Highly sensitive voltammetric determination of hydrochlorothiazide using a glassy carbon electrode modified with Super P carbon black nanoparticles.

Hydrochlorothiazide is an extremely important diuretic that regulates body functions, which can prevent several diseases. However, the abuse of this diuretic is concerning since it does not require a medical prescription, particularly for aesthetic purposes such as weight loss, which can lead to various health problems, including ventricular arrhythmia. The present work aims to use a glassy carbon electrode modified with Super P carbon black (SPCB/GCE) to quantify hydrochlorothiazide through Linear Sweep Adsorptive Stripping Voltammetry (LSAdSV). The modification of the GCE with SPCB significantly improved the response of hydrochlorothiazide. Furthermore, due to the adsorptive nature of charge transport, applying preconcentration time enhanced sensitivity. The optimized system provided a linear range of 0.5 to 30.0 µmol L-1 with a detection limit of 0.083 µmol L-1. Pharmaceutical tablet analyses indicated approximately 25 mg per tablet, which was confirmed by the UV-vis and in agreement with that indicated by the manufacturer. Furthermore, analyses of the tea, synthetic urine, tap water and lake water samples indicated recovery values close to 100%, demonstrating that there was no matrix effect. Therefore, it is possible to infer that the proposed method together with the sensor modified with carbon black nanoparticles presented excellent results, demonstrating that it can be an alternative method of monitoring this drug in different samples.

Simultaneous determination of hydrochlorothiazide, amlodipine, and telmisartan with spectrophotometric and HPLC green chemistry applications.

For the quantifiable amounts of Telmisartan (TLM) and Hydrochlorothiazide (HYD) in the presence of Amlodipine (AML) in a ternary mixture of synthetic laboratory mixture, a novel, sensitive, quick, and practical reversed-phase high-performance liquid chromatography (RP-HPLC) method was given. In order to separate, a Waters Spherisorb ODS-2 C18 column was used. For HYD, TLM, and AML, these techniques were viable over linearity ranges of 4-12 µg/mL, 4-25 µg/mL, and 5-40 µg/mL, respectively. The mobile phase system was acetonitrile:methanol: phosphate buffer at pH 2.5 (65:5:30 v/v/v), and the flow rate was 1.5 mL/min. Novel spectrophotometric methods were applied for active substances to determine simultaneously. The first method is absorptivity centering using factorized spectrum, and the second method is dual amplitude difference coupled with absorbance subtraction. These approaches have been effectively applied to bulk, laboratory synthetic mixtures to employ active components quantitatively. Correlation coefficients were found to be higher than 0.99 and the limit of detection values lower than 0.49 µg/mL in both spectrophotometric methods. The methodologies were validated following ICH recommendations. In the developed HPLC method, the limit of detection values was found to be 0.01 µg/mL for HYD and 0.02 µg/mL for AML and TLM. The correlation coefficients for the HPLC method were found to be 0.9971 for HYD, 0.9990 for AML, and 0.9983 for TLM. The suggested HPLC technique is a simple, effective, sensitive, environmentally friendly, and time-saving approach for determining TLM and HYD in the presence of AML.

Eco-friendly spectrophotometric evaluation of triple-combination therapies in the treatment strategy of patients suffering from hypertension during coronavirus pandemic - Spectralprint recognition study.

Recent studies have reported that using certain antihypertensive therapies such as angiotensin II receptor blockers (ARBs) and calcium channel blocker (CCBs) is associated with reduction of fatal outcomes and improving clinical characteristics of patients suffering from hypertension during coronavirus pandemic. Thus, in the current work an effective, innovative and eco-friendly spectrophotometric manner namely, parent spectrum extraction (PSE)was established for evaluation of recommended triple antihypertensive combination therapies incorporate valsartan (VAL) as ARBs, amlodipine besylate as CCBs (AML) and hydrochlorothiazide (HCT)as diuretic into single-pill in challengeable ratio. PSE manner composed of two complementary steps, auxiliary resolution coupled with data analysis resolution(DAR)and it is characterized by resolving the spectral bands of the drugs and extraction of their discrete parent spectra (D0); accordingly, enabling determination of each analyte at its λmax. Auxiliary resolution of AML in triple mixture was applied to decrease complexity of overlapped spectra via constant multiplication (CM) followed by spectrum subtraction (SS) to obtain resolved mixture of VAL and HCT while data analysis resolution (DAR) of this binary mixture was applied via one of three novel methods namely, absorbance extraction (AE), peak-amplitude extraction (PE) and ratio extraction (RE) along with SS method. The proposed methods had analyzed VAL, AML and HCT in the range of 4.0-44.0 µg/mL, 4.0-40.0 µg/mL and 2.0-24.0 µg/mL, respectively with an excellent correlation coefficient (r ≥ 0.9999). Further, the proposed methods in PSR manner were validated as stated by ICH guidelines and it was found that accuracy and precision results are within the acceptable limit. The suggested procedures were effectively utilized for the concurrent quantification of VAL, AML and HCT in synthetic mixtures and tablets. The greenness of the proposed spectrophotometric methods was evaluated by National Environmental Methods Index (NEMI), the Analytical Eco-Scale, the Green Analytical Procedure Index (GAPI) and Analytical greenness metric (AGREE) where the four tools affirmed the eco-friendly nature of the proposed methods. A comparison between the outcomes of the studied methods with the official and reported ones was performed and no statistical difference was arisen between the methods regarding to accuracy and precision.The achieved results along with the simplicity, affordability and low-cost of the proposed methods recommended their appropriateness for the regular quality control examination and analysis of pure materials and pharmaceutical formulations as well as their applicability for the spectralprint recognition of the studied drugs.

Development of a multivariate model with desirability-based optimization for determination of atenolol and hydrochlorothiazide by eco-friendly HPLC method with fluorescence detection.

Determination of a widely used antihypertensive combination of atenolol and hydrochlorothiazide was achieved by rapid and eco-friendly high-performance liquid chromatography method combined with fluorescence detection. The response surface methodology is conducive to the complete separation of the two drugs in a shorter analysis time. The separation of the mixture was achieved using an Inertsil C18 analytical column (150 × 4.6 mm, 5 µ). The mobile phase used was ethanol: potassium dihydrogen phosphate at pH 3 (65:35 v/v) and the flow rate was 0.7 mL/min. The fluorescence detector operated at excitation and emission wavelengths of 230 and 310 nm (atenolol) and 270 and 375 nm (hydrochlorothiazide). The linearity of the developed method covered a concentration of atenolol of 0.05-5 µg/mL and a concentration of hydrochlorothiazide of 0.02-1 µg/mL. The greenness of the developed method was evaluated by analytical eco-scale and the recently reported evaluation method, that is, green analytical procedure index, and it was found to be an excellent, sensitive, and green alternative to the reported methods. The developed method was validated according to the ICH guidelines and compared with the reference method. No significant difference was found in terms of accuracy.

Photostability study of multicomponent drug formulations via MCR-ALS: The case of the hydrochlorothiazide-amiloride mixture.

The kinetics and photodegradation mechanism of the pharmaceutical mixture of hydrochlorothiazide (HCT) and amiloride (AML) has been studied in depth using a chemometric approach. Water solutions of HCT and AML, separately or in binary mixtures, were irradiated with forced light at different pH values (3, 7, 9 and 12). Multivariate Curve Resolution - Alternating Least Squares (MCR-ALS) modelling has been applied to the experimental data recorded by UV spectrophotometry and HPLC-UV/MS. 78 data sets were collected and their chemometric processing has allowed the simultaneous determination of the behaviour of the two drugs in the mixture when exposed to light and the dependence of their photodegradation kinetics on pH. MCR-ALS has been applied using three different implementations. Soft-MCR-ALS and hybrid Hard/Soft-MCR-ALS have been used to resolve the experimental data and to get the equilibrium and kinetic parameters of the investigated chemical processes. A third implementation of the MCR-ALS method has been used in the analysis of the incomplete data sets obtained when UV spectrophotometric and HPLC-UV/MS data were simultaneously analysed, using a row- and column-wise incomplete augmented data matrix arrangement. In these matrices, information from HPLC-UV detector was used as a bridge between the data recorded by UV spectrophotometry (acid-base and kinetic reactions monitoring) and the data obtained by HPLC-MS.

First identification of a diuretic, hydrochlorothiazide, in hair: Application to a doping case and interpretation of the results.

An athlete contested an adverse analytical finding involving hydrochlorothiazide, and requested our laboratory for testing his hair. As there is no reference in the literature about identification of hydrochlorothiazide in hair, several volunteers were first enrolled (4 after a single 25 mg administration and 10 with daily therapeutic treatment). A specific method was developed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS. Hair samples were decontaminated with dichloromethane and 30 mg were incubated in buffer at pH 7.0 for 15 hours at 50°C. Then, 5 mL ethyl acetate was added for extraction. Linearity was observed for hydrochlorothiazide concentrations ranging from 5 to 2000 pg/mg. The limit of quantification was 5 pg/mg. The coefficients of variation (CVs) of repeatability and matrix effect were lower than 20%. Analysis of the 0-2-cm segment of the 4 volunteers having received a single dose, collected 1 month after administration, was negative at the limit of quantification. The hair of the 10 patients (proximal 2 cm) on daily treatment was positive with concentrations ranging from 12 to 1845 pg/mg, with no correlation between daily dose and concentration. The athlete's hair tested positive for hydrochlorothiazide at 36 pg/mg in the segment corresponding to the period of the urinary control. Since a single exposure to hydrochlorothiazide is not detectable in hair and based on the results of the patients on daily treatment, the concentration found in the athlete has been interpreted as corresponding to repeated exposures, where it was not possible to establish the dosage and the frequency.

Simultaneous Determination of Acetylsalicylic Acid, Hydrochlorothiazide, Enalapril, and Atorvastatin in a Polypill-Based Quaternary Mixture by TLC.

A new chromatographic-densitometric method has been developed for the qualitative and quantitative determination of the active ingredients in a simulated mixture corresponding to the PolyIran polypill, composed of acetylsalicylic acid, hydrochlorothiazide (HCT), enalapril (ENA), and atorvastatin (ATR), whose efficacy in the treatment and prevention of cardiovascular disease has been documented in clinical trials. Chromatographic separation was performed using TLC silica gel 60 plates with fluorescent indicator F254 as the stationary phase and a mixture of n-hexane-ethyl acetate-methanol-water-acetic acid (8.4 + 8 + 3 + 0.4 + 0.2, v/v/v/v/v) as the mobile phase. Densitometric measurements were carried out at λ = 210 nm when determining ENA and at λ = 265 nm in the case of the other drugs. Peaks of examined substances were well separated in the recorded chromatograms, enabling the evaluation of the results in terms of both qualitative and quantitative analysis. The method was specific for the analyzed components and was characterized by high sensitivity. The LOD was between 0.043 and 0.331 µg/spot, and LOQ was between 0.100 and 0.942 µg/spot. Recovery was in the range of 97.02-101.34%. The linearity range was broad and ranged from 0.600 to 6.000 µg/spot for acetylsalicylic acid, from 0.058 to 1.102 µg/spot for HCT, from 0.505 to 6.560 µg/spot for ENA, and from 0.100 to 1.000 µg/spot for ATR. The method was characterized by good precision, with RSD values that ranged from 0.10 to 2.26%.

Photocatalytic degradation of 4-amino-6-chlorobenzene-1,3-disulfonamide stable hydrolysis product of hydrochlorothiazide: Detection of intermediates and their toxicity.

In this work we have investigated in details the process of degradation of the 4-amino-6-chlorobenzene-1,3-disulfonamide (ABSA), stable hydrolysis product of frequently used pharmaceutical hydrochlorothiazide (HCTZ), as one of the most ubiquitous contaminants in the sewage water. The study encompassed investigation of degradation by hydrolysis, photolysis, and photocatalysis employing commercially available TiO2 Degussa P25 catalyst. The process of direct photolysis and photocatalytic degradation were investigated under different type of lights. Detailed insights into the reactive properties of HCTZ and ABSA have been obtained by density functional theory calculations and molecular dynamics simulations. Specifically, preference of HCTZ towards hydrolysis was confirmed experimentally and explained using computational study. Results obtained in this study indicate very limited efficiency of hydrolytic and photolytic degradation in the case of ABSA, while photocatalytic degradation demonstrated great potential. Namely, after 240 min of photocatalytic degradation, 65% of ABSA was mineralizated in water/TiO2 suspension under SSI, while the nitrogen was predominantly present as NH4+. Reaction intermediates were studied and a number of them were detected using LC-ESI-MS/MS. This study also involves toxicity assessment of HCTZ, ABSA, and their mixtures formed during the degradation processes towards mammalian cell lines (rat hepatoma, H-4-II-E, human colon adenocarcinoma, HT-29, and human fetal lung, MRC-5). Toxicity assessments showed that intermediates formed during the process of photocatalysis exerted only mild cell growth effects in selected cell lines, while direct photolysis did not affect cell growth.

Simultaneous determination of candesartan and hydrochlorothiazide in human plasma by LC-MS/MS

Abstract A simple, sensitive, rapid and highly efficient LC-MS/MS method was developed for the determination of Candesartan and Hydrochlorothiazide simultaneously in human plasma. The method employed Zorbax eclipse C18 (150 X 4.6 mm, 5µ) column using acetate buffer: acetonitrile (25:75%, v/v) as the mobile phase. The mobile phase flow rate is 1 mL/min which was delivered into the mass spectrometer electron spray ionization chamber. The Liquid/liquid extraction procedure was used in the method for the extraction of analytes. The chromatograph was attached to a negative ion mode tandem mass spectrometer and the method was validated for all the parameters as per the guidelines of US-FDA. The ions were detected in multiple reaction monitoring mode and the transitions are m/z 439.00®309.10 and 295.80®268.80 for candesartan and hydrochlorothiazide respectively. Isotopic standards were used as internal standards for effective recovery of the analytes. The drugs were analyzed over a calibration range of 1.027-302.047 ng/mL for candesartan and 1.044-306.945 ng/mL for hydrochlorothiazide respectively with regression coefficient greater than 0.99. The mean extraction recoveries are 96.95±5.61 and 100.55±4.82 for candesartan and hydrochlorothiazide respectively. The precision and accuracy values for all the studies were within the range of ≤15% and 85-115%. The performed stability studies indicate that the developed method is stable in plasma for 15 h at room temperature (bench top); 52 h (in injector); for 112 days at -70 ºC for long term stability; five successive freeze and thaw cycles. The developed method could be successfully employed for the determination of selected drugs in biological samples.

Novel Pure Component Contribution Algorithm (PCCA) and UHPLC Methods for Separation and Quantification of Amlodipine, Valsartan, and Hydrochlorothiazide in Ternary Mixture.

Two accurate and sensitive methods were developed and validated for the simultaneous determination of amlodipine (AML), valsartan (VAL), and hydrochlorothiazide (HCT) in their ternary mixture. The first method is a novel simple algorithm capable of extracting the contribution of each component from a mixture signal in which the components are partially or completely overlapped. It is based on the use of a coded function that eliminates the signal of interfering components using mean centering as a processing tool. Determination was performed at 237.6, 250.0, and 270.6 nm for AML, VAL, and HCT, respectively. Two fit values were developed and calculated for optimization of the method for each drug, one to test that the absorptivity values of the extracted spectra are within the confidence limits of the slope, and the other for correlation between the pure and extracted spectra. The fit values for AML, VAL, and HCT were α = 0.0449, 0.03981, and 0.07251, respectively, and r = 1 for each drug. The second method is an ultra-HPLC (UHPLC®) method in which separation of AML, VAL, and HCT was carried out on a UHPLC C18 column (100 × 2.1 mm, 2.2 µm) using a mobile phase of acetonitrile-methanol-phosphate buffer (pH 2.8; 25 + 50 + 25, v/v/v). The flow rate was 0.5 mL/min, and the detection was set at 255.0 nm. The proposed methods were successfully applied to the analysis of AML, VAL, and HCT in pharmaceutical formulations, without interference from the dosage-form additives. The results were statistically compared to a previously reported method, and no significant difference was found regarding accuracy or precision.

Kinetics study of hydrochlorothiazide lactose liquid state interaction using conventional isothermal arrhenius method under basic and neutral conditions

ABSTRACT The Maillard reaction of hydrochlorothiazide (HCTZ) and lactose has been previously demonstrated in pharmaceutical formulations. In this study, the activation energy of - hydrohlorothiazide and lactose interaction in the liquid state was ascertained under basic and neutral conditions. Conventional isothermal High Performance Liquid Chromatography (HPLC) technique was employed to ascertain the kinetic parameters using Arrhenius method. Results: The activation energy obtained was 82.43 and 100.28 kJ/mol under basic and neutral conditions, respectively. Consequently, it can be inferred that Maillard reaction is significantly affected by pH, which can be used as a control factor whenever the reaction potentially occurs.

Simultaneous determination of valsartan, amlodipine besylate and hydrochlorothiazide using capillary zone electrophoresis (CZE).

A capillary zone electrophoresis method was developed for the simultaneous determination of valsartan (VAL), amlodipine besylate (AML) and hydrochlorothiazide (HCZ) in their combined tablets. Separation was achieved on a fused silica capillary by applying a potential of 15 kV (positive polarity) and a running background electrolyte containing 40 mM phosphate buffer at pH 7.5 with UV detection at 230 nm. The samples were injected hydrodynamically for 3s at 0.5 psi and the temperature of the capillary cartridge was kept at 25 degrees C. Pyrazinoic acid was used as an internal standard. The method was validated according to ICH guidelines regarding specificity, linearity, limits of detection and quantitation, accuracy and precision, (Supplementary materials, Table S2). The method showed satisfactory linearity in the ranges of 10-200, 2-20 and 2-20 µg mL(-1) with LODs of 1.82, 0.39, 0.65 µg mL(-1) and LOQs of 5.51, 1.17, 1.96 µg mL(-1) for VAL, AML and HCZ, respectively. The proposed method was successfully applied for the analysis of the studied drugs in their laboratory prepared mixtures and co-formulated tablets. The results were compared with reported methods and no significant differences were found. The proposed method can be used for quality control of the cited drugs in ordinary laboratories.

Continuous Wavelet Transform, a powerful alternative to Derivative Spectrophotometry in analysis of binary and ternary mixtures: A comparative study.

A comparative study was established between two signal processing techniques showing the theoretical algorithm for each method and making a comparison between them to indicate the advantages and limitations. The methods under study are Numerical Differentiation (ND) and Continuous Wavelet Transform (CWT). These methods were studied as spectrophotometric resolution tools for simultaneous analysis of binary and ternary mixtures. To present the comparison, the two methods were applied for the resolution of Bisoprolol (BIS) and Hydrochlorothiazide (HCT) in their binary mixture and for the analysis of Amlodipine (AML), Aliskiren (ALI) and Hydrochlorothiazide (HCT) as an example for ternary mixtures. By comparing the results in laboratory prepared mixtures, it was proven that CWT technique is more efficient and advantageous in analysis of mixtures with severe overlapped spectra than ND. The CWT was applied for quantitative determination of the drugs in their pharmaceutical formulations and validated according to the ICH guidelines where accuracy, precision, repeatability and robustness were found to be within the acceptable limit.

Novel spectrophotometric methods for simultaneous determination of Amlodipine, Valsartan and Hydrochlorothiazide in their ternary mixture.

This work represents a comparative study of two smart spectrophotometric techniques namely; successive resolution and progressive resolution for the simultaneous determination of ternary mixtures of Amlodipine (AML), Hydrochlorothiazide (HCT) and Valsartan (VAL) without prior separation steps. These techniques consist of several consecutive steps utilizing zero and/or ratio and/or derivative spectra. By applying successive spectrum subtraction coupled with constant multiplication method, the proposed drugs were obtained in their zero order absorption spectra and determined at their maxima 237.6 nm, 270.5 nm and 250 nm for AML, HCT and VAL, respectively; while by applying successive derivative subtraction they were obtained in their first derivative spectra and determined at P230.8-246, P261.4-278.2, P233.7-246.8 for AML, HCT and VAL respectively. While in the progressive resolution, the concentrations of the components were determined progressively from the same zero order absorption spectrum using absorbance subtraction coupled with absorptivity factor methods or from the same ratio spectrum using only one divisor via amplitude modulation method can be used for the determination of ternary mixtures using only one divisor where the concentrations of the components are determined progressively. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs. Moreover comparative study between spectrum addition technique as a novel enrichment technique and a well established one namely spiking technique was adopted for the analysis of pharmaceutical formulations containing low concentration of AML. The methods were validated as per ICH guidelines where accuracy, precision and specificity were found to be within their acceptable limits. The results obtained from the proposed methods were statistically compared with the reported one where no significant difference was observed.

Different approaches in Partial Least Squares and Artificial Neural Network models applied for the analysis of a ternary mixture of Amlodipine, Valsartan and Hydrochlorothiazide.

Different chemometric models were applied for the quantitative analysis of Amlodipine (AML), Valsartan (VAL) and Hydrochlorothiazide (HCT) in ternary mixture, namely, Partial Least Squares (PLS) as traditional chemometric model and Artificial Neural Networks (ANN) as advanced model. PLS and ANN were applied with and without variable selection procedure (Genetic Algorithm GA) and data compression procedure (Principal Component Analysis PCA). The chemometric methods applied are PLS-1, GA-PLS, ANN, GA-ANN and PCA-ANN. The methods were used for the quantitative analysis of the drugs in raw materials and pharmaceutical dosage form via handling the UV spectral data. A 3-factor 5-level experimental design was established resulting in 25 mixtures containing different ratios of the drugs. Fifteen mixtures were used as a calibration set and the other ten mixtures were used as validation set to validate the prediction ability of the suggested methods. The validity of the proposed methods was assessed using the standard addition technique.

Comparative study between derivative spectrophotometry and multivariate calibration as analytical tools applied for the simultaneous quantitation of Amlodipine, Valsartan and Hydrochlorothiazide.

Four simple, accurate and specific methods were developed and validated for the simultaneous estimation of Amlodipine (AML), Valsartan (VAL) and Hydrochlorothiazide (HCT) in commercial tablets. The derivative spectrophotometric methods include Derivative Ratio Zero Crossing (DRZC) and Double Divisor Ratio Spectra-Derivative Spectrophotometry (DDRS-DS) methods, while the multivariate calibrations used are Principal Component Regression (PCR) and Partial Least Squares (PLSs). The proposed methods were applied successfully in the determination of the drugs in laboratory-prepared mixtures and in commercial pharmaceutical preparations. The validity of the proposed methods was assessed using the standard addition technique. The linearity of the proposed methods is investigated in the range of 2-32, 4-44 and 2-20 µg/mL for AML, VAL and HCT, respectively.

Mechanism considerations for photocatalytic oxidation, ozonation and photocatalytic ozonation of some pharmaceutical compounds in water.

Aqueous solutions of four pharmaceutical compounds, belonging to the group of emergent contaminants of water: atenolol (ATL), hydrochlorothiazide (HCT), ofloxacin (OFX) and trimethoprim (TMP), have been treated with different oxidation systems, mainly, photocatalytic oxidation, ozonation and photocatalytic ozonation. TiO2 has been used as semiconductor for photocatalytic reactions both in the presence of air, oxygen or ozone-oxygen gas mixtures. Black light lamps mainly emitting at 365 nm were the source of radiation. In all cases, the influence of some variables (concentrations of semiconductor, ozone gas and pharmaceuticals and pH) on the removal of pharmaceuticals, total polyphenol content (TPC) and total organic carbon (TOC) was investigated. A discussion on the possible routes of pharmaceutical and intermediates (as TPC and TOC) elimination has been developed. Thus, OFX TiO2/UVA degradation mechanism seems to develop through the participation of non-hydroxyl free radical species. Furthermore, the presence of OFX inhibits the formation of hydroxyl radicals in the photocatalytic process. The most effective processes were those involving ozone that lead to complete disappearance of parent compounds in less than 30 min for initial pharmaceutical concentrations lower than 2.5 mg L(-1). In the ozonation systems, regardless of the pH and the presence of TiO2, pharmaceuticals are degraded through their direct reaction with ozone. Photocatalytic ozonation was the most efficient process for TPC and TOC removals (≥ 80% and ≥60% elimination after 2 h of treatment, respectively) as well as in terms of the ozone consumption efficiency (1, 5.5 and 4 mol of ozone consumed per mol of TOC mineralized, at pH 4, 7 and 9, respectively). Weakly acid conditions (pH 4) resulted to be the most convenient ones for TPC and TOC removal by photocatalytic ozonation. This was likely due to formation of hydroxyl radicals through the ozonide generated at these conditions.

Bioanalytical method development and validation for determination of metoprolol tartarate and hydrochlorothiazide using HPTLC in human plasma

A simple, sensitive, rapid and economic chromatographic method has been developed for determination of metoprolol tartarate and hydrochlorothiazide in human plasma using paracetamol as an internal standard. The analytical technique used for method development was high-performance thin-layer chromatography. HPTLC Camag with precoated silica gel Plate 60F254 (20 cm×10 cm) at 250 µm thicknesses (E. Merck, Darmstadt, Germany) was used as the stationary phase. The mobile phase used consisted of chloroform: methanol: ammonia (9:1:0.5v/v/v). Densitometric analysis was carried out at a wavelength of 239 nm. The rf values for hydrochlorothiazide, paracetamol and metoprolol tartarate were 0.13±0.04, 0.28±0.05, 0.48±0.04, respectively. Plasma samples were extracted by protein precipitation with methanol. Concentration ranges of 200, 400, 600, 800, 1000, 1200 ng/mL and 2000, 4000, 6000, 8000, 10000, 12000 ng/mL of hydrochlorothiazide and metoprolol tartarate, respectively, were used with plasma for the calibration curves. The percent recovery of metoprolol tartarate and hydrochlorothiazide was found to be 77.30 and 77.02 %, respectively. The stability of metoprolol tartarate and hydrochlorothiazide in plasma were confirmed during three freeze-thaw cycles (-20 ºC) on a bench for 24 hours and post-preparatively for 48 hours. The proposed method was validated statistically and proved suitable for determination of metoprolol tartarate and hydrochlorothiazide in human plasma.

Um método simples, sensível, rápido e econômico empregando a cromatografia em camada delgada de alta eficiência (HPTLC) foi desenvolvido para determinação do tartarato de metoprolol e hidroclorotiazida em plasma humano, usando paracetamol como padrão interno. Placas prontas de sílica-gel 60F254 (20 cm×10 cm), 250 µm de espessura, para HPTLC Camag (E. A Merck, Darmstadt, Alemanha) foramutilizadas como fase estacionária. A fase móvel utilizada consistiu de clorofórmio: metanol: amônia (9:1:0,5 v/v/v). A análise densitométrica foi realizada no comprimento de onda 239 nm. Os valores de Rf de hidroclorotiazida, paracetamol e tartarato de metoprolol foram 0.13±0.04, 0.28±0.05, 0.48±0.04 respectivamente. As proteínas do plasma foram extraídas por precipitação com metanol. Para construção das curvas de calibração, empregaram-se intervalos de concentração de 200, 400, 600, 800, 1000, 1200 ng/mL e 2000, 4000, 6000, 8000, 10000, 12000 ng/mL de hidroclorotiazida e tartarato de metoprolol, respectivamente. Os percentuais de recuperação do tartarato de metoprolol e de hidroclorotiazida foram de 77,30 e 77,02, respectivamente. A estabilidade do tartarato de metoprolol e de hidroclorotiazida no plasma foi confirmada durante três ciclos de congelamento e descongelamento (-20 ºC), durante 24 horas e póspreparação durante 48 horas. O método proposto foi validado estatisticamente, sendo adequado para determinação do tartarato de metoprolol e hidroclorotiazida em plasma humano.

A new application of continuous wavelet transform to overlapping chromatograms for the quantitative analysis of amiloride hydrochloride and hydrochlorothiazide in tablets by ultra-performance liquid chromatography.

A new application of continuous wavelet transform (CWT) to overlapping peaks in a chromatogram was developed for the quantitative analysis of amiloride hydrochloride (AML) and hydrochlorothiazide (HCT) in tablets. Chromatographic analysis was done by using an ACQUITY ultra-performance LC (UPLC) BEH C18 column (50 x 2.1 mm id, 1.7 pm particle size) and a mobile phase consisting of methanol-0.1 M acetic acid (21 + 79, v/v) at a constant flow rate of 0.3 mL/min with diode array detection at 274 nm. The overlapping chromatographic peaks of the calibration set consisting of AML and HCT mixtures were recorded rapidly by using an ACQUITY UPLC H-Class system. The overlapping UPLC data vectors of AML and HCT drugs and their samples were processed by CWT signal processing methods. The calibration graphs for AML and HCT were computed from the relationship between concentration and areas of chromatographic CWT peaks. The applicability and validity of the improved UPLC-CWT approaches were confirmed by recovery studies and the standard addition technique. The proposed UPLC-CWT methods were applied to the determination of AML and HCT in tablets. The experimental results indicated that the suggested UPLC-CWT signal processing provides accurate and precise results for industrial QC and quantitative evaluation of AML-HCT tablets.

LC and LC-MS methods for the investigation of polypills for the treatment of cardiovascular diseases. Part 1. Separation of active components and classification of their interaction/degradation products.

"Polypill" is a fixed-dose combination (FDC) containing three or more drugs in a single pill. The same is under development for the treatment and prevention of cardiovascular diseases. In the present study, gradient LC methods were developed for simultaneous determination of the possible components of a polypill, i.e., lisinopril, aspirin and one each among atenolol/hydrochlorothiazide and atorvastatin/simvastatin/pravastatin, in the presence of a total of 13 major interaction/degradation products. The drugs and the products were well separated using a reversed-phase (C-8) column and a mobile phase comprising of acetonitrile: phosphate buffer (pH 2.3). Other HPLC parameters were flow rate, 1 ml/min; detection wavelength, 210 nm; column oven temperature, 60 degrees C; and injection volume, 5 microl. The methods were validated for linearity, precision, accuracy, and specificity. These were further modified to make them compatible for LC-MS studies by removal of the phosphate buffer and adjustment of pH by formic acid. The suitability of the methods for LC-MS studies was established by matching the theoretical mass values of the drugs with those obtained experimentally. These methods were used to determine mass values of the major interaction/degradation products, which helped to know the source of their origin.