiment using the statistical analysis of linear regression, is proposed. This model has been applied to spectrophotometric, spectrofluorimetric and chromatographic methods. The values obtained are independent of the instrument used and can be applied as a criterion of comparison between different methods proposed for the same analyte. Also, these characteristics have been calculated using the IUPAC suggested model and both results have been compared.     

Theoretical study of the spectral behavior of the complex of a recently synthesized aminoxanthone derivative with copper(II) ion in water and methanol

The complexation of a recently synthesized aminoxanthone derivative, 1-({2-[(2-aminoethyl)amino]ethyl}amino)-6-methyl-9H-xanthen-9-one with Cu(II) in methanol and water solutions, was investigated by spectrofluorimetric and spectrophotometric methods. The possible molecular geometries, bindings, and spectroscopic properties for the formed complex were theoretically studied in detail by the Hyperchem program. The stoichiometry of the complex was determined from spectrophotometric molar ratio methods at 20°C. The spectral data were further treated by KINFIT program to calculate the formation constant of the 1:3 complex and its molar absorptivity. Program DATAN was used to calculate the spectral behavior of the complex in each solution for different mole ratios. A simple equation for the determination of complex stability constant was also evaluated from titration data. Under the optimal conditions, the ligand can be used as a fluorometric indicator for measuring Cu²⁺ ions in aqueous solution.     

Spectrofluorimetric and spectrophotometric stability-indicating methods for determination of some oxicams using 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl)

Two sensitive and selective spectrofluorimetric and spectrophotometric stability-indicating methods have been developed for the determination of some non-steroidal anti-inflammatory oxicam derivatives namely lornoxicam (Lx), tenoxicam (Tx) and meloxicam (Mx) after their complete alkaline hydrolysis. The methods are based on derivatization of alkaline hydrolytic products with 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl). The products showed an absorption maximum at 460 nm for the three studied drugs and fluorescence emission peak at 535 nm in methanol. The color was stable for at least 48 h. The optimum conditions of the reaction were investigated and it was found that the reaction proceeds quantitatively at pH 8, after heating in a boiling water bath for 30 min. The methods were found to be linear in the ranges of 1-10 microg ml(-1) for Lx and Tx and 0.5-4.0 microg ml(-1) for Mx for spectrophotometric method, while 0.05-1.0 microg ml(-1) for Lx and Tx and 0.025-0.4 microg ml(-1) for Mx for the spectrofluorimetric method. The validity of the methods was assessed according to USP guidelines. Statistical analysis of the results revealed high accuracy and good precision. The suggested procedures could be used for the determination of the above mentioned drugs in pure and dosage forms as well as in the presence of their degradation products.     

Normal spectrophotometric and stopped-flow spectrofluorimetric sequential injection methods for the determination of alendronic acid, an anti-osteoporosis amino-bisphosphonate drug, in pharmaceuticals

A normal spectrophotometric and a stopped-flow (SF) spectrofluorimetric method have been developed and optimized for the determination of alendronic acid (ALD) in its pharmaceutical formulations. Both methods are automated using the sequential injection analysis (SIA) principle. The spectrophotometric assay is based on the reaction of the analyte with Cu(II) ions in acidic medium to form an UV-absorbing derivative (λ_max = 240 nm). The SF spectrofluorimetric method is based on the reaction of ALD with o-phthalaldehyde (OPA) in the presence of 2-mercaptoethanol at basic medium (λ_ex = 340 nm/λ_em = 455 nm). Linear calibration curves were obtained in the range 1.0-60.0 mg l⁻¹ ALD for the UV method, and in the range 0.13-10.0 mg l⁻¹ ALD for the SF spectrofluorimetric one. The sampling rates were 60 and 30 h⁻¹, respectively. The developed assays are critically compared and their advantages are discussed. Both methods were applied to the analysis of an ALD containing pharmaceutical formulation with satisfactory accuracy and precision.     

Spectrofluorimetric and spectrophotometric determination of gliclazide in pharmaceuticals by derivatization with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole

Accurate, sensitive, and simple spectrophotometric and spectrofluorimetric methods were developed for the determination of gliclazide in pharmaceutical formulations and biological fluids. Both methods are based on a coupling reaction between gliclazide and 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole in borate buffer, pH 7.8, in which a yellow reaction product that can be measured spectrophotometrically at 400 nm was developed. The same product exhibited a yellow fluorescence at 470 nm upon excitation at 400 nm. The absorbance-concentration plot was rectilinear over the range of 2-20 microg/mL with minimum detectability [signal-to-noise (S/N) ratio = 2] of 0.2 microg/mL (6.18 x 10(-7) M); the fluorescence-concentration plot was rectilinear over the range of 0.2-2.5 microg/mL with minimum detectability (S/N = 2) of 0.02 microg/mL (6.18 x 10(-8) M). The different experimental parameters affecting the development and stability of the color were carefully studied and optimized. Both methods were successfully applied to the analysis of commercial tablets. The results were in good agreement with those obtained with the official and reference spectrophotometric methods. A proposal of the reaction pathway was presented.     

Trace zinc determination by synchronous derivative fluorimetry

A sensitive and selective synchronous-scanning derivative spectrofluorimetric determination of zinc based on the formation of a fluorescent chelate with 2-furaldehyde 2-pyridylhydrazone (FAPH) is described, and its analytical performance compared with that of the ordinary fluorimetric method. The detection limits lie in the ng ml range and the coefficient of variation is below 2% in both cases. The methods have been applied to the trace determination of zinc in pig liver tissue and environmental fume samples.     

Spectrophotometric, spectrofluorimetric, and densitometric methods for the determination of indapamide

Three sensitive spectrophotometric, spectrofluorimetric, and densitometric methods are described for the determination of indapamide. The first and second methods are based on the oxidative coupling reaction of indapamide with 3-methyl-2-benzothiazolinone hydrazone HCl (MBTH) in the presence of cerium(IV) ammonium sulfate in an acidic medium. The absorbance of the reaction product is measured at the lambdamax, 601 nm. With the same reaction, indapamide is determined by its quenching effect on the fluorescence of excess cerous ions at the emission lambdamax, 350 nm, and the excitation at lambdamax, 300 nm. The reaction conditions were optimized, and Beer's law was obeyed for indapamide at 1.2-9.6 microg/mL with mean recoveries of 99.92 +/- 0.83 and 99.97 +/- 1.11%, respectively. The third method, a stability-indicating densitometric assay, was developed for the determination of indapamide, using toluene-ethyl acetate-glacial acetic acid (69 + 30 + 1, v/v/v) as the developing system and scanning at the lambdamax, 242 nm, in the presence of the degradation product and related substance; for the indapamide concentration range of 0.6-6 microg/spot, the mean recovery was 99.73 +/- 0.71%. The proposed methods were successfully applied to the determination of indapamide in bulk powder and commercial tablets, and the results of the analysis agreed statistically with those obtained with the official method. Furthermore, the methods were validated according to the guidelines of the U.S. Pharmacopeia and also assessed by applying the standard additions technique.     

Application of H-point standard additions method to spectrophotometric and spectrofluorimetric determinations of glafenine and glafenic acid in mixtures

H-point standard additions method (HPSAM), based on spectrophotometric and spectrofluorimetric measurements, was proposed for simultaneous determination of glafenine (G) and glafenic acid (GA). A study of the absorption spectra of G and GA in various pH media has been carried out. Reasonably resolved UV-absorption spectra were obtained with a solution adjusted at pH 4.5 with citric acid–phosphate buffer. Additionally, the fluorescence properties in aqueous micellar systems of anionic, cationic and non-ionic surfactants were investigated. Well resolved fluorescence spectra were established in aqueous Triton X-100 solution at pH 7.8 (citric acid–phosphate buffer). As a comparative method, UV-derivative spectrophotometry (based on zero-crossing technique) was suggested. First-derivative value at 352 nm (¹D₃₅₂) and second-derivative value at 366 nm (²D₃₆₆) were selected for the quantification of G and GA, respectively. The relative standard deviations of the proposed methods approximate 2%. The proposed methods were evaluated through the analysis of commercial tablets. The results were accurate and precise.