HYPERTHERMAL SURFACE-IONIZATION AS A NEW INTERFACING APPROACH IN LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY

A hyperthermal surface ionization (HSI) interface is constructed for the coupling of liquid chromatography (LC) and mass spectrometry (MS). A liquid stream of 0.1-10 mu L.min(-1) is nebulized in a low molecular mass carrier gas of either hydrogen or helium. After expansion of the gas mixture into an expansion chamber, which is held at a background pressure of 0.5 Pa, a supersonic molecular beam is sampled with a skimmer into the vacuum of the mass spectrometer. Collision of the supersonic molecular beam with a platinum, tungsten, or rhenium surface leads to the formation of ions. These ions have been analyzed with a quadrupole analyzer. Sensitive LC/HSI-MS detection is illustrated for a mixture of some polycyclic aromatic hydrocarbons. With HSI, an up to 10-fold better ion intensity is obtained compared to electron impact. The significantly lower chemical noise in HSI leads to on-column detection limits of less than 200 pg.