On-site Analysis of Cu, Pb and Zn in Polymetallic Ores from Qimantage Area by Vehicle-loaded Polarized Energy Dispersive X-ray Fluorescence Spectrometer with Acid Digestion

Polarized Energy Dispersive X-ray Fluorescence Spectrometer is used as a common analytical method for exploration and prospecting on-site, but it constraints the on-site analysis of the high salinity geological or ore sample, for the serious matrix effects and insufficient calibration sample with matrix matching and affects the accuracy of the analysis results, even returning incorrect results. A method is presented in this paper for on-site analysis of Cu, Pb and Zn in polymetallic ores in Qimantage area, Qinghai province. The method is based on a vehicle-loaded Polarized Energy Dispersive X-ray Fluorescence Spectrometry (PE-EDXRF) with solution preparation of samples. Calibrations were conducted by utilizing standard solutions. Compton scattering intensities of Mo Kα from the secondary target were used as the internal standard to compensate for the matrix effect. The precision of the method was examined by on-site analyzing two geological samples from the local mine. Two kinds of double cabin sample cups with acid absorbent and double supporting films were developed to prevent the spectrometer from damage by the possible leakage and evaporation of the acidic sample solution. Two different procedures of ore sample digestion were tested on site and are described in this paper. The relative standard deviations (RSD, n=10) were in the range of 1.08% to 2.13%, when samples were pretreated by the second procedure. The accuracy and reliability of the method were tested by on-site analyzing of 4 quality control samples from Application Center for Geological Test of Qinghai Province and 13 geological samples from the local mine. When samples were pretreated using the second procedure, relative errors less than 5.0% were obtained for the 4 quality control samples with the element concentration higher than 0.5%. For the 13 local mine samples, PE-EDXRF results were compared with Atomic Absorption Spectroscopy (AAS) ones, the obtained correlation coefficients for Cu, Pb and Zn were 0.9984, 0.9986, 0.9997 respectively, and the corresponding linear regression equations were w_AAS(Cu)＝0.9882×w_PE-EDXRF+0.0213, w_AAS(Pb)=1.0365 0.1265，w_PE-EDXRF-0.1265, w_AAS(Zn)=1.0250×w_PE-EDXRF+0.0186. When the concentration of Cu was 0.75%-8.57%, Pb was 0.78%-29.1%, Zn was 0.11%-2.51%, average relative deviations of Cu, Pb and Zn, between PE-EDXRF results and AAS ones of the 13 local mine samples were 2.87%, 2.82% and 6.84%. We conclude that the vehicle-loaded PE-EDXRF coupled with the double cabin sample cups and the second procedure offers a satisfactory solution for high precision on-site polymetallic ore sample analysis. The above work is to expand the capability of PE-EDXRF on-site analysis to various metal ore matrix samples and is a supplement to the already established powder sample preparation method.