System and method for detecting analytes dissolved in liquids by plasma ionisation mass spectrometry

Abstract

Bubble plasma ionisation probe for analysing liquids by mass spectrometry. A means of a detecting analytes dissolved in a liquid by mass spectrometry is described. Gas flows from a source through a first conduitand thereafter through a coaxial second conduitthat also serves as the inlet to the mass spectrometer. The coaxial arrangement of conduits is submerged in the liquid to be analysed. Using a feedback loop, the gas pressure is adjusted and controlled such that an attached bubbleforms at the open end of the first conduit. A plasmais provided in the bubble. The plasma is preferably generated by a dielectric barrier discharge between a collar electrodeand mass spectrometer inlet. Analytes dissolved in the liquid are both desorbed form the gas-liquid interface and ionised by the action of the plasma. Ions formed in this way become entrained in the gas flow and are consequently transferred to the mass spectrometer, where they are analysed.