On-line coupling of liquid chromatography with thin-layer chromatography

Abstract

On-line coupling of high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC) represents a very promising two-dimensional technique because it allows the combination of two completely different separation principles. This is especially so for the combination of reversed-phase HPLC for the first separation and HPTLC with automated multiple development on a normal-phase thin-layer plate for the second separation. The system consists of a microbore HPLC syringe pump and a modified TLC autosampler (CAMAG ATS3-C) which is controlled by new software for a personal computer running under MS Windows. The new dedicated software enables the analyst to spray the effluent from the HPLC column in fractions onto the plate in a freely definable manner. In order to address different analytical problems, six transfer modes are made available. A complete profiling analysis can be carried out with the whole effluent from the liquid chromatographic column being transferred in fractions to the TLC plates. On the other hand, the program supports typical target compound analyses with multiple switching activated according to individual elution times. Typical applications are pesticide residue analysis in foodstuffs or environmental samples. The new dedicated software is expected to fill the gap considered to be the main obstacle for the widespread application of on-line coupling of HPLC with TLC.