ICP-AES analysis of nonconductive materials after spark ablation

Abstract

Two modifications were applied to a commercial spark ablation system. A cyclone spray chamber system was installed between the spark device and the inductively coupled plasma (ICP) torch and as outer gas, a mixture of argon and 10% oxygen, was used at 1200 W incident power. The control of the aerosol particle size by the cyclone system leads to an improvement in the reproducibility of the method compared to a commercial system and prevents deposition of material on the torch injector. The modified system was tested for the analysis of nonconductive powders. The samples were briquetted into pellets with graphite and wax. The addition of wax (Höchstwachs C, Höchst, F.R.G.) enables a better ablation of the material. At the same time the mechanical properties of the pellets are improved. The optimum amounts of additives for preparation of the pellets were found to be 20% graphite and 2.4% wax. The applicability of the method was demonstrated using Siemens standard rock materials. For small amounts of powdered samples a graphite cup method was applied. Values of background equivalent concentrations (BEC) achieved for geological samples are comparable to the values achievable with a DC arc and even better than the BEC values for ICP solution analysis. For the elements determined (Sr, Co, Nb, Zn, Cu, Pb, Zr, Ni, Mn, P, Mg, and Cr) the detection limits range from 0.2 to 9 μg g .