A design of experiment based RP-HPLC method for the simultaneous estimation of antihypertensive drugs with greenness assessment.

The correlation between blood pressure (BP) and cardiovascular risk has a continuous, positive, and linear pattern. Lowering high BP decreases the risk associated with cardiovascular disease. Chlorthalidone (CHD) and Losartan potassium (LOS) combination is used to treat hypertension. The analytical community was concerned with minimizing or reducing the use of toxic chemicals and solvents. Therefore, the current study aimed to develop a rapid, sensitive, and cost-effective green RP-HPLC method to determine CHD and LOS simultaneously in a short analysis of time. Method optimization was performed by Central composite design (CCD), the flow rate and the change of time were chosen as factors. Effective separation was conducted on Zorbax SB-C18 (4.6 mm × 150 mm, 5 µm) column by gradient mobile phase comprising phosphate buffer and ethanol flowing at 0.859 ml/min, and the wavelength detected at 230 nm. As per ICH criteria, the technique was proven to be precise, accurate, and linear over the concentration range of 4.3-8.1 µg/ml for CHD and 35-65 µg/ml for LOS. Furthermore, the method's greenness was examined by three different metrics, confirming that less toxic effect on the environment. Hence, the optimized approach proves to be eco-friendly, simple, and robust for the concurrent evaluation of CHD and LOS in pharmaceutical formulations.

Simultaneous Estimation of Telmisartan, Chlorthalidone, Amlodipine Besylate and Atorvastatin by RP-HPLC Method for Synchronous Assay of Multiple FDC Products Using Analytical FMCEA-Based AQbD Approach.

Numerous reversed-phase high-pressure liquid chromatography (RP-HPLC) and high-performance thin-layer chromatography (HPTLC) techniques have been published for the estimation of fixed-dose combinations (FDCs) of telmisartan (TEL). No published literature has been reported to date which described the synchronous estimation of FDCs of TEL using a single chromatography condition. Hence, the RP-HPLC method has been developed and validated for synchronous analysis of FDCs of TEL using an enhanced analytical quality by design (AQbD) approach to save time, cost and solvent for analysis. The implementation of AQbD was initiated with the identification of failure modes (FMs) using the Ishikawa diagram, and their critical effect analysis was carried out by risk priority number ranking and filtering method. The identified critical FMs were optimized by design of experiments-based response surface modeling using the Box-Behnken design. The method operable design region was navigated and control strategy was framed to mitigate the risk of critical FM. The RP-HPLC method was developed using Shim-Pack octadecyl silane C18 column and acetonitrile: 1.0%v/v triethylamine (pH 6.5 adjusted using perchloric acid; 42:58, %v/v). The developed method was found to be validated as per the International Council For Harmonization Q2 (R1) guideline. The method was applied for the synchronous assay of seven different FDCs of TEL and assay results were found in good compliance with the respective labeled claim.

HPLC method transfer study for simultaneous determination of seven angiotensin II receptor blockers.

In this study, a sensitive high-performance liquid chromatography method was developed and validated for the simultaneous determination of seven angiotensin II receptor blockers, namely, hydrochlorothiazide, chlorthalidone, eprosartan mesylate, valsartan, losartan potassium, irbesartan, and candesartan cilexetil. Different chromatographic parameters were tested and fully optimized. Best chromatographic separation was accomplished on a reversed-phase octadecylsilyl column (250 × 4.6 mm id; 5 µm) under gradient elution using methanol/sodium phosphate monobasic buffer (0.01 M, pH 6.5) as mobile phase. The detection of target analytes was obtained at 254 nm. The pH of the buffer has been selected according to Marvin® sketch software. The proposed method was validated according to ICH guidelines and showed good precision (relative standard deviation < 1), good linearity (square of correlation coefficient ≥ 0.999), and high accuracy (between 98 and 102%) with detection limit and quantitation limit (40 and 160 ng/mL, respectively) for all the detected analytes.

QbD-based development of an extraction procedure for simultaneous quantification of telmisartan, amlodipine besylate and chlorthalidone in combination complex matrix formulation.

The main objective of this study was to establish an efficient extraction procedure for the estimation of telmisartan, amlodipine and chlorthalidone from their combination in sample matrix using an analytical quality by design approach. Initial screening studies were performed for optimization of a suitable diluent to extract active components from sample matrix. Further, the same study was extended for the identification of critical method attributes and the factors affecting the analytical target profile. This study also explains the rugged and robust quantitative determination of combinations drugs with a shorter run time. The design of experimental studies confirms that the current center point parameters are well suited to recoveries. The chromatographic separation was achieved with an X-Terra RP8, 150 × 4.6 mm, 3.5 µm column with an isocratic mobile phase (mixture of 20 mm aqueous ammonium acetate and acetonitrile). To demonstrate the stability-indicating nature of the optimized method, forced degradation studies were conducted and proved. The optimized method was validated according to International Conference on Harmonization guidelines.

Stability-Indicating RP-UPLC Method for Simultaneous Determination of Azilsartan Medoxomil and Chlorthalidone in Tablets in the Presence of Its Degradation Products.

Azilsartan Medoxomil (AZL) angiotensin II receptor blocker and chlorthalidone (CLT) were determined by ultraperformance liquid chromatography (UPLC) method in their combined dosage form, they were both subjected to forced degradation studies under extensive stress conditions. The method is a stability indicating by resolving the investigated drugs from their degradation products. Moreover, the degradation products for both drugs obtained from forced degradation were subjected to LC-MS for structure elucidation. The UPLC technique depends on the measurement of spectra for AZL and CLT at 254 nm. Linearity, accuracy and intermediate precision were acceptable over the concentration range of 67.2-268.8 and 40-160 µg/mL for AZL and CLT, respectively. The method was applied for the determination of the studied drugs in their dosage forms. The UPLC method is inexpensive, simple and considered as green chemistry method for the routine analysis and quality control of both drugs in their combined dosage form.

Identification and proportion of the enantiomers of the antihypertensive drug chlortalidone in its Form II by high quality single-crystal X-ray diffraction data.

Chlortalidone (CTD) is a diuretic drug largely used as part of antihypertensive therapies. It is marketed as an equimolar mixture of its enantiomers in the racemic crystal phase named Form I, despite of the higher aqueous solubility of another crystal form. The latter, named Form II, was thought to contain both enantiomers as a racemic conglomerate, i.e., in the form of a mixture of crystals, half of which consists solely of the (R)-enantiomer, the other half the (S)-enantiomer. The occurrence of both enantiomers in individual crystals of CTD Form II was demonstrated in this study. Spontaneous resolution does really occur upon crystallization, as presumed previously even without physical evidence of the (S)-enantiomer. Both (R) and (S)-enantiomers were successfully identified as two domains of a twinned by inversion single crystal of CTD Form II. A reliable Flack parameter of 0.14(4) allowed to determine the proportion of the enantiomers in the crystal, which is formed with 86% of the (R)-enantiomer and 14% of the (S)-enantiomer.

Stability-indicating RP-LC method for determination of azilsartan medoxomil and chlorthalidone in pharmaceutical dosage forms: application to degradation kinetics.

A RP-LC method was developed and validated for simultaneous determination of the active components, azilsartan medoxomil (AZL) and chlorthalidone (CLT), in their novel antihypertensive combined recipe. The chromatographic separation was achieved on an Eclipse XDB-C18 (4.6 × 150 mm, 5 µm) column using a mobile phase consisting of methanol/potassium hydrogen phosphate buffer (pH 8, 0.05 M) (40:60, v/v) in isocratic mode. The flow rate was maintained at 0.8 mL min(-1) at ambient temperature. Detection was carried out at 210 nm. The method was validated according to the ICH guidelines. Linearity, accuracy, and precision were satisfactory over the concentration range of 5.0-50.0 and 2.5-25.0 µg mL(-1) for AZL and CLT, respectively (r (2) = 0.9999). LODs for AZL and CLT were 0.90 and 0.32 µg mL(-1), whereas LOQs were 2.72 and 0.98 µg mL(-1), respectively. Both drugs were subjected to forced degradation studies under hydrolysis (neutral, acidic, and alkaline), oxidative, and photolytic extensive stress conditions. The proposed method is stability indicating by the resolution of the investigated drugs from their degradation products. Moreover, the kinetics of the acidic degradation of AZL as well as the kinetics of the alkaline degradation of CLT were investigated. Arrhenius plots were constructed and the apparent first-order rate constants, half-life times, shelf-life times, and the activation energies of the degradation processes were calculated. The method was successfully applied for the determination of the studied drugs simultaneously in their coformulated tablet. The developed method is specific and stability indicating for the quality control and routine analysis of the cited medications in their pharmaceutical preparations.

Analysis of chlorthalidone polymorphs in raw materials and tablets and the effect of forms I and II on the dissolution properties of drug products.

Chlorthalidone (CTD) is an antihypertensive drug and exhibits four crystalline forms: I, II, III and IV. In this paper, the incidence of CTD polymorphs in raw materials and in tablets as well as the solubility and dissolution properties of forms I and II have been studied. Raw materials were named as A, B, C, D, and E and tablets as Reference, G1, G2 and S. Using powder X-ray diffraction and infrared spectroscopy analyses we found that A, B, E, Reference and G1 contain CTD form I; C, D and S contain predominantly form II; and G2 contain a mixture of both forms. Solubility experiments showed that form II is up to 49% more soluble than form I and dissolution studies showed a significantly effect of the polymorphism on the dissolution of CTD from tablets. Based on these results, it was concluded that only the CTD form I is acceptable for preparation of tablet form. Moreover, we proposed the polymorphic quality control of CTD raw materials and tablets.

Phase quantification of antihypertensive drugs - Chlorthalidone, Hydrochlorothiazide, Losartan and combinations, Losartan/Chlorthalidone and Losartan/Hydrochlorothiazide - by the Rietveld method.

The identification and quantification of crystalline phases of antihypertensive drugs - Losartan potassium (LOS-K), Hydrochlorothiazide (HCTZ) and Chlorthalidone (CTD) were carried out by means of X-ray powder diffraction data and the Rietveld method. Quantitative phase analyses of Losartan potassium/Chlorthalidone (LOS-K/CTD) and Losartan potassium/Hydrochlorothiazide (LOS-K/HCTZ) combinations were also evaluated. The results indicated that for diuretics (HCTZ and CTD) only one crystalline phase was found in samples, and for LOS-K the crystal structure showed similarity between the Bragg peaks to the phase described as monoclinic and space group P21/c. After one year storage, the orthorhombic one was also observed in this sample.

Simultaneous determination of atenolol, chlorthalidone and amiloride in pharmaceutical preparations by capillary zone electrophoresis with ultraviolet detection.

Capillary zone electrophoresis methods for the simultaneous determination of the beta-blocker drugs, atenolol, chlorthalidone and amiloride, in pharmaceutical formulations have been developed. The influences of several factors (buffer pH, concentration, applied voltage, capillary temperature and injection time) were studied. Using phenobarbital as internal standard, the analytes were all separated in less than 4 min. The separation was carried out in normal polarity mode at 25 degrees C, 25 kV and using hydrodynamic injection (10 s). The separation was effected in an uncoated fused-silica capillary (75 mum i.d. x 52 cm) and a background electrolyte of 25 mm H(3)PO(4) adjusted with 1 m NaOH solution (pH 9.0) and detection at 198 nm. The method was validated with respect to linearity, limit of detection and quantification, accuracy, precision and selectivity. Calibration curves were linear over the range 1-250 microg/mL for atenolol and chlorthalidone and from 2.5-250 microg/mL for amiloride. The relative standard deviations of intra- and inter-day migration times and corrected peak areas were less than 6.0%. The method showed good precision and accuracy and was successfully applied to the simultaneous determination of atenolol, chlorthalidone and amiloride in various pharmaceutical tablets formulations.

Development and validation of a reversed-phase high-performance liquid chromatographic method for the simultaneous determination of amiloride hydrochloride, atenolol, hydrochlorothiazide, and chlorthalidone in their combined mixtures.

A high-performance liquid chromatographic method was developed for the simultaneous determination of 2 ternary mixtures containing amiloride hydrochloride, atenolol, hydrochlorothiazide, and chlorthalidone used in hypertension therapy. The use of cyanopropyl column results in satisfactory separation of both mixtures. The mobile phase consisted of 10 mM KH2PO4 buffer (pH 4.5) and methanol in a ratio of (75 + 25% v/v), at a flow rate of 1 mL/min. UV detector was operated at 275 nm. Calibration graphs were linear in the concentration ranges of 2-10, 20-200, 10-100, and 5-50 microg/mL for amiloride hydrochloride, atenolol, hydrochlorothiazide, and chlorthalidone, respectively. Intraday and interday precision values (relative standard deviation) were <1.13 for mixture I (amiloride hydrochloride, atenolol, chlorthalidone), and <0.93 for mixture II (amiloride hydrochloride, atenolol, hydrochlorothiazide). The method was successfully applied for the determination of the 2 combinations in laboratory-prepared mixtures and commercial pharmaceutical formulation with high accuracy and precision. Statistical comparison of the results with those of the published methods showed excellent agreement and indicates no significant difference between them.

HPLC method for the simultaneous determination of atenolol and chlorthalidone in human breast milk.

A high-performance liquid chromatographic method was optimized and validated for the determination of atenolol and chlorthalidone (CT) in human breast milk. The milk samples were extracted and purified using ACN and phosphoric acid for precipitation of proteins followed by removal of ACN and milk fats by extraction with methylene chloride. The samples were applied, after an extraction procedure, to a cyanide column using a mobile phase consisting of ACN/water (35:65 v/v) and buffered at pH 4.0 with flow rate of 1.0 mL/min. Quantitation was achieved with UV detection at 225 nm using guaifenesin as the internal standard. The effectiveness of protein precipitation and clean up procedure were investigated. The method was validated over the range of 0.3-20 microg/mL for atenolol and 0.25-5 microg/mL for CT.

Determination of antihypertensive mixtures by use of a chemometrics-assisted spectrophotometric method.

A simple multivariate calibration method for analysis of two types of hypotensive mixture is described. The mixtures are composed of chlorthalidone with atenolol or chlorthalidone with both amiloride hydrochloride and atenolol. The components of the mixtures result in substantial spectral overlap-between 87.5 and 91.0%. Resolution of the mixtures under investigation has been accomplished mainly by using CLS and PCR methods. The components in each mixture have been simultaneously determined in three commercial dosage forms with high accuracy and without interference from commonly encountered excipients and additives. Good recoveries were obtained with both synthetic mixtures and commercial tablets. The results obtained were compared with those from pharmacopeial methods and found to be in good agreement. The results obtained from CLS and PCR were also compared with those obtained from a 1D spectrophotometric method.

HPLC and chemometric-assisted spectrophotometric methods for simultaneous determination of atenolol, amiloride hydrochloride and chlorthalidone.

Three methods are presented for the simultaneous determination of atenolol (AT), amiloride hydrochloride (AM) and chlorthalidone (CD). The high performance liquid chromatographic (HPLC) method depends on the separation of each drug on a reversed phase, RP (18) column. Elution was carried out with a mobile phase consisting of acetonitrile -5mM heptansulphonic acid sodium salt (20:80, v/v, pH 4.4). Quantitation was achieved with UV detection at 274 nm based on peak area. The other two-chemometric-assisted spectrophotometric methods applied were principal component regression (PCR) and partial least squares (PLS-1). These approaches were successfully applied to quantify each drug in the mixture using the information included in the absorption spectra of appropriate solutions in the range 240-290 nm with the intervals Deltalambda=0.2 nm. The three methods were successfully applied to a pharmaceutical formulation (tablets), and the results were compared with each other.

The control of impurities in chlortalidone using a reversed-phase stationary phase.

A reversed-phased liquid chromatographic method for the control of impurities of nine impurities in Chlortalidone drug substance is presented. The method is sufficiently sensitive to quantify down to the level of 0.0015 per cent equivalent to a concentration of 15 microg/ml.

Chemometrics-assisted simultaneous determination of atenolol and chlorthalidone in synthetic binary mixtures and pharmaceutical dosage forms.

Resolution of binary mixtures of atenolol (ATE) and chlorthalidone (CTD) with minimum sample pre-treatment and without analyte separation has been successfully achieved, using a new and rapid method based on partial least squares (PLS1) analysis of UV spectral data. The simultaneous determination of both analytes was possible by PLS1 processing of sample absorbances between 255 and 300 nm for ATE and evaluation of absorbances in the 253-268 nm region for CTD. The mean recoveries for synthetic samples were 100.3 +/- 1.0% and 100.7 +/- 0.7% for ATE and CTD, respectively. Application of the proposed method to two commercial tablet preparations in the content uniformity test showed them to contain 103.5 +/- 0.8% and 104.9 +/- 1.8% ATE respectively, as well as 103.4 +/- 1.2% and 104.5 +/- 2.2% CTD. Use of this method also allowed the elaboration of dissolution profiles of the drugs in two commercial combined formulation products, through the simultaneous determination of both drugs during the dissolution test. At the dissolution time of 45 min specified by USP XXIV, both pharmaceutical formulations complied with the test.

Simultaneous determination of chlorthalidone and spironolactone with univariate and multivariate calibration: wavelength range selection.

Chlorthalidone and spironolactone were determined simultaneously with the aid of univariate and multivariate calibration methods. Univariate calibration was performed by the zero-crossing and derivative ratio spectrum methods. Extensive spectral overlap and the scarcity of wavelengths in derivative spectra allowing one analyte to be distinguished and quantitated in the presence of the other gave rise to poor results that called for multivariate calibration. Partial least-squares regression was used in combination with a suitable method for selecting the optimum wavelength range and number of factors for analysis. The ensuing method was applied to simultaneous determination of chlorthalidone and spironolactone in a commercially available pharmaceutical preparation. The results were validated by high-performance liquid chromatography.

A micellar liquid chromatographic procedure for the determination of amiloride, bendroflumethiazide, chlorthalidone, spironolactone and triamterene in pharmaceuticals.

A procedure for the determination of amiloride, bendroflumethiazide, chlorthalidone, spironolactone and triamterene in pharmaceutical preparations (tablets) by micellar liquid chromatography, using a 0.07 M SDS-0.5% pentanol mobile phase, is proposed. Recoveries were found in the 100-108% range, with relative standard deviations of 0.4-3.1%. Elution of the most retained diuretics occurred in less than 18 min (at a 1 ml min-1 flow rate). The change in the values of the solute-micelle binding constants and the partition coefficients of the diuretics between the stationary phase and water, upon addition of pentanol, was also studied.

Thin layer densitometry in the quantitative assay of drugs. Note V--Assay of reserpine and chlorthalidone in the presence of the potential impurities of their solid pharmaceutical forms.

Densitometric detection of compounds separated by thin layer was applied to the assay of a mixture of reserpine and chlorthalidone and their possible impurities. The method of analysis gave satisfactory results in the quality control of pharmaceutical preparations. Good results were obtained in urine tests for the detection of chlorthalidone, reserpine and methylreserpate. The times for the development of fluorescence in reserpine and methylreserpate directly in the chromatographic plate, are also described.