Influence of organic modifier and separation modes for lipophilicity assessment of drugs using thin layer chromatography indices.

Lipophilicity constitutes one of the most important physicochemical properties in the design and development of drug molecules. In the present work thin layer chromatography (TLC) has been utilized to evaluate lipophilicity of 11 representative drugs, which included six proton pump inhibitors (omeprazole, pantoprazole, rabeprazole, lansoprazole, ilaprazole, and tenatoprazole), an anti-vertigo drug, betahistine, nonsteroidal anti-inflammatory drug, ibuprofen, anti-malarial drug, atovaquone, an anti-HIV agent, atazanavir and a hormonal drug, calcitriol. Normal as well as reversed-phase separation modes were evaluated to study the effect of different organic modifiers for the estimation of lipophilicity. The quantitative descriptor of lipophilicity, the partition coefficient (logP) was estimated by suitably optimizing the solvent systems for both the modes. The best mobile phase pairs for NPTLC and RPTLC were toluene-acetonitrile and water-methanol respectively. Principal component analysis, hierarchical cluster analysis, as well as non-parametric methods like sum of ranking differences and generalized pair wise correlation revealed the dominant pattern in the data. The results obtained from both the separation modes were comparable and were in good agreement with the computational data for all the drugs.

Combining simplicity with cost-effectiveness: Investigation of potential counterfeit of proton pump inhibitors through simulated formulations using thin-layer chromatography.

A simple, accurate and precise high-performance thin-layer chromatographic method has been developed and validated for the analysis of proton pump inhibitors (PPIs) and their co-formulated drugs, available as binary combination. Planar chromatographic separation was achieved using a single mobile phase comprising of toluene: iso-propranol: acetone: ammonia 5.0:2.3:2.5:0.2 (v/v/v/v) for the analysis of 14 analytes on aluminium-backed layer of silica gel 60 FG254. Densitometric determination of the separated spots was done at 290nm. The method was validated according to ICH guidelines for linearity, precision and accuracy, sensitivity, specificity and robustness. The method showed good linear response for the selected drugs as indicated by the high values of correlation coefficients (≥0.9993). The limit of detection and limit of quantiation were in the range of 6.9-159.2ng/band and 20.8-478.1ng/band respectively for all the analytes. The optimized conditions afforded adequate resolution of each PPI from their co-formulated drugs and provided unambiguous identification of the co-formulated drugs from their homologous retardation factors (hRf). The only limitation of the method was the inability to separate two PPIs, rabeprazole and lansoprazole from each other. Nevertheless, it is proposed that peak spectra recording and comparison with standard drug spot can be a viable option for assignment of TLC spots. The method performance was assessed by analyzing different laboratory simulated mixtures and some marketed formulations of the selected drugs. The developed method was successfully used to investigate potential counterfeit of PPIs through a series of simulated formulations with good accuracy and precision.

LC-MS-ESI for the determination of loratadine and descarboethoxyloratadine in human plasma.

A rapid, sensitive, and accurate liquid chromatography-tandem mass spectrometry assay for simultaneous determination of loratadine (L) and its active metabolite, descarboethoxyloratadine (DCL), in human plasma is developed using desipramine as internal standard (IS). The analytes and IS are separated on a Betabasic cyano (100 mm x 2.1 mm, 5 microm) column and detected by tandem mass spectrometry with a turbo ion spray interface operating in positive ion and multiple reaction monitoring acquisition mode. The total chromatographic runtime is 3.0 min with retention time for L, DCL, and IS at 0.82, 1.58, and 1.97 min, respectively. The method is validated over a dynamic linear range of 0.05-15.00 ng/mL for both L and DCL with a correlation coefficient of r(2) 0.9984 and 0.9979, respectively. The intra-batch and inter-batch precision (%CV) across five levels (LLOQ, LQC, MQC, HQC, and ULOQ) is less than 9%. The method is successfully applied to a bioequivalence study of 10 mg loratadine tablet formulation in 28 healthy Indian male subjects under fasted condition.