BACKGROUNDThe abundances and variation characteristics of silver, boron and tin reflect the regional metallogenic conditions and indicate the existence of deposits or mineralization. Silver, boron and tin in carbonate minerals are elements that must be determined in exploration geochemistry and multi-objective geochemistry. The analytical method was one of the essential methods in the matching analysis scheme of geochemical elements. Because carbonate minerals are different from common rocks, soils and water-based sediments, these minerals are mainly limestone, dolomite and other rock samples with relatively high calcium and magnesium elements, and the technical difficulty in determining silver, boron and tin in these samples is that the high content of calcium and magnesium matrix will seriously disturb the elements with low contents to be measured, and the sample is easily contaminated due to carbon dioxide during the spectrum recording process.

OBJECTIVESTo solve the problems of rapid and accurate determination of silver, boron and tin in carbonate minerals.

METHODSIn view of the particularity of carbonate minerals, an analytical method for the simultaneous determination of silver, boron and tin in carbonate minerals by alternating current-arc optoelectronic direct reading-optical spectrometry (AC-Arc-OES) was established.

RESULTSBy using 10% hydrochloric acid to digest the sample, the interference of matrix elements, calcium and magnesium, was eliminated. Germanium was used as the internal standard element for quantitative analysis, which eliminated the influence of external factors, such as the change of arc excitation conditions and matrix composition of the sample. The silver element and the long wave germanium element were used to form the analysis line pair, and the boron and tin element and the short wave germanium element were used to form the analysis line pair with good sensitivity. Twelve national geochemical reference materials, such as natural carbonate rock and synthetic limestone, were selected as the standard series. The matrix components were similar to those of the samples. The method of off-line subtraction was used to correct the background. The detection limits of the method for silver, boron and tin were 0.008μg/g, 0.49μg/g and 0.18μg/g, respectively. The precision of the method was larger than 10% for silver, and that of other elements was better than 10%. The accuracy of the method was verified by the national level geochemical reference materials, and the logarithm difference between the average value and the certified value of the reference materials was less than or equal to ±0.05.

CONCLUSIONSThis method was used to solve the problem of rapid determination of silver, boron and tin in carbonate minerals. It is simple and fast, and suitable for the determination of a large numbers of samples. All of the technical indices of the method meet the requirements of multi-objective regional geochemical survey specifications.