Effects of mobile phase solvents and vacuum UV lamps on APPI-MS: Implications of photoabsorption cross sections and photon energies

摘要

The analytical detection of large molecular weight, non-polar compounds from the mobile phase of a liquid chromatography - mass spectrometer (LC-MS) has seen considerable growth in the last 5 years. This has been in part due to the development of newer source technologies, as well as intelligent applications of mobile phase(s) for chromatographic separation. Recent work has focused on the direct comparison of different sources (APPI, APLI, APCI and ESI) with specific target compounds, e.g., polyaromatic hydrocarbons, hydrophobic peptides, pesticides, as well as fatty acids and lipids. We have focused on an atmospheric pressure photoionization (APPI) source because (1) low cost, (2) extended linear dynamic range, (3) enhanced sensitivity and (4) reduced or no off-line sample cleanups in comparison to direct APCI or ESI. There is also the possibility of adding a dopant to the effluent, increasing sensitivity at the expense of selectivity.