Improvement of National Standard Method for Determination of 5 Arsenic Species in Marine Products

There were many steps in the pretreatment of national standard GB 5009.11-2014 for determination of arsenic species in food, including overnight storage, thermal extraction, centrifugation, extraction and filtration, which took a long time. The mobile phase of high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) should be prepared with 4 kinds of inorganic salts with different contents and the acidity of mobile phase should be adjusted, which was more complex. In order to solve these problems, the pretreatment of national standard was improved and the chromatographic conditions of the second method of national standard were optimized. A method for rapid determination of 5 arsenic species in food by HPLC-ICP-MS with microwave-assisted enzyme extraction was proposed. 1.0 g of the sample, 0.004 g of streptoproteinase E enzyme and 20 mL of water were placed into a microwave extractor for extraction at 35℃ for 45 min, and the extract was centrifuged for 10 min, and then filtered by 0.45 μm water-borne filter membrane. Hamilton PRP-X100 column was used as stationary phase, a mixture of 2.0 mmol·L^-1 NH₄H₂PO₄ solution (pH 8.0) and ethanol at a volume ratio of 99:1 was used as the mobile phase for isocratic elution, and the determination was carried out according to the working conditions of the instrument. As shown by the results, the linear ranges of the standard curves of 5 arsenic species were all 2.5-30.0 μg·L^-1, with detection limits (3s/k) in the range of 0.50-0.60 μg·L^-1. Test for recovery was made by standard addition method, giving results in the range of 90.0%-103%, with RSDs (n=5) of the determined values in the range of 0.80%-5.0%. The method was applied for analysis of samples and in comparison with the results given by the second method of GB 5009.11-2014, showing that there was no significant difference between the improved method and GB 5009.11-2014 (P>0.05).