OMA Protocol Review: OMAMAN-56 Sulfites in Shrimp

Figure 6. Linearity and residual plot of the BIOFISH 300 SUL method.

Matrix Study

( a ) Methodology.-- The BIOFISH 300 SUL 7-30 mg/kg method was compared to OMA 990.28, the optimized Monier-Williams method for determination of sulfites in foods (1) for calculation of accuracy,

bias, repeatability, intermediate reproducibility and recovery, using both incurred shrimp and spiked

shrimp samples. For each incurred matrix (raw head-off and boiled shrimp), 5 lots of product known to

contain sulfites at low levels were obtained. In addition, a blank sample of each matrix was also included.

Three hundred g of each lot were mixed, and three 50-g test portions were weighed out for the OMA

method and ten 2-g test portions for the BIOFISH 300 SUL method. Each 2-g blind coded test portion was

extracted and analyzed according to the BIOFISH 300 SUL method as written on two different

days/analyst/device and each 50-g blind coded test portion was analyzed according to the OMA 990.28

method (1).

Each spiked matrix was fortified at 5 concentrations (5, 10, 15, 20, and 25 mg/kg of SO 2 ) with

formaldehyde sodium bisulfite solution using the following method. Raw head-off and boiled shrimp with

the lowest concentration of sulfite found were peeled and minced. Sixty 2-g test portions were weighed

in Falcon-type tubes and then inoculated with a known concentration of formaldehyde sodium bisulfite

. A stock solution of 1000 mg/L of SO 2

was prepared [22.0 mg

solution to reach the desire addition of SO 2

of formaldehyde sodium bisulfite adduct (CAS 870-72-4, MW 134.09 g/mol) was dissolved in 10 mL of

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