Determinação de elementos-traço em rochas graníticas por espetrofotometria de absorção atômica

Abstract

This work is part of the ongoing research project at the Department of Chemistry for the chemical analysis of geological materials, mainly the analysis of granitic rocks from Mozambique. With this work, we intend to show the possibility of determination of Ba, Be, Co, Cu, Pb, and Sr in 30 samples of granitic rocks by atomic absorption spectrophotometry (EAA). The analyzed granites are located in the provinces of Zambézia and Nampula. The samples were dissolved by a mixture of concentrated acids HF-HNO3-HCIO4. After the optimization and calibration of the device, the determinations of trace elements in the samples were carried out and later, the statistical treatment of the data was carried out. The accuracy of the method was controlled by comparing the values ​​obtained and recommended from reference materials, the GH, GA and G2 granites; it translates, quantitatively, into calculations of relative errors. The accuracy of the method was good for Ba, Cu and Sr in the GA and G2 granites; and Be in the GH and G2 granites; and it was bad for Co and Pb in the GH, GA and G2 granites; Ba, Cu and Sr in the GH granite; and Be on granite G2. The mean relative standard deviations of the samples were: 20.9% (Ba), 19.9% ​​(Be), 28.1% (Co), 8.3% (Cu), 23.8% (Pb) and 5.1% (Sr). The results obtained from the samples by EAA were compared using two methods: emission spectrography (EE) and X-ray fluorescence (FRX), using statistical methods based on paired data t-test and linear regression method. obtained by the two methods are concordant for Mr, but discordant for the remaining elements. (TRADUÇÃO NOSSA)