Thin-Layer Chromatography and Mass Spectrometry Coupled Using Desorption Electrospray Ionization

Abstract

Desorption electrospray ionization (DESI) was demonstrated as a means to couple thin-layer chromatography (TLC) with mass spectrometry. The experimental setup and its optimization are described. Development lanes were scanned by moving the TLC plate under computer control while directing the stationary DESI emitter charged droplet plume at the TLC plate surface. Mass spectral data were recorded in either selected reaction monitoring mode or in full scan ion trap mode using a hybrid triple quadrupole linear ion trap mass spectrometer. Fundamentals and practical applications of the technique were demonstrated in positive ion mode using selected reaction monitoring detection of rhodamine dyes separated on hydrophobic reversed-phase C8 plates and reversed-phase C2 plates, in negative ion full scan mode using a selection of FD&C dyes separated on a wettable reversed-phase C18 plate, and in positive ion full scan mode using a mixture of aspirin, acetaminophen, and caffeine from an over-the-counter pain medication separated on a normal-phase silica gel plate.

Transmission mode desorption electrospray ionization

“…Variation of the electrospray voltage showed a maximum response at 4.0 kV, with a range of values greater than 3.0 kV providing adequate response (see Supplementary material, Figure S3). While the results for nebulizing gas pressure and electrospray voltages are typical for both standard electrospray experiments and DESI analyses [5], the optimal flow rate of 10 L/min concurred with several values reported for DESI [7,17], but was higher than others performed with lower flow rates of only 2-5 L/min [5,12]. As discussed in the previous section, this optimal flow rate is likely an artifact of the chosen geometry and would be reduced if the geometry were more compact.…”

Recent developments in the rapid analysis of plants and tracking their bioactive constituents

“…A natural products example is the analysis of an HPTLC separation of glycosphingolipids by IR-MALDI-MS (Distler et al 2008). DESI-MS is a relatively new technique that can also be combined with HPTLC (Takáts et al 2004;Van Berkel et al 2005). Additionally DESI-MS allows for the first time, the direct probing of analytes in intact living plants by MS under ambient conditions without any sample preparation.…”

Comparative TOF‐SIMS and MALDI TOF‐MS analysis on different chromatographic planar substrates

“…Desorption electrospray ionisation (DESI) was demonstrated as a means of coupling TLC with mass spectrometry. Development lanes were scanned by moving the TLC plate under computer control while directing the stationary DESI emitter charged droplet plume at the TLC plate surface [16]. Surface-activated chemical ionisation versus electrospray ionisation in the study of selected aluminium (III)/ligand solution equilibria has also been demonstrated [17].…”