The development and application of coupled HPLC-TLC for pharmaceutical analysis

Successful coupling of high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC) facilitates correlation of the retention factor (Rf) of a component in a TLC separation with a peak observed in HPLC, thus eliminating the need for isolation of the component. Experiments were designed to optimize flow and spotting rates for typical HPLC mobile phases, evaluating such parameters as band broadening and on-plate loading. Also investigated were the application of flow splitting and semi-microbore HPLC columns. The problems encountered with the development of TLC plates upon which the HPLC eluent has been applied as a linear streak were studied, as were detection methods for the resulting spots. This paper describes the successful development of the technique, using model compounds of pharmaceutical interest.