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.     

Liquid chromatographic determination of cetirizine in oral formulations

The development and validation of a reversed-phase liquid chromatographic (LC) method for the determination of cetirizine dihydrochloride in oral formulations are described. An isocratic LC analysis was performed on a reversed-phase C18 column (250 x 4.6 mm id, 5 microm particle size). The mobile phase was 1% orthophosphoric acid solution, pH 3.0-acetonitrile (60 + 40, v/v), pumped at a constant flow rate of 1.0 mL/min. Measurements were made at a wavelength of 232 nm. The calibration curves were linear over the range of 10-30 microg/mL (r2 = 0.9999). The relative standard deviation (RSD) values for intraday precision were 0.94 and 1.43% for tablets and compounded capsules, respectively. The RSD values for interday precision were 0.13 and 0.82% for tablets and compounded capsules, respectively. Recoveries ranged from 97.7 to 101.8% for tablets and from 98.4 to 102% for compounded capsules. No interferences from the excipients were observed. Because of its simplicity and accuracy, the method is suitable for routine quality-control analysis for cetirizine in tablets and compounded capsules.     

Development and application of spectrophotometric methods for the determination of citalopram hydrobromide in dosage forms

Study was carried out to develop two simple, fast, accurate and sensitive spectrophotometric methods (A and B) for the determination of citalopram hydrobromide in commercial tablet formulations. In method A, UV spectrophotometer determined the contents of citalopram hydrobromide in tablets at 240 nm in methanol solvent. The linear range was 5-40 microg ml-1 with molar absorptivity 1.4x10(4) l mol-1 cm-1. While the method B based on the reaction of citalopram base as n-electron donor with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone as pi-acceptors to give highly colored complex species that absorb maximally at 590 nm. Beer's law was obeyed in the concentration limit of 10-250 microg ml-1 with molar absorptivity 3.3x10(3) l mol-1 cm-1 for citalopram hydrobromide. The limits of detection and limit of quantification was calculated and found to be 5.2 microg ml-1 and 17.4 microg ml-1 respectively. The proposed methods were found to be rapid, accurate, precise and sensitive for the determination of citalopram hydrobromide in commercial tablet formulations with out interferences from common additives encountered.     

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.     

Determination of L-carnitine in food supplement formulations using ion-pair chromatography with indirect conductimetric detection

A novel method for the determination of L-carnitine in food supplement formulations was developed and validated, using ion-pair chromatography with indirect conductimetric detection. The chromatographic method was based on a non-polar (C18) column and an aqueous octanesulfonate (0.64 mM) eluent, acidified with trifluoroacetic acid (5.2 mM). The retention time was 5.4 min and the asymmetry factor 0.65. A linear calibration curve from 10 to 1000 microg/ml (r= 0.99998), with a detection limit of 2.7 microg/ml (25 microl injection volume), a repeatability %RSD of 0.8 (40 microg/ml, n = 5) and reproducibility %RSD of 2.6 were achieved. The proposed method was applied for the determination of carnitine in oral solutions and capsules. No interference from excipients was found and the only pretreatment step required was the appropriate dilution with the mobile phase. Recovery from spiked samples was ranged from 97.7 to 99.7% with a precision (%RSD, n = 3) of 0.01-2.1%.     

Development and validation of three stability-indicating methods for determination of bisacodyl in pure form and pharmaceutical preparations

Three new, simple, sensitive, and accurate stability-indicating methods were developed for quantitative determination of bisacodyl in the presence of its degradation products, monoacetyl bisacodyl (I) and desacetyl bisacodyl (II), in enteric coated tablets, suppositories, and raw material. The first is a spectrodensitometric method in which the drug is separated from I and II on silica gel plates using chloroform-acetone (9 + 1, v/v) as the mobile phase with ultraviolet detection of the separated bands at 223 nm over a concentration range of 0.2-1.4 microg/band for bisacodyl with mean recovery 100.35 +/- 1.923%. The second method is fourth derivative D4 spectrophotometry, which allows determination of bisacodyl in the presence of its degradation products in raw material at 223 nm using acetonitrile as the solvent with adherence to Beer's law over the concentration range 2-18 microg/mL with mean recovery 99.77+/-1.056%. In the third method, the spectrophotometric data of bisacodyl, I, and II using absolute ethanol as solvent were processed by 3 chemometric techniques: classical least-squares, principal component regression, and partial least-squares. A training set consisting of 15 mixtures containing different ratios of bisacodyl, I, and II was used for construction of the 3 models. A validation set consisting of 6 mixtures was used to validate the prediction ability of the suggested models. The 3 chemometric methods were applicable over a concentration range between 2-14microg/mL for bisacodyl with mean recovery of 99.97+/-0.865, 100.01 +/- 0.749, and 99.97 +/- 0.616% for the 3 models, respectively. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied to the analysis of raw material and pharmaceutical formulations containing bisacodyl, except for the second method that applies only for raw material. The validity of the suggested procedures was further assessed by applying the standard addition technique; the recoveries obtained were in accordance with those given by the reference method.     

Spectrophotometric methods for the determination of anti-emetic drugs in bulk and in pharmaceutical preparations.

Four rapid, simple, reproducible and sensitive methods (A-D) for assaying domperidone (I) and metoclopramide (II) in a bulk sample and in dosage forms were investigated. The first and second methods, A and B, are based on the oxidation of I and/or II 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. Methods C and D involve the addition of excess Ce4+ and the determination of unreacted oxidant by a decrease of the red color of chromotrope 2R (C2R) at a suitable lambda(max) of 528 nm for method C, or a decrease in the orange pink color of Rhodamine 6G (Rh6G) at a suitable lambda(max) value of 525 nm for method D. A regression analysis of Beer-Lambert plots showed a good correlation in the concentration range of 0.2-5.8 microg ml(-1). The apparent molar absorptivity, Sandell sensitivity, detection and quantification limits were calculated. For a more accurate analysis, the Ringbom optimum concentration ranges are 0.35-5.6 microg ml(-1). The developed methods were successfully applied to the determination of domperidone and metoclopramide in bulk and pharmaceutical preparations without any interference from common excipients.     

Univariate and simplex optimization for the flow-injection spectrophotometric determination of copper using nitroso-R salt as a complexing agent.

A simple colorimetric flow-injection system for the determination of Cu(II) based on a complexation reaction with nitroso-R salt is described. The chemical and FIA variables were established using the univariate and simplex methods. A small volume of Cu(II) was mixed with merged streams of nitroso-R salt and acetate buffer solutions. The absorbance of the complex was continuously monitored at 492 nm. The calibration curve over the concentration range 1.0-7.0 microg ml(-1) was obtained. The relative standard deviation for determining 4.0 microg ml(-1) Cu(II) was 0.47% (n = 11). The detection limit (3sigma) was 0.68 microg ml(-1) and the sample throughput was 150 h(-1). The validity of the method has been satisfactorily examined for the determination of Cu(II) in wastewater and copper ore samples. The accuracy was found to be high, because the student t-values were calculated to be less than the theoretical values when the results were compared with those obtained by FAAS.     

Determination of nifuroxazide and drotaverine hydrochloride in pharmaceutical preparations by three independent analytical methods

Three new, different, simple, sensitive, and accurate methods were developed for quantitative determination of nifuroxazide (I) and drotaverine hydrochloride (II) in a binary mixture. The first method was spectrophotometry, which allowed determination of I in the presence of II using a zero-order spectrum with an analytically useful maximum at 364.5 nm that obeyed Beer's law over a concentration range of 2-10 microg/mL with mean percentage recovery of 100.08 +/- 0.61. Determination of II in presence of I was obtained by second derivative spectrophotometry at 243.6 nm, which obeyed Beer's law over a concentration range of 2-10 microg/mL with mean recovery of 99.82 +/- 1.46%. The second method was spectrodensitometry, with which both drugs were separated on a silica gel plate using chloroform-acetone-methanol-glacial acetic acid (6 + 3 + 0.9 + 0.1) as the mobile phase and ultraviolet (UV) detection at 365 nm over a concentration range of 0.2-1 microg/band for both drugs, with mean recoveries of 99.99 +/- 0.15 and 100.00 +/- 0.34% for I and II, respectively. The third method was reversed-phase liquid chromatography using acetonitrile-water (40 + 60, v/v; adjusted to pH 2.55 with orthophosphoric acid) as the mobile phase and pentoxifylline as the internal standard at a flow rate of 1 mU/min with UV detection at 285 nm at ambient temperature over a concentration range of 2-10 microg/mL for both drugs, with mean recoveries of 100.24 +/- 1.51 and 100.08 +/- 0.78% for I and II, respectively. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulations containing the above drugs with no interference from other dosage form additives. The validity of the suggested procedures was further assessed by applying the standard addition technique which was found to be satisfactory, and the percentage recoveries obtained were in accordance with those given by the EVA Pharma reference spectrophotometric method.     

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

Two simple, sensitive and rapid extractive spectrophotometric methods have been developed for the assay of the antidepressant drug nortriptyline (NOR) hydrochloride in pure form and in different dosage forms. The methods involve the formation of colored ion-pairs between the drug and the complex of niobium(V)-thiocyanate (Nb-SCN) or iron(III)-thiocyanate (Fe-SCN) followed by their extraction with butanol or a mixture of butanol and chloroform and quantitative determination at 360 nm and 490 nm, using Nb-SCN and Fe-SCN, respectively. The experimental conditions were optimized to obtain the maximum colour intensity. The methods permit the determination of nortriptyline over a concentration range of 15-100 microg/ml and 5-24 microg/ml with the detection limit of 0.84 microg/ml and 0.32 microg/ml, using Nb-SCN and Fe-SCN, respectively. The proposed methods are applicable for the assay of the investigated drug in different dosage forms and the results are in good agreement with those obtained by the official and HPLC methods. No interference was observed from common excipients present in pharmaceutical formulations. The proposed procedures were applied to determine the amount of nortriptyline hydrochloride as active ingredient in the presence of its degradation product, dibenzosuberone. The extractive spectrophotometric methods can also be used to determine the amount of nortriptyline hydrochloride in tablets after its solid phase extraction (SPE).     

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.     

A sequential injection method for the determination of piroxicam in pharmaceutical formulations using europium sensitized fluorescence

A simple, selective and sensitive luminescence method for the assay of piroxicam (PX) in pharmaceutical formulation is developed. The method is based on the luminescence sensitization of europium (Eu³⁺) by complexation with PX. The signal for PX–EU is monitored at λ_ex=358 nm and λ_em=615 nm. Optimum conditions for the formation of the complex in methanol were 0.01 M TRIS buffer and 0.2 mM of Eu³⁺ which allows the determination of 100–2000 ppb of pX in batch method and 100–1000 ppb with limit of detection (LOD) = 23.0 ppb using sequential injection analysis (SIA). The relative standard deviations of the method range between 2 and 3% indicating excellent reproducibility of the method. The proposed method was successfully applied for he assay of PX in pharmaceutical formulations (Feldene capsules and tablets). Average recoveries of 101.0±0.3 and 98.8±2.7% were obtained for capsules in methanol using batch and sequential injection (SI) methods, respectively.     

Rapid determination of chromium(VI) in electroplating waste water by use of a spectrophotometric flow injection system

A new rapid and sensitive FI method is reported for spectrophotometric determination of trace chromium(VI) in electroplating waste water. The method is based on the reaction of Cr(VI) with sodium diphenylamine sulfonate (DPH) in acidic medium to form a purple complex (lambda(max) = 550 nm). Under the optimized conditions, the calibration curve is linear in the range 0.04-3.8 microg ml(-1) at a sampling rate of 30 h(-1). The detection limit of the method is 0.0217 microg ml(-1), and the relative standard deviation is 1.1% for eight determinations of 2 microg ml(-1) Cr(VI). The proposed method was applied to the determination of chromium in electroplating waste water with satisfactory results.     

Validated spectrophotometric methods for the estimation of moxifloxacin in bulk and pharmaceutical formulations

New, simple, cost effective, accurate and reproducible UV-spectrophotometric methods were developed and validated for the estimation of moxifloxacin in bulk and pharmaceutical formulations. Moxifloxacin was estimated at 296 nm in 0.1N hydrochloric acid (pH 1.2) and at 289 nm in phosphate buffer (pH 7.4). Beer's law was obeyed in the concentration range of 1-12 microg ml(-1) (r2=0.9999) in hydrochloric acid and 1-14 microg ml(-1) (r2=0.9998) in the phosphate buffer medium. The apparent molar absorptivity and Sandell's sensitivity coefficient were found to be 4.63 x 10(4) l mol(-1) cm(-1) and 9.5 ng cm(-2)/0.001 A in hydrochloric acid; and 4.08 x 10(4) l mol(-1) cm(-1) and 10.8 ng cm(-2)/0.001 A in phosphate buffer media, respectively indicating the high sensitivity of the proposed methods. These methods were tested and validated for various parameters according to ICH guidelines. The detection and quantitation limits were found to be 0.0402, 0.1217 microg ml(-1) in hydrochloric acid and 0.0384, 0.1163 microg ml(-1) in phosphate buffer medium, respectively. The proposed methods were successfully applied for the determination of moxifloxacin in pharmaceutical formulations (tablets, i.v. infusions, eye drops and polymeric nanoparticles). The results demonstrated that the procedure is accurate, precise and reproducible (relative standard deviation <2%), while being simple, cheap and less time consuming and hence can be suitably applied for the estimation of moxifloxacin in different dosage forms and dissolution studies.     

Smart stability-indicating spectrophotometric methods for determination of binary mixtures without prior separation

Ratio subtraction and isosbestic point methods are 2 innovating spectrophotometric methods used to determine vincamine in the presence of its acid degradation product and a mixture of cinnarizine (CN) and nicergoline (NIC). Linear correlations were obtained in the concentration range from 8-40 microg/mL for vincamine (I), 6-22 microg/mL for CN (II), and 6-36 microg/mL for NIC (III), with mean accuracies 99.72 +/- 0.917% for I, 99.91 +/- 0.703% for II, and 99.58 +/- 0.847 and 99.83 +/- 1.039% for III. The ratio subtraction method was utilized for the analysis of laboratory-prepared mixtures containing different ratios of vincamine and its degradation product, and it was valid in the presence of up to 80% degradation product. CN and NIC in synthetic mixtures were analyzed by the 2 proposed methods with the total content of the mixture determined at their respective isosbestic points of 270.2 and 235.8 nm, and the content of CN was determined by the ratio subtraction method. The proposed method was validated and found to be suitable as a stability-indicating assay method for vincamine in pharmaceutical formulations. The standard addition technique was applied to validate the results and to ensure the specificity of the proposed methods.     

Development and validation of column high-performance liquid chromatographic and ultraviolet spectrophotometric methods for citalopram in tablets

Column high-performance liquid chromatographic (LC) and UV spectrophotometric methods for the quantitative determination of citalopram, a potent and selective serotonin reuptake inhibitor, in tablets were developed. The parameters linearity, precision, accuracy, specificity, robustness, limit of detection, and limit of quantitation were studied according to International Conference on Harmonization guidelines. Chromatography was carried out by the reversed-phase technique on an ACE C18 column with a mobile phase composed of 0.30% triethylamine solution-acetonitrile (55 + 45, v/v) adjusted to pH 6.6 with 10% ortho-phosphoric acid at a flow rate of 1.0 mL/min and 25 degrees C. The UV spectrophotometric method was performed at 239 nm. The linearity of the LC method was in the range of 10.00-70.00 microg/mL, and 2.50-17.50 microg/mL for the UV spectrophotometric method. The interday and intraday assay precision was < 1.5% (relative standard deviation) for the LC and UV spectrophotometric methods. The recoveries were in the range 100.70-101.35% for the LC method and 98.48-98.65% for the UV spectrophotometric method. Statistical analysis by Student's t-test showed no significant difference between the results obtained by the 2 methods. The proposed methods are highly sensitive, precise, and accurate and can be used for the reliable quantitation of citalopram in tablets.     

Spectrofluorimetric determination of drugs containing active methylene group using N1-methyl nicotinamide chloride as a fluorigenic agent

A spectrofluorimetric method was described for the determination of drugs containing active methylene groups adjacent to carbonyl groups. The method was applied successfully to the determination of three life saving cardiovascular drugs, with narrow therapeutic indices: pentoxifylline (I), propafenone hydrochloride (II) and acebutolol hydrochloride (III), in laboratory-prepared mixtures, in commercial tablets and in plasma samples. The method involved the reaction of each of the tested drugs with N1-methyl nicotinamide chloride (NMNCl) in the presence of alkali, followed by addition of formic acid, where highly fluorescent reaction products were produced. The produced fluorescence were measured quantitatively at 472 nm (lambdaex 352 nm), 409 nm (lambdaex 310 nm) and 451 nm (lambdaex 266 nm) for (I), (II), and (III) respectively. The method was linear over concentration ranges of 10-1000 microg/ml , 0.2-12 microg/ml and 0.08-10 microg/ml in standard solutions for (I), (II), and (III) respectively. In spiked human plasma samples, calibration graphs were linear over concentration ranges of 20-1000 microg/ml, 0.2-15 microg/ml and 0.08-10 microg/ml for (I), (II), and (III) respectively. The method showed good accuracy, specificity and precision in both laboratory-prepared mixtures and spiked human plasma samples. The proposed method is simple, with low instrumentation requirements, suitable for quality control application, bioavailability and bioequivalency studies.     

Kinetic-spectrophotometric determination of palladium in hydrogenation catalyst by its catalytic effect on the oxidation of pyrogallol red by hydrogen peroxide

A new kinetic-spectrophotometric method is described for the determination of ultra trace amounts of Pd(II). The methods based on catalytic action of Pd(II) on the oxidation of pyrogallol red (PGR) with hydrogen peroxide at pH 9.7. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of the PGR at 540 nm, for the first 4.5 min from initiation of the reaction. Calibration curve was linear in the range of 0.02-1.00 microg ml(-1) Pd(II). The limit of detection is 0.017 microg ml(-1) Pd(II). The relative standard deviation (R.S.D.) for ten replicate analyses of 0.03 and 0.60 microg ml(-1) Pd(II) was 1.5 and 0.9%, respectively. The influence of more than 40 potential interfering ions was studied for the selectivity. The proposed method was used for the determination of palladium in catalytic material.     

A sensitive and simple extractive-spectrophotometric method for the determination of microgram amount of cobalt by using alpha-benzilmonoxime.

Alpha-benzilmonoxime has been used for the extraction and determination of cobalt at microgram amount. The reagent reacts with cobalt(II) in the pH range of 8.8 - 9.3 to form a yellow-color chelate, which is extracted in chloroform, toluene, and some other non-polar solvents. The chelate is stable in chloroform for about one day. Under the optimum conditions of the a-benzilmonoxime concentration and pH of 9.0, Beer's law was obeyed in the concentration range of 0.08 - 2.2 microg/ml cobalt. The molar absorptivity of the extracted species was 2.55 x 10(4) dm3/mol cm at 380 nm, with a detection limit of 0.01 microg/ml cobalt. Relative standard deviations of 0.4, 0.8 and 2.3% were found for the determination of cobalt concentrations of 2.2, 1.1 and 0.08 microg/ml, respectively. The effect of diverse ions on the determination of 1.00 microg/ml of cobalt has been studied. The method was applied to the determination of cobalt in vitamin B12 and B-complex ampoules, a Co2O3-Co3O4 laboratory chemical mixture and some synthetic alloy samples. The method is sensitive, simple, rapid and accurate.     

微波消解-石墨炉原子吸收光谱法测定胶囊中的痕量铬

研究了微波消解-石墨炉原子吸收光谱法测定胶囊中痕量铬的方法.选择HNO3作为微波消解的酸,通过干扰试验,发现该方法的选择性满足要求.方法线性关系良好,相关系数r2=0.999 8,检出限为1.7×10-14g,测定结果的相对标准偏差为2.63%(n=7),加标回收率为95.0%～104.0%.方法灵敏度高,重复性好,适...