Comparison of High - Performance Liquid Chromatography and Absorbance Ratio Methods for the Determination of Hydrochlorothiazide and Lisinopril in Pharmaceutical Formulations

Development of membrane electrodes for selective determination of lisinopril in pharmaceuticals

Background

Lisinopril (LNP) is an angiotensin-converting enzyme inhibitor used as anti-hypertensive, cardiovascular, in anti-prophylactic and anti-diabetic nephropathy drug. Development of two new, simple, low cost, and selective membrane-based ion-selective electrodes has been proposed for the determination of LNP in pharmaceuticals.

Methods

The electrodes are based on poly(vinyl)chloride membrane doped with LNP-phosphotungstic acid (LNP-PTA) and LNP-phosphomolybdic acid (LNP-PMA) ion-pairs as molecular recognition materials.

Results

The developed LNP-PTA and LNP-PMA electrodes are applicable for the determination of LNP over the linear range of 5 × 10−5–2.4 × 10−3 mol l−1. The working pH ranges to measure potentials were 2.5 to 6.4 and 2.3 to 6.0 for LNP-PTA and LNP-PMA ISEs, respectively. The electrodes displayed the rapid Nernstian responses as revealed by the values of slopes 55.06 and 52.39 mV/decade, with limit of detection (LOD) values of 1.2 × 10−5 and 1.18 × 10−5 mol l−1 for LNP-PTA and LNP-PMA electrodes, respectively. The limits of quantitation (LOQ) values have also been calculated for both the electrodes. The developed electrodes have potential stability for up to 1 month and emerged as highly selective for the determination of LNP over other spiked ions and compounds.

Conclusions

The proposed electrodes have been validated and found that they are suitable for the determination of LNP in pharmaceuticals in pure form and in dosage forms. The results obtained in the analysis of LNP using proposed electrodes have been compared statistically with reference method’s results to assess the accuracy and precision. Robustness and ruggedness of the developed electrodes have also been checked and found satisfactory. The recovery studies have been performed by standard addition procedure to assess the role of excipients in tablets containing LNP and the results obtained are satisfactory.

Comparative Study of RP-HPLC and UV Spectrophotometric Techniques for the Simultaneous Determination of Amoxicillin and Cloxacillin in Capsules

Reversed-phase HPLC and UV spectrophotometric techniques using water as solvent have been developed and validated for the simultaneous determination of amoxicillin and cloxacillin in capsules. For both techniques, the linearity range of 60.073x2013;140.0 µg/mL was studied. The spectrophotometric data show that non-derivative techniques, such as absorbance ratio and compensation, and ratio spectra first-order derivative could be successfully used for the co-assay of amoxicillin and cloxacillin. Based on the statistical comparison of spectrophotometric and chromatographic data, the interchangeability between HPLC and UV spectrophotometric techniques has been suggested for the routine analysis.

Development and validation of a stability indicating HPLC method for determination of lisinopril, lisinopril degradation product and parabens in the lisinopril extemporaneous formulation

The purpose of the research described herein was to develop and validate a stability-indicating HPLC method for lisinopril, lisinopril degradation product (DKP), methyl paraben and propyl paraben in a lisinopril extemporaneous formulation. The method developed in this report is selective for the components listed above, in the presence of the complex and chromatographically rich matrix presented by the Bicitra and Ora-Sweet SF formulation diluents. The method was also shown to have adequate sensitivity with a detection limit of 0.0075 microg/mL (0.03% of lisinopril method concentration). The validation elements investigated showed that the method has acceptable specificity, recovery, linearity, solution stability, and method precision. Acceptable robustness indicates that the assay method remains unaffected by small but deliberate variations, which are described in ICH Q2A and Q2B guidelines.

Spectophotometric quantitative resolution of hydrochlorothiazide and spironolactone in tablets by chemometric analysis methods

Spectrophotometric simultaneous determination of hydrochlorothiazide and spironolactone in tablets was performed by classical least-squares (CLS), inverse least-squares (ILS), principal component regression (PCR) and partial least-squares (PLS). The methods of the chemometric analysis do not require sample pretreatment procedure. A training set of 25 standard mixture containing both drugs was prepared in the concentration range of 2-20 mug/ml according to mixture design. The multivarate calibrations were obtained by measuring the zero-order and first-derivative absorbances at 15 points from 220 to 290 nm using the training set. The validation of the multivariate methods was realised by analysing the synthetic mixtures of hydrochlorothiazide and spironolactone. The result obtained on the synthetic mixture and tablets were statistically compared by the one-way ANOVA test. The chemometrics analysis methods were satisfactorily applied to the simultaneous determination of hydrochlorothiazide and spironolactone in the pharmaceutical tablet formulation.

Spectrophotometric quantitative determination of cilazapril and hydrochlorothiazide in tablets by chemometric methods

Four chemometric methods were applied to simultaneous determination of cilazapril and hydrochlorothiazide in tablets. Classical least-square (CLS), inverse least-square (ILS), principal component regression (PCR) and partial least-squares (PLS) methods do not need any priori graphical treatment of the overlapping spectra of two drugs in a mixture. For all chemometric calibrations a concentration set of the random mixture consisting of the two drugs in 0.1 M HCI and methanol (1:1) was prepared. The absorbance data in the UV-Vis spectra were measured for the 15 wavelength points (from 222 to 276 nm) in the spectral region 210-290 nm considering the intervals of deltalambda = 4 nm. The calibration of the investigated methods involves only absorbance and concentration data matrices. The developed calibrations were tested for the synthetic mixtures consisting of two drugs and using the Maple V software the chemometric calculations were performed. The results of the methods were compared each other as well as with HPLC method and a good agreement was found.

Spectrophotometric determination of lisinopril in tablets using 1-fluoro-2,4-dinitrobenzene reagent

A spectrophotometric method for the determination of lisinopril (LN) in single and multicomponent tablets also containing hydrochlorothiazide (HCT), based on the derivatization reaction with 1-fluoro-2,4-dinitrobenzene (FDNB, Sanger reagent) is described. Aqueous solutions of LN (4.5-27.2 x 10(-5) M) react with FDNB (in acetonitrile) at pH 8.2 (borate buffer) in dark at 60 degrees C for 45 min. After acidification with HCl to decolourize 2,4-dinitrophenolate (the alkaline hydrolysis product of FDNB), the LN-derivative is measured at 356.5 or 405.5 nm (only at 405.5 nm if HCT is present). The calibration curves are linear (r>0.996 at both wavelengths) with a between days precision of slopes of 1.8 and 2.3% at 405.5 and 356.5 nm, respectively. The quantification limit is 3.49 x 10(-5) M (0.014 mg) at 405.5 nm and 5.69 x 10(-5) M (0.023 mg) at 356.5 nm. The accuracy and precision of the method were evaluated with the analysis of synthetic mixtures (Er%: 0.30-0.60 and 0.27-1.00 at 405.5 and 356.5 nm, respectively; RSD%: 0.48-0.92 and 0.35-0.51 at 405.5 and 356.5 nm, correspondingly; recovery%: 99.2-100.4 at 405.5 nm and 97.9-104.3 at 356.5 nm). Results obtained from the analysis of commercial preparations with the proposed method are in good agreement with those obtained with the official HPLC method (% relative difference 0.2-2.5%). The developed method can be used for rapid routine analysis for content uniformity, dissolution profile studies and assay of pharmaceutical preparations.

Chemometric resolution of a mixture containing hydrochlorothiazide and amiloride by absorption and derivative spectrophotometry

Four chemometric techniques, classical least squares (CLS) and inverse least squares (ILS) and principal component regression (PCR) and partial least squares regression (PLSR) were applied to the absorption and derivative spectrophotometric determinations of amiloride and hydrochlorothiazide in a pharmaceutical preparation. Four chemometric calibrations for both zero-order and first derivative spectra were constructed by measuring the absorbance and their dA/dlambda values at 34 points in the wavelength range 205-395 nm for a training set containing 2-10 microg/ml amiloride and 4-28 microg/ml hydrochlorothiazide corresponding to 25 point mixture design. The building chemometric calibrations were confirmed by using the synthetic mixtures containing two drugs. The results obtained by the proposed techniques based on the use of the measurements at the absorption spectra and at the first derivative spectra were statistically compared with each other.

Simultaneous determination of hydrochlorothiazide and several inhibitors of angiotensin-converting enzyme by capillary electrophoresis

A capillary electrophoresis method was developed for the simultaneous determination of hydrochlorothiazide and several angiotensin-converting enzyme (ACE) inhibitors: enalapril, lisinopril, quinapril, fosinopril, ramipril, and cilazapril. The most critical parameter is the pH of the running buffer. Separation was performed on a fused-silica capillary (52 cm total length x 75 microm I.D.) using a sodium phosphate buffer (pH 7.25; 100 mM). The method was successfully applied to the quantitative determination of these compounds in their corresponding pharmaceutical formulation. The method was validated in terms of linearity of response, reproducibility and accuracy.