Miniaturization of Instrumental Planar Chromatography with Focus on Mass Spectrometry

Abstract

The universal trends to miniaturization and to automation of technologies affect the further development of analytical instrumentation and methodologies. In planar chromatography, these trends are characterized by decreasing dimensions and thickness of the stationary phase and the development of respectively tailored equipment. The miniaturization of instrumental planar chromatography is reflected in the interdisciplinary office chromatography concept, in which achievements in office technologies (print and media technologies) and miniaturized layer developments are integrated. The office chromatography concept stimulates research towards miniaturization and will at last implement a fully online miniaturized system. The use of print techniques is still at its infancy in separation science, whereas printing of materials already became an accepted tool in the life sciences. Commercially, available printers were used for sample application on miniaturized plates and were stepwise modified for a precise and quantitative performance. Further miniaturization attempts led to miniaturized layers with different physical and chromatographic properties. The method transfer to such ultrathin-layer chromatography (UTLC) plates demonstrated the synergetic potential of this instrumental concept. Detection and evaluation tools have to be adjusted and integrated, too. Since the beginning of this millennium, several ionization techniques have been introduced or improved, and paved the way for mass spectrometry (MS) directly from miniaturized surfaces. UTLC was already coupled to MS via several ion source interfaces, such as secondary ionization, matrix-assisted laser desorption and ionization, electrospray ionization, desorption electrospray ionization and direct analysis in real time. However, the hyphenation to targeted, scanning or imaging MS still requires adaptations and methodic efforts to utilize UTLC layers.