电感耦合等离子体质谱(ICP-MS)法测定土壤中的有效钼

准确快速测定土壤中的有效钼，是评价土壤肥力的重要指标，对指导作物生产有重大意义。本文采用草酸-草酸铵溶液浸提土壤样品，待测浸提液稀释5倍后通过电感耦合等离子体质谱法在氦气模式下测定土壤中有效钼的含量，建立了土壤中有效钼高灵敏度分析的检测方法。选择103Rh为内标元素，校正仪器在测定过程中引起的信号飘移。对两种前处理方式进行比较，确定了震荡30 min、放置过夜的浸提方法浸提效果更好且更利于大批量样品的分析。使用震荡30 min、放置过夜的浸提方法对5个土壤标准物质有效钼进行前处理，其测定值均在标准值范围内；分别在无气体模式和氦气模式下比较了浓度为0mg/L、1mg/L、2mg/L、5mg/L、10mg/L、50mg/L的Mn对5ug/L 95Mo测定浓度的影响，结果表明氦气模式下的动能歧视可有效去除95Mo测定过程中的多原子离子的干扰，氦气模式测定有效钼明显优于无气体模式；分别对待测溶液稀释5倍和未稀释的内标回收率趋势进行监测，发现未稀释的样品内标回收率随着测量样品数的增多呈下降趋势，而稀释5倍对基体干扰的消除有显著效果。对5个土壤样品分别重复测定6次，其RSD均小于4.1%；线性相关系数为1.0000；方法检出限为0.0012 mg/kg。综上，该方法测定土壤有效钼结果准确，重现性好，灵敏度高，且适合大批量样品的分析。

Determination of available molybdenum in soil by inductively coupled plasma mass spectrometry

Accurate and rapid determination of available molybdenum in soil is an important indicator for evaluating soil fertility and it has significant implications for guiding crop production. Inductively coupled plasma mass spectrometry (ICP-MS),in He mode after the extraction solution was diluted five times ,was developed to determin the content of available molybdenum in soil samples, which were extracted by Oxalic acid-ammonium oxalate solution, a high sensitivity method for the determination of available molybdenum in soil was established. Using 103Rh as the internal standard element to correct the instrument signal drift during the determination. Comparing the two pretreatment methods, the results showed that the method of shaking for 30 min and staying overnight had better extraction effect and was more suitable to the analysis of large quantities of samples. The contents of available molybdenum in five soil reference materials were analyzed, and the measured values were within the range of standard values. The effects of Mn with concentrations of 0 mg/L, 1 mg/L, 2 mg/L, 5 mg/L, 10 mg/L and 50 mg/L on the concentration of 5 ug/L 95Mo were compared in the no gas mode and the He mode respectively, the results showed that kinetic energy discrimination in the He mode could effectively remove the interference of polyatomic ion in the determination of 95Mo.The He mode is significantly superior to the no gas mode in determining effective molybdenum. The RSD of 5 soil samples were less than 4.1% after repeated determination for 6 times. The linear correlation coefficient was 1.0000. The detection limit was 0.0012 mg/kg. In conclusion, the method is accurate, reproducible, sensitive and suitable for the analysis of large quantities of samples.