Spectrophotometric and Spectrofluorimetric Methods for the Determination of Dothiepin Hydrochloride in its Pure and Dosage Forms using Eosin

Spectrophotometric and spectrofluorimetric methods were developed for the determination of dothiepin hydrochloride (DOP) in different dosage forms. The spectrophotometric method (Method I) is based on formation of a binary complex with eosin at 540 nm in acetate buffer of pH3.7. The absorbance-concentration plot is rectilinear over the range 1-10 μg/mL with LOD of 0.18 μg/mL and LOQ of 0.54 μg/mL. The spectroflurimetric method (Method II) is based on the quantitative quenching effect of Dothiepin on the native fluorescence of eosin at the same pH. The quenching of the fluorescence of eosin was measured at 543 nm after excitation at 304 nm. The fluorescence-concentration plot is rectilinear over the range 0.3-8 μg/ mL with LOD of 0.11 μg/mL and LOQ of 0.34 μg/mL. The proposed methods were successfully applied to the analysis of commercial tablets and capsules containing the drug. Statistical comparison of the results with those of the reference method revealed good agreement and proved that there were no significant differences in the accuracy and precision between the two methods respectively.

Determination of oxybutynin in pharmaceuticals via reaction with mixed acids anhydrides: application to content uniformity testing

Sensitive and simple spectrophotometric (Method I) and spectrofluorimetric (Method II) methods were developed and validated for the determination of oxybutynin HCl (OXB) in its dosage forms. The method was based on the reaction of OXB with malonic acid anhydride in acetic acid anhydride to form a highly yellow colored product that was measured at 375 nm spectrophotometrically. The same reaction product exihibits strong fluorescence that was measured at 440 nm after excitation at 390 nm. The factors affecting formation and stability of the reaction product were carefully studied and optimized, and the reaction mechanism was postulated. The absorbance-concentration plot is rectilinear over the range 4-40 μg/mL with LOD of 1.12 μg/mL and LOQ of 3.39 μg/mL. The fluorescence-concentration plot is rectilinear over the range 0.5-6 μg/mL with LOD of 0.11 μg/mL and LOQ of 0.33 μg/mL. The method was applied to the analysis of commercial tablets Detronin® and Uripan®. Statistical comparison of the results with those of the reference method revealed good agreement and proved that there were no significant difference in the accuracy and precision between the two methods respectively. The study was extended to content uniformity testing.

Spectrophotometric Determination of the Antidepressants Sertraline and Paroxetine HCl using 2,4-Dinitrofluorobenzene

A simple and sensitive spectrophotometric method was developed for the determination of each of sertraline (SER) and paroxetine HCl (PXT) in dosage forms. The method is based upon reaction of PXT and SER with 2,4-dinitrofluorobenzene (DNFB) to form colored products. The absorbance of the products were measured at 375and 390 nm for SER and PXT respectively. The absorbance concentration plots were rectilinear over the concentration rang of 1-10 and 2-20 μg/mL with lower detection limits (LOD) of 0.11 and 0.28 μg/mL and quantification limits (LOQ) of 0.32 and 0.85 μg/mL for SER and PXT, respectively. The developed method was successfully applied for the determination of SER and PXT in dosage forms. The common excipients and additives did not interfere in their determinations. There was no significant difference between the results obtained by the proposed and the reference methods regarding Student t-test and the variance ratio F-test respectively. A proposal of the reaction pathway was postulated.

Simple and sensitive spectrofluorimetric method for the determination of pregabalin in capsules through derivatization with fluorescamine

A new, simple and sensitive spectrofluorimetric method has been developed for the determination of pregabalin (PG) in capsules. The method is based on the reaction between pregabalin and fluorescamine in borate buffer solution of pH 10 to give a highly fluorescent derivative that is measured at 487 nm after excitation at 390 nm. The different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized. The fluorescence intensity concentration plot was rectilinear over the range of 0.01-0.3 µg mL⁻¹ with a lower detection limit of 0.0017 µg mL⁻¹ and limit of quantitation of 0.005 µg mL⁻¹. The developed method was successfully applied to the analysis of the drug in its commercial capsules. The mean percentage recovery of PG in its capsule was 99.93±1.24 (n = 3). Statistical comparison of the results with those of the comparison method revealed good agreement and proved that there was no significant difference in the accuracy and precision of the two methods. A proposed reaction pathway was postulated.

Second derivative synchronous fluorescence spectroscopy for the simultaneous determination of chlorzoxazone and Ibuprofen in pharmaceutical preparations and biological fluids

A rapid, simple and highly sensitive second derivative synchronous fluorometric method has been developed for the simultaneous analysis of binary mixture of chlorzoxazone (CLZ) and ibuprofen (IP). The method is based upon measurement of the synchronous fluorescence intensity of these drugs at Δλ=60 nm in methanol. The different experimental parameters affecting the fluorescence of the two drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the range of 0.2-4 μg/mL and 0.1-1.6 μg/mL for CLZ and IP, respectively with lower detection limits (LOD) of 0.028 and 8.3 × 10(-3) μg/mL and quantification limits (LOQ) of 0.086 and 0.03 μg/mL for CLZ and IP, respectively. The proposed method was successfully applied for the determination of the two compounds in synthetic mixtures and in commercial capsules. The high sensitivity attained by the proposed method allowed the determination of both drugs and real human plasma samples. The mean % recoveries in real human plasma (n=3) were 87.69 ± 6.15 and 92.57 ± 4.39 for each of CLZ and IP respectively.

Kinetic Spectrofluorometric Determination of Certain Calcium Channel Blockers via Oxidation with Cerium (IV) in Pharmaceutical Preparations

A simple and sensitive kinetic spectrofluorometric method was developed for the determination of some calcium channel blockers namely, verapamil hydrochloride, diltiazem hydrochloride, nicardipine hydrochloride and flunarizine. The method is based upon oxidation of the studied drugs with cerium (IV) ammonium sulphate in acidic medium. The fluorescence of the produced Ce (III) was measured at 365 nm after excitation at 255 nm. The different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized. The fluorescence-concentration plots were rectilinear for all the studied compounds over the concentration range of 0.01 to 0.12 μg mL(-1). The limits of detections for the studied compounds ranged from 2.93 × 10(-3) to 0.012 μg mL(-1) and limits of quantification from 9.76 × 10(-3) to 0.04 μg mL(-1) were obtained. The method was successfully applied to the analysis of commercial tablets. The results obtained were in good agreement with those obtained with reference methods.

Second-derivative Synchronous Fluorometric Method for the Simultaneous Determination of Cinnarizine and Domperidone in Pharmaceutical Preparations. Application to Biological Fluids

A rapid, simple and highly sensitive second derivative synchronous fluorometric method has been developed for the simultaneous analysis of binary mixture of cinnarizine (CN) and domperidone (DOM). The method is based upon measurement of the native fluorescence of these drugs at Deltalambda=80 nm in aqueous methanol (50% V/V). The different experimental parameters affecting the native fluorescence of the studied drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the range of 0.1 to 1.3 microg mL(-1) and 0.1-3.0 microg mL(-1) for CN and DOM, respectively with lower detection limits of 0.017 and 5.77 x 10(-3) microg mL(-1) and quantification limits of 0.058 and 0.02 microg mL(-1) for CN and DOM. The proposed method was successfully applied for the determination of the studied compounds in synthetic mixtures and in commercial tablets. The results obtained were in good agreement with those obtained with reference methods. The high sensitivity attained by the synchronous fluorometric method allowed the determination of CN in real and spiked human plasma. The mean % recoveries in case of spiked human plasma (n=3) were 96.39+/-1.18 while that in real human plasma (n = 3) was 104.67+/-4.16.

Voltammetric determination of montelukast sodium in dosage forms and human plasma

The voltammetric behaviour of montelukast (MKST) was studied using cyclic voltammetry, direct current (DCt), differential pulse polarography (DPP) and alternating current (ACt) polarography. MKST exhibited well-defined cathodic waves over the range pH range 1-5. No anodic waves were produced over the same pH range. At pH 1, the analytical pH; the diffusion current constant (Id) was 2.2+/-0.01 microA l mmol-1. The current concentration plot was rectilinear over the range 2-20 microg ml-1 with correlation coefficient (n=10) of 0.9943. The lower limit of detection (S/N=2) was 0.2 microg ml-1 (3.41x10(-7) M). The wave has been characterised as being diffusion-controlled, although adsorption phenomenon played a limited role in the electrode reaction. The proposed method was successfully applied to the determination of MKST in commercial tablets, and results were in agreement with those given with a reference HPLC method. The method was further extended to the in vitro determination of the drug in spiked human plasma. The mean % recovery (n=5) was 101.38+/-3.85. The number of electrons transferred in the reduction process could be accomplished and a proposal of the electrode reaction was proposed.