PRELIMINARY CHARACTERIZATION OF INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY WITH FLOW-INJECTION INTO A GASEOUS (AIR) CARRIER

An assessment of some of the advantages and disadvantages of using air rather than water as a carrier in flow injection with inductively coupled plasma mass spectrometric detection was carried out for several analytes (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Cd, Sb and Pb). Although the background increased in many instances,the enhancement in sensitivity was such that the corresponding detection limits were either similar or significantly improved (by a factor of 2-6), the greatest improvement being observed for elements with high ionization potentials. The only exception was nickel, for which a huge increase in background, presumably due to a stronger etching of the nickel sampler and skimmer by the no longer 'water-cooled' plasma, led to a drastic degradation of the detection limit (by a factor of 30). For all elements, a significant memory effect was observed, which could only be eliminated by flushing with water between injections. A preliminary evaluation of flow injection into air bubbles was carried out, showing that an enhancement in sensitivity could also be observed, dependent on the size of the injection loop. With too large a loop (e.g., 0.5 ml instead of 0.1 ml), little change occurred.