G. Xiao et D. Beauchemin, REDUCTION OF MATRIX EFFECTS AND MASS DISCRIMINATION IN INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY WITH OPTIMIZED ARGON-NITROGEN PLASMAS, Journal of analytical atomic spectrometry, 9(4), 1994, pp. 509-518
The effect of power (1.2-1.4 kW) and the addition of N2 (2-10%) to the
outer gas of an Ar plasma was studied in an attempt to improve the an
alytical capability of inductively coupled plasma mass spectrometry (I
CP-MS) for multi-element analysis. The experiments were all conducted
at an optimum sampling position, i.e., by adjusting the aerosol carrie
r gas flow rate for maximum sensitivity after each change in power and
/or addition of N2. For each set of conditions, the analytical capabil
ities of Ar-N2 plasmas in terms of sensitivity, detection limits, mass
discrimination and susceptibility to the effect of 0.01 and 0.1 mol d
m-3 Na on various analytes (Al, V, Cr, Mn, Fe-59, Fe-57, Co, Ni, Zn, C
u, AS, Se-77 , Se-78, Mo, Cd, Sb and Pb) were evaluated. Some improvem
ent in sensitivities and detection limits were observed upon addition
of N2 to the outer gas in comparison with an Ar plasma at the same pow
er. Both mass discrimination and the effect of either 0.01 or 0.1 mol
dm-3 Na were reduced with the addition of N2. Compared with convention
al operating conditions (i.e., 1.2 kW, no N2), a mixed-gas plasma with
1 0% N2 at 1.3 kW led to only slightly degraded sensitivities and det
ection limits (in fact, improvements were observed for a few elements)
; but the effect of 0.01 mol dm-3 Na was eliminated across the mass ra
nge, and that of 0.1 mol dm-3 Na was reduced to a uniform level across
the mass ran e, allowing the use of a single internal standard.