Determination of High Content of Tin in Rock and Mineral Samples by Alternating Current Arc-Optoelectronic Direct Reading Emission Spectrometry

A method on determination of high content of tin in rock and mineral samples by alternating current arc-optoelectronic direct reading emission spectrometry was established. The sample and solid buffercomposed of potassium pyrosulfate, sodium fluoride, aluminum oxide, and carbon powder with mass ratio of 22:20:44:14(containing 0.007% internal standard germanium dioxide) were mixed by vibration. After direct injection in solid form, the sample was pre-excited by primary current of 3 A and excited by secondary current of 15 A, with the exposure time of 25 s. The sub-sensitive line (Sn 242.1700 nm) was selected as analytical line for tin, to form an analytical line pair with the germanium element analytical line (Ge 270.9626 nm). The CCD detector was used for determination. The background interference was removed by off-line subtraction which tin and germanium signal intensities were subtracted from their respective background intensities. The calibration curve was made with the geochemical reference materials and the mixed samples consisted of reference material and base-material (composed of silicon dioxide, aluminum oxide, iron oxide, pure dolomite, sodium sulfate, and potassium sulfate with the mass ratio of 72:15:4:4:2.5:2.5). The results showed that the detection range available for this method ranged from 370 to 12700μg·g^-1, with detection limit (3s) of 62.41μg·g^-1; RSDs of the measured values were not more than 2.0% after twelve times of analysis of three reference materials; the 3 mixed samples consisted of reference materials and base-materials were analyzed, the absolute values of the logarithm difference between the determined values and the known values were all less than 0.05.