Agriculture Reference
In-Depth Information
Figure 5.4.
The comparison of the cleanup ef
ciencies of four cleanup methods for 77 environmental
pollutants in 5 g fat samples.
on the instrument; thus, GPC cleanup was
finally selected. The GC
-
MS/MS TIC plots
of four cleanup methods are shown in Figures 5.5
-
5.8 for comparison.
5.3.5 Linear Range, LOD, and LOQ
Two hundred and ninety-
ve environmental pollutants are detected using the above
method. The results show that the concentrations show a good linear relationship with
the responses in the linear ranges, and the correlation coef
cients are between 0.9684
and 1.0000. The correlation coef
cients of 270 environmental pollutants are higher
than 0.9900, accounting for 91.5% of the total. The linear ranges, linear equations, and
correlation coef
cients are given in Tables 5.1
-
5.3. The LODs (a S/N ratio of
>
5) of
295 pesticides are 0.1
-
233.0
μ
g/kg, and LODs of 275 pesticides are lower than
10.0
μ
g/kg, accounting for 93.2% of the total. The LOQ (S/N
>
10) of the method is
0.2
g/kg. The LOD and LOQ data are given in Table 5.4. For each
concentration (LOQ, 2 LOQ, and 4 LOQ),
-
466.0
μ
five standard added samples and
one matrix standard are prepared for calculating recoveries of 295 environmental
pollutants. The results of
five standard added samples are averaged before the
calculation of recoveries.
5.3.6 Recoveries and Precisions
Pork samples are obtained from the markets in China. The fat of the pork is separated
from other tissues manually and homogenized by grinding in a meat blender. Two
hundred and ninety-
ve standard solutions are added to the homogenized samples to
measure the recoveries of the samples spiked with LOQ, 2 LOQ, and 4 LOQ and to
measure the precisions (
n
=
6); the results are given in Table 5.4. The recoveries of
259 standards with LOQ concentrations are between 60.0 and 120.0%, accounting for
87.8% of the total. The RSDs of 278 standards with LOQ concentrations are 20%,
accounting for 94.2% of the total. The recoveries of 248 standards with 2 LOQ
concentrations are between 60.0 and 120.0%, accounting for 84.1% of the total. The
