原子捕集-火焰原子吸收光谱法测定中草药中痕量镉

Determination of Cadmium in Chinese Herbs by Atomic Absorption Spectrometry Using Atom Trapping Technique

考察了火焰条件、捕集管与燃烧器和光束的距离、冷却水流量、捕集时间等实验条件对原子捕集 火焰原子吸收光谱法测定镉的灵敏度的影响 ,实验优选出的最佳实验条件为 :乙炔流量 90L·h- 1 ,捕集管距离燃烧器缝口 5mm ,捕集管距离光束 2mm ,冷却水流量 1 5L·min- 1 ;采用 5 0ng·mL- 1 的镉标准溶液对吸光度与捕集时间的关系进行了考察 ,结果发现 ,在 0～ 6min的捕集时间内二者呈良好的线性关系。在最佳实验条件下 ,捕集时间为 2min时 ,镉的特征浓度为 1 8ng·mL- 1 ,检出限为 0 4 2ng·mL- 1 ,分别较常规火焰原子吸收光谱法的特征浓度和检出限改善了 16倍和 5倍 ,方法的精密度 (RSD)为 1 8%。利用所建立的原子捕集 火焰原子吸收光谱法 ,在最佳实验条件下 ,对人参、丹参、苦参和党参及其水煎液中的痕量镉进行了测定 ,样品的测定回收率在 89 5 %～ 10 4 %之间 ,结果令人满意。

A method has been proposed for the determination of cadmium by flame atomic absorption spectrometry (FAAS) using atom trapping technique. The experimental conditions including the flame condition, the trap position, the coolant water flow rate and the collection time, which affected on the absorbance of cadmium, were studied, and the optimum experimental conditions were the acetylene flow rate of 90 L·h -1 ,the distance of tube from the burner of 5 mm,the distance of tube from the light path of 2mm and the coolant water flow rate of 1 5 L·min -1 . The results showed that the absorbance was linearly dependent on the collection time in the range of 0-6 min for cadmium solution of 50 ng·mL -1 . For 2 min collection time, the characteristic concentration and the detection limit for cadmium were 1 8 ng·mL -1 and 0 42 ng·mL -1 , which were 16 and 5 times better than those of conventional flame atomic absorption spectrometry, respectively. The relative standard deviation(RSD) was 1 8% and the proposed method was successfully applied to the determination of cadmium in Chinese herbs with a recovery range of 89 5%-104%.