Investigation of Stable Coatings forin SituTrapping of Se and Te in Flow-Injection Hydride Generation and Graphite Furnace Atomic Absorption Spectrometry for Automated Determination

Abstract

Flow-injection hydride generation andin situconcentration of Se and Te hydrides in graphite furnace atomic absorption spectrometry (AAS) can be automated using a highly stable trapping reagent replacing the Pd modifier. In a systematic study, carbide-forming elements (Zr, Nb, Ta, W) and noble metals (Ir, Ir/Mg, Pd/Ir) were investigated as stable adsorbers which require only a single application. Effective trapping of the Se and Te hydrides is achieved on Ir- and Ir/Mg-coated graphite tubes at 550–800°C. Selenium-75 radiotracer was used to measure the trapping efficiency and about 61% was obtained on an Ir-coated tube. Signal stability and reproducibility were tested over 400 trapping and atomization cycles. The adsorptive “carryover effect,” which can lead to errors in absorbance values, was observed with Te, not with Se, at trapping temperatures above 600°C (the “critical temperature”). The characteristic mass is about 11 pg for Se and 12 pg for Te, and the detection limits (3σ) are about 0.011 and 0.007 ng, respectively, on Ir-coated tubes using a 1-ml sample loop. The method was tested by determination of the elements in low-alloy steel certified reference materials.