Agriculture Reference
In-Depth Information
Table 5.2. Names, Retention Times, Selective Ions, Relative Abundances, Linear
Ranges, Linear Equations, and Correlation Coefficients of Endosulfans Determined
by GC-NCI-MS
Retention
Time
(min)
Linear
Range
(
Selective
Ion
Relative
Abundance
Correlation
Coef
No.
Name
μ
g/l)
Linear Equation
cient
1
Endosulfan I
11.14
406, 408,
372
100:55:44.6
0.5-30.0
y
=
2022.5831
x
+
486.7318
0.9973
2
Endosulfan II
12.56
406, 408,
372
100:78:17.5
0.5-30.0
y
=
822.2465
x
+
14.4991
0.9995
C; data acquisitionmode:
MRM; MRM transitions, CEs, declustering potentials (DPs), and collision cell exit
potentials of nine environmental pollutants are given in Table 5.3.
flow rate of auxiliary gas: 6 l/min; ion source temperature: 350
°
5.2.6 Qualitative and Quantitative Determination
5.2.6.1 Qualitative Determination
When the samples are determined, if the retention times of peaks of the sample
solution are the same as those of the peaks of the working standard mixed solution, the
selected ions appeared in the background-subtracted mass spectrum, and the abun-
dance ratios of the selected ions are within the expected limits (abundance ratios
>
50%, permitted tolerances are
±
20%; abundance ratios
>
20
-
50%, permitted
tolerances are
±
25%; abundance ratios
>
10
-
20%, permitted tolerances are
±
30%;
abundance ratios
10%, permitted tolerances are
±
50%), then the sample is con-
firmed to contain the environmental pollutants.
5.2.6.2 Quantitative Determination
An internal standard calibration curve is used for quantitative determination in GC
-
MS/MS, and the internal standard is heptachlor epoxide. External standard calibration
curve is used for quantitative determination in GC
-
MS and LC
-
MS/MS. To decrease
the in
uences of the matrix, the matrix mixed standard solutions are used as the
standard solutions for quantitative determination and standard working curve.
Furthermore, the responses of environmental pollutants in the samples are all in
the linear ranges of the instrument.
5.3 RESULTS AND DISCUSSION
5.3.1 Selection of GPC Cleanup Conditions
Ninety-one pesticides and environmental pollutant monomers and mixed standard
solution of 16 PCBs are used in this section, and they are called
“
environmental
