应用S930树脂富集薄样-X射线荧光光谱现场分析环境水体中8种重金属的方法研究

使用便携式X射线荧光光谱法结合富集技术已能分析液体样品中近20种金属元素,但检出限相对较高(0.1~100μg/L)、富集操作繁多、一种富集法可测元素种类较少等因素制约了该技术的发展。本文研究了一种适应于现场测试环境水样的XRF分析方法。使用20 mg S-930螯合树脂对100 m L水体中8种重金属(V、Mn、Fe、Co、Ni、Cu、Zn和Pb)进行预富集,控制溶液p H=4,搅拌30 min,经真空抽滤系统过滤制得均匀薄样,再使用自制的双层膜包夹样品盒并利用小型台式波长色散XRF测定。结果表明,8种元素标准曲线的相关性R20.997,检测范围为10~1000μg/L,检出限为1.0~6.2μg/L,方法精密度(RSD,n=12)小于5%,加标回收率为80%~120%;标准水样和模拟水样的测定结果分别与标准值和理论值基本一致。本方法巧妙地使用双层聚丙烯膜包夹薄试样的制样方法,较好解决了薄膜样品的污染等问题,简化了水样的预富集操作,制备的树脂薄样可直接供XRF测量。方法检出限较低,稳定性较好,适用于检测Ⅰ~Ⅴ类水体中Fe、Co、Ni和Cu,Ⅱ~Ⅴ类水体中V和Zn,Ⅲ~Ⅴ类水体中Mn和Pb,基本具备对8种重金属污染水体进行环境监测、水质调查等现场分析的能力。

Portable EDXRF Analysis of Eight Heavy Metals in Environmental Water Using Pre-concentration with Purolite S930 and Thin-layer Sample Technique

Analysis of environmental water samples is primarily conducted in the laboratory, which costs considerable time and money. Pre-concentration methods coupled with portable X-ray Fluorescence (XRF) have been developed for the determination of almost twenty kinds of heavy metals, but with a relatively high detection limit, complex operation, and less element types can be measured using one pre-concentration strategy. All of these problems restrict the development of the technique. To solve these issues an on-site-oriented rapid and convenient analysis method of heavy metal ions in aqueous solutions has been developed utilizing a bench-top type portable Energy-Dispersive X-ray Fluorescence (EDXRF). Based on pre-concentration with purolite S930 chelating resin and thin-layer sample preparation technique, the method could determine trace V⁵⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Pb²⁺ in environmental water samples. After the heavy metal ions have been absorbed by 20 mg of S-930 resin powder for about 30 min in the pH=4 solution, the resin powders are filtrated onto a 0.45 m filter to form a thin-layer sample which can be directly measured by EDXRF using a homemade double polypropylene film sample cup. With an amount of 100 mL of solution, the linear ranges were 10-1000 g/L and the correlation coefficients of the calibration curves were good (R²>0.997) for all the eight elements. The lower limit of detection was between 1.0 and 6.2 g/L. Precision tests carried out on multi-element mixed solutions showed that the relative standard deviations (RSD, n=12) were better than 5% except for those of Zn and Pb at the concentration level of 20 g/L. Most of the recoveries were 80%-120% with spikes of 20 g/L for each element. The analysis results of DW standard substances and simulation samples were consistent with reference values and the theoretical value respectively. This method skillfully uses a double polypropylene membrane preparation method to make a thin-layer film sample which solves the pollution problem and simplifies the pre-concentration steps. The resin film samples can be directly measured by XRF. A lower detection limit and better stability make the method suitable for a spot investigation, water quality monitoring, and assessment of Fe, Co, Ni, Cu, V, Zn, Mn and Pb in heavy metal polluted environmental water.