Application of π-acceptors to the spectrophotometric determination of lisinopril in commercial dosage forms

Study of the dissolution kinetics of drugs in solid dosage form with lisinopril and atorvastatin and intestinal permeability to assess their equivalence in vitro

Atorvastatin and lisinopril are a successful combination for the treatment of patients with chronic heart failure and hypertension. Study of the dissolution kinetics of drugs in solid dosage form with lisinopril and atorvastatin and intestinal permeability to assess their equivalence in vitro were described. In medium with hydrochloric acid pH 1.2, in the medium of acetate buffer solution with a pH of 4.5 and in the medium phosphate buffer solution with a pH of 6.8 for 15 min more than 85% of the active substance passes into solution, hence the dissolution profiles these drugs in these environments are similar, and the drugs in them are “very quickly soluble”. Among the in vitro models that make it possible to assess the degree of absorption of API, the most widely used culture of adenocarcinoma cells of the colon – Caco-2. The development of the analytical methodology and its validation is the final stage of both the dissolution study and the Caco-2 test, as well as the biowaver procedure. It plays the most important role in the reliability of the results for all the above procedures and tests. To study permeability, method LC-MS/MS was developed. According to the obtained results, atorvastatin and lisinopril showed low permeability. The values ​​of recovery of transport of test and control substances through the monolayer of cells of the Caco-2 line indicate that the results of the experiment can be considered reliable. The equivalence of the drugs “Lisinopril”, tablets of 10 mg and “Atorvastatin”, tablets of 10 mg, belongs to class III BCS proven by in vitro studies.

Spectrophotometric methods for the determination of lisinopril in medicines

Two simple, rapid and green spectrophotometric methods are described for the determination of lisinopril medicines. The determination is based on the reaction of the primary amino group of the lisinopril with ninhydrin in aqueous medium (Method I) and reaction on the carboxylic group of the lisinopril with copper (II) sulfate (Method II). For both methods, optimal spectrophotometric conditions were established. The linear relationship was found between absorbance at λmax and concentration of drug in the range 40–60 µg/mL (Method I) and 0.592–2.072 mg/mL (Method II). Regression analysis of Beer’s law plot at 400 nm yielded the regression equation, y = 7.4929x – 0.0545 (Method I) and at 730 nm y = 0.0443x – 0.0832 (Method II). High values of correlations coefficient (R2 = 0.9917 (Method I) and R2 = 0.999 (Method II)) and small values of intercept validated the linearity of calibration curve and obedience to Beer’s law. The LOD and LOQ values were calculated to be 6.91 µg/mL and 23.01 µg/mL respectively (Method I) and 0.11 mg/mL and 0.36 mg/mL respectively (Method II). Intra-day and inter-day accuracy and precision were in acceptable limits. The proposed methods were applied for the quantification of lisinopril in tablets pertaining to three commercial formulations. Analytical eco-scale for greenness assessment of the proposed spectrophotometric methods showed that both methods correspond to excellent green analysis.

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.

A novel analytical approach for reducing the consumption of organic solvents in the charge transfer-based spectrophotometric analysis: application in the analysis of certain antihypertensive drugs

The present study describes the development of a novel analytical approach that can reduce by 50-fold the consumption of organic solvents in the charge transfer (CT)-based spectrophotometric analysis. The proposed approach employed 96-microwell assay plates for carrying out the reaction. The CT reaction between the electron-donating analyte and electron-accepting reagent was performed in microwells (200-μL of organic solvent) and the color signals were measured with a microwell-plate reader. Optimum conditions for the proposed approach were established for two antihypertensive drugs, namely ramipril (RML) and lisinopril (LSL) as model compounds for the electron-donating analytes, and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as a π-electron acceptor. Under the optimum conditions, Beer's law was obeyed in the concentration range of 6-100 and 6-60 μg mL-1 for RML and LSL, respectively. The limits of detection were 0.97 and 1.10 μg mL-1 for RML and LSL, respectively. The precision of the methods was satisfactory; the values of relative standard deviations did not exceed 1.1 %. The proposed approach was successfully applied to the analysis of pharmaceutical dosage forms with good accuracy and precision. The results were comparable with those of the reported methods. The approach described herein is of great practical value in pharmaceutical analysis because it reduces the exposure of analysts to the toxic effects of organic solvents, lowers the analysis cost by 50-fold, and it has a high throughput property. Although the approach was validated for RML and LSL, the same methodology could be used for any electron-donating analyte for which a CT-reaction can be performed.

Highly sensitive and selective spectrophotometric and spectrofluorimetric methods for the determination of ropinirole hydrochloride in tablets

Three sensitive, selective, accurate spectrophotometric and spectrofluorimetric methods have been developed for the determination of ropinirole hydrochloride in tablets. The first method was based on measuring the absorbance of drug solution in methanol at 250 nm. The Beer's law was obeyed in the concentration range 2.5-24 microg ml(-1). The second method was based on the charge transfer reaction of drug, as n-electron donor with 7,7,8,8-tetracyanoquinodimethane (TCNQ), as pi-acceptor in acetonitrile to give radical anions that are measured at 842 nm. The Beer's law was obeyed in the concentration range 0.6-8 microg ml(-1). The third method was based on derivatization reaction with 4-chloro-7-nitrobenzofurazan (NBD-Cl) in borate buffer of pH 8.5 followed by measuring the fluorescence intensity at 525 nm with excitation at 464 nm in chloroform. Beer's law was obeyed in the concentration range 0.01-1.3 microg ml(-1). The derivatization reaction product of drug with NBD-Cl was characterized by IR, 1H NMR and mass spectroscopy. The developed methods were validated. The following analytical parameters were investigated: the molar absorptivity (epsilon), limit of detection (LOD, microg ml(-1)) and limit of quantitation (LOQ, microg ml(-1)), precision, accuracy, recovery, and Sandell's sensitivity. Selectivity was validated by subjecting stock solution of ropinirole to acidic, basic, oxidative, and thermal degradation. No interference was observed from common excipients present in formulations. The proposed methods were successfully applied for determination of drug in tablets. The results of these proposed methods were compared with each other statistically.

Kinetic Spectrophotometric Analysis of Pantoprazole in Commercial Dosage Forms

A kinetic spectrophotometric method has been developed which is based on the oxidation of pantoprazole with Fe(III) in sulfuric acid medium. Fe(III) subsequently reduces to Fe(II), which is coupled with potassium ferricyanide to form Prussian blue. The reaction is followed spectrophotometrically by measuring the increase in absorbance with time (1-8 min) at 725 nm. The initial rate method is adopted for constructing the calibration graph, which is linear in the concentration range of 5-90 microg ml(-1). The regression analysis yields the calibration equation, nu = 3.467 x 10(-6) + 4.356 x 10(-5)C. The limits of detection and quantitation are 1.46 and 4.43 microg ml(-1), respectively. The proposed method was optimized and validated both statistically and through recovery studies. The experimental true bias of all samples is < +/-2.0%. The method has been successfully applied to the determination of pantoprazole in pharmaceutical preparations.