LAUSR

In this work, a novel solid sampling method of Cd in grain samples was established based on electrothermal vaporization atomic absorption spectrometry (ETV-AAS). The solid sampling system was mainly composed of a quartz ETV tube, a pyrolysis furnace with a kaolin filler, an integrated outlet tube (IOT), an AAS detector and a gas generation system. The gas system generated oxidizing (containing O2) and reducing (containing H2 and N2) atmospheres, in that order, from only air and water to ash the sample and vaporize and transport Cd, respectively. After drying at 350 °C for 20 s and ashing at 350–725 °C for 55 s under a 300 mL min−1 air atmosphere, ∼4.5% Cd was pre-vaporized and then captured by the kaolin filler at 700–850 °C; when H2 was introduced at 350 mL min−1 to react with O2 in the air to yield a N2/H2 atmosphere, Cd in the sample residue and that captured on the filler were completely vaporized from 725 °C to 800 °C (50 s ETV) and then detected by N2/H2 flame AAS. Under optimum conditions, the detection limit (LOD) was 0.03 ng with <10% relative standard deviation (RSD), namely 0.15 ng g−1 for a 200 mg sample. The method was validated using certified reference materials (CRMs) and the Cd concentrations that were measured agreed with the certified values, and these were consistent with those obtained by microwave digestion graphite furnace AAS; furthermore, the recoveries were 95–103% for a series of real grain samples. The instrumental analytical time could be controlled within 3 min and the overall analysis time, including sample preparation time, within 10 min without the acid digestion process. The proposed solid sampling Cd analysis is thus suitable for fast detection of Cd in grain samples.