Determination of lamivudine and stavudine in pharmaceutical preparations using chemometrics-assisted spectrophotometry

A simple chemometrics-assisted spectrophotometric method for the simultaneous determination of lamivudine and stavudine in pharmaceutical tablets is described. The UV absorption spectra of the studied drugs, in the range of 200–310 nm, showed a considerable degree of spectral overlapping ([D_i]^0.5 = 94.9%). Resolution of the mixture has been accomplished by using classical least-squares regression analysis (CLS) and principle components regression analysis methods (PCR). Beer’s law was obeyed for both drugs in the general concentration ranges of 2–12 and 3–15 μg ml⁻¹ for lamivudine and stavudine, respectively. The proposed methods were successfully applied for the determination of the two drugs in laboratory prepared mixtures. The overall recoveries percent were found 98.58 ± 1.53–101.30 ± 1.35 (CLS) and 98.62 ± 1.65–101.13 ± 1.04 (PCR) for lamivudine and 98.43 ± 1.62–99.42 ± 1.55 (CLS) and 98.23 ± 1.97–101.20 ± 1.79 (PCR) for stavudine, respectively. The commercial tablets percentage content was found 98.10 ± 2.5–102.47 ± 2.94 (CLS) and 99.12 ± 1.71–100.92 ± 1.54 (PCR) for lamivudine and 96.00 ± 2.94–98.17 ± 1.72 (CLS) and 97.40 ± 1.55–97.80 ± 1.92 (PCR) for stavudine, respectively. Good percentage recoveries and proper statistical data obtained with both the laboratory prepared mixtures and the commercial tablets proved the suitability and efficiency of the proposed procedures for routine analysis and quality control purposes with quite satisfactory precision. A comparison of the obtained results from CLS and PCR were also performed with those obtained from reported method. The obtained F- and t-values obtained indicating no significant differences between the results of the proposed and reported methods.     

Determination of miconazole in pharmaceutical creams using internal standard and second derivative spectrophotometry

A simple method is proposed for miconazole determination in pharmaceutical creams, based on extraction and second derivative spectrophotometry. In the presence of sodium lauryl sulfate (0.5%) and sulphuric acid (0.4 mol l(-1)), the miconazole and internal standard (IS) (methylene blue) were extracted to 100 microl of methylene chloride. The organic phase was evaporated in the nitrogen stream and the dry residue was dissolved in methanol (1.5 ml). The analytical signal was obtained as the ratio between second derivative absorbances measured at 236.9 nm (miconazole) and at 663.2 nm (IS). The use of IS in such multi-stage procedure enabled quite good analytical performance in calibration range 50.0 400 mg l(-1): linear correlation coefficient 0.9995, precision (measured as CV for ten replicates) at 50.0 mg l(-1) and at 400 mg l(-1) of miconazole was 1.5 and 0.5% respectively. Four commercial pharmaceutical creams were analyzed and the results obtained were in good agreement with the results obtained by reversed-phase high performance liquid chromatography (HPLC).     

Simultaneous determination of acetaminophen and codeine in pharmaceutical preparations by derivative spectrophotometry

First derivative UV spectrophotometry has been used for the simultaneous determination of acetaminophen and codeine. Acetaminophen has been assayed by measuring the first derivative absorbances at 263.4 nm and codeine at 251.2 nm. The concentrations of acetaminophen and codeine have been calculated without interference of each other. The procedure is simple and rapid and provides accurate and precise results.     

Determination of zinc in pharmaceutical preparations by atomic absorption spectrophotometry

The analysis for Zn content of a variety of pharmaceutical preparations by atomic absorption spectrophotometry is recorded. The method for creams, ointments and pastes involves extraction with ether, dissolving the residue in HCl, followed by suitable dilution of the extract to bring the Zn content within the limits of the calibration graph, and measurement of the Zn content using the 213·9 nm resonance line. For lotions and dusting powders the initial ether extraction is neglected; for liquid preparations a simple dilution is required. The method showed a good degree of accuracy and precision and was specific for Zn no interference being encountered from a variety of metals and other common excipient materials that are used in pharmaceutical preparations.     

Applications of derivative UV spectrophotometry for the determinations of cetirizine dihydrochloride in pharmaceutical preparations

A method for the determination of cetirizine dihydrochloride in pharmaceuticals by first-, second-, third- and fourth- order derivative spectrophotometry is described, using "peak-peak" (P-P), and "peak-zero" (P-0) measurements. The calibration curves are linear within the concentration range of 7.5-22.5 microg ml(-1) for cetirizine dihydrochloride. The procedure is simple, rapid and the results are reliable.     

Applications of derivative UV spectrophotometry for the determinations of fenbufen and ketoprofen in pharmaceutical preparations

A methods for the determination of fenbufen and ketoprofen in pharmaceuticals by classical spectrophotometry--zero order derivative, first and second order derivatives spectrophotometry is described. using "peak-peak" (P-P) and, "peak-zero" (P-O) measurements. The calibration curves are linear within the concentration range of 2.0 - 12.0 microg x mL(-1) for fenbufen and ketoprofen. The procedure is simple, rapid and the results are reliable.     

Determination of ranitidine hydrochloride in pharmaceutical preparations by titrimetry and visible spectrophotometry using bromate and acid dyes

Four new methods using titrimetry and spectrophotometry are described for the determination of ranitidine hydrochloride (RNH) with potassium bromate as the oxidimetric reagent and acid dyes, methyl orange, indigo carmine and metanil yellow. In direct titrimetry (method A), the drug is titrated directly with bromate in acid medium and in the presence of excess of bromide using methyl orange indicator. In back titrimetry (method B), the drug is treated with a measured excess of bromate in the presence of bromide and acid, and the unreacted bromine is determined iodometrically. Both spectrophotometric methods are based on the oxidation of RNH by a known excess of bromate in acid medium and in the presence of excess of bromide followed by estimation of surplus oxidant by reacting with either indigo carmine (method C) or metanil yellow (method D), and measuring the absorbance at 610 or 530 nm. In methods B, C and D, reacted oxidant corresponds to the drug content. The experimental conditions are optimized. Titrimetric procedures are applicable over the ranges 1-10 mg (A) and 1-17 mg (B), and the reaction stoichiometry is found to be 1:1 (BrO(-)(3): RNH). In spectrophotometric methods, the absorbance is found to increase linearly with increasing concentration of RNH, which is corroborated by the calculated correlation coefficient (r) of 0.9984 (C) and 0.9976 (D). The systems obey Beer's law for 2-12 and 1-7 microg ml(-1), for methods C and D, respectively. Method D with a molar absorptivity of 9.82 x 10(4) l mol(-l) cm(-1) is found to be more sensitive than method C ( epsilon = 2.06 x l0(4) l mol(-1) cm(-1)). The limits of detection and quantification are reported for both the spectrophotometric methods. The proposed methods were applied successfully to the determination of RNH in tablets and injections. The reliability of the assay was established by parallel determination by the official method and by recovery studies.     

Application of derivative spectrophotometry for determination of enalapril, hydrochlorothiazide and walsartan in complex pharmaceutical preparations

A derivative spectrophotometry method was developed to determine enalapril, hydrochlorothiazide, candesartan and walsartan in complex antihypertensive drugs. The pharmaceutical preparations containing hydrochlorothiazide and one of the angiotensin convertase inhibitors were investigated. It was found that the developed method enables the constituents of the investigated drugs to be determined directly despite evident interference of the zero order absorption spectra. For determination of enalapril and hydrochlorothiazide as well as candesartan and hydrochlorothiazide the first derivative was used, while for walsartan and hydrochlorothiazide the second derivative was employed. The method was of high sensitivity; the LOD accuracy for enalapril was 2.81 microg x mL(-1), 0.56 microg x mL(-1) for candesartan, 4.02 microg x mL(-1) for walsartan and ranged from 0.31 microg x mL(-1) to 1.78 microgxmL(-1) for hydrochlorothiazide, depending on preparation under investigation. The recovery of individual constituents was within the limit of 100% +/- 5%, RSD varied from 1.11% to 2.94%, and the linearity range was from 4.1 microg x mL(-1) to 20.5 microg x mL(-1) for enalapril, from 6.45 microg x mL(-1) to 32.25 microg x mL(-1) for walsartan, from 2.36 microg x mL(-1) to 11.80 microg x mL(-1) for candesartan, and from 0.96 microg x mL(-1) to 26.00 microg x mL(-1) for hydrochlorothiazide.     

Determination of nimesulide in pharmaceutical dosage forms by second order derivative UV spectrophotometry

In this study, nimesulide which has been used as an analgesic, antipyretic and anti-inflammatory agent, was analyzed by using second order derivative UV spectrophotometry. The solvent, the degree of derivation, ranges of wavelength and n-value were chosen in order to optimize the conditions. The concentration of nimesulide in its solutions in ethanol and chloroform were determined between the wavelength ranges of 200 and 500 nm (n = 6, delta lambda = 21) and in the linearity ranges of 2.0-90.0 microg ml(-1) in ethanol and 2.0-50.0 microg ml(-1) in chloroform by using the values obtained from the second derivative UV spectrum of the substance. The developed second derivative UV spectrophotometric method was applied to the pharmaceutical preparations such as tablet, sachet (granule) and suspension. Tablet and sachet were analysed in ethanol while the suspension was analysed in chloroform. The results obtained from derivative UV spectrophotometry were compared with those obtained by using HPLC. It was found that the difference was not statistically important between these methods. It was concluded that developed derivative UV spectrophotometric method was accurate, sensitive, precise, reproducible and could be applied directly and easily to the pharmaceutical preparations.     

Determination of astemizole in pharmaceutical preparations using spectrophotometric methods

UV absorption and second derivative spectrophotometric methods were developed for the determination of astemizole in commercial pharmaceutical formulations containing this compound alone. Solutions of astemizole in 0.1 M HCl:methanol (1:3) were used in the methods and the linearity range was 4.6-45.8 microg ml(-1) in both methods. The mean recoveries and relative standard deviations were calculated and the method was applied to two commercial preparations marketed in Turkey. Results were compared with the literature method, HPLC. Also, two new spectrophotometric methods are described for the simultaneous determination of astemizole and pseudoephedrine hydrochloride in their combination. In the first method, first derivative spectrophotometry, dA/dlambda values were read at selected wavelengths in zero-crossing points in the first derivative spectra of the mixture solution in 0.1 M HCl:methanol (1:3). In the second, ratio spectra derivative spectrophotometry, analytical signals were measured at the wavelengths corresponding to either maximums and minimums for both drugs in their solution in 0.1 M HCl:methanol (1:3) in the first derivative spectra of their ratio spectra. The procedures do not require any separation step. The mean recoveries were found satisfactory in the methods.     

Determination of diosmin in pharmaceutical formulations using Fourier transform infrared spectrophotometry

A Fourier transform infrared (FT-IR) spectrometric method was developed for the rapid, direct measurement of diosmin in different pharmaceutical drugs. Conventional KBr-spectra were compared for best determination of active substance in commercial preparations. The Beer–Lambert law and two chemometric approaches, partial least squares (PLS) and principal component regression (PCR+) methods, were tried in data processing.     

Determination of diphenhydramine hydrochloride in some single tertiary alkylamine pharmaceutical preparations by flow injection spectrophotometry

A simple and rapid spectrophotometric method with flow injection is proposed for determination of diphenhydramine hydrochloride in some single tertiary alkylamine pharmaceutical preparations (capsule and syrup). It is based on ion pair formation with bromocresol green in a pH 3 buffer which a yellow ion pair compound is extracted into chloroform layer. An aqueous layer containing excess bromocresol green is injected into a carrier stream of 0.01 M borax solution and absorbance of the stream is continuously monitored at 610 nm. Diminution of the bromocresol green is related to an amount of diphenhydramine hydrochloride that can be evaluated from a calibration graph established by a plot of diphenhydramine hydrochloride concentration (micro gm l(-1)) and peak height (mV). Optimization will be discussed. The calibration graph is linear over the concentration ranges of 5-21 and 75-188 micro gm l(-1). A throughput of 100 injections h(-1) can be obtained. Application to assay for capsule and syrup samples has been demonstrated. The method is validated by comparing the results with HPLC analyses.     

Determination of lidocaine in pharmaceutical preparations using thin-layer chromatographic densitometry

A thin-layer chromatographic (TLC)—UV-densitometric method has been developed for the analysis of lidocaine in ointments, suppositories and gels. The method is quantitative, rapid and able to separate lidocaine from other components in the pharmaceutical dosage forms investigated without preliminary extraction. The method gave precise and reproducible results.     

Determination of dipyridamole in pharmaceutical preparations using square wave voltammetry

An analytical methodology using square wave voltammetry (SWV) at a hanging mercury drop electrode (HMDE) was developed for the quantitative determination of dipyridamole (DIP), a drug used for the treatment of several cardiovascular diseases, in pharmaceutical tablets and injections of Persantin^® in phosphate buffer (pH 3.0; 0.1 M). After optimization of the parameters for SWV, analytical curves were obtained for application in the range of 1.28 × 10⁻⁶ M to 7.02 × 10⁻⁶ M. It was found a detection limit (DL) of 1.88 × 10⁻⁸ M (9.50 ng/ml). The repeatability and the reproducibility of the method were determinated by successive measurements of DIP solutions on the range of the analytical curve with a coefficient variation of 0.97% (n = 5) and 1.15%, respectively. The apparent recoveries were obtained by the IUPAC recommended procedure using the second reduction peak. Recoveries obtained by SWV were compared with the UV–vis spectrophotometric method. It was found that the determination of DIP in Persantin^® tablets gave a mean value of 75.6 ± 0.4 mg (100.8%) and 68.9 ± 0.3 mg (91.8%) for SWV and UV–vis spectrophotometry, respectively. In the case of injections, it was found 10.4 ± 0.1 mg (103.4%) and 9.9 ± 0.2 mg (99.9%) for SWV and UV–vis spectrophotometry. Both apparent recoveries for the two types of formulations are in good accordance with the declared value of 75 mg (tablets) and 10 mg (injections).     

Determination of tetrahydrozoline hydrochloride and fluorometholone in pharmaceutical formulations by HPLC and derivative UV spectrophotometry

Two methods for the quantitative determination of tetrahydrozoline hydrochloride (1) and fluorometholone (2) in pharmaceutical eye drops (Efemoline) are described. The procedures are based on derivative UV spectrophotometry and HPLC. In the former method, d2A/d lambda 2 values were measured in methanol at 226 and 282 nm for 1 and 2, respectively. The relative standard deviations for the method were found to be 1.06% for 1 and 0.98% for 2. The latter method based on a reversed phase HPLC system using a Partisil 5 ODS analytical column. The mobile phase used for the separation of 1, 2 and internal standard (lidocaine) was methanol/acetonitrile/water (50:50:10 v/v) and the compounds in the eye drops were detected at 220 nm using an UV detector. The relative standard deviations for the HPLC method were determined to be 0.61% and 0.50% for 1 and 2, respectively. The proposed methods, which give thoroughly comparable data, are simple, rapid, and allow precise and accurate results and could be used for commercial formulations containing tetrahydrozoline hydrochloride and fluorometholone in combination.