Agriculture Reference
In-Depth Information
Figure 5.1.
GPC chromatogram of a blank sample.
pollutants
hereinafter. Chromatographic behavior of these environmental pollutants
is estimated by GPC within the experiment. One hundred and two environmental
pollutants elute at 16
”
56 min, and 77 environmental pollutants elute after 23 min,
accounting for 72.0% of the total.
cis
-Chlordane, benzo(
g
,
h
,
i
)pyrene, dimehypo,
monosultap, and paraquat may not have UV absorption at 254 nm, and thus their
collection times cannot be determined.
For multiresidue analysis, it is essential to meet the requirements of the detection
methods for most analytes, to improve the removal of impurities (fat, etc.), and to ensure
that the instrument is not contaminated. The blank samples are selected to compare
the conditions of cleanup. The contents of samples collected at 21
-
-
60, 22
-
60, 23
-
60,
24
60min are compared. It is found that if the start collect time is set
at 21 and 22min, the eluate contains a little fat, and if the start collect time is set at
23min, the interferences caused by fat can be mostly excluded. The GPC chromato-
grams of blank and standard forti
-
60, 25
-
60, and 26
-
ed samples are shown in Figures 5.1 and 5.2.
In Figure 5.1, fat elutes between 14 and 23 min, and in Figure 5.2, most pesticides
elute between 28 and 50min. Thus, the condition of GPC is determined: 23
60min is
the start collect time. But the recovery of
cis
-chlordane is only about 90%, the
recovery of benzo(
g
,
h
,
i
)pyrene is unstable (may be in
-
uenced by the matrix), and
dimehypo, monosultap, and paraquat are not detected. The cleanup conditions
determined by this method are suitable for
cis
-chlordane and most environmental
pollutants and unsuitable for dimehypo, monosultap, and paraquat.
5.3.2 Selection of Extraction Solvent
Seven solvents
—
n
-hexane,
n
-hexane
-
acetone (1
+
1, v/v),
n
-hexane
-
acetone
(3
+
1, v/v), ethyl acetate
-
cyclohexane (1
+
1, v/v),
n
-hexane
-
dichloromethane
