Abstract:
BACKGROUND The fast detection of Cu, Pb, Zn and Ni in geochemical samples helps to determine the level of heavy metal pollution, thus assisting in the employment of efficient treatments.
OBJECTIVES To establish a method for the simultaneous determination of Cu, Pb, Zn and Ni in geochemical samples by AC Arc direct reading atomic emission spectrometry with solid sampling technique.
METHODS With sodium fluoride, alumina, silicon dioxide and carbon powder as buffer agents and germanium as the internal standard element, the element analysis line pairs were optimized, and the exposure time was also optimized at 25s. The standard curve of synthetic silicate was corrected using national first-class reference materials (soil, rock and sediment), so as to reduce the interference of the matrix. Sensitive line and hyposensitive line were selected to enhance the accuracy as well as expand the measurable linear range of elements. Average value of two parallel analyses was adopted for further improved analytical precision.
RESULTS The detection limits of Cu, Pb, Zn and Ni were 0.45μg/g, 1.46μg/g, 2.40μg/g and 1.58μg/g, respectively. The precision ranges of the method were 1.36%-6.25% for Cu, 1.17%-8.06% for Pb, 1.64%-9.68% for Zn and 0.91%-5.31% for Ni. Measured values with this method for the national first-class reference materials of soil, sediment and rock were consistent with the certified values (|△logC| ≤ 0.05), qualification rates of the actual samples and external quality control samples were all above 90%.
CONCLUSIONS With simple operation, direct solid sampling technique is applied. The method reported here is more environmentally friendly compared to the acid dissolving method, sample contamination caused by reagent blank and vessels used is avoided at the same time. The average results of twice spectral acquisitions are calculated, which is more accurate and precise than the single analysis reported in the literature. All indicators of this method are better than the requirements of regulation (1:250000) DZ/T 0130.5-2006.
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