Automated interface for hyphenation of planar chromatography with mass spectrometry

A fully automated interface to couple high-performance thin-layer chromatography (HPTLC) with mass spectrometry (MS) is described. This universal hands-free interface connects intact normal-phase plates to any liquid chromatography/mass spectrometry (LC/MS) system without any adjustments or modifications to the mass spectrometer. The interface extracts the complete substance band with its depth profile and thus allows detections in the pg/band range. The high performance of the automated interface was evaluated through caffeine quantification in real samples, viz., energy drinks and pharmaceutical tablets, without internal standard. Following chromatographic separation on silica gel 60 F-254 HPTLC plates, caffeine bands were eluted from the plate by means of the automated interface to the electrospray ionization (ESI) source of a triple-quadrupole mass spectrometer. Since in full scan mode only the protonated molecule [M+H](+) was observed, caffeine quantification was performed using the selected-ion monitoring (SIM) mode at m/z 195. The validation showed highly reliable results for the linear range (R-2 = 0.9973), repeatability (RSD = 5.6%, n = 6) and intermediate precision (RSD = 1.5%, n = 3). Regarding accuracy the results obtained by HPTLC/MS were not statistically different (F-test, t-test) from those obtained by validated HPTLC/UV methods. Hence, this interface proved to be one of the most reliable and universal interfaces for HPTLC/MS. Copyright (c) 2007 John Wiley & Sons, Ltd.