Direct spectrophotometric determination of diacerhein in capsules

A simple, rapid and precise ultraviolet spectrophotometric method using 0.1 N sodium hydroxide has been developed and validated for the assay of diacerhein. The drug can be estimated at 277 nm (ultraviolet region, UV) as well as at 502 nm (visible region, VIS). The absorbances were linearly correlated with concentration in the 6.0-24 microg mL(-1) range (r = 0.9999) and 10-34 microg mL(-1) range (r = 0.9998), respectively at 277 and at 502 nm. The relative standard deviation values for intra (n = 6) and inter-day (n = 3) precision were <2%. Recoveries ranged between 99.0 and 101.7%. The method has been successfully applied to the drug assay in capsules. It was also found that the excipients in the commercial capsules did not interfere with the method. Statistical analysis showed no significant difference between the results obtained at two wavelengths (277 nm or 502 nm).     

Spectrophotometric and spectrofluorimetric determination of atomoxetine in pharmaceutical preparations

Visible spectrophotometric and spectrofluorimetric methods were developed for the determination of atomoxetine in pharmaceutical preparations. The spectrophotometric method was based on a nucleophilic substitution reaction of atomoxetine with 1,2-naphthoquinone-4-sulphonate (NQS) in an alkaline medium to form an orange-colored product. The absorbance-concentration plot is rectilinear over the range 5-40 microg mL(-1). The limits of detection and quantification were calculated to be 0.02 microg mL(-1) and 0.06 microg mL(-1), respectively. The spectrofluorimetric method was based on the derivatization reaction of 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) with atomoxetine to produce a fluorescent derivative. The formed highly fluorescent derivative that was measured at 462 nm after excitation at 533 nm. The fluorescence-concentration plot is rectilinear over the range 10-500 ng mL(-1). The limits of detection and quantification were calculated to be 0.19 ng mL(-1) and 0.57 ng mL(-1). The analytical performance of both methods was fully validated, and the results were satisfactory. The methods have been successfully applied for the determination of the studied drug in capsules and the results obtained ware in good agreement with those obtained by the reference method.     

Colorimetric determination of gabapentin in pharmaceutical formulation

Three accurate, simple and precise colorimetric methods for the determination of gabapentin in capsules are developed. The first method is based on the reaction of gabapentin with vanillin (Duquenois reagent) in the presence of McIlvain buffer pH 7.5 and the color developed was measured at 376 nm. The linearity range was found to be 80-360 microg ml(-1). The second is based on the reaction of the primary amino group of gabapentin with ninhydrin reagent in N,N'-dimethylformamide (DMF) medium producing a colored product which absorbs maximally at 569 nm. Beer's law is obeyed in the concentration range 40-280 microg ml(-1) of gabapentin. The third method is based on the reaction of gabapentin with p-benzoquinone (PBQ) to form a colored product with lambda(max) at 369 nm. The products of the reaction were stable for 2 h at 30 degrees C, shifts of the wavelength of maximum absorbance were not observed for up to 24 h after starting the reaction. The absorbance is proportional to gabapentin concentration in the range 80-320 microg ml(-1). The optimum experimental parameters for the reactions have 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 suggested procedures could be used for the determination of gabapentin in capsules. The procedures were rapid, simple and suitable for quality control application.     

Spectrophotometric and titrimetric determination of nizatidine in capsules

Four simple and accurate methods are described for the determination of nizatidine (NIZ) in pharmaceutical preparations. The first method is based on the formation of an ion-pair complex between the drug and either of bromocresol purple or picric acid with subsequent measurement of the developed colors at 411 and 400 nm, respectively. The second method depends on the condensation of mixed anhydrides of citric acid/acetic anhydride, with the tertiary amino group of the drug, where the developed color is measured spectrophotometrically at 545 nm. The oxidation of nizatidine by N-bromosuccinimide was utilized as a basis for the titrimetric method for its assay in capsules. The last method depends on the oxidation of nizatidine by ammonium cerium IV sulfate in the presence of perchloric acid with subsequent measurement of the absorbance at 314 nm; this principle is adopted to develop a kinetic method for the determination of NIZ in capsules. All the reaction conditions have been studied. The detection limits were varied from 0.44 to 0.78 microg ml(-1). The proposed methods were successfully applied to the assay of nizatidine in capsules.     

Sensitive spectrophotometric method for the determination of indomethacin in capsules

A simple, sensitive and selective spectrophotometric method for the determination of indomethacin (INM) either in pure form or in capsules is described. The method is based on the coupling reaction of hydrolyzed INM with diazotized p-phenylenediamine dihydrochloride (PPDD) in sulphuric acid medium to give a red coloured product having the absorption maximum at 510 nm. The product is stable for 20 h. Beer's law is obeyed in the concentration range of 0.2-10 microg/ml. Results of the proposed method compare favourably with those of the official methods and offer the merits of sensitivity and stability. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed method.     

Indirect atomic absorption spectrometric determination of pindolol, propranolol and levamisole hydrochlorides based on formation of ion associates with manganese thiocyanate and potassium ferricyanide

A new simple, accurate, precise and sensitive indirect method for the determination of pindolol HCl (1), propranolol HCl (2) and levamisole HCl (3) using atomic absorption spectrometry has been developed. The method is based on precipitation of the ion associates formed from the reaction of (1), (2) or (3) with manganese thiocyanate and/or potassium ferricyanide. The solubility of the solid complexes at the optimum conditions of pH and ionic strength values have been studied. Saturated solutions of each ion-associate were prepared under the optimum conditions and the metal ion content in the supernatant was determined. The method has been used for the determination of 1.14-17.07, 1.18-17.75 and 1.08-16.24 microg/ml of (1), (2) and (3), respectively using manganese thiocyanate and 1.71-25.60, 1.77-26.62 and 1.62-24.36 microg/ml of (1), (2) and (3), respectively using potassium ferricyanide. The method developed applied for analysis of bulk drugs and some of their pharmaceutical preparations.     

Iminodibenzyl as a novel coupling agent for the spectrophotometric determination of sulfonamide derivatives.

A rapid, selective and simple spectrophotometric method for the determination of sulfa-drugs is described. The method is based on the formation of violet colored azo product by the diazotization of sulfonamides, viz. sulfathiazole (SFT), sulfadiazine (SFD), sulfacetamide (SFA), sulfamethoxazole (SFMx), sulfamerazine (SFMr), sulfaguanidine (SFG) and sulfadimidine (SFDd) followed by a coupling reaction with iminodibenzyl in alcohol medium. Absorbance of the resulting violet azo product is measured at 570-580 nm and is stable for 24 h at 27 degrees C. Beer's law is obeyed in the concentration range of 0.05-6.0 microg ml(-1) at the wavelength of maximum absorption. The method is successfully employed for the determination of sulfonamides in various pharmaceutical preparations and common excipients used as additives in pharmaceuticals do not interfere in the proposed method. The method offers the advantages of simplicity, rapidity and sensitivity without the need for extraction or heating. A reaction mechanism is proposed for the formation of the violet azo product.     

Comparison of UV spectrophotometric method and high performance liquid chromatography for the analysis of flunarizine and its application for the dissolution test

This study aimed to develop a simple UV spectrophotometric method for the analysis and the dissolution test of flunarizine in capsules. The UV absorbance was both measured directly and by the first derivative measurements at 254 and 268 nm, respectively. The developed methods were validated for their linearity, accuracy, precision, limit of detection (LOD) and limit of quantitation (LOQ) in comparison with the reported HPLC method. The UV spectrophotometric method illustrated excellent linearity (r2 > 0.9999) in the concentration range of 6-24 microg/mL. Precision (%R.S.D. < 1.50) and recoveries were good (%R > 99.62). The LOD of direct UV and first derivative measurements were 0.09 and 0.84 microg/mL, respectively, and the LOQ were 0.26 and 2.55 microg/mL, respectively. Results from the assay of flunarizine in capsules by the UV spectrophotometric methods, both direct and first derivative measurements were not significantly different from those of the HPLC method (P > 0.05). Additionally, the method was successfully used for the dissolution test of flunarizine capsule and was found to be reliable, simple, fast, and inexpensive.     

Facile and sensitive determination of selenium (IV) in pharmaceutical formulations by flow injection spectrophotometry

An automated flow injection spectrophotometric method has been developed for the rapid, simple, selective, and sensitive determination of selenium (IV) from various pharmaceutical multivitamin and mineral formulations. The method was based on the oxidation of 4-aminoantipyrine (4-amino-l,2-dihydro-1,5-dimethyl-2-phenyl-3H-pyrazole-3-one; 4-AAP) by selenium in presence of acidic medium and the coupling with N-(naphthalen-l-yl)ethane-1,2-diamine dihydrochloride (NEDA) to give a violet color derivative. Gilson P2 mini pulse peristaltic pump has been used for introducing the selenium (IV), dilute HCl, 4-AAP and NEDA solutions into reaction coil by an automatic system. The absorbance of the 4-AAP-NEDA color derivative was measured at 563 nm after a reaction time of 3 min in stop flow of 4-AAP-NEDA. Beer's law was obeyed for selenium in the concentration range 0.05-5.0 microg mL(-1) and Sandell's sensitivity was found to be 0.00286 microg cm2. The performance of the present method was compared with the official method in terms of Student's F- and t-tests, and no significant difference was observed. This method was found to be suitable for estimating the selenium (IV) concentration in various pharmaceutical multivitamin and mineral formulations such as tablets and capsules.     

A specific and rapid HPLC assay for the determination of cefroxadine in human plasma and its application to pharmacokinetic study in Korean

A specific and rapid high performance liquid chromatographic (HPLC) method with UV detection (254 nm) was developed for the determination of cefroxadine in human plasma. The sample extraction was performed by a simple procedure, vortexing and centrifugation of sample following addition of 60% trichloroacetic acid. Cephalexin was used as an internal standard (I.S.). The HPLC analysis was carried out on a Capcell Pak C18 analytical column with a mobile phase of 50 mM ammonium formate buffer/pH 3.5 and acetonitrile (90:10, v/v). No interference was observed near the peaks of cefroxadine and I.S. The calibration curve was linear over the range of 0.5-40 microg/mL and the lower limit of quantification (LLOQ) was 0.5 microg/mL. The method was validated with excellent sensitivity, accuracy, precision and stability. This assay was successfully applied to determine the pharmacokinetic parameters of cefroxadine in Korean healthy volunteers after an oral administration of two 250 mg cefroxadine capsules. As a result, the plasma half-life was 1.00+/-0.26 h and the mean AUC(0-6 h) was 46.25+/-6.41microgh/mL. The maximum plasma concentration (C(max)) of 17.62+/-4.87 microg/mL reached 1.44+/-0.39 h after administration.     

Quantitative determination of some pharmaceutical piperazine derivatives through complexation with iron(III) chloride

A simple, accurate and sensitive spectrophotometric method has been developed for the determination of three pharmaceutical piperazine derivatives, namely ketoconazole (KC), trimetazidine hydrochloride (TMH) and piribedil (PD). This method is based on the formation of yellow orange complexes between iron(III) chloride and the investigated drugs. The optimum reaction conditions, spectral characteristics, conditional stability constants and composition of the water soluble complexes have been established. The method permits the determination of KC, TMH and PD over a concentration range 1-15, 1-12 and 1-12 microg ml(-1), respectively. Sandell sensitivity is found to be 0.016, 0.013 and 0.013 microg cm(-2) for KC, TMH and PD, respectively. The method was sensitive, simple, reproducible and accurate within +/-1.5%. The method is applicable to the assay of the three drugs under investigation in different dosage forms and the results are in good agreement with those obtained by the official methods (USP and JP).     

Comparison of classical and derivative UV-spectrophotometric methods for the quantification of diltiazem and mexiletine

A first order derivative UV-spectrophotometric method for the determination of diltiazem hydrochloride and mexiletine hydrochloride has been developed and validated. In the assay, the first- and second-order measurements with the use of the "peak-zero" and "peak-peak" techniques were applied. The linear correlation (r < 0.9999) between the amplitude of the peak and the concentration of the examined drugs in the range of 3.0-8.0 microg mL(-1) for diltiazem and 50-100 microg mL(-1) for mexiletine was obtained. The proposed method was successfully applied for accurate (mean recovery about 100%), precise (RSD about 1%) and selective determination of the studied drug in the pure and dosage forms.     

A validated UV spectrophotometric method for determination of duloxetine hydrochloride

A simple, sensitive and accurate UV spectrophotometric method was developed for the assay of duloxetine hydrochloride in raw material and capsules. Validation of the method yielded good results concerning range, linearity, precision and accuracy. The absorbance was measured at 290 nm for duloxetine capsule solution. The linearity range was found to be 5-50 microg/mL for the drug. It was found that the excipients in the commercial formulation did not interfere with the methods.     

高锰酸钾-甲醛流动注射化学发光体系测定美洛昔康胶囊的含量

在盐酸酸性条件下，美洛昔康与高锰酸钾发生化学发光反应，甲醛对此发光体系有强烈的增敏作用。在此基础上．建立了一种快速、准确的测定美洛昔康胶囊含量的流动注射化学发光法。在最佳实验条件下，测得的线性范围为1．0-20．0μg／mL，检测限为25．6ng／mL，相对标准偏差为2．1％。常见药物赋形剂对本法没有干扰，方法用于美洛昔康胶囊含量的测定．结果令人满意。     

Analysis of gabapentin in serum and plasma by solid-phase extraction and gas chromatography-mass spectrometry for therapeutic drug monitoring

A simple method for the determination of gabapentin (Neurontin) is described. The method uses solid-phase extraction by disk column and derivatization followed by gas chromatographic-mass spectrometric analysis. The single-step derivatization with MTBSTFA produces a t-BDMS derivative of both the carboxylic and amine moieties of the molecule. Each step of the procedure was optimized to assure reliable performance of the method. The assay limit of detection was 0.1 microg/mL with a linear range from 1.0 to 35 microg/mL. Within-run (n = 3) and between-run (n = 40) coefficients of variation were less than 8.2 and 15.9%, respectively. The method has proven reliable in routine production for more than a year, producing clean chromatography with unique ion fragments, consistent ion mass ratios, and no interferences. Statistical analysis of the gabapentin concentrations measured in 1020 random specimens over a 2-month period showed a mean concentration of 6.07 microg/mL with a standard deviation of 5.28.     

Determination of olmesartan medoxomil in tablets by UV-Vis spectrophotometry

A simple, rapid and reliable UV spectrophotometric method was developed for the determination of olmesartan medoxomil in pharmaceutical dosage forms. The solutions of standard, tablet and synthetic tablet were prepared in acetonitrile and in NaOH-Water. 258 nm and 250 nm were chosen for acetonitrile and for NaOH-Water solutions respectively. The developed method was validated with respect to stability, linearity, sensitivity, specificity, precision, accuracy, robustness and ruggedness. The linearity range of the method was 1.0-70.0 microg x mL(-1) for acetonitrile solutions and 1.0-75.0 microg x mL(-1) for NaOH-Water solutions. The developed and validated method was applied for the determination of olmesartan medoxomil in pharmaceutical dosage forms.     

Spectrophotometric determination of rosuvastatin calcium in tablets

Rosuvastatin calcium is a synthetic lipid lowering agent which is used in hypercholesterolemia. It is a selective and competitive inhibitor of HMG-CoA reductase. In this study a simple, rapid and reliable spectrophotometric method was developed for the determination of rosuvastatin calcium in pharmaceutical preparations. The solutions of standard and pharmaceutical samples were prepared in methanol. 243 nm was chosen for measuring absorbances of rosuvastatin calcium. The developed method was validated with respect to linearity range, limit of detection and quantitation, accuracy, precision, specificity and ruggudness. The linearity range of the method was 1.0-60.0 microg mL(-1). The limit of detection was 0.33 microg mL(-1). The developed and validated method was applied to the determination of rosuvastatin calcium in pharmaceutical preparations.     

Indirect atomic absorption spectrometric determination of pindolol, propranolol and levamisole hydrochlorides based on formation of ion-associates with ammonium reineckate and sodium cobaltinitrite

A new simple, accurate, precise and sensitive indirect method for the determination of pindolol HCl (1), propranolol HCl (2) and levamisole HCl (3) using atomic absorption spectrometry has been developed. The method is based on precipitation of the ion-associates formed from the reaction of (1), (2) or (3) with ammonium reineckate and/or sodium cobaltinitrite. The solubility of the solid complexes at the optimum conditions of pH and ionic strength values have been studied. Saturated solutions of each ion-associate were prepared under the optimum conditions and the metal ion content in the supernatant was determined. The method has been used for the determination of 1.14-17.07, 1.18-17.75 and 1.08-16.24 microg/ml of (1), (2) and (3), respectively, using ammonium reineckate, and 1.71-25.60, 1.77-26.62 and 1.62-24.36 microg/ml of (1), (2) and (3), respectively, using sodium cobaltinitrite. The method developed was applied for analysis of bulk drugs and some of their pharmaceutical preparations.     

Determination of carvedilol by its quenching effect on the luminescence of terbium complex in dosage form

A new, simple, sensitive luminescence methods for the determination of carvedilol have been developed and validated. Carvedilol was remarkably quenching the luminescence intensity of the Tb(III) ion in the new terbium complex with 1-butyl-4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylic acid-(4-methyl-pyridin-2-yl)-amide (R) in aqueous solutions containing urotropine buffer (pH 7.5) at lambda(ex) = 317 nm and lambda(em) = 545 nm. Under optimal conditions, the quenching of luminescence intensity was found to be proportional to the concentration of carvedilol in the range of 0.5-400 microg/mL. The detection limit was 0.16 microg/mL. This method was applied for the determination of carvedilol in tablets "Coryol".