Simple, sensitive, selective and validated spectrophotometric methods for the estimation of a biomarker trigonelline from polyherbal gels

Simple, accurate, reproducible, selective, sensitive and cost effective UV-spectrophotometric methods were developed and validated for the estimation of trigonelline in bulk and pharmaceutical formulations. Trigonelline was estimated at 265 nm in deionised water and at 264 nm in phosphate buffer (pH 4.5). Beer's law was obeyed in the concentration ranges of 1-20microg mL(-1) (r2=0.9999) in deionised water and 1-24 microg mL(-1) (r2=0.9999) in the phosphate buffer medium. The apparent molar absorptivity and Sandell's sensitivity coefficient were found to be 4.04 x 10(3)L mol(-1)cm(-1) and 0.0422 microg cm(-2)/0.001A in deionised water; and 3.05 x 10(3)L mol(-1)cm(-1) and 0.0567 microg cm(-2)/0.001A in phosphate buffer media, respectively. These methods were tested and validated for various parameters according to ICH guidelines. The detection and quantitation limits were found to be 0.12 and 0.37 microg mL(-1) in deionised water and 0.13 and 0.40 microg mL(-1) in phosphate buffer medium, respectively. The proposed methods were successfully applied for the determination of trigonelline in pharmaceutical formulations (vaginal tablets and bioadhesive vaginal gels). The results demonstrated that the procedure is accurate, precise, specific and reproducible (percent relative standard deviation <2%), while being simple and less time consuming and hence can be suitably applied for the estimation of trigonelline in different dosage forms and dissolution studies.     

Analysis of metformin dosage formulations by capillary electrophoresis at nano scale detection

An inexpensive, rapid and reproducible capillary electrophoretic method has been developed and validated for the determination of metformin in pharmaceutical preparations. The method was developed utilizing a fused silica capillary (60 cm x 50 microm I.D.), phosphate buffer (50 mM, 3.0 pH)-acetonitrile (95:5, v/v) as background electrolyte (BGE), 20 kV applied voltage with UV detection at 254 nm and at a working temperature of 23 +/- 1 degrees C. Linearity was observed in the concentration range from 100 ng/L to 5 microg/L, with a correlation coefficient (R2) of 0.9998. The limits of detection and quantification achieved were 60 and 100 ng/mL, respectively. The recovery of metformin from pharmaceutical preparations was 99.1%. These validation parameters demonstrate the precision of the method and its suitability for the determination of metformin in pharmaceutical tablet formulations.     

Development and validation of a method for quantitative determination of econazole nitrate in cream formulation by capillary zone electrophoresis

A simple, fast, inexpensive and reliable capillary zone electrophoresis (CZE) method for the determination of econazole nitrate in cream formulations has been developed and validated. Optimum conditions comprised a pH 2.5 phosphate buffer at 20 mmol L(-1) concentration, +30 kV applied voltage in a 31.5 cm x 50 microm I.D. capillary. Direct UV detection at 200 nm led to an adequate sensitivity without interference from sample excipients. A single extraction step of the cream sample in hydrochloric acid was performed prior to injection. Imidazole (100 microg mL(-1)) was used as internal standard. Econazole nitrate migrates in approximately 1.2 min. The analytical curve presented a coefficient of correlation of 0.9995. Detection and quantitation limits were 1.85 and 5.62 microg mL(-1), respectively. Excellent accuracy and precision were obtained. Recoveries varied from 98.1 to 102.5% and intra- and inter-day precisions, calculated as relative standard deviation (RSD), were better than 2.0%. The proposed CZE method presented advantageous performance characteristics and it can be considered suitable for the quality control of econazole nitrate cream formulations.     

Stability indicating HPLC method for the simultaneous determination of moxifloxacin and prednisolone in pharmaceutical formulations

ABSTRACT: BACKGROUND: A simple, specific, and fast stability indicating reverse phase liquid chromatographic method was established for instantaneous determination of moxifloxacin and prednisolone in bulk drugs and pharmaceutical formulations. RESULTS: Optimum chromatographic separations among the moxifloxacin, prednisolone and stressinduced degradation products were achieved within 10 minutes by use of BDS Hypersil C8 column (250 X 4.6 mm, 5 mum) as stationary phase with mobile phase consisted of a mixture of phosphate buffer (18 mM) containing 0.1% (v/v) triethylamine, at pH 2.8 (adjusted with dilute phosphoric acid) and methanol (38:62 v/v) at a flow rate of 1.5 mL min-1. Detection was performed at 254 nm using diode array detector. The method was validated in accordance with ICH guidelines. Response was a linear function of concentrations over the range of 20-80 mug mL-1 for moxifloxacin (r2 [greater than or equal to] 0.998) and 40-160 mug mL-1 for prednisolone (r2 [greater than or equal to] 0.998). The method was resulted in good separation of both the analytes and degradation products with acceptable tailing and resolution. The peak purity index for both the analytes after all types of stress conditions was [greater than or equal to] 0.9999 indicated a complete separation of both the analyte peaks from degradation products. The method can therefore, be regarded as stabilityindicating. CONCLUSIONS: The developed method can be applied successfully for simultaneous determination of moxifloxacin and prednisolone in pharmaceutical formulations and their stability studies.     

Sensitive and rapid spectrophotometric methods for determination of anticancer drugs

Sensitive, rapid, and simple spectrophotometric methods were developed for determination of the anticancer drugs vinblastine sulfate (VBS) and vincristine sulfate (VCS), which belong to the class of vinca alkaloids. The first method is based on the reaction of VBS and VCS with diazotized dapsone, forming yellow azo products with absorption maxima at 430 nm. The colored species obey Beer's law in the concentration range of 0.5-24 microg/mL for VBS and 0.5-12 microg/mL for VCS. The second method describes the reaction of VBS and VCS with iron(III) and subsequent reaction with ferricyanide in hydrochloric acid medium to yield blue products with absorption maxima at 750 nm. The Beer's law range for this method is 0.1-4 microg/mL for VBS and 0.5-10 microg/mL for VCS. With both methods, colored species were stable for 1 h. The methods are simple and reproducible and are applied for determination of VBS and VCS in pharmaceutical formulations. Commonly encountered pharmaceuticals added as excipients do not interfere in the analysis and the results obtained in the analysis of dosage forms agree well with the labeled contents.     

Spectrophotometric determination of some drugs for osteoporosis

Three simple, accurate and sensitive spectrophotometric methods are developed for the determination of some new drugs for the treatment of osteoporosis: risedronate sodium (I), alendronate sodium (II) and etidronate disodium (III). The first method is based on the measurement of difference in absorbance (Delta A) of risedronate sodium in 0.01 mol l(-1) hydrochloric and 0.1 mol l(-1) sodium hydroxide at 262 nm. Beer's law is obeyed over a concentration range of 15-150 microg ml(-1) with mean recovery 99.75+/-1.22 and molar absorptivity (epsilon) 1.891 x 10(3). The second method is based on the reaction of the primary amino group of (II) with ninhydrin reagent in methanolic medium in the presence of 0.05 mol l(-1) sodium bicarbonate. The colored product is measured at 568 nm, and the linearity range is found to be 3.75-45 microg ml(-1) with mean recovery 99.77+/-0.73 and epsilon 9.425 x 10(3). The third method is based on oxidation of the three mentioned drugs with ceric (IV) sulphate in 0.5 mol l(-1) sulphuric acid at room temperature and subsequent measurement of the excess unreacted cerium (IV) sulphate at 320 nm. The method obeyed Beer's law over a concentration range of 2-24 microg ml(-1) for the three drugs with mean recovery 99.79+/-1.16, 99.73+/-1.38 and 99.86+/-1.13 and epsilon 14.427 x 10(3), 13.813 x 10(3) and 14.000 x 10(3) for drugs I, II, III respectively. The proposed methods were successfully applied for the determination of the studied drugs in bulk powder and in pharmaceutical formulations. The results were found to agree statistically with those obtained the reported methods. Furthermore, the methods were validated according to USP regulations and also assessed by applying the standard addition technique.     

Sensitive extractive spectrophotometric methods for the determination of trazodone hydrochloride in pharmaceutical formulations

Two simple, rapid and sensitive extractive spectrophotometric methods have been developed for the assay of trazodone hydrochloride (TRH) in pure and pharmaceutical formulations. These methods are based on the formation of chloroform soluble ion-association complexes of TRH with bromothymol blue (BTB) and with bromocresol purple (BCP) in KCl-HCl buffer of pH 2.0 (for BTB) and in NaOAc-AcOH buffer of pH of 3.6 (for BCP) with absorption maximum at 423 nm and at 408 nm for BTB and BCP, respectively. Reaction conditions were optimized to obtain the maximum color intensity. The absorbance was found to increase linearly with increase in concentration of TRH, which was corroborated by the calculated correlation coefficient values (0.9996, 0.9945). The systems obeyed Beer's law in the range of 0.2-14.5 and 0.2-14.1 microg/ml for BTB and BCP, respectively. Various analytical parameters have been evaluated and the results have been validated by statistical data. No interference was observed from common excipients present in pharmaceutical formulations. The proposed methods are simple, accurate and suitable for quality control applications.     

Simultaneous spectrophotometric determination of levodopa and carbidopa in pharmaceutical formulations and water samples by using mean centering of ratio spectra and H-point standard addition methods

Two spectrophotometric methods are described for the simultaneous determination of binary mixtures of carbidopa and levodopa in pharmaceutical formulations, without prior separation steps, using the mean centering of ratio spectra and H-point standard addition methods (HPSAM). The methods are based on the difference in the absorption spectra for the products of the reaction of carbidopa and levodopa with 4-aminobenzoic acid in the presence of periodate ion at pH 4.0. The methods allow rapid and accurate determination of carbidopa and levodopa. The results showed that the methods were capable to simultaneous determination of 0.30-10.00 microg ml(-1) and 0.50-10.00 microg ml(-1) each of carbidopa and levodopa. The proposed methods were successfully applied to the simultaneous determination of carbidopa and levodopa in pharmaceutical samples.     

Stability-indicating methods for determination of pyritinol dihydrochloride in the presence of its precursor and degradation product by derivative spectrophotometry

A first-derivative spectrophotometric (1D) method and a derivative-ratio zero-crossing spectrophotometric (1DD) method were used to determine pyritinol dihydrochloride (I) in the presence of its precursor (II) and its degradation product (III) with 0.1N hydrochloric acid as a solvent. Linear relationships were obtained in the ranges of 6-22 microg/mL for the (1D) method and 6-20 microg/mL for the (1DD) method. By applying the proposed methods, it was possible to determine pyritinol dihydrochloride in its pure powdered form with an accuracy of 100.36 +/- 1.497% (n = 9) for the (1D) method and an accuracy of 99.92 +/- 1.172% (n = 8) for the (1DD) method. Laboratory-prepared mixtures containing different ratios of (I), (II), and (III) were analyzed, and the proposed methods were valid for concentrations of < or = 10% (II) and < or = 50% (III). The proposed methods were validated and found to be suitable as stability-indicating assay methods for pyritinol in pharmaceutical formulations.     

Rapid determination of cinchocaine in skin by high-performance liquid chromatography

A simple, rapid, accurate, precise and specific analytical method has been developed, validated and applied for determination of cinchocaine in guinea pig and albino rabbit dorsal skins, after in vivo application of cinchocaine formulations. Extraction was performed using a solvent mixture of ethanol and 0.1 M hydrochloric acid (90:10; v/v). Samples were chromatographed on Spheri-5, RP(18) column with a particle size of 5 microm and 220 mm x 4.6 mm i.d. The mobile phase was a mixture of acetonitrile and triethylamine phosphate buffer (pH 2.8; 0.04 M) (60:40, v/v). UV detection was carried out at 247 nm and the run time was 6 min with typical retention time of cinchocaine of 3.63 +/- 0.02 min. Specificity was demonstrated, showing that the cinchocaine peak was free of interference from skin endogenous components. The detector response was found to be linear in the concentration range 0.96-56.00 microg/mL with a coefficient of correlation r = 0.99996. The relative standard deviations of within- and between-day analyses were all below 5%. The drug extraction procedure was validated. Satisfactory recoveries with relative standard deviation values below 5% were obtained, indicating efficient quantitative reproducible extraction procedure.     

Development and validation of a stability-indicating micellar electrokinetic chromatography method for the determination of ezetimibe in pharmaceutical formulations.

A micellar electrokinetic chromatography (MEKC) method was validated for the analysis of ezetimibe. The method was carried out on a fused-silica capillary (50 microm i.d.; effective length, 40 cm). The background electrolyte consisted of a 25 mM borate buffer and 25 mM anionic detergent SDS (pH 9.75)/methanol (90:10, v/v). The capillary temperature was maintained at 35 degrees C, the applied voltage was 30 kV; the injection was performed using a pressure mode at 50 mbar for 5 s, with detection at 232 nm. The method was linear in the range of 2-150 microg/mL (R2=0.9999). The specificity and the stability-indicating capability were proven through degradation studies, which also showed that there was no interference of the excipients. The limits of quantitation and detection were 2 and 0.41 microg/mL, respectively. The method was applied for the analysis of ezetimibe pharmaceutical formulations, and the results were compared to those of the liquid-chromatography method.     

Spectrophotometric study of the reaction mechanism between DDQ Pi- and iodine sigma-acceptors and chloroquine and pyrimethamine drugs and their determination in pure and in dosage forms

Two simple and accurate spectrophotometric methods are presented for the determination of anti-malarial drugs, chloroquine phosphate (CQP) and pyrimethamine (PYM), in pure and in different pharmaceutical preparations. The charge transphere (CT) reactions between CQP and PYM as electron donors and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) pi-acceptor and iodine sigma-acceptor reagents to give highly coloured complex species have been spectrophotometrically studied. The optimum experimental conditions have been studied carefully. Beer' law is obeyed over the concentration range of 1.0-15 microg ml(-1) for CQP and 1.0-40 microg ml(-1) for PYM using I(2) and at 5.0-53 microg ml(-1) for CQP and 1.0-46 microg ml(-1) for PYM using DDQ reagents, respectively. For more accurate results, Ringbom optimum concentration range is calculated and found to be 10-53 and 8-46 microg ml(-1) for CQP and PYM using DDQ, respectively and 5-15 and 8-40 microg ml(-1) for CQP and PYM using iodine, respectively. The Sandell sensitivity is found to be 0.038 and 0.046 g cm(-2) for DDQ method and 0.0078 and 0.056 g cm(-2) for I(2) method for CQP and PYM, respectively which indicates the high sensitivity of both methods. Standard deviation (S.D.=0.012-0.014 and 0.013-0.015) and relative standard deviation (R.S.D.=0.09-1.4 and 1.3-1.5%) (n=5) for DDQ and I(2) methods respectively, refer to the high accuracy and precision of the proposed methods. These results are also confirmed by between day precision of percent recovery of 99-100.6%, and 98-101% for CQP and PYM by DDQ method and 99-102% and 99.2-101.4% for CQP and PYM by I(2) method respectively. These data are comparable to those obtained by British and American pharmacopoeias assay for the determination of CQP and PYM in raw materials and in pharmaceutical preparations.     

Development and validation of a selective online dissolution method for rosiglitazone maleate

A new specific, accurate, precise, and reproducible selective online dissolution method for rosiglitazone maleate is developed and validated for the dissolution of rosiglitazone maleate in pharmaceutical formulations. The rationale of the method is based on the direct measurement of the absorbance of the analyte in the buffer medium at 242 nm using buffer as blank. Dissolution is achieved on a dissolution test apparatus consisting of photo diode array spectrophotometer, peristaltic pump, and temperature controller, using 0.01N HCl and 0.05M potassium chloride as the dissolution medium. The proposed method is developed, optimized, and validated in terms of linearity, reproducibility, accuracy, and selectivity for the dissolution of rosiglitazone maleate in pharmaceutical formulations. The method is found to be linear in the range of 1 to 14 microg/mL of rosiglitazone maleate with a correlation coefficient of 0.999. The dissolution studies of rosiglitazone maleate tablets obtained by the proposed method are in good agreement with those by high-performance liquid chromatography.     

Highly sensitive and selective spectrophotometric and spectrofluorimetric methods for the determination of ropinirole hydrochloride in tablets

Three sensitive, selective, accurate spectrophotometric and spectrofluorimetric methods have been developed for the determination of ropinirole hydrochloride in tablets. The first method was based on measuring the absorbance of drug solution in methanol at 250 nm. The Beer's law was obeyed in the concentration range 2.5-24 microg ml(-1). The second method was based on the charge transfer reaction of drug, as n-electron donor with 7,7,8,8-tetracyanoquinodimethane (TCNQ), as pi-acceptor in acetonitrile to give radical anions that are measured at 842 nm. The Beer's law was obeyed in the concentration range 0.6-8 microg ml(-1). The third method was based on derivatization reaction with 4-chloro-7-nitrobenzofurazan (NBD-Cl) in borate buffer of pH 8.5 followed by measuring the fluorescence intensity at 525 nm with excitation at 464 nm in chloroform. Beer's law was obeyed in the concentration range 0.01-1.3 microg ml(-1). The derivatization reaction product of drug with NBD-Cl was characterized by IR, 1H NMR and mass spectroscopy. The developed methods were validated. The following analytical parameters were investigated: the molar absorptivity (epsilon), limit of detection (LOD, microg ml(-1)) and limit of quantitation (LOQ, microg ml(-1)), precision, accuracy, recovery, and Sandell's sensitivity. Selectivity was validated by subjecting stock solution of ropinirole to acidic, basic, oxidative, and thermal degradation. No interference was observed from common excipients present in formulations. The proposed methods were successfully applied for determination of drug in tablets. The results of these proposed methods were compared with each other statistically.     

Quality control of benserazide-levodopa and carbidopa-levodopa tablets by capillary zone electrophoresis

In modern practice, the treatment of Parkinson's disease and syndrome is carried out using pharmaceutical formulations containing a combination of levodopa and a decarboxylation inhibitor (carbidopa or benserazide). Two pharmaceutical formulations were quantified by capillary zone electrophoresis using two procedures which differed only in the kind of background electrolyte used. One procedure used a 25 mM phosphate buffer, pH 2.5, while the second one used a 25 mM borate buffer, pH 8.5. The electrophoretic analysis was carried out using an uncoated fused- silica capillary, a separation voltage of 20 kV with currents typically less than 60 microA, and spectrophotometric detection at 205 nm. Calibration curves were performed for levodopa (concentration range 1-100 microg/mL), for carbidopa and benserazide (1-50 microg/mL), and the plots of the peak area versus concentration were found to be linear with a correlation coefficient better than 0.9990. Satisfactory results were obtained when commercial tablets were analyzed in terms of accuracy (98-102%), repeatability (0.6-2.0%), and intermediate precision (1.1-2.6%).     

Validated kinetic spectrophotometric method for the determination of metoprolol tartrate in pharmaceutical formulations

A kinetic spectrophotometric method has been described for the determination of metoprolol tartrate in pharmaceutical formulations. The method is based on reaction of the drug with alkaline potassium permanganate at 25+/-1 degrees C. The reaction is followed spectrophotometrically by measuring the change in absorbance at 610 nm as a function of time. The initial rate and fixed time (at 15.0 min) methods are utilized for constructing the calibration graphs to determine the concentration of the drug. Both the calibration graphs are linear in the concentration range of 1.46 x 10(-6)-8.76 x 10(-6) M (10.0-60.0 microg per 10 ml). The calibration data resulted in the linear regression equations of log (rate)=3.634+0.999 log C and A=6.300 x 10(-4)+6.491 x 10(-2) C for initial-rate and fixed time methods, respectively. The limits of quantitation for initial rate and fixed time methods are 0.04 and 0.10 microg ml(-1), respectively. The activation parameters such as E(a), DeltaH(double dagger), DeltaS(double dagger) and DeltaG(double dagger) are also evaluated for the reaction and found to be 90.73 kJ mol(-1), 88.20 kJ mol(-1), 84.54 J K(-1) mol(-1) and 63.01 kJ mol(-1), respectively. The results are validated statistically and through recovery studies. The method has been successfully applied to the determination of metoprolol tartrate in pharmaceutical formulations. Statistical comparison of the results with the reference method shows excellent agreement and indicates no significant difference in accuracy and precision.     

High-performance liquid chromatographic determination of pantoprazole and its main impurities in pharmaceuticals

An RP-HPLC method for simultaneous separation and quantification of pantoprazole and its five main impurities in pharmaceutical formulations was developed and validated. The separation was accomplished on a Zorbax Eclipse XDB C18 column (5 microm particle size, 150 x 4.6 mm id) using a gradient with mobile phase A [buffer-acetonitrile (70 + 30, v/v)], and mobile phase B [buffer-acetonitrile (30 + 70, v/v)]. The buffer was 0.01 M ammonium acetate solution with addition of 1 mL triethylamine/L of the solution, adjusted to pH 4.5 with orthophosphoric acid. The eluent flow rate was 1 mL/min, the temperature of the column was 30 degrees C, and the eluate was monitored at 290 nm. Linearity (r = 0.999), recovery (97.6-105.8%), RSD (0.55-1.90%), and LOQ (0.099-1.48 microg/mL) were evaluated and found to be satisfactory. The proposed method can be used for simultaneous identification and quantification of the analyzed compounds in pharmaceutical formulations.     

Capillary zone electrophoresis method for the determination of famotidine and related impurities in pharmaceuticals

A simple and rapid capillary zone electrophoresis (CZE) method with UV detection has been developed for the determination of famotidine and its potential impurities in pharmaceutical formulations. The electrophoretic separation of these compounds was performed using a fused silica capillary and 37.5mmolL(-1) phosphate buffer pH 3.5 as the electrolyte. Under the optimised conditions, six impurities could be resolved from the famotidine peak in less than 7min. The calibration curves obtained for the seven compounds were linear over the concentration range investigated (from 1.5 to 78.5microg mL(-1)). The intra- and inter-day relative standard deviations for the migration times and corrected peak areas were less than 2% and 5%, respectively. The detection limits were found to be 0.09microg mL(-1) for famotidine, and from 0.1 to 0.62microg mL(-1) depending on the impurities. The method has been successfully applied to the determination of famotidine in commercial dosage forms.     

Spectrophotometric determination of pipazethate hydrochloride in pure form and in pharmaceutical formulations

Three simple, sensitive, and reproducible spectrophotometric methods (A-C) for the determination of pipazethate hydrochloride (PiCl) in pure form and in pharmaceutical formulations are described. The first and second methods, A and B, are based on the oxidation of the drug by Fe3+ in the presence of o-phenanthroline (o-phen) or bipyridyl (bipy). The formation of tris-complex upon reactions with Fe3+-o-phen and/or Fe3+-bipy mixture in an acetate buffer solution of the optimum pH values was demonstrated at 510 and 522 nm, respectively, with o-phen and bipy. The third method, C, is based on the reduction of Fe(III) by PiCl in acid medium and subsequent interaction of Fe(II) with ferricyanide to form Prussian blue, which exhibits an absorption maximum at 750 nm. The concentration ranges are from 0.5 to 8, 2 to 16, and 3 to 15 microg/mL for Methods A-C, respectively. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The molar absorptivity, Sandell sensitivity, and detection and quantitation limits were calculated. The developed methods were successfully applied to the determination of PiCl in bulk and pharmaceutical formulations without any interference from common excipients. The relative standard deviations were < or =0.83% with recoveries of 98.9-101.15%.     

Indirect resolution of enantiomers of penicillamine by TLC and HPLC using Marfey's reagent and its variants

TLC and HPLC methods were developed for indirect chiral separation of penicillamine (3,3-dimethylcysteine) enantiomers after derivatization with Marfey's reagent (FDNP-Ala-NH(2)) and two of its structural variants, FDNP-Phe-NH(2) and FDNP-Val-NH(2). The binary mobile phase of phenol-water (3:1 v/v) and solvent combinations of acetonitrile and triethylamine phosphate buffer were found to give the best separation in normal and reversed-phase TLC, respectively. The diastereomers were also resolved on a reversed-phase C18 HPLC column with gradient elution of acetonitrile and 0.01 m trifluoroacetic acid. The results due to these three reagents were compared. The method was successful for checking the enantiomeric impurity of l-penicillamine in d-penicillamine and to check the enantiomeric purity of pharmaceutical formulations of d-penicillamine. The method was validated for linearity, repeatability, limit of detection and limit of quantification.