OMA Protocol Review: OMAMAN-56 Sulfites in Shrimp

Figure 7. Correlation between official method and BIOFISH 300 SUL for boiled and raw head off shrimp

It is interesting to note that the OMA results from one of the raw samples gave results of <10 mg/kg,

10 ± 2 mg/kg and 11 ± 2 mg/kg. This implies a range of results from below the quantification limit of 10

up to 13 mg/kg. For this sample, BIOFISH 300 SUL results were 7.92 mg/kg on day 1 and 8.71 on day 2,

values lower than 5%. This indicates that the precision of the BIOFISH 300 SUL at this critical

with RSD r

level is better than the precision from the modified Monier Williams.

Limit of detection (LOD) and limit of quantitation (LOQ) were determined by first plotting S r against

the mean results of BIOFISH 300 SUL and performing linear regression for each matrix. Next, LOD was

calculated as

( ) b s m

0 3.3 1 1.65 + −

X

LOD =

X

s

where,

is the mean analytical value of the known negative matrix; is the intercept of the plot; and

0

b

m

is the slope of the plot. LOQ is then estimated as LOQ = 3 x LOD. The LOD and LOQ results are presented

in Table 4.

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