Dissolution tests of benazepril-HCl and hydrochlorothiazide in commercial tablets: comparison of spectroscopic and high performance liquid chromatography methods

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.

In vivo multispectral photoacoustic and photothermal flow cytometry with multicolor dyes: a potential for real-time assessment of circulation, dye-cell interaction, and blood volume

Recently, photoacoustic (PA) flow cytometry (PAFC) has been developed for in vivo detection of circulating tumor cells and bacteria targeted by nanoparticles. Here, we propose multispectral PAFC with multiple dyes having distinctive absorption spectra as multicolor PA contrast agents. As a first step of our proof-of-concept, we characterized high-speed PAFC capability to monitor the clearance of three dyes (Indocyanine Green [ICG], Methylene Blue [MB], and Trypan Blue [TB]) in an animal model in vivo and in real time. We observed strong dynamic PA signal fluctuations, which can be associated with interactions of dyes with circulating blood cells and plasma proteins. PAFC demonstrated enumeration of circulating red and white blood cells labeled with ICG and MB, respectively, and detection of rare dead cells uptaking TB directly in bloodstream. The possibility for accurate measurements of various dye concentrations including Crystal Violet and Brilliant Green were verified in vitro using complementary to PAFC photothermal (PT) technique and spectrophotometry under batch and flow conditions. We further analyze the potential of integrated PAFC/PT spectroscopy with multiple dyes for rapid and accurate measurements of circulating blood volume without a priori information on hemoglobin content, which is impossible with existing optical techniques. This is important in many medical conditions including surgery and trauma with extensive blood loss, rapid fluid administration, and transfusion of red blood cells. The potential for developing a robust clinical PAFC prototype that is safe for human, and its applications for studying the liver function are further highlighted.

Development and application of a validated HPLC method for the analysis of dissolution samples of mexiletine hydrochloride capsules

The aim of this work was to develop and validate a simple, efficient, sensitive and selective method for the analysis of dissolution samples of mexiletine hydrochloride capsules by HPLC without the necessity of any time-consuming extraction, dilution or evaporation steps prior to drug assay. Separation was performed isocratically on a 5 ?m LiChrospher 60, RP-Select B column (250 x 4 mm ID) using the mobile phase buffer-acetonitrile (60:42, v/v) at a flow rate of 1.2 mL min-1 and UV detection at 262 nm. The elution occurred in less than 10 minutes. The assay was linear in the concentration range 50-300 ?g mL-1 (r2 = 0.9998). The validation characteristics included accuracy, precision, linearity, specificity, limits of detection and quantification, stability, and robustness. Validation acceptance criteria were met in all cases (the percent recoveries ranged between 100.01 and 101.68 %, RSD < 0.44 %). The method could be used for the determination of mexiletine hydrochloride and for monitoring its concentration in in vitro dissolution studies.

Simultaneous determination of captopril and hydrochlorothiazide in human plasma by reverse-phase HPLC from linear gradient elution

A simple, rapid and sensitive high-performance liquid chromatographic method for the simultaneous determination of captopril and hydrochlorothiazide in human plasma samples was developed. Captopril was derivatized with 2,4'-dibromoacetophenone (pBPB) to form a captopril-pBPB adduct. From acidified serum plasma samples, the hydrochlorothiazide and derivatized captopril was extracted with 5 ml ether, then with 5 ml dichloromethane. Effective chromatographic separation was achieved using a C(18) column (DIAMONSIL 150 mmx4 mm i.d., 5 microm) based on an acetonitrile-trifluoroacetic acid-water gradient elution at a flow rate of 1.2 ml/min. The internal standard (IS), derivatized captopril and hydrochlorothiazide were detected at 263 nm and were eluted at 4.2, 6.8 and 16.9 min, respectively. No endogenous substances were found to interfere. The limit of quantification for hydrochlorothiazide and derivatized captopril in plasma were 3.3 and 7 ng/ml. The calibration curve for derivatized captopril showed linearity in the range 20-4000 ng/ml, with a regression coefficient corresponding to 0.9993 and the coefficient of the variation of the points of the calibration curve being lower than 10%. The calibration curve for hydrochlorothiazide showed linearity in the range 10-1200 ng/ml, with a regression coefficient corresponding to 0.9999 and the coefficient of the variation of the points of the calibration curve being lower than 10%. The method was suitably validated and successfully applied to the determination of captopril and hydrochlorothiazide in human plasma samples.

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 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.