An improved matrix deposition technique for thin layer chromatography coupled to MALDI-TOF mass spectrometry (TLC-MALDI)

•Critical for TLC-MALDI is the application of a sufficient amount of matrix.•Conventional techniques often lead to the decomposition of the TLC layer.•Conventional techniques often require UV-absorbing properties of the analytes.•Matrix lines at right angles to the TLC bands overcomes these problems.•Matrix lines provide a convenient method for matrix application. Analytical thin layer chromatography (TLC) is a simple yet powerful chromatographic technique that is widely used for the qualitative characterization of complex mixtures such as plant extracts. For their qualitative and visual characterisation, a large number of more or less specific colour reactions are at hand and numerous reference substances are available as well. However, the identification of extract components by colour and the comparison of retention times is not straightforward. In contrast, the coupling of TLC with MALDI-TOF mass spectrometry can enable the identification of components and contribute to the optimization of TLC protocols. One of the most important steps for a successful TLC-MALDI process is the deposition of a sufficient amount of matrix onto the TLC plate. Standard methods such as the dip-coating protocol have major drawbacks. Here we present an improved and robust procedure for matrix application by means of matrix lines. The practicability of the method was tested on plant extracts from Agrostemma githago L. and Papaver somniferum L. (opium).