Quantification of Total Sulfites in Shrimp by BIOFISH 300/3000 SUL Method, Collaborative Study: Final Action 2021.09.

Abstract

In December 2021, the BIOFISH 300 SUL method for the determination of total sulfites in shrimp was adopted as First Action Official Method of AnalysisSM by the AOAC INTERNATIONAL. A collaborative study was conducted in February 2023 in order to test the reproducibility of the method. The method is based on the use of a benchtop biosensor device that relates the concentration of sulfite to a quantifiable electric current signal. The sensing element, the Biotest, harbors an enzyme that specifically oxidizes sulfite, and the reaction products are electrochemically detected by the device in less than 3 minutes. The sulfite is extracted from the solid using an aqueous based buffer solution, which ensures that all sulfite is present as a free anion. 11 collaborators participated in the study of nine different shrimp samples. Values of RSDr and RSDR obtained from the statistical analysis of valid data ranged from 2.1-8.1% and 7.5-14.3%, respectively, for shrimp samples above the quantification limit of the method, set at 7 mg/kg. These results showed good repeatability and reproducibility of the method, even at concentrations below the legal threshold for sulfite in food, where the reference Optimised Monier-Williams method shows relatively high imprecision.