Pm. Outridge et al., ABLATIVE AND TRANSPORT FRACTIONATION OF TRACE-ELEMENTS DURING LASER SAMPLING OF GLASS AND COPPER, Spectrochimica acta, Part B: Atomic spectroscopy, 52(14), 1997, pp. 2093-2102
The fractionation of trace elements due to ablation and transport proc
esses was quantified during Q-switched infrared laser sampling of glas
s and copper reference materials. Filter-trapping of the ablated produ
ct at different points in the sample introduction system showed ablati
on and transport sometimes caused opposing fractionation effects, lead
ing to a confounded measure of overall (ablative + transport) fraction
ation. An unexpected result was the greater ablative fractionation of
some elements (Au, Ag, Bi, Te in glass and Au, Be, Bi, Ni, Te in coppe
r) at a higher laser fluence of 1.35 x 10(4) W cm(-2) than at 0.62 x 1
0(4) W cm(-2), which contradicted predictions from modelling studies o
f ablation processes. With glass, there was an inverse logarithmic rel
ationship between the extent of ablative and overall fractionation and
element oxide melting point (OMPs), with elements with OMPs < 1000 de
grees C exhibiting overall concentration increases of 20-1340%. Fracti
onation during transport was quantitatively important for most certifi
ed elements in copper, and for the most volatile elements (Au, Ag, Bi,
Te) in glass. Elements common to both matrices showed 50-100% higher
ablative fractionation in copper, possibly because of greater heat con
ductance away from the ablation site causing increased element volatil
isation or zone refinement. These differences between matrices indicat
e that non-matrix-matched standardisation is likely to provide inaccur
ate calibration of laser ablation inductively coupled plasma-mass spec
trometry analyses of at least some elements. (C) 1997 Elsevier Science
B.V.