Premium
Electrospray ionization/atmospheric pressure photoionization multimode source for low‐flow liquid chromatography/mass spectrometric analysis
Author(s) -
Short Luke C.,
Hanold Karl A.,
Cai ShengSuan,
Syage Jack A.
Publication year - 2007
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.2999
Subject(s) - chemistry , photoionization , ionization , atmospheric pressure chemical ionization , analytical chemistry (journal) , electrospray ionization , ion source , mass spectrometry , chemical ionization , chromatography , ion , organic chemistry
Analysis of several polar and non‐polar compounds is performed with a newly developed dual electrospray ionization/atmospheric pressure photoionization (ESI/APPI) or ESPI source. Several variables are considered in the source, such as ESI probe heater temperature, solvent flow, dopant effects, repeller plate voltage, source geometry and photon energy (Kr vs. Ar lamp). Direct photoionization resulting in a molecular radical cation [M] . + dominates at high temperatures (>400°C) and low flow rates (<200 µL/min). Indirect photo‐induced chemical ionization (PCI) involving solvent molecules becomes important at lower temperatures and higher solvent flow rates. Indirect PCI is enhanced using an Ar lamp, which yields comparable [M+H] + signal but poorer [M] . + signal than the Kr lamp at lower temperatures and higher flow rates. This is in support of our recent finding that the Ar lamp results in a solvent‐dependent enhancement of analyte molecules via PCI. Analysis of 12 compounds in methanol under low‐flow conditions (10 µL/min) demonstrates that the dual ESPI source performs favorably for most compounds versus the standard ESCI source, and significantly better than ESCI for the analysis of unstable drugs, like flurbiprofen. Several factors contributing to the benefits of the ESPI source are the shared optimal geometry for ESI and APPI sources and soft ionization of APPI versus APCI. Copyright © 2007 John Wiley & Sons, Ltd.