An electropneumatic-heated nebulizer for enhancing spray ionization in PhotoSpray atmospheric pressure photoionization sources for liquid chromatography/mass spectrometry

We introduce a novel electropneumatic-heated nebulizer (EPn-HN), incorporating an electrified internal pneumatic nebulizer, to enhance the yield of sprayed ions from PhotoSpray (TM) atmospheric pressure photoionization (APPI) sources for liquid chromatography/mass spectrometry (LC/MS). Spray ionization from the pneumatic-heated nebulizers used in APPI sources provides a supplemental, complementary ionization method to be used for involatile and thermally labile compounds, otherwise intractable to APPI. Details of the construction and operation of the EPn-HN device are provided. The performance of the EPn-HN is demonstrated using two model compounds: substance P, a peptide used as a standard in studies of ion fragmentation mechanisms, and aztreonam, a thermally labile antibiotic. At the optimum voltage for spray ionization, improvements in sensitivity of two orders of magnitude are obtained relative to when the sprayer is grounded, the conventional case. Since both substance P and aztreonam cannot be detected using the APPI method alone, the results demonstrate how spray ionization from the EPn-HN may be used to extend the range of compounds amenable to PhotoSpray sources. Copyright (C) 2009 John Wiley & Sons, Ltd.