固相萃取掺氧空气-乙炔火焰原子吸收光谱法测定水和植物样品中的痕量镓

目前研究萃取分离富集镓大多偏向在强酸性体系中,一定程度上给操作带来安全风险,另需耐酸器皿设备,易污染,空白背景值高。本文开发了一种在弱酸性条件下萃取分离富集痕量镓的方法。以大孔吸附树脂为载体,十六烷基三甲基溴化铵调节其表面极性,热固化负载2-乙基己基磷酸(2-乙基己基)酯,制备了镓的萃取树脂。动态考察了固相萃取镓的吸附容量,优化选择固相萃取分离富集条件,实验表明萃取条件温和,分离富集痕量镓效果理想。当溶液酸度为pH 2.5时,Ga(Ⅲ)达到最大的回收率99%,并确定了掺氧空气乙炔火焰原子吸收光谱法(FAAS)测定镓的最佳参数,提升了常规空气乙炔FAAS测定镓的灵敏度。方法检出限(3σ)为2.6ng/mL,相对标准偏差(RSD,n=7)为2.87%,加标回收率在95.7%～102.0%之间,理论富集倍数为40。本方法已应用于自来水、中药材和水培蔬菜样品中痕量镓的测定,简便、快速、可靠。

Determination of Trace Ga in Water and Plant Samples by O2-doped Air-Acetylene FAAS with Solid Phase Extraction Preconcentration

BACKGROUND: At present, research on the extraction separation and enrichment of gallium is mostly biased to the strong acidic system, which brings a safety risk to the operation and needs acid-proof apparatus. Furthermore, the procedure is easily contaminated, resulting in high background values.
OBJECTIVES: To develop a method for extraction separation and preconcentration of trace Ga under weakly acidic condition.
METHODS: Solid phase extraction medium for Ga was prepared by using modified large porous adsorption resin with cetyl-trimethyl-ammonium bromide and loading it with 2-ethylhexyl phosphonic acid-2-ethylhexyleste. The separation and enrichment conditions of solid phase extraction were studied in detail.
RESULTS: Experiments showed that the separation and enrichment of trace gallium was ideal when the extraction conditions were mild. The maximum recovery (99%) of Ga was achieved in sample solution with pH of 2.5. The determination parameters of gallium were optimized for oxygen doped air-acetylene flame atomic absorption spectrometry (FAAS), and the sensitivity was improved on that of the current method. The detection limit of the overall method (3σ) was 2.6ng/mL by IUPAC definition and the relative standard deviation (RSD, n=7) was 2.87%. The recoveries for spiked solution ranged from 95.7% to 102.0%, and a theory enrichment factor of 40 was obtained.
CONCLUSIONS: This method has been successfully applied to the determination of trace gallium in tap water, Chinese medicine and hydroponic vegetable samples. It is simple, quick and reliable.