Application of LC and HPTLC-densitometry for the simultaneous determination of benazepril hydrochloride and hydrochlorothiazide

Validated capillary zone electrophoretic method for simultaneous analysis of benazepril in combination with amlodipine besylate and hydrochlorothiazide

In this work, a novel, simple, and quick capillary zone electrophoresis (CZE) method was proposed for simultaneous analysis of benazepril (BEN) with other co-administrated antihypertensive drugs, amlodipine besylate (AML) and hydrochlorothiazide (HCT), using a diode array detector (DAD). A fused silica capillary (78.5 cm total length, 70 cm effective length, and 75 μm id) was used in separation using a 40 mM phosphate buffer pH 7.5 as a running background electrolyte (BGE) under a positive potential of 30 KV, at a stable temperature of 25 °C for capillary during separation. Hydrodynamic injections were performed for 12 s at 50 mbar, and detection was performed at 210 nm for AML and BEN, at 225 nm for HCT, and at 232 nm for xipamide (XIP) added as an internal standard (IS). Separation of the three analyzed drugs and the IS was performed in less than 8 min. Migration times were 4.06, 5.23, 6.69, and 7.3 min for AML, HCT, BEN, and XIP, respectively. The findings proved that the proposed method was linear in the range of 10–80 μg/mL for all drugs with correlation coefficients >0.9994. The limit of detection (LOD) values of AML, HCT, and BEN were 1.004, 1.224, and 0.896 μg/mL, respectively, whereas the limit of quantification (LOQ) values were 3.124, 3.727, and 2.749 μg/mL for the cited drugs, respectively. Peak identity and purity were confirmed by DAD. The developed CZE method was applied for the analysis of the three antihypertensive drugs successfully in their combined pharmaceutical tablets, and it can be used for the quality control of single-pill combination (SPC) samples of these drugs in short time.

Comparative study between univariate spectrophotometry and multivariate calibration as analytical tools for simultaneous quantitation of Moexipril and Hydrochlorothiazide

Three simple, accurate, reproducible, and selective methods have been developed and subsequently validated for the simultaneous determination of Moexipril (MOX) and Hydrochlorothiazide (HCTZ) in pharmaceutical dosage form. The first method is the new extended ratio subtraction method (EXRSM) coupled to ratio subtraction method (RSM) for determination of both drugs in commercial dosage form. The second and third methods are multivariate calibration which include Principal Component Regression (PCR) and Partial Least Squares (PLSs). A detailed validation of the methods was performed following the ICH guidelines and the standard curves were found to be linear in the range of 10-60 and 2-30 for MOX and HCTZ in EXRSM method, respectively, with well accepted mean correlation coefficient for each analyte. The intra-day and inter-day precision and accuracy results were well within the acceptable limits.

Linear support vector regression and partial least squares chemometric models for determination of Hydrochlorothiazide and Benazepril hydrochloride in presence of related impurities: a comparative study

Partial least squares regression (PLSR) and support vector regression (SVR) are two popular chemometric models that are being subjected to a comparative study in the presented work. The comparison shows their characteristics via applying them to analyze Hydrochlorothiazide (HCZ) and Benazepril hydrochloride (BZ) in presence of HCZ impurities; Chlorothiazide (CT) and Salamide (DSA) as a case study. The analysis results prove to be valid for analysis of the two active ingredients in raw materials and pharmaceutical dosage form through handling UV spectral data in range (220-350 nm). For proper analysis a 4 factor 4 level experimental design was established resulting in a training set consisting of 16 mixtures containing different ratios of interfering species. An independent test set consisting of 8 mixtures was used to validate the prediction ability of the suggested models. The results presented indicate the ability of mentioned multivariate calibration models to analyze HCZ and BZ in presence of HCZ impurities CT and DSA with high selectivity and accuracy of mean percentage recoveries of (101.01±0.80) and (100.01±0.87) for HCZ and BZ respectively using PLSR model and of (99.78±0.80) and (99.85±1.08) for HCZ and BZ respectively using SVR model. The analysis results of the dosage form were statistically compared to the reference HPLC method with no significant differences regarding accuracy and precision. SVR model gives more accurate results compared to PLSR model and show high generalization ability, however, PLSR still keeps the advantage of being fast to optimize and implement.

Design and optimization of a chemometric-assisted spectrophotometric determination of telmisartan and hydrochlorothiazide in pharmaceutical dosage form

Two chemometric methods were developed for the simultaneous determination of telmisartan and hydrochlorothiazide. The chemometric methods applied were principal component regression (PCR) and partial least square (PLS-1). These approaches were successfully applied to quantify the two drugs in the mixture using the information included in the UV absorption spectra of appropriate solutions in the range of 200-350 nm with the intervals Δλ = 1 nm. The calibration of PCR and PLS-1 models was evaluated by internal validation (prediction of compounds in its own designed training set of calibration) and by external validation over laboratory prepared mixtures and pharmaceutical preparations. The PCR and PLS-1 methods require neither any separation step, nor any prior graphical treatment of the overlapping spectra of the two drugs in a mixture. The results of PCR and PLS-1 methods were compared with each other and a good agreement was found.

Derivative and Q-analysis Spectrophotometric Methods for Estimation of Hydrochlorothiazide and Olmesartan Medoxomil in Tablets

Two methods for simultaneous estimation of hydrochlorothiazide and olmesartan medoxomil in combined tablet dosage form have been developed. The first method is the application of Q-analysis method (absorbance ratio), which involves the formation of Q-absorbance equation at 264 nm (isobestic point) and at 271 nm, the maximum absorption of hydrochlorothiazide. The linearity ranges for hydrochlorothiazide and olmesartan medoxomil were 2.5-22.5 mug/ml and 4-36 mug/ml, respectively. The second method is based on the derivative spectrophotometric method at zero crossing wavelengths. The linearity ranges for hydrochlorothiazide and olmesartan medoxomil were 2.5-20 mug/ml and 4-32 mug/ml, respectively. The accuracy of the methods were assessed by recovery studies and was found to be 100.45% +/-0.4215 and 100.24% +/-0.3783 for absorbance ratio method and 99.39% +/-0.221 and 99.72% +/-0.11 for first derivative method, for hydrochlorothiazide and olmesartan medoxomil, respectively. These methods are simple, accurate and rapid, those require no preliminary separation and can therefore be used for routine analysis of both drugs in quality control laboratories.

RP-LC and HPTLC Methods for the Determination of Olmesartan Medoxomil and Hydrochlorothiazide in Combined Tablet Dosage Forms

Two new, rapid, precise, accurate and specific chromatographic methods were described for the simultaneous determination of olmesartan medoxomil and hydrochlorothiazide in combined tablet dosage forms. The first method was based on reversed phase liquid chromatography using an Eurosphere 100 RP C18 column (250 x 4.6 mm ID, 5 mum). The mobile phase was methanol-0.05% o-phosphoric acid (60:40 v/v) at a flow rate of 1.0 mL min(-1). Commercially available tablets and laboratory mixtures containing both drugs were assayed and detected using a UV detector at 270 nm. The second method involved silica gel 60 F(254) high performance thin layer chromatography and densitometric detection at 254 nm using acetonitrile-ethyl acetate-glacial acid (7:3:0.4 v/v/v) as the mobile phase. Calibration curves ranged between 200-600 and 125-375 ng spot(-1) for olmesartan and hydrochlorothiazide, respectively.

Application of first-derivative, ratio derivative spectrophotometry, TLC-densitometry and spectrofluorimetry for the simultaneous determination of telmisartan and hydrochlorothiazide in pharmaceutical dosage forms and plasma

Four sensitive methods are described for the direct determination of telmisartan (TELM) and hydrochlorothiazide (HCT) in combined dosage forms without prior separation. The first method is a first derivative spectophotometry (1D) using a zero- crossing technique of measurement at 241.6 and 227.6 nm for TELM and HCT, respectively. The second method is the first derivative of ratio spectrophotometry (1DD) where the amplitudes were measured at 242.7 nm for TELM and 274.9 nm for HCT. The third method is based on TLC separation of the two drugs followed by the densitometric measurements of their spots at 295 and 225 nm for TELM and HCT, respectively. The separation was carried out on silica gel 60 F254 using butanol: ammonia 25% (8:2 v/v) as mobile phase. The fourth method is spectrofluorimetric determination of TELM, depending on measuring the native fluorescence of the drug in 1 M sodium hydroxide at lambda excitation 230 nm and emission at 365 nm. The proposed methods were applied successfully for the determination of the two drugs in bulk powder and in pharmaceutical formulations. The spectrofluorimetric method was utilized for the analysis of TELM in human plasma.

Stability indicating RP-HPLC method for simultaneous determination of amlodipine and benazepril hydrochloride from their combination drug product

A stability indicating reversed-phase HPLC method has been developed and subsequently validated for simultaneous estimation of amlodipine (AM) present as amlodipine besylate (AB), and benazepril hydrochloride (BH) from their combination product. The proposed RP-HPLC method utilizes a Zorbax SB C18, 5 microm, 250 mm x 4.6 mm i.d. column, mobile phase consisting of phosphate buffer and acetonitrile in the proportion of 65:35 (v/v) with apparent pH adjusted to 7.0, and UV detection at 240 nm using a photodiode array detector. AB, BH, and their combination drug product were exposed to thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were analysed by the proposed method. Peak homogeneity data of AM and BH peaks obtained using photodiode array detector, in the stressed sample chromatograms, demonstrated the specificity of the method for their estimation in presence of degradants. The described method was linear over a range of 6-14 microg/ml for AM and 12-28 microg/ml for BH. The mean recoveries were 99.91 and 100.53% for AM and BH, respectively. F-test and t-test at 95% confidence level were used to check the intermediate precision data obtained under different experimental setups; the calculated value was found to be less than critical value.

Determination of hydrochlorothiazide and irbesartan in pharmaceuticals by fourth-order UV derivative spectrophotometry

The fourth-order derivative spectrum from the alcoholic sample is used. HCT can be determined by a specific peak-trough, of low intensity, at 330-340 nm. For IST evaluation, a peak-trough around 250-310 nm is available, common to both products, whose amplitude increases linearly only for low concentration values, while it decreases at higher values. The most difficult aspect of the analysis lies in how to find the optimal concentration range, so that both signals can be evaluated simultaneously. The best results were achieved by using a linear regression for HCT and a regression plane for IST.

Simultaneous determination of moexipril hydrochloride and hydrochlorothiazide in tablets by derivative spectrophotometric and high-performance liquid chromatographic methods

Two new simple and selective assay methods have been presented for the binary mixtures of moexipril hydrochloride (MOEX) and hydrochlorothiazide (HCTZ) in pharmaceutical formulations. The first method depends on second-derivative ultraviolet spectrophotometry with zero-crossing measurements at 215 and 234 nm for MOEX and HCTZ, respectively. The assay was linear over the concentration ranges 1.0-11.0 microg ml(-1) for MOEX and 0.5-9.0 microg ml(-1) for HCTZ. The determination limits for MOEX and HCTZ were found to be 1.0 and 0.5 microg ml(-1), respectively; while the detection limits were 0.2 microg ml(-1) for MOEX and 0.1 microg ml(-1) for HCTZ. The second method was based on isocratic reversed-phase liquid chromatography by using a mobile phase acetonitrile-20 mM phosphate buffer (pH 4.0) (50:50, v/v). Lisinopril was used as an internal standard (IS) and the substances were detected at 212 nm. The linearity range for both drugs was 0.5-12.0 microg ml(-1). The determination and detection limits were found to be 0.100 and 0.010 microg ml(-1) for MOEX and 0.025 and 0.005 microg ml(-1) for HCTZ, respectively. The proposed methods were successfully applied to the determination of these drugs in synthetic mixtures and commercially available tablets with a high percentage recovery, good accuracy and precision.

Simultaneous determination of irbesartan and hydrochlorothiazide in human plasma by liquid chromatography

A simple, selective, sensitive and precise high-performance liquid chromatographic plasma assay for the antihypertensive drugs, irbesartan and hydrochlorothiazide is described. Good chromatographic separation was achieved using a Supelcocil C(18) (5 micrometer 15 cmx4.6 mm) column and a mobile phase consisting of 10 mM potassium dihydrogen phosphate:methanol:acetonitrile (5:80:15 v/v/v) (pH:2.5) while at a flow-rate of 1.0 ml min(-1). Irbesartan and hydrochlorothiazide were detected at 275 nm and were eluted 5.8 and 7.8 min, respectively, after injection. No endogenous substances were found to interfere. The method utilizes protein precipitation with acetonitrile as the only sample preparation involved prior to reversed-phase high-performance liquid chromatography. No internal standard was required. Linearity range for irbesartan and hydrochlorothiazide was 10.0-60.0 microgram ml(-1) and 4.0-20.0 microgram ml(-1), respectively. The determination of intra- and inter-day precision (RSD) was less than 2.5 and 3.5%, at all concentration levels, while the inter- and intra-day accuracy (% difference) was less than 4.9-6.2%. This method is being used in a therapeutic drug monitoring service to quantitate these therapeutic agents in patients for pharmacokinetic studies.

Potentiometric and thermal studies of a coated-wire benazepril-selective electrode

A coated-wire benazepril-selective electrode based on incorporation of the benazepril-tetraphenylborate ion pair in a poly(vinylchloride) coating membrane was constructed. The influences of membrane composition, temperature, pH of the test solution, and foreign ions on the electrode performance were investigated. The electrode showed a Nernstian response over a benazepril concentration range of 1.26x10(-5) to 0.58x10(-2) M, at 25 degrees C, and was found to be very selective, precise, and usable within the pH range 2.5-9.2. The standard electrode potentials, E degrees, were determined at 20, 25, 30, 35, 40 and 45 degrees C, and used to calculate the isothermal temperature coefficient (dE degrees /dT) of the electrode. Temperatures higher than 45 degrees C seriously affect the electrode performance. The electrode was successfully used for potentiometric determination of benazepril hydrochloride both in pure solutions and in pharmaceutical preparations.