OMA Protocol Review: OMAMAN-56 Sulfites in Shrimp

expected (76% and 78% respectively for boiled and raw head off shrimp), but not so on day 2

(110 % and 106% respectively). This marked difference in the recovery value at this level between

days may be due to the fact that the starting values of the incurred samples are lower than the

validated LOQ (around 3 mg/kg). That is why on day 2, although the values obtained for the

spiked samples at 5 mg/kg are the same as on day 1 (6.79 and 7.02 mg/kg for boiled shrimps and

7.56 and 8.13 mg/kg for raw head off shrimp, for day 1 and day 2, respectively), the experimental

calculated addition is greater due to the lower value of the blank samples (76% vs 110% for boiled

shrimp and 78% vs 106% for raw head off shrimp).

Figure 8 shows the linear regression between the additions of sulfite and the values obtained

by the BIOFIHS HIS 300 for both days for each matrix. In addition to the good correlation obtained

(R 2 ≥0,99) between theoretical and experimental values for each case, it is clear from the figure

that the values obtained for both days are comparable, as the parameters of the linear regression

within a matrix are almost the same.

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