Reversed-phase thin-layer chromatography of three new oral antidiabetics and densitometric determination of pioglitazone

The thin-layer chromatographic behavior of new oral antidiabetic drugs, pioglitazone, rosiglitazone, and repaglinide has been investigated. For reversed-phase (RP) chromatography, chemically bonded cyanopropyl plates with mobile phases comprising 1,4-dioxane with phosphate buffers were used. The influence of the pH on the separation of the drugs was also examined. Then, a simple, rapid, and stability-indicating high performance thin-layer chromatographic method has been developed and validated for the quantitative determination of pioglitazone in tablets. Analysis was performed with 1,4-dioxane-phosphate buffer of pH 4.4 (5: 5) as the mobile phase. Detection and quantification were per-formed by classical densitometry at the wavelength of maximum absorption of pioglitazone, 266 nm. A calibration plot was constructed in the range of 0.4-2.4 mug/10 muL and was linear with a good correlation coefficient (r = 0.9957). Precision was validated by replicate analyses of standard solutions, and accuracy by analysis of fortified samples. The precision of the proposed chromatographic method expressed as mean relative standard deviation (RSD) was 4.99% and 2.57%, respectively, for the lowest and the highest calibration levels. Recovery from the fortified samples ranged from 98.09% to 103.28%. The mean (+/-SD) recovery from tablets was 99.79% +/- 1.57%.