交流电弧光电直读发射光谱法测定地球化学样品中银硼锡

基于交流电弧是依靠固体进样技术而不需要酸溶或碱熔分解样品,操作简便、绿色环保、稳定性好,且摄谱仪能实现数据直读等优点,建立了以交流电弧光电直读发射光谱测定地球化学样品中银、硼、锡等3元素的分析方法。用光谱样品全自动搅拌机混匀样品,1次能混匀30件,提高了分析效率。对实验条件进行了最佳优化,选用一级激发电流3A,起弧3s后升到二级激发电流15A,保持22s,共截取曝光时间为25s;采用锗(Ge)为内标元素,并且银元素与长波锗元素组成分析线对,硼和锡与短波锗元素组成分析线对,灵敏度高;选择基体组分与样品相类似的岩石、土壤、水系沉积物和矿石等14种国家一级地球化学标准物质作为标准系列,建立二次方程拟合校准曲线,避免了基体干扰的影响;采用差值法背景校正,曲线平滑,相关系数好,测定高含量值样品时,差值法背景校正与不扣背景的测定结果可能相差不大,但对于测定低含量值的样品,差值法背景校正结果较好。结果表明:在最佳的实验条件下,各元素测定结果的相对标准偏差(RSD)均小于10%;测定范围较宽,银、硼、锡的检出限分别为0.016、0.63、0.32μg/g;采用国家一级地球化学标准物质验证方法准确度,测定值与认定值吻合,3元素测定平均值与认定值的对数差值的绝对值(ΔlgC)均小于0.05,满足多目标地球化学填图中对于方法准确度的要求。

Determination of silver,boron and tin in geochemical samples by alternating current arc optoelectronic direct reading emission spectrometry

The alternating current arc (AC-Are) has many advantages, for example, depended on solid sampling technology, no need of sample decomposition by acid dissolution or alkali fusion, simple operation, green and environmental protection, good stability and direct reading of data by spectrometer. The analysis method of silver, boron and tin in geochemical sample by AC Arc-optoelectronic direct reading emission spectrometry was established. The sample was uniformly mixed using automatic mixer for spectral samples. Thirty specimens could be mixed once, thus improving the analysis efficiency. The experimental conditions were optimized: the primary excitation current of 3A was used; it increased to secondary excitation current of 15A after arcing for 3s and kept for 22s; the total time of exposure was 25s; germanium (Ge) was selected as the internal standard element; silver and long wavelength germanium formed analysis line pair, while boron and tin formed analysis line pair with shortwave germanium. The sensitivity was high. Fourteen types of national first-class geochemical standard substance including rock, soil and stream sediment with similar composition to the matrix were used as standard series to establish the quadratic equation for the fitting of calibration curve, which avoided the influence of matrix interference. The background was corrected by difference method. It was found that the curve was smooth with good correlation coefficient. During the determination of sample with high content, the measurement results with and without background correction were basically same. However, for the determination of sample with low content, the measurement results of background correction by difference method were better. The results indicated that the relative standard deviations (RSD) were all less than 10% under the optimized experimental conditions. The determination range was wide. The detection limit of silver, boron and tin was 0.016, 0.63 and 0.32μg/g, respectively. The accuracy was verified using national first-class geochemical standard substance, and the found results were consistent with the certified values. The absolute value of logarithmic difference (ΔlgC) between the average of measurement results and certified value was less than 0.05 for three elements. The proposed method could meet the accuracy requirements in multi-objective geochemical mapping.