An efficient hydrophilic interaction liquid chromatographic method for the simultaneous determination of metformin and pioglitazone using high-purity silica column.

Hydrophilic interaction liquid chromatography (HILIC) provides a feasible approach to effectively separate polar compounds in complex matrices. Herein, a simple, reproducible and efficient HILIC method was developed for the simultaneous determination of pioglitazone. HCl (PIO) and metformin HCl (MET) in rabbit plasma. High-purity silica column was used for rapid and efficient separation of these co-administered drugs. The chromatographic parameters were optimized for best separation. The proposed HILIC system provides high separation efficiency with good peak shape compared to reversed phase (RP) chromatography. Additionally, a simple isocratic elution mode with a mobile phase composed of a mixture of methanol and 10mM phosphate buffer (pH 3.0) (94:6, v/v) was used and the effluent was monitored at 230nm. The method was validated in accordance with the requirements of US-FDA guidelines and was found to behave efficiently for the intended purpose. The correlation coefficient of 0.9992 was obtained in the concentration ranges of 0.5-100µgmL(-1). The limits of detection (S/N=3) and quantification (S/N=10) were 0.16 and 0.5ngmL(-1), respectively. The retention times were 3.4 and 5.0min for PIO and MET, respectively. Plasma levels were successfully determined in rabbit with satisfactory precision and accuracy. In addition, the stability tests in rabbit plasma proved reliable stability under the experimental conditions. The developed HILIC method was applied successfully to study the pharmacokinetic behaviors of the studied analytes in rabbit plasma after a single oral dose containing PIO and MET.

New Salting Out Stability-Indicating and Kinetic Thin Layer Chromatographic Method for Determination of Glimepiride and Metformin HCl Binary Mixture.

A simple, selective salting out and stability-indicating thin layer chromatographic (SOTLC) technique was developed for determination of two antidiabetic drugs; glimepiride and metformin HCl in pure and in tablets as a binary mixture. Separation was performed on silica gel 60 F254 plates using aqueous ammonium sulfate and acetonitrile (7:3, v/v) as a mobile phase. The Rf values were 0.26 ± 0.02 and 0.73 ± 0.02 for glimepiride and metformin HCl, respectively. The separated bands were scanned at λ 237 nm using CAMAG TLC scanner III. The proposed method focusing on study of all the factors that play important role in the mechanism of salting out process. The proposed method was validated according to ICH guidelines and complied with USP31-NF26 validation guidelines. The correlation coefficients of calibration curves were 0.996 and 0.997 for glimepiride and metformin HCl, respectively, in the concentration range of 60-1,400 ng/band for both drugs. The investigated drugs were also subjected to acidic, basic, oxidative and photo-degradation and kinetic study was carried out.

Ethambutol-Cobalt (II) ions complexation spectral characteristics and applications for quantitative analysis.

Ethambutol (EMB) has no significant absorption characteristics beyond 200 nm due to its aliphatic saturated nature. Thus, direct EMB determination in the UV range is not feasible due to its very low molar absorptivity and must requiring a derivatization reaction. Since EMB can act as a chelating agent that disrupts one of several metal-containing enzyme systems in the nucleic acid structure of mycobacteria. This chelating property can be used for quantitative analysis of EMB by formation of UV-Vis absorbing metal complexes. The study in this work describes simple, accurate and sensitive spectrophotometric procedure for the determination of EMB in its pure form and in pharmaceutical formulations. The method depends on the interaction of EMB with cobalt (II) ions in presence of ammonia solution (4 N). The absorbance was measured either at 250, 348 or 521 nm respectively. All parameters affecting the reaction were carefully studied and optimized. Beers-Lamberts law was obeyed within the concentration ranges 5-25, 40-240 and 100-700 µg ml-1 for the three studied wavelengths respectively. The developed method was validated according to the ICH guidelines and applied to pharmaceutical formulation analysis with good recovery ranges. The results were compared to those obtained by an official method and found satisfactorily matched and no significant differences were found within the 95% confidence level. The proposed procedures were suitable for simple routine work and quality control analysis of EMB.

Salting-out thin-layer chromatography and computational analysis of some oral hypoglycemic drugs.

A quantitative structure-retention relationship study of some oral hypoglycemic drugs was carried out using a salting-out thin-layer chromatographic technique. Aqueous solution of ammonium sulfate and acetonitrile was used as a mobile phase. It was established that the applied mobile phase has different effects on retention of the studied oral antidiabetic drugs. The factors that affect the salting-out process were determined. In this study a good correlation between the structures of the investigated drugs with the retention data and molecular descriptors was established throughout computational analysis and using molecular operating environment software, focusing on octanol/water partition coefficient, molar refractivity, total hydrophobic surface area, hydrophobic volume, Van der Waals energy and solvation energy. Quantitative structure-retention relationship modeling for the separation of the investigated drugs was carried out, validated and evaluated.