Gr. Peters et D. Beauchemin, EFFECT OF PRE-EVAPORATING THE SOLVENT ON THE ANALYTICAL PERFORMANCE OF INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY, Spectrochimica acta, Part B: Atomic spectroscopy, 48(12), 1993, pp. 1481-1494
The effect of heating the sample aerosol was studied by installing a h
eated extension (at 400-degrees-C) between the spray chamber and the t
orch. Both 5- and 2-mm i.d. extensions were characterized in terms of
sensitivities and detection limits for aqueous solutions containing Al
, V, Cr, Mn, Co, Ni, Zn, Ga, As, Mo, Cd, Sb, La and Pb. The best analy
tical figures of merit were obtained with the 2-mm i.d. extension, whi
ch resulted in detection limits being lowered to an average of 30% of
those obtained with the traditional (i.e. extension-free) sample intro
duction system. This improvement was greater than that expected from t
he concurrent increase (by an average factor of 1.63) in sensitivities
(including no change for Zn and Ga, and a degradation for Cd and Pb).
The heated extension therefore significantly reduced noise as a resul
t of the pre-evaporation process which decreased the average droplet s
ize entering the plasma. The greatest improvement in sensitivity was o
bserved for V, Mo and La, three elements forming relatively strong oxi
des; investigations using Ce and Th (which form even stronger oxides)
clearly showed that elements prone to oxide formation were experiencin
g a shift in their optimum nebulizer flow rate toward that used for mu
ltielemental analysis. Thus, the heated extension results in multielem
ental conditions that are optimal for a wider range of elements.