二乙基三胺五乙酸浸取-电感耦合等离子体质谱法测定石灰性土壤中有效态铜锌铁锰

采用二乙基三胺五乙酸(DTPA)浸提石灰性土壤样品中有效态Cu、Zn、Fe、Mn后,样品溶液基体盐分较大,此时若直接采用电感耦合等离子体质谱法(ICP-MS)进行测定,极易使仪器的采样锥和截取锥发生堵塞,雾室和炬管积盐,进而影响测定准确性。据此,实验用DTPA浸提样品后,采用对样品溶液稀释10~30倍和在标准溶液系列中加入DTPA溶液进行基体匹配的方法以消除基体干扰,利用氦碰撞模式进行测定以消除多原子离子⁴⁰Ar¹⁶O对⁵⁶Fe的质谱干扰,最终实现了ICP-MS对石灰性土壤中有效态Cu、Zn、Fe、Mn的测定。对氦气流量进行了优化,并确定氦气流量为4.5mL/min。在优化的实验条件下,Cu、Zn的质量浓度为5~200ng/mL、Fe的质量浓度为100~3000ng/mL、Mn的质量浓度为30~1000ng/mL时,各元素质量浓度分别与其计数值呈线性关系,相关系数均不小于0.9998。方法检出限为0.003~0.01mg/kg。按照实验方法测定土壤有效态成分分析标准物质中的有效态Cu、Zn、Fe、Mn,测定值与认定值一致,相对标准偏差(RSD)为1.3%~3.1%。采用实验方法和标准方法HJ 804—2016(电感耦合等离子体原子发射光谱法)进行方法对照试验,二者测定值基本一致。

Determination of available copper,zinc, iron and manganese incalcareous soil by inductively coupled plasma mass spectrometrywith diethylenetriaminepentaacetic acid extraction

The available Cu, Zn, Fe and Mn in calcareous soil sample were extracted by diethylenetriaminepentaacetic acid (DTPA). Since the contents of matrix salts in sample solution were high, the sampling cone and skimmer cone of instrument were easily blocked if the sample solution was directly determined by inductively coupled plasma mass spectrometry (ICP-MS). The salification in atomizing chamber and torch tube would influence on the determination accuracy. After leaching sample with DTPA, the sample solution was diluted for 10-30 times. Meanwhile, DPTA solution was added into standard solution series for matrix matching to eliminate the matrix interference. The mass spectrometry interference of polyatomic ion ⁴⁰Ar¹⁶O with the determination of ⁵⁶Fe was eliminated using helium collision mode. Consequently, the determination of available Cu, Zn, Fe and Mn in calcareous soil by ICP-MS was realized. The flow rate of helium was optimized and the optimum flow rate was 4.5mL/min. Under the optimized experimental conditions, the mass concentration of elements had linear relationship with the counting value for Cu, Zn (5-200ng/mL), Fe (100-3000ng/mL) and Mn (30-1000ng/mL). The correlation coefficients were all not less than 0.9998. The detection limit was 0.003-0.01mg/kg. The contents of available Cu, Zn, Fe and Mn in certified reference materials of soil for available composition analysis were determination according to the experimental method. The found results were consistent with the certified values, and the relative standard deviations (RSD) were between 1.3% and 3.1%. The proposed method was compared with the standard method HJ 804-2016 (inductively coupled plasma atomic emission spectrometry), and the determination results were basically consistent.