Page 149 - Analytical method for food addtives

94 Analytical methods for food additives

Table 8.5 Performance characteristics for total sulphite in shrimp, orange juice, dried
apricots, dehydrated potato flakes and peas 8,9
Interlaboratory test carried out by FDA 9
Sample Shrimp Orange juice

Spike 0 12 80 10 35
No. of laboratories 14 14 14 14 12
Units µg/g µg/g µg/g µg/g µg/g
Mean value 1.8 6.8 60.6 8.0 30
S 0.33 1.5 5.2 1.4 4.0
r
RSD r 18.3 % 22.1 % 8.5 % 17.5 % 13.3 %
S R 1.1 2.5 8.1 1.6 4.8
RSD 61.1 % 36.8 % 13.4 % 20.0 % 16.0 %
R
Sample Dried apricots Dehydrated potato Peas
Spike 40 1100 20 400 10 25
No. of laboratories 12 14 10 12 14 16
Units µg/g µg/g µg/g µg/g µg/g µg/g
Mean value 22.0 975.6 4.6 289.6 5.7 15.8
S r 3.9 61.4 0.28 34.2 1.0 1.5
RSD 17.7 % 6.3 % 6.1 % 11.8 % 17.5 % 9.5 %
r
S R 4.1 94.1 1.6 34.1 1.8 3.4
RSD 18.6 % 9.6 % 34.8 % 11.8 % 31.6 % 21.5 %
R
Key
Mean The observed mean. The mean obtained from the collaborative trial data.
r Repeatability (within laboratory variation). The value below which the absolute difference
between two single test results obtained with the same method on identical test material under the
same conditions may be expected to lie with 95 % probability.
S The standard deviation of the repeatability.
r
RSD The relative standard deviation of the repeatability (S × 100/mean).
r r
R Reproducibility (between-lab variation). The value below which the absolute difference between
two single test results obtained with the same method on the identical test material under different
conditions may be expected to lie with 95 % probability.
S The standard deviation of the reproducibility.
R
RSD The relative standard deviation of the reproducibility (S × 100/mean).
R R