Procedure optimization of silicate rocks dissolution in open vissels for icp-aes analysis

Abstract

The mam variables found on procedure of the dissolution silicate rocks using acid dissolution in teflon open vessel for analysis of micro elements by ICP-AES has been determined. The results obtained for some samples showed strong dependence of the rock mineralogical composition, then it was recommended an alkaline fusion step after acid dissolution. The decomposition procedure use 20 ml of an acid mixture ofHF:HN03in the proportion 3:1 for a fraction of250 mg pulverized sample. The recommended temperatures were 60°C for attack and 9(PC for acid volatilization. The fusion step with 50 mg LiB0? at 1000°C may be used if non-attacked residue is observed in the solution. The whole time was 6 h per sample. Nine types os silicate rocks that show mineralogical and chemical different compositions were chosen for obtaining the optimization of the variables. The elements used were Ce, Y. Yb and Zr. In addition, ultrassonic nebulization has been used. The percentual standard deviations obtained for five determinations were 0.7 and 1.4 for triplicate samples. The mineralogical and textural information from the petrographical analysis of the samples indicated the need of increasing the fusion step on the optimized procedure.