Dina T. El-Sherbiny

Microemulsion electrokinetic chromatography – or solvent-modified micellar electrokinetic chromatography?

An overview of the microemulsion electrokinetic chromatography technique and its fields of applications in analytical chemistry are given. The separation mechanisms involved are discussed and the technique is compared to solvent-modified micellar electrokinetic chromatography.

Spectrophotometric determination of propranolol in formulations via oxidative coupling with 3-methylbenzothiazoline-2-one hydrazone

A simple spectrophotometric method has been developed for the determination of propranolol hydrochloride in pure as well as in dosage forms. The method is based on the oxidative coupling reaction with 3-methylbenzothiazoline-2-one hydrazone. A mixture of an acidic solution of the chromogenic agent and the drug upon treatment with ceric ammonium sulfate produces an orange color peaking at 496 nm. The absorbance-calibration plot was linear over the range 1-10 microg/ml with minimum detectability (S/N=2) of 0.1 microg/ml (3.38x10(-7) M). The molar absorbitivity was 3.195x10(3) l/M/cm with correlation coefficient (n=10) of 0.9999. The different experimental parameters affecting the development and stability of the color were carefully studied and optimized. The proposed method was applied successfully to the determination of propranolol in its dosage forms. A proposal of the reaction pathway was presented.

Spectrofluorometric Determination of Drotaverine Hydrochloride in Pharmaceutical Preparations

Abstract A highly sensitive, spectrofluorometric method was developed for the determination of drotaverine HCl in pharmaceutical preparations. The proposed method is based on the measurement of the native fluorescence of the drug in 0.1 M H2SO4 at emission 465 nm after excitation at 295 nm. The relative fluorescence intensity-concentration plot was rectilinear over the range of 0.16–4 µg·ml−1, with good correlation (r = 0.9999) and a lower limit of detection (LOD) of 0.032 µg·ml−1. The proposed method was successfully applied for the determination of drotaverine HCl in tablets and ampoules with a recovery percentage of 100.42 ± 0.601,99.83 ± 0.82 and 99.43 ± 1.08, respectively, which were in accordance with those obtained by a compendial method.

Microemulsion liquid chromatographic method for simultaneous determination of simvastatin and ezetimibe in their combined dosage forms.

A rapid HPLC procedure using a microemulsion as an eluent was developed and validated for analytical quality control of antihyperlipidemic mixture containing simvastatin (SIM) and ezetimibe (EZT) in their pharmaceutical preparations. The separation was performed on a column packed with cyano bonded stationary phase adopting UV detection at 238 nm using a flow rate of 1 mL/min. The optimized microemulsion mobile phase consisted of 0.2 M sodium dodecyl sulphate, 1% octanol, 10% n-propanol, and 0.3% triethylamine in 0.02 M phosphoric acid at pH 5.0. The developed method was validated in terms of specificity, linearity, lower limit of quantification (LOQ), lower limit of detection (LOD), precision, and accuracy. The proposed method is rapid (8.5 min), reproducible (RSD < 2.0%) and achieves satisfactory resolution between SIM and EZT (resolution factor = 2.57). The mean recoveries of the analytes in pharmaceutical preparations were in agreement with those obtained from a reference method, as revealed by statistical analysis of the obtained results using Students t-test and the variance ratio F-test.

Spectrofluorimetric determination of two β-agonist drugs in bulk and pharmaceutical dosage forms via derivatization with dansyl chloride

A sensitive, simple and rapid spectrofluorimetric method has been developed for the determination of both Fenoterol hydrobromide (FNT) and Ritodrine hydrochloride (RTH) in pure and dosage forms. The method is based on derivatization using dansyl chloride (DNS-Cl) as fluorogenic agent and measuring the fluorescence of the products at emission wavelengths of 517 and 515 nm after excitation at 348 and 343 nm for FNT and RTH, respectively. Different experimental parameters affecting the fluorescence intensities were carefully studied and optimized. The relation between fluorescence intensities and drug concentrations were rectilinear over the concentration range of 0.25–6.0 μg/mL for both drugs with a minimum detectability of 0.065 and 0.045 μg/mL for FNT and RTH, respectively. The percentage recoveries ±SD were 100.1 ± 0.9, 99.9 ± 0.6 for FNT and RTH respectively. The proposed method was successfully applied to the determination of both drugs in their commercial dosage forms. The obtained results were statistically validated and agreed well with those obtained with reference methods. A suggestion for the reaction pathway with DNS-Cl was postulated.

SIMULTANEOUS IN VITRO HPLC DETERMINATION OF ENALAPRIL MALEATE AND LERCANIDIPINE HCL

A reversed-phase liquid chromatographic (RP-HPLC) method was developed for the simultaneous determination of a binary mixture of enalapril maleate and Lercanidipine HCl in pure form, synthetic mixture, and synthetic tablets. The analysis was carried out using Hibar® C18, pre-packed column. Mobile phase, containing acetonitrile:methanol:water:orthophosphoric acid (35:35:30:0.2) adjusted to pH 3.0 with triethylamine, was pumped at a flow rate of 1.0 mL min−1 with UV-detection at 210 nm. The method showed good linearity in the range of 5.0–100.0 μg mL−1 for both drugs. The detection limit of the proposed method was 0.80 and 0.93 μg mL−1, and the quantitation limit was 2.42 and 2.80 μg mL−1 for ENM and LER, respectively.

Multiobjective optimization strategy based on desirability functions used for the microemulsion liquid chromatographic separation and quantification of norfloxacin and tinidazole in plasma and formulations

The aim of the present study was to optimize a microemulsion liquid chromatography method for the simultaneous determination of norfloxacin and tinidazole binary mixture using a chemometric protocol. Optimization experiments were conducted through a process of screening and optimization. A 2(7-4) fractional factorial design was used as screening design. While the location of optimum conditions was established by applying Derringers desirability function. The optimal mobile phase composition was predicted to be: 3.5% w/v SDS, 10.03% v/v 1-propanol, 0.5% v/v 1-octanol, and 0.3% triethylamine in 0.02 M phosphoric acid at pH 6.5. The mobile phase was delivered isocratically at a flow rate of 1 mL/min with UV detection at 290 nm. Tinidazole and norfloxacin were eluted with retention times of 1.8 and 5.8 min, respectively. The calibration plots displayed good linear relationships in the concentration ranges of 0.5-50 and 0.75-75 μg/mL for norfloxacin and tinidazole, respectively. The method was successfully applied for determination of both drugs in pharmaceutical dosage forms and real human plasma. Where the accuracy was proved by the low values of % error and high values of recovery, also the relative standard deviation for the results did not exceed 1.5%, proving the precision of the method.

Simultaneous Determination of Enalapril and Hydrochlorothiazide in Pharmaceutical Preparations Using Microemulsion Liquid Chromatography

A rapid high-performance liquid chromatography procedure for analytical quality control of mixture containing enalapril maleate (ENM) and hydrochlorothiazide (HCT) in their pharmaceutical preparations was developed using a microemulsion as an eluent. The separation was performed on a column packed with cyano-bonded stationary phase adopting UV detection at 210 nm using a flow rate of 1 mL/min. The optimized microemulsion mobile phase consisted of 0.2 M sodium dodecyl sulfate, 1% octanol, 10% n-propanol and 0.3% triethylamine in 0.02 M phosphoric acid, and pH was adjusted at 3.5. The proposed method was found to be linear over the concentration ranges 1-100 and 0.05-5 μg/mL for ENM and HCT, respectively with a correlation coefficient of 0.9999 for both drugs. The developed method was validated in terms of specificity, linearity, lower limit of quantification, lower limit of detection, precision and accuracy. The proposed method is rapid (5 min), reproducible (relative standard deviation <2.0%) and achieves a satisfactory resolution between ENM and HCT (resolution factor = 3.62). The mean recoveries of the analytes in tablets were in agreement with those obtained from a comparison method, as revealed by statistical analysis of the obtained results using Students t-test and the variance ratio F-test.

SIMULTANEOUS DETERMINATION OF RITODRINE AND ISOXSUPRINE IN PHARMACEUTICAL PREPARATIONS USING LIQUID CHROMATOGRAPHY

Simultaneous determination of two structurally related ß2 adrenergic receptor agonists namely, Ritodrine HCl (RTH) and Isoxsuprine HCl (ISP) was performed using reversed phase HPLC. The separation was performed on a C18 column adopting UV detection at 221 nm using a flow rate of 1 mL/min. The mobile phase consisted of acetonitrile: methanol: acid phosphate buffer (25:25:50) pH 4.5. The developed method was validated in terms of specificity, linearity, lower limit of quantification, lower limit of detection, precision, and accuracy. With the proposed method, satisfactory resolution between the two drugs was obtained (resolution factor = 2.76). Linear determination range of both drugs was 1–100 µg/mL. The proposed method was applied to the determination of RTH and ISP in synthetic mixtures and pharmaceutical samples. The method requires a minimum of sample handling and is rapid (within 3 min) and reproducible (RSD < 2.0%). The mean recoveries of the analytes in pharmaceutical preparations were in agreement with those obtained from reference methods, as revealed by statistical analysis of the obtained results using the Students t-test and the variance ratio F-test.

Voltammetric Determination of Rosiglitazone in Pharmaceutical Preparations and Human Plasma

Abstract The voltammetric behavior of rosiglitazone was studied using direct current (DCt), differential pulse (DPP), and alternating current (ACt) polarography. The drug manifests cathodic waves over a pH range of 2–11.2. In Britton‐Robinson buffer (BRb; pH 4), the diffusion current–concentration relationship was found to be rectilinear over a range of 4–24 µg · mL−1 and 0.1–16 µg · mL−1 using DCt and DPP modes, respectively, with minimum limits of detection (LOD) of 0.15 µg · mL−1 and 0.07 µg · mL−1 using the DCt and DDP modes, respectively. The diffusion‐current constant (I d) was 6.63±0.03 (n=5). The proposed method was successfully applied to the determination of the studied compound both in pure form and in formulations. The mean percentage recoveries in tablets were 100.09±1.18 and 100.85±0.88 (n=5) using DCt and DPP modes, respectively. Furthermore, the proposed method, adopting the DPP mode, was applied to the determination of rosiglitazone in spiked human plasma and the obtained mean percentage recoveries were 99.14±3.29 (n=4).