Rapid Determination of Low-level Sulfite in Dry Vegetables and Fruits by LC-ICP-MS

This paper describes a liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS) method for the determination of low-level sulfite in dry vegetables and fruits. Aqueous 0.1% solution of formaldehyde was chosen as extraction solution for releasing the bound sulfite and forming the more stable hydroxymethanesulfonate (HMS). Sulfite was separated using an anion exchange column with isocratic elution by a 50 mmol.L-1 ammonium nitrate in 0.1% formaldehyde solution (pH 7). Sulfite was detected as (SO+)-S-32-O-16 by ICP-MS in DRC O-2 gas mode. In the optimum conditions, the linearity of the method is 0.05 - 5 mg.L-4 for sulfite, and the detection limit is 0.02 mg.L-1. The results demonstrated that the method achieved acceptable quantitative recoveries of 78.5% to 91.6% with relative standard deviations (RSDs) < 5%. Compared to the AOAC official method, the proposed method presented advantages of rapid and sensitive.