Sol-gel coated ion sources for liquid chromatography-direct electron ionization mass spectrometry

Advances in interfacing liquid chromatography and electron ionization mass spectrometry are presented. New ion source coatings synthesized by sol-gel technology were developed and tested as vaporization surfaces in terms of peak intensity, peak width and peak delay for the liquid chromatography-direct electron ionization mass spectrometry (Direct-EI) determination of environmental pollutants like polycyclic aromatic hydrocarbons and steroids. Silica-, titania-, and zirconia-based coatings were sprayed inside the stainless steel ion source and characterized in terms of thermal stability, film thickness and morphology. Negligible weight losses until 350-400 degrees C were observed for all the materials, with coating thicknesses in the 6 (+/- 1)-11 (+/- 2) mm range for optimal ionization process. The best performances in terms of both peak intensity and peak width were obtained by using the silica-based coating: the detection of the investigated compounds was feasible at low ng mu l(-1) levels with a good precision (RSD < 9% for polycyclic aromatic hydrocarbons and < 11% for hormones). (C) 2017 Elsevier B.V. All rights reserved.