研究持久性化学改进剂钨-铱电热原子吸收光谱法测定水和植物性食品中痕量镉.用钨-铱溶液(适宜用量为钨250 μg,铱200 μg)作为持久化学改进剂处理石墨平台并进行试验,与常规化学改进剂NH4H2PO4+Mg(NO3)2比较,灵敏度高且背景信号低,且可用较低的原子化温度,可延长石墨管使用寿命;例如测镉时,可连续使用300~350次.分别测定水和植物性食品中痕量镉,相对标准偏差(n=5)在0.7%~3.3%之间,样品加标回收率在92.0%~111.3%之间,水和植物性食品中镉的检出限分别为0.036 μg·L-1和0.102 μg·L-1,特征质量为1.3 pg.

Mixed solution of tungsten and iridium was proposed to be used as endurable chemical modifier in the electrothermal AAS determination of trace amounts of cadmium in water and vegetable food samples.The W+Ir solution was applied on the surface of the graphite platform.The optimum amount of W+Ir used was found to be 250 μg and 200 μg respectively.As compared with the conventionally used modifier of NH4H2PO4+Mg(NO3)2,the graphite platform coated with W+Ir was proved to have higher sensitivity,lower background signal,lower atomization temperature and longer service time.As shown by experimental results,the W-Ir treated graphite platform was used continuously for 300-350 times still keeping high sensitivity and precision,in the determination of cadmium.In its application to the analysis of samples of water and vegetable (including 3 CRM′s) for their cadmium contents,values of RSD′s (n=5) obtained were in the range of 0.7%-3.3%,and values of recovery found were in the range of 92.0%-111.3%.Detection limit of cadmium found for water samples was 0.036 μg·L-1 and for vegetable samples was 0.102 μg·L-1.The characteristic mass of the method was 1.3 pg of Cd/1% A.