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

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

DEVELOPMENT OF EFFICIENT CLOUD POINT EXTRACTION METHOD FOR PRECONCENRATION AND SPECTROPHOTOMETRIC DETERMINATION OF NICKEL IN WATER SAMPLES USING 2-(BENZOTHIAZOLYLZAO)ORCINOL

Objective: Efficient cloud point extraction (CPE) methodology was developed for pre concentration of trace nickel in water samples prior to their determination by spectrophotometry.Methods: The method is based on the reaction of nickel with 2-(benzothiazolyl azo) orcinol reagent (BTAO) at pH 7.0 and micelle-mediated extraction using the nonionic surfactant Triton X-114 medium.Results: The surfactant-rich phase was diluted with methanol and the nickel content was determined at 558 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 10–250 ng/ml of nickel and the limit of detection of the method was 2.0 ng/ml with a pre concentration factor of  50. The relative standard deviation (RSD) and relative error were found to be 1.10% (N = 6). The interference effect of some cations and anions was also studied.Conclusion: The method was applied to the determination of nickel in water samples with a recovery from the spiked samples in the range of 95.85–98.50%. Â

SENSITIVE SPECTROPHOTOMETRIC ASSAY OF MUSCARINIC RECEPTOR ANTAGONIST TOLTERODINE TARTRATE IN BULK DRUG AND PHARMACEUTICAL FORMULATIONS

Objective: Simple, sensitive, and accurate spectrophotometric methods have been developed for the assay of tolterodine tartrate (TOL) in bulk drugand pharmaceutical formulations.Methods: The proposed methods are based on oxidation reaction of TOL with a known excess of cerium(IV) ammonium sulfate as an oxidizing agentin acid medium followed by determination of unreacted oxidant by adding a fixed amount of dye, e.g., amaranth (AM), rhodamine 6G (Rh6G), andindigo carmine (IC) followed by measuring the absorbance at 520, 530, and 610 nm, respectively. The effect of experimental conditions was studiedand optimized.Results: The Beer's law was obeyed in the concentration ranges of 1.0-10, 1.0-12, and 0.5-9.0 μg/mL using AM, Rh6G, and IC dyes, respectively, witha correlation coefficient ≥0.9995. The calculated molar absorptivity values are 1.868×104, 1.008×104, and 1.623×104 L/mol/cm using AM, Rh6G, andIC dyes, respectively. The limits of detection and quantification were reported. Intraday and interday accuracy and precision of the methods have beenevaluated. No interference was observed from the additives.Conclusion: The proposed methods were successfully applied to the assay of TOL in tablets preparations, and the results were statistically comparedwith those of the reported method by applying Student's t-test and F-test. The reliability of the methods was further ascertained by performingrecovery studies using the standard addition method

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

UTILITY OF CERTAIN σ AND π-ACCEPTORS FOR THE SPECTROPHOTOMETRIC DETERMINATION OF VORICONAZOL ANTIFUGAL DRUG IN PHARMACEUTICAL FORMULATION

Objective: Studies were carried out, for the first time, to investigate the charge-transfer reactions of voriconazole antifungal drug (VOR) as n-electron donor with the σ-acceptor iodine (I2) and various Ï€-acceptors: 7,7,8,8-tetracyanoquinodimethane (TCNQ); 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and p-chloranilic acid (p-CLA).Methods: The formation of the colored charge-transfer complexes were utilized in the development of simple, rapid and accurate spectrophotometric methods for the analysis of voriconazole in pure form as well as in its pharmaceutical formulation (tablets). Different variables affecting the reactions were studied and optimized.Results: Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9994–0.9999) were found between the absorbance and the concentration of voriconazole in the range of 2.0–120 μg mL−1. For more accurate analysis, Ringbom optimum concentration range was found to be between 4.0-110 μg mL-1. The limits of detection ranged from 0.36 to 1.23 μg mL−1andthe limits of quantification ranged from 1.20 to 4.10 μg mL−1. A Job's plot of the absorbance versus the molar ratio of voriconazole to each of acceptors under consideration indicated (1:1) ratio.Conclusion: The proposed methods were applied successfully for simultaneous determination of voriconazole in tablets with good accuracy and precision and without interferences from common additives. The results were compared favourably with the reported method.Â

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

DEVELOPMENT AND VALIDATION OF NEW SPECTROPHOTOMETRIC METHODS FOR ESTIMATION OF ANTIPSYCHOTIC DRUG ASENAPINE MALEATE IN PURE AND DOSAGE FORMS

Objective: Three sensitive, simple, precise, reproducible, and validated spectrophotometric methods have been developed for the determination of anti-psychotic drug (asenapine maleate) in pure and pharmaceutical dosage forms. Methods: The methods are based on the formation of yellow-colored ion-pair complex between asenapine maleate and three acid dyes, namely, bromocresol purple (BCP), bromophenol blue (BPB) and bromothymol blue (BTB) with absorption maxima at 410, 414 and 416 nm, respectively. Several parameters such as pH, buffer type and volume, reagent volume, the sequence of addition and effect of extracting solvent were optimized. Results: Under the optimum experimental conditions, beer’s law is obeyed over the concentration ranges of 1.0–20, 1.0–14, and 1.0-16 μg/ml for BCP, BPB and BTB, respectively, with good correlation coefficients (0.9994-0.9998). The apparent molar absorptivity and Sandell’s sensitivity values are reported for all methods. The limit of detection (LOD) and the limit of quantification (LOQ) values are found to be 0.27, 0.30, and 0.25 μg/ml and 0.90, 1.0, and 0.83 μg/ml for BCP, BPB and BTB, respectively. The stoichiometric ratio of the formed ion-pair complexes was found to be 1:1 (drug: reagent) for all methods, as deduced by Job's method of continuous variation. Conclusion: The proposed methods were successfully applied for the determination of asenapine maleate in pharmaceutical formulations with good accuracy and precision. Statistical comparison of the results was performed using Student's t-test and variance ratio F-test at the 95% confidence level and there was no significant difference between the reported and proposed methods regarding accuracy and precision. Further, the validity of the proposed methods was confirmed by recovery studies via standard addition technique in accordance with ICH guidelines

A GREEN VORTEX-ASSISTED IONIC LIQUID-BASED DISPERSIVE LIQUID–LIQUID MICROEXTRACTION METHOD FOR PRECONCENTRATION AND DETERMINATION OF TRACE CADMIUM IN FOOD SAMPLES

Objective: Green, easy, and sensitive vortex-assisted ionic liquid-based dispersive liquid–liquid microextraction technique (VA-IL-DLLME) was developed to preconcentrate and determine trace quantities of cadmium (Cd2+) ions from real food samples, before detection by flame atomic absorption spectrometry. Methods: The proposed technique base on the utilization of IL (1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate) as an extraction solvent for Cd2+ ions after the complexation with 2-(2’-benzothiazolylazo) chromotropic acid at pH 8.0. The impact of different analytical parameters on microextraction efficiency was investigated. The validation of the proposed procedure was verified by the test of certified reference material (SRM spinach leaves 1570A) applying the standard addition method. Results: In the range of 1.0–300 μg/L, the calibration graph was linear. Limit of detection, preconcentration factor and the relative standard deviation (RSD%, 25, 150, and 250 μg/L, n=5) were 0.2 μg/L, 100, and 2.0–3.2%, respectively. Conclusion: Green, VA-IL-DLLME method was developed and applied to preconcentrate and determine of trace quantities of Cd2+ in real food samples with satisfactory results. The obtained recovery values showed good agreement with the certified values