Direct determination of trace mercury and cadmium in food by sequential electrothermal vaporization atomic fluorescence spectrometry using tungsten and gold coil trapsElectronic supplementary information (ESI) available. See DOI: 10.1039/c8ja00009c

• Main Authors: Wang, Bo, Feng, Li, Mao, Xuefei, Liu, Jixin, Yu, Chongchong, Ding, Lan, Li, Siqi, Zheng, Chuangmu, Qian, Yongzhong
• Format: Article
• Language: English
• ISSN: 0267-9477; 1364-5544
• DOI: 10.1039/c8ja00009c

On the basis of the vaporization temperature difference principle between Hg and Cd analytes, a novel solid sampling system coupled with atomic fluorescence spectrometry (AFS) was developed for the sequential determination of trace Hg and Cd in food samples. The solid sampling system mainly comprised a gold coil trap for Hg and a tungsten coil (TC) trap for Cd to eliminate matrix interference, and an on-line Ni-Cr heating coil as the Hg electrothermal vaporizer (ETV) as well as a sample ashing furnace, and a porous carbon tube as the Cd ETV. These units were connected by a modified gas line system integrating air and Ar/H 2 (v/v = 9 : 1). The optimal vaporization (500-600 °C), trapping (ambient temperature), and pre-heating conditions of the gold coil (800 °C for 14-16 s) for Hg were all investigated, as well as the sample ashing (the same as Hg vaporization), vaporization (1200 °C for 20 s), and releasing (2000 °C for 1 s) conditions for Cd at 600 mL min −1 of both air and Ar/H 2 carrier gases. Under the optimum conditions, the detection limits (LODs) could reach 0.7 pg for Hg and 0.5 pg for Cd with less than 15% relative standard deviations (RSDs), namely 0.07 μg kg −1 and 0.05 μg kg −1 when introducing 10 mg sample mass, respectively. Furthermore, the spiked recoveries were 95.0-115.0% for Hg and 84.0-113.0% for Cd. The Hg and Cd concentrations measured by the proposed solid sampling method were all consistent with the certified reference material (CRM) values and those obtained by microwave digestion inductively coupled plasma mass spectrometry. The solid sampling Hg-Cd analyzer was extremely suitable for the in-field, rapid and accurate monitoring of Hg and Cd in food samples. On the basis of vaporization temperature difference, a novel solid sampling AFS was developed for the sequential determination of trace Hg and Cd in food samples.