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Ionisation in the absence of high voltage using supercritical fluid chromatography: a possible route to increased signal
Author(s) -
Thite Mohini A.,
Boughtflower Robert,
Caldwell Jeff,
Hitzel Laure,
Holyoak Clare,
Lane Stephen J.,
Oakley Paul,
Pullen Frank S.,
Richardson Stefan,
Langley G. John
Publication year - 2008
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3784
Subject(s) - chemistry , supercritical fluid chromatography , chromatography , mass spectrometry , electrospray , ionization , electrospray ionization , analytical chemistry (journal) , detection limit , thermospray , supercritical fluid , high performance liquid chromatography , atmospheric pressure chemical ionization , gas chromatography , chemical ionization , tandem mass spectrometry , organic chemistry , selected reaction monitoring , ion
Supercritical fluid chromatography (SFC) is fast becoming a technique of choice for the analysis of a wide range of compounds and has been found to be complementary to high‐performance liquid chromatography (HPLC). The combination of SFC and mass spectrometry (MS) affords a very useful tool in the separation and analysis of compounds. In this study the ionisation of samples in the absence of an applied electrospray voltage has been observed when using SFC/MS, with some compounds showing increased sensitivity when all ionisation source high voltage (HV) is removed. In an attempt to understand the mechanism of ionisation, a series of test compounds were analysed using standard electrospray ionisation (ESI) and atmospheric pressure chemical ionisation (APCI) source configurations and also different API source designs. In both cases, data were acquired with the applied high voltage on (normal conditions) or with the high voltage off, i.e. no vo ltage spray (novo‐spray). The standards were analysed with a range of pressure and modifier percentage conditions. To understand the nature of the ionisation process observed, this was compared with three established liquid‐to‐gas ionisation mechanisms. These were thermospray (TSP), charge residue model (CRM) of ESI and sonic spray ionisation (SSI). Experiments were undertaken in an attempt to explain this ionisation phenomenon and quantify any observed change in sensitivity. The most important point to note is that enhanced ionisation was observed under novo‐spray conditions in a SFC/MS configuration, which in certain cases provides a lowering in the overall limit of detection (LOD). Copyright © 2008 John Wiley & Sons, Ltd.