Integration of cobalt ion assisted Fenton digestion and photochemical vapor generation: a green method for rapid determination of trace cadmium in rice

In this work, a novel strategy integrating Fenton-like digestion as well as metal ion assisted photochemical vapor generation (PVG), plus inductively coupled plasma-mass spectrometry (ICP-MS) measurements, was first proposed for the analysis of cadmium (Cd) in rice samples. Cobalt ions were used not only as the catalyst in the Fenton-like digestion for accelerating the decomposition of the sample matrix but also as the “sensitizer” for enhancing the PVG of the analytes for the first time. Compared to conventional microwave digestion, the consumption of HNO3 in the Fenton-like digestion was reduced significantly to 4% (v/v), and the digestion time was substantially decreased to 25 min. In addition, the PVG efficiency of Cd is largely improved in the presence of Co2+ and the analytical sensitivity of Cd, using Co2+-PVG as a sample introduction method, was increased seven-fold compared to that obtained from direct solution nebulization. The interferences from co-existing ions were greatly reduced in comparison with those found using either ferric ion assisted PVG or direct solution nebulization with ICP-MS measurement. Under the optimized experimental conditions, the limit of detection (LOD, 3σ) was 1.6 μg kg−1 using a 0.050 g rice sample and the relative standard deviation (RSD) was 1.8% for the replicate measurement of 1 μg L−1 Cd2+ (n = 7). The method was successfully applied to the determination of Cd in rice and wheat flour samples.