Electrospray Ionization on Porous Supporting Tip for Mass Spectrometric Analysis: from Material Studies to Real Sample Analysis

Abstract

Electrospray lonization (ESI) on porous materials has recently been developed and applied to the direct analysis of a wide variety of samples, due to its simplicity in sample preparation. In order to have a better understanding on choosing and designing porous materials as spraying tip, MS detection sensitivity for different analytes using porous tips of different properties, such as polarities and porosities, had been investigated.''' Our results showed that hydrophobic tips gave higher detection sensitivity for polar analytes, while hydrophilic tips were more suitable for the detection of non-polar compounds. Porosity of tips also affected the MS detection sensitivity by mean of offering stable spraying of solvent. Based on the findings, we had successfully applied porous hydrophobic tips for sampling nitroaromatic-based explosives and for their detection by ESI-MS in negative ion mode. The nitroaromatic-based explosives were ionized through electron-capture ionization and detected in radical anion form. Apart from using porous supports as spraying tips, we had also reported the direct analysis of raw herbs (ginseng tissue) by tissue-spray ionization mass spectrometry. Various phytochemicals, metabolites and even thermally labile malonyl-ginsenoside in ginseng tissues could be detected by using the herbal tissue itself as the tip for ESI-MS. lt is anticipated that with the use of proper choice of porous supporting tips, the application of ESI-MS can be further expanded as a versatile detection technique.