电热蒸发钨丝在线捕获原子荧光光谱法直接测定菠菜中痕量镉

Direct Determination of Ultratrace Cadmium in Spinach by Electrothermal Vaporization Atomic Fluorescence Spectrometry Using On-line Atom Trap of Tungsten Coil

利用钨丝（TC）常温下特异性捕获镉（Cd）消除基体干扰，泡沫碳材料电热蒸发器串联原子荧光光谱仪，实现了固体直接进样测定菠菜鲜样中痕量cd。研究表明，泡沫碳电热蒸发器性能稳定，样品个体差异对测定无影响；经液氮冷冻粉碎的菠菜鲜样均匀度良好，Pauwels公式估算最小取样量为16．3mg，满足仪器微量进样要求。采用灰化（50w保持50s，70W保持80s）、蒸发（70W保持30s）过程分离，Ar-H2（9：1，V/V）载气流速为600mL／min时，方法检出限可达0．2μg/kg，回收率为90．1％-106．1％，RSD小于10％，分析时间少于5min，常见金属元素和有机物质对测定无干扰，且与微波消解石墨炉原子吸收光谱法结果无显著性差异（p〉0．05）。

A novel solid sampling method of detecting cadmium in spinach by electrothermal vaporization atomic fluorescence spectrometer （SS-ETV-AFS） was established, which made use of a tungsten-coil as a Cd trap at room temperature to remove matrix interferences and foam graphite as a electrothermal vaporizer and a sample boat. In our wok, it was proven that the foam graphite vaporizer had a stable performance and different sample boats had no difference for testing; there was good homogeneity and representativeness for fresh spinach sample grinded with liquid nitrogen, 16.3mg was calculated by the Pauwels equation as the minimum sample mass which satisfied microsampling of SS-ETV-AFS. After optimization, the ashing （50 W for 50 s then 70 W for 80 s） and evaporating （70 W for 30 s） procedures were separated, and 600 mL/min Ar/H2 （9： 1, WV） was chosen as the carrier gas. Under the optimized conditions, the limit of detection was 0.2 i.tg/kg; the recovery was 90.1%- 106.1%, the relative standard deviation was less than 10%, and the analysis time was within 5 min. There was no interference from the other elements and organic matrix, and there was no significant difference （p 〉 0. 05 ） between the methods of SS-ETV-AFS and microwave digestion graphite furnace atomic absorption spectrometer.