OMA Protocol Review: OMAMAN-56 Sulfites in Shrimp

( c ) Results from spiked shrimp.- -Results for the recovery experiment are presented in Tables 6-8. It is worth noting that the experiment must be carried out with samples that already

contained a certain amount of sulfite, since we have verified that if the addition is made over

truly blank samples, the obtained recoveries are much lower than the acceptable ones of 80-

110% (see results in Table 6 for recoveries over a blank sample). The possible reason for this

behavior may be the presence of certain molecules in the dead-bed samples without having

been treated with sulfite, which differs from those formed when the shrimp is previously

sulfited, that combines irreversibly with sulfites and are not released under the conditions of

the extraction step.

Table 6. Recovery results with spiked blank samples of raw shrimp. Mean values of 5 replicate test portions at each level of addition for Day 1 /Analyst 1 / Device 1.

SO 2 theoretical addition (mg/kg)

BIOFISH 300 SUL Mean (mg/kg)

RSD r (%) SO 2 experimental addition (mg/kg)

S r

Recovery (%)

0 5

0.0

0.0 0.1 0.2 0.2 0.3 0.7

1.25 3.32 7.69

9.6 5.1 2.5 2.9 3.7

1.25 3.32 7.69

25 33 51 51 63

10 15 20 30

RAW HEAD OFF SHRIMP

10.11 18.75

10.11 18.75

Tables 7 and 8 show the results for the recovery experiment when spiking low level incurred

samples of both types of matrixes. As can be seen, the recovery values are much greater than

those obtained when spiking truly blank samples, and mostly between the acceptable 80-110%

range. On day 1, for both matrixes, the recovery for the addition of 5 mg/kg SO 2 is lower than

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