EXTRACTION-SPECTROPHOTOMETRIC DETERMINATION OF SOME ANTIHYPERTENSIVE DRUGS IN PHARMACEUTICAL AND BIOLOGICAL FLUIDS USING TWO SULPHONPHTHALEIN DYES

Objective: Two simple and sensitive extractive spectrophotometric methods have been described for the determination of some antihypertensive drugs namely, bisoprolol (BIS), carvedilol (CAR), propranolol (PRP) and telmisartan (TLM) either in pharmaceutical formulations or biological fluids. Methods: The proposed methods involve the formation of yellow colored ion-pair complexes of the studied drugs with two sulphonphthalein dyes as bromophenol blue (BPB) and bromocresol purple (BCP) in acidic medium. Results: The colored products are extracted into methylene chloride and measured spectrophotometrically at 402 nm for all the drugs. Beer's law limits, Sandell sensitivity values, limits of detection (LOD) and quantification (LOQ) values have also been reported for both the methods. The composition of the ion-pair complexes was found 1: 1 by Jobʼs continuous variations method. The effects of concentration of dye, pH and interference of excipients have been studied and optimized. The accuracy and precision of the methods were evaluated on intra-day and inter-day basis; the relative standard deviation (RSD) was<1.72%. Various analytical parameters have been evaluated and the results have been validated by statistical data and indicated no significant difference in accuracy and precision. Conclusion: The proposed methods were successfully applied to the determination of the studied drugs in pharmaceutical formulations and in biological fluids. Keywords: Antihypertensive drugs, Sulphonphthalein dyes, Ion-pair, Pharmaceuticals

CHARGE-TRANSFER COMPLEXES OF CHLORPHENOXAMINE HYDROCHLORIDE WITH CHLORANILIC ACID, 2,3-DICHLORO-5,6-DICYANO-1,4-BENZOQUINONE AND 7,7,8,8-TETRACYANOQUINODIMETHANE AS π-ACCEPTORS

Objective: To develop simplified, accurate and precise visible spectrophotometric strategies for the assay of chlorphenoxamine hydrochloride (CPX) in pure drug and in its pharmaceutical preparations. Methods: The described methods depended on the formation of charge-transfer (CT) complexes of intense color between CPX as donor with three π-acceptors, chloranilic acid (CLA), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), and 7,7,8,8-tetracyanoquinodimethane (TCNQ) and the colored reaction products were estimated spectrophotometrically at 520 nm, 460 nm and 840 nm for CLA, DDQ, and TCNQ complexes, individually. All the optimum conditions were established. The proposed methods were validated in term of linearity, limit of detection as per the international conference on harmonization guidelines ICH Q2 (R1). Results: The complexes obeyed Beer’s law in the concentration range of 16-144, 6-54 and 4-76 μg/mlwith molar absorptivity at 0.30×104, 0.68×104 and 0.58×104 l/mol/cm for CLA, DDQ, and TCNQ, individually. According to Benesi-Hildebrand plots, the association constants and changes of standard free energy were determined. 1:1 was the ratio of composition of the formed CT-complex. Conclusion: The obtained results revealed that the developed method can be applied successfully for the determination of CPX in drug formulations samples with good accuracy and precision

DIRECT SPECTROPHOTOMETRIC DETERMINATION OF ATENOLOL AND TIMOLOL ANTI-HYPERTENSIVE DRUGS

Objective: Direct and sensitive spectrophotometric method is described for the quantitative determination of some anti-hypertensive drugs such as atenolol (ATN) and timolol (TIM) in pure forms as well as in their dosage forms.Methods: The proposed method is based on the redox reaction between the selected drugs and KMnO4 in alkaline medium. The method involves treating the aqueous solution of the selected drugs with KMnO4 in alkaline medium and measuring the bluish-green product at 610 nm. The different experimental parameters affecting the development and stability of the color were carefully studied and optimized.Results: The fixed-time method is adopted for constructing the calibration curves, which were found to be linear over the concentration ranges of 2.0–14 mg/ml and 2.0–28 mg/ml for ATN and TIM, respectively. The determination of the studied drugs by initial rate, variable time and rate constant method was workable with the calibration equations obtained but the fixed time method has been found to be more applicable.Conclusion: The applicability of the proposed method was demonstrated by the determination of the selected drugs in both pure and in commercial dosage forms and has met the validation requirements

Kinetic spectrophotometric method for the determination of some fourth generation fluoroquinolones in bulk and in pharmaceutical formulations

A kinetic spectrophotometric method for accurate and sensitive determination of gemifloxacin (GMFX) and gatifloxacin (GTFX) has been described. The method is based on the reaction of the studied drugs with potassium permanganate in the presence of sodium hydroxide to form a water-soluble green product which shows maximum absorbance at 604 nm. The determination of GMFX and GTFX drugs by rate constant, fixed-concentration, and fixed time methods was feasible with the calibration equations obtained but the fixed time method had been found to be more applicable. The concentration of the selected drugs is calculated using the calibration equation for the fixed time method. The absorbance–concentration plot is linear over the range of 4–36 μg mL−1 and 4–40 μg mL−1 with correlation coefficient of 0.9998 and 0.9991, for GMFX and GTFX, respectively. The molar absorptivity, Sandell sensitivity, detection and quantification limits were also calculated. The different experimental parameters affecting the development and stability of the color were carefully studied and optimized. The intra- and inter-day RSD values indicated the ruggedness of the method. The proposed method has been successfully applied to pharmaceutical formulations of each drug. Statistical comparison of the results with a well established reported method showed excellent agreement and proved that there is no significant difference in the accuracy and precision