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Design and evaluation of a dopant‐delivery system for an orthogonal atmospheric‐pressure photoionization source and its performance in the analysis of polycyclic aromatic hydrocarbons
Author(s) -
Ehrenhauser Franz S.,
Wornat Mary J.,
Valsaraj Kalliat T.,
Rodriguez Paul
Publication year - 2010
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.4518
Subject(s) - chemistry , photoionization , atmospheric pressure , dopant , environmental chemistry , analytical chemistry (journal) , organic chemistry , optoelectronics , ionization , doping , meteorology , ion , physics
Atmospheric‐pressure photoionization (APPI) mass spectrometry benefits from the addition of an ionization‐enhancing dopant such as benzene. A passive dopant‐delivery system has therefore been designed for use with the orthogonal APPI source within a commercial liquid chromatographic instrument with mass spectrometric detector. By providing the dopant in the gas phase, the newly designed equipment avoids mixing problems and other difficulties associated with liquid dopant addition. The system is a simple and durable design that can reliably deliver virtually any dopant with sufficient vapor pressure in the temperature range of 20 to 120°C. At the optimum dopant flow rate (10% of the mobile phase flow rate) for high‐performance liquid chromatography with narrow‐bore (2.1 mm) columns, the system allows for uninterrupted routine analysis for up to two weeks. The performance of the device has been evaluated with benzene as dopant and with a test mixture consisting of four polycyclic aromatic hydrocarbons (PAH): naphthalene, 9 H ‐fluorene, anthracene, and phenanthrene. All four PAH can be detected with an excellent signal‐to‐noise ratio in the scanning mode and a limit of detection down to 0.42 ng on column (51 pg in single‐ion monitoring mode). The concentration calibration curves are linear over a range of three orders of magnitude, with correlation coefficients greater than 0.99. The utilization of benzene as dopant not only increases the sensitivity significantly – 20‐fold, compared with dopant‐free operation – but the low m/z values of the background ions observed also allow for the effective quantitative and qualitative analysis of PAH. Copyright © 2010 John Wiley & Sons, Ltd.