ABSTRACT
A new dimension in planar chromatography started in 2001 with the introduction of miniaturized ultrathin-layer chromatography (UTLC) layers. In contrast to TLC/ HPTLC layers, the different layers developed so far do not use irregular particulate
9.1 Scope of Ultrathin-Layer Chromatography-Mass Spectrometry Layers: Introduction to Miniaturized Planar Chromatography................................. 141 9.1.1 Monolithic UTLC Layers ................................................................. 142 9.1.2 Electrospun UTLC Layers ................................................................ 142 9.1.3 GLAD-Fabricated UTLC Layers ..................................................... 145 9.1.4 Carbon Nanotube-Templated Microfabrication of UTLC Layers .... 145 9.1.5 Other Miniaturized UTLC Layers ................................................... 146
9.2 Overview of Approaches and Mass Spectra of UTLC-MS ......................... 147 9.2.1 UTLC-Time-of-Flight-Secondary Ion Mass Spectrometry ............. 147 9.2.2 UTLC-Matrix-Assisted Laser Desorption Ionization-Mass
Spectrometry..................................................................................... 151 9.2.3 UTLC-Electrospray Ionization-Mass Spectrometry ....................... 156 9.2.4 UTLC-Desorption Electrospray Ionization-Mass Spectrometry
and UTLC-Direct Analysis in Real-Time Mass Spectrometry ....... 158 9.3 Desorption-Based and Elution-Based Instrumental Challenges and
Workow ...................................................................................................... 160 9.3.1 UTLC-Matrix-Assisted Laser Desorption Ionization-Mass
Spectrometry..................................................................................... 160 9.3.2 UTLC-Electrospray Ionization-Mass Spectrometry ....................... 164 9.3.3 UTLC-Desorption Electrospray Ionization-Mass Spectrometry .... 165 9.3.4 UTLC-Direct Analysis in Real-Time Mass Spectrometry .............. 166
9.4 Outlook ......................................................................................................... 167 References .............................................................................................................. 167
adsorbents, and thus provide the benet that no classical binder is needed to x the layer material on the carrier substrate which may contribute to background signals in the mass spectra. Faster separations, lower limits of detection, a reduced amount of analyte (several nanoliters), and low-mobile phase consumption were reached in various applications throughout the further development of different layer materials and production techniques (Table 9.1). Compared to HPTLC, the separation number is reduced for most layers because of the shorter migration distance and smaller specic surface area for adsorption. However, recent developments mitigated this disadvantage and showed an improved performance along with a multiple plate usage at an increased mechanical stability [1,2].
