基于钨丝原子阱与直接进样技术的原子荧光光谱法快速测定贝类中的镉

摘要

本研究利用集成多孔石墨管电热蒸发器和钨丝捕获阱技术的原子荧光光谱分析系统,基于固体进样技术建立了适用于现场快速检测贝类中镉(Cd)的测定方法,实现了贝类中Cd的快速灵敏检测.结果显示,仪器在最佳参数条件下稳定性良好,采用“在线原子阱”捕获后释放的信号可以消除大多数基体干扰.贝类样品匀浆后在酸性条件下直接进样可快速测定Cd,且使用1％硝酸进样效果最好.采用标准曲线和标准加入法验证,均线性良好(R2≥0.995),样品加标回收率分别为98.1％-110.6％和96.4％-105.5％,相对标准偏差(RSD)分别为3.3％-11.6％和7.5％-8.7％,方法检出限分别为3 pg和0.6 pg,满足贝类样品的现场快速检测要求.但相对标准曲线法,标准加入法具有更好的准确度、精密度和稳定性,用标准物质验证,检测结果在参考值范围内.因此,标准加入法更适合贝类中Cd的快速测定.%Cadmium is among the most toxic metals in the aquatic environment.It particularly affects shellfish because the latter can accumulate large amounts of cadmium from the water.To reduce the potential risk on the health of public consumers,it is necessary to measure and monitor the level of cadmium in shellfish.Conventional analysis methods are usually time-consuming due to the prolonged sample digestion and pretreatments.A direct solid sampling technology without digestion treatment has been applied in the fast determination of cadmium concentration in agricultural produces such as grains and vegetables.Here,we tried to employ this method in the rapid measurement of cadmium concentration in shellfish.Solid sampling (SS) device was coupled with atomic fluorescence spectrometry (AFS),and the SS-AFS instrument was assembled with a tungsten coil trap (TCT) and porous carbon ETV.Meanwhile,electrothermal vaporization atomic fluorescence spectrometry (ETV-AFS) with a tungsten coil trap was optimized,and SS-ETV-AFS was established as a novel direct sampling method of detecting cadmium in shellfish.The results showed that a tungsten coil could work as a cadmium trap and eliminate most of the matrix interferences.Samples were homogenized and diluted with different acids,and 1％ HNO3 was determined to be the optimal acid reagent.Under the optimized conditions,the fitting with both the standard addition method and the standard curve method showed good linearity with regression coefficient (R2) larger than 0.995.The relative standard deviation (RSD) of the standard addition method and the standard curve method were 6.5％-7.7％ and 3.3％-8.6％ respectively;the spiked recoveries of them were 96.4％-105.5％ and 98.1％-110.6％;the limit of detection (LOD) were 0.6 pg and 3 pg.Moreover,the time elapsed (including sample pretreatments) was within 5 min.The standard addition method generated data with similar accuracy to those measured with graphite furnace atomic absorption spectrophotometry (GFAAS) or certified reference materials (CRMs) (P ＞ 0.05).Therefore,the standard addition method could be suitable to the field analysis and monitoring of cadmium in shellfish.