VALIDATED SPECTROPHOTOMETRIC METHODS FOR DETERMINATION OF ENALAPRIL MALEATE IN PURE AND DOSAGE FORMS

Objective: Simple, sensitive, precise, reproducible and validated visible spectrophotometric methods have been developed for the determination of an angiotensin converting enzyme inhibitor (ACE) drug, namely enalapril maleate (ENP) in pure and pharmaceutical dosage forms. Methods: The methods are based on the formation of yellow colored ion-pair complexes between enalapril with two sulphonphthalein acid dyes, bromocresol purple (BCP) and bromophenol blue (BPB) at pH 2.8 and 3.0 using BCP and BPB, respectively followed by their extraction with chloroform. Several parameters such as pH, buffer type, reagent volume, sequence of addition and effect of extracting solvent were optimized to achieve high sensitivity, stability, low blank reading and reproducible results.Results: The absorbance is measured at 408 and 414 nm using BCP and BPB reagents, respectively. The stoichiometric ratio of the formed ion-pair complexes was found to be 1:1 (drug: reagent) for both methods as deduced by Job's method of continuous variation. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9993-0.9996) were found between the absorbance's and the concentrations of enalapril over the concentration ranges of 2.0–24 μg ml-1 and 2.0–28 μg ml-1 with limits of detection (LOD) of 0.39 and 0.45 μg ml-1, using BCP and BPB methods, respectively. Various analytical parameters have been evaluated and the results have been validated by statistical data.Conclusion: The proposed methods were validated in accordance with ICH guidelines and successfully applied to the determination of enalapril in pure and Dosage forms. Statistical comparison of the results obtained by applying the proposed methods with those of the official method revealed good agreement and proved that there were no significant difference in the accuracy and precision between the results.Â

CHARGE TRANSFER SPECTROPHOTOMETRIC METHODS FOR THE DETERMINATION OF TWO ANTIHISTAMINIC DRUGS IN PHARMACEUTICAL FORMULATIONS

Objective: Simple, accurate and precise spectrophotometric methods have been developed for the determination of two antihistaminic drugs (desloratadine (DES) and ebastine (EBS)) in pure forms and pharmaceutical formulations. Methods: The proposed methods were based on the charge transfer complexation reaction of both drugs as ‘n' electron donor with chloranilic acid (p-CLA) or 2, 3-Dichloro-5,6-dicyano-p-benzoquinone (DDQ) as π acceptors to give highly coloured complex species. The coloured products were quantitated spectrophotometrically at 459 and 460 nm using DDQ and at 532 and 533 nm using p-CLA for DES and EBS, respectively. Optimization of the different experimental conditions were studied. Results: Beer's law was obeyed in the concentration ranges of 5.0-120 and 10-180 mg mL-1 with good correlation coefficients were ≥ 0.9995 and 0.9992 and a relative standard deviation (R.S.D.) of ≤ 0.98 and 1.24% using DDQ and p-CLA methods, respectively. The molar absorptivity, Sandell's sensitivity, detection and quantification limits were also calculated. The developed methods were successfully applied for determination of the studied drugs in pharmaceutical formulations with good accuracy and precision and without interferences from common additives by applying the standard addition technique. Conclusion: The developed methods have been validated statistically for their accuracy, precision, sensitivity, selectivity, robustness and ruggedness as per ICH guidelines and the results compared favorably with those obtained using the reported methods

An efficient ionic liquid-based cloud point extraction to preconcentrate mercury in environmental samples and hair of occupational workers before spectrophotometric detection

ABSTRACT. Mercury preconcentration in environmental samples and hair of occupational workers prior to spectrophotometric detection was described using a unique, eco-friendly, and quick ionic liquid-based cloud point extraction method. The discovered method used an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate with Triton X-114 as an extracting phase in the presence of a new chelating agent 3-(2-hydroxy-5-ethoxycarbonylphen-1-ylazo)-1,2,4-triazole at pH 7.0 to separate mercury and measure the complex spectrophotometrically at wavelength 550 nm. The effects of several analytical factors on extraction performance were investigated. With a correlation coefficient of 0.9997. The calibration graph was linear in the range of 2.0-400 µg/L. The limit of detection and preconcentration factor, respectively, were 0.5 µg/L and 100. The relative standard deviation of 100 and 300 µg/L mercury (n = 10) was 1.5 and 2.2, respectively, indicating the precision and reliability of the new IL-CPE approach. The accuracy of the proposed approach confirmed through the certified reference materials analysis. The applicability of the established technique was demonstrated successfully by the estimation of trace mercury in environmental samples and hair of occupational workers.     KEY WORDS: Mercury, Ionic liquid-based cloud point extraction, Environmental and hair samples, Spectrophotometry   Bull. Chem. Soc. Ethiop. 2022, 36(4), 767-778.                                                         DOI: https://dx.doi.org/10.4314/bcse.v36i4.

SENSITIVE SPECTROPHOTOMETRIC DETERMINATION OF ACETYLCHOLINESTRASE INHIBITOR DONEPEZIL HYDROCHLORIDE IN PURE FORM AND PHARMACEUTICAL FORMULATIONS USING SULPHONPHETHALIN DYES

Objective: Four sensitive, selective, rapid, validated and easily reproducible spectrophotometric methods have been developed for the determination of acetylcholinesterase inhibitor donepezil hydrochloride (DNP) in pure form and in pharmaceutical formulationsMethods: The proposed methods are based on ion-pair complex formation between donepezil hydrochloride with four acidic (sulphonphthalein) dyes; namely bromocresol green (BCG), bromothymol blue (BTB), bromophenol blue (BPB) and bromocresol purple (BCP) which extracted into dichloromethane followed by the measurement of the yellow colored ion-pair complexes at 420, 413, 415 and 409 nm for DNP-BCG, DNP-BTB, DNP-BPB and DNP-BCP complexes, respectively.Results: Beer's law was obeyed in the concentration ranges of 1.0-12 and 1.0-10 μg ml-1for (BCG or BCP) and (BTB or BPB) methods, respectively with limits of detection (LOD) of 0.16, 0.24, 0.19 and 0.25 μg/ml using BCG, BCP, BTB and BPB methods, respectively. The stoichiometry of the ion-pair complex formed between the dug and dye found to be (1:1) was determined by Job's method of continuous variations. Various analytical parameters have been evaluated and the results have been validated by statistical data.Conclusion: The proposed methods were validated in accordance with ICH guidelines and successfully applied to the determination of donepezil hydrochloride in pure and dosage forms. Statistical comparison of the results obtained by applying the proposed methods with those of the reported method revealed good agreement and proved that there was no significant difference in the accuracy and precision between the results.Â

SPECTROPHOTOMETRIC DETERMINATION OF OXYBUTININE HYDROCHLORIDE BY ION-PAIR EXTRACTIONIN IN PHARMACEUTICAL PREPARATIONS

Objective: Simple, sensitive, precise, reproducible and validated visible spectrophotometric methods have been developed for the determination of an antimuscarinic drug, namely oxybutynin hydrochloride (OXB) in pure form and in pharmaceutical preparations.Methods: Two spectrophotometric methods are based on the formation of yellow colored ion-pair complexes between the studied drug, and two sulphonphthalein acid dyes, bromocresol purple (BCP) and bromophenol blue (BPB) with absorption maxima at 410 and 416 nm, respectively.Results: The stoichiometric ratio of the formed ion-pair complexes was found to be 1:1 (drug: reagent) for both methods as deduced by Job's method of continuous variation. Several parameters such as pH, buffer type, and reagent volume, sequence of addition and effect of extracting solvent were optimized to achieve high sensitivity, stability, low blank reading and reproducible results. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9996-0.9999) were found between the absorbance's and the concentrations of oxybutynin over the concentration ranges of 1.0–8.0 μg ml-1 and 1.0–12 μg ml-1 with LOD of 0.21 and 0.19 μg ml-1, using BCP and BPB methods, respectively. Various analytical parameters have been evaluated and the results have been validated by statistical data.Conclusion: The proposed methods were validated in accordance with ICH guidelines and successfully applied to the analysis of pharmaceutical formulation. Statistical comparison of the results obtained by applying the proposed methods with those of the reference method revealed good agreement and proved that there was no significant difference in the accuracy and precision between the results.Â

CLOUD POINT EXTRACTION, PRECONCENRATION AND SPECTROPHOTOMETRIC DETERMINATION OF COBALT IN WATER SAMPLES

Objective: A new cloud point extraction (CPE) method was developed for pre concentration of trace cobalt (II) in water samples.Methods: The method is based on the complexation reaction of Co (II) with 2-(benzothiazolyl azo)-4-nitrophenol reagent (BTANP) at pH 7.0 and micelle-mediated extraction using the nonionic surfactant Triton X-114 of the complex.Results: The enriched analyte in the surfactant-rich phase was diluted with methanol and the cobalt content was determined by spectrophotometry at 549 nm. The optimum conditions (e. g. pH, reagent and surfactant concentrations, and temperature and centrifugation times) were evaluated and optimized. The proposed CPE method showed linear calibration within the range 10–300 ng/ml of Co(II) and the limit of detection of the method was 1.5 ng/ml with a pre concentration factor of 50. The relative standard deviation (RSD) was found to be 1.20% (N = 6). The interference effect of some cations and anions was also studied.Conclusion: The proposed method has been successfully applied to the determination of Co(II) in water samples with a recovery from spiked samples in the range of 96.60–98.70%.Â

High performance liquid chromatography for simultaneous determination of xipamide, triamterene and hydrochlorothiazide in bulk drug samples and dosage forms

A novel, simple and robust high-performance liquid chromatography (HPLC) method was developed and validated for simultaneous determination of xipamide (XIP), triamterene (TRI) and hydrochlorothiazide (HCT) in their bulk powders and dosage forms. Chromatographic separation was carried out in less than two minutes. The separation was performed on a RP C-18 stationary phase with an isocratic elution system consisting of 0.03 mol L–1orthophosphoric acid (pH 2.3) and acetonitrile (ACN) as the mobile phase in the ratio of 50:50 at 2.0 mL min–1 flow rate at room temperature. Detection was performed at 220 nm. Validation was performed concerning system suitability, limits of detection and quantitation, accuracy, precision, linearity and robustness. Calibration curves were rectilinear over the range of 0.195–100 µg mL–1 for all the drugs studied. Recovery values were 99.9, 99.6 and 99.0 % for XIP, TRI and HCT, respectively. The method was applied to simultaneous determination of the studied analytes in their pharmaceutical dosage forms

Utility of inorganic oxidants for the spectrophotometric determination of ganciclovir in dosage forms

Eight direct spectrophotometric methods for determination of ganciclovir has been developed and validated. These methods were based on the oxidation of the drug by different inorganic oxidants: ceric ammonium sulphate, potassium permanganate, ammonium molybdate, ammonium metavanadate, chromium trioxide, potassium dichromate, potassium iodate and potassium periodate. The oxidation reaction were performed in perchloric acid medium for ceric ammonium sulphate and in sulfuric acid medium for the other reagents. Different variables affecting the reaction conditions were carefully studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9987- 0.9993) were found between the reading and the corresponding concentration of the drug in the ranges of 2.0-1500 μg.mL–1 The limits of detection ranged from 0.26-18.25 μg mL–1 . The precision of the methods . was satisfactory; the values of relative standard deviations did not exceed 2.0 %. The proposed methods were successfully applied to the analysis of ganciclovir in dosage forms with good accuracy and precisions; the label claim percentages ranged from 99.9–100.4 ± 0.62–1.05 %.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Sensitive spectrophotometric methods for determination of some organophosphorus pesticides in vegetable samples

Three rapid, simple, reproducible and sensitive spectrophotometric methods (A, B and C) are described for the determination of two organophosphorus pesticides, (malathion and dimethoate) in formulations and vegetable samples. The methods A and B involve the addition of an excess of Ce4+ into sulphuric acid medium and the determination of the unreacted oxidant by decreasing the red color of chromotrope 2R (C2R) at a suitable lmax = 528 nm for method A, or a decrease in the orange pink color of rhodamine 6G (Rh6G) at a suitable lmax = = 525 nm. The method C is based on the oxidation of malathion or dimethoate with the slight excess of N-bromosuccinimide (NBS) and the determination of unreacted oxidant by reacting it with amaranth dye (AM) in hydrochloric acid medium at a suitable lmax = 520 nm. A regression analysis of Beer-Lambert plots showed a good correlation in the concentration range of 0.1-4.2 μg mL−1. The apparent molar absorptivity, Sandell sensitivity, the detection and quantification limits were calculated. For more accurate analysis, Ringbom optimum concentration ranges are 0.25-4.0 μg mL−1. The developed methods were successfully applied to the determination of malathion, and dimethoate in their formulations and environmental vegetable samples

VALIDATED SPECTROPHOTOMETRIC METHODS FOR DETERMINATION OF MONTELUKAST SODIUM IN PURE AND DOSAGE FORMS USING N-BROMOSUCCINIMIDE AND DYES

Objective: Simple, sensitive, precise, reproducible and validated spectrophotometric methods have been developed for the quantification of montelukast sodium as leukotriene receptor antagonist drug, in pure and dosage forms (tablets). Methods: The methods use N-bromosuccinimide (NBS) as an oxidant and three dyes, amaranth, methylene blue, and indigo carmine, as auxiliary reagents. The three methods are based on oxidation reaction of montelukast sodium with a known excess of N-bromosuccinimide (NBS) in acid medium, followed by determination of unreacted NBS by the reaction with a fixed amount of dyes, amaranth, methylene blue, and indigo carmine followed by the measurement of the absorbance at 520, 664 and 610 nm, respectively. Results: Under the optimum conditions, linear relationships with good correlation coefficients (0.9993-0.9996) were found over the concentration ranges of 0.5-10, 1.0-12 and 0.5-8.0 µg/ml with a limit of detection (LOD) of 0.15, 0.3 and 0.14 µg/ml using amaranth, methylene blue, and indigo carmine methods, respectively. Intra-day and inter-day accuracy and precision of the methods have been evaluated. No interference was observed from the common tablet excipients. Conclusion: The proposed methods were validated in accordance with ICH guidelines and successfully applied to the analysis of montelukast sodium in dosage forms (tablets). The reliability of the methods was further ascertained by performing recovery studies using the standard addition method. Statistical comparison of the results obtained by applying the proposed methods with those of the reported method by applying student’s t-test and F-test revealed good agreement