Use of Iridium as Endurable Chemical Modifier in ETAAS Determination of Trace Amount of Lead in Food

Iridium was proposed to be used as endurable chemical modifier in the ETAAS determination of trace amounts of lead in food sample.Fifty μL of 1.000 g·L-1 iridium(Ⅲ) solution was apllied to the graphite platform and treated according to the prescribed program.It was shown that the graphite platform treated with Ir kept good sensitivity and reproducibility even after its used for at least 400 times.The optimum temperature and time for ashing and atomization with this modified graphite platform were found to be 900 ℃,10 s and 1 800 ℃,3 s respectively.As shown by the results of companative study with the conventionally used modifiers,e.g.,NH4H2PO4+Mg(NO3)2 and PdCl2,lower values of background signal and detection limit were found with the Irmodified platform.In its application to the ETAAS determination of lead in food samples,values of detection limit (3S/N) and characteristic mass found were 8 pg and 30 pg respectively.Tests for recovery and precision were made by standard addition method,the results of recovery obtained were in the range of 93.2% to 104.5%,with RSD′s (n=7) less than 3.5%.