Insecticides and herbicides in soils 65
Figure 3.1 Elution and recovery curves for a polluted soil (◦) and an artificially polluted soil (•) using
a acetone: toluene (1:1).
Reprinted from Mangani et al, Analytical Chemistry 1981, 53, 1627, © 1981 American
Chemical Society [25].
(1:1). These are reported in Figure 3.1. Although the overall recovery using 25 mL of
solvent for the extraction is the same in both instances, a very significant difference is
observed in the elution curves. These tail to a greater degree in the naturally polluted
soil than in the artificially polluted soil. This shows, definitely, that pesticides can be
adsorbed on higher energy sites due to the porous structure of the material. A longer
time is required by the organic molecules to be occluded with the pores of the soil.
Teichman et al [28] separates polychlorobiphenyls from chlorinated insecticides
in soil samples using gas chromatography coupled to mass spectrometry. Polychlorobiphenyls were separated from DDT and its analogues and from the other common
chlorinated insecticides by adsorption chromatography on columns of alumina and
charcoal. Elution from alumina columns with increasing fractional amounts of hexane first isolated Dieldrin and Heptachlor from a mixture of chlorinated insecticides
and polychlorobiphenyls. The remaining fraction, when added to a charcoal column,
could be separated into two fractions, one containing the chlorinated insecticides,
the other containing the polychlorobiphenyls, by eluting with acetone-diethyl ether
(25:75) and benzene respectively. The polychlorobiphenyls and the insecticides were
then determined by gas chromatography on the separate column eluates without
cross-interference.
Teichman et al [28] used a gas chromatograph containing a glass column packed
with 4% SE-30, 6% SP-4201 on Chromosorb W (100–120) mesh) or a glass column
packed with 4% SE-30, 6% QF-I on Chromosorb W (80–100 mesh). The operating
conditions were:
Model:
Column temperature
180
◦ –185
◦
Injector temperature
100
◦ –215
◦
Detector temperature
200
◦
Nitrogen gas flow rate
25 ml to 30 ml min
−1
Figure 3.1 Elution and recovery curves for a polluted soil (◦) and an artificially polluted soil (•) using
a acetone: toluene (1:1).
Reprinted from Mangani et al, Analytical Chemistry 1981, 53, 1627, © 1981 American
Chemical Society [25].
(1:1). These are reported in Figure 3.1. Although the overall recovery using 25 mL of
solvent for the extraction is the same in both instances, a very significant difference is
observed in the elution curves. These tail to a greater degree in the naturally polluted
soil than in the artificially polluted soil. This shows, definitely, that pesticides can be
adsorbed on higher energy sites due to the porous structure of the material. A longer
time is required by the organic molecules to be occluded with the pores of the soil.
Teichman et al [28] separates polychlorobiphenyls from chlorinated insecticides
in soil samples using gas chromatography coupled to mass spectrometry. Polychlorobiphenyls were separated from DDT and its analogues and from the other common
chlorinated insecticides by adsorption chromatography on columns of alumina and
charcoal. Elution from alumina columns with increasing fractional amounts of hexane first isolated Dieldrin and Heptachlor from a mixture of chlorinated insecticides
and polychlorobiphenyls. The remaining fraction, when added to a charcoal column,
could be separated into two fractions, one containing the chlorinated insecticides,
the other containing the polychlorobiphenyls, by eluting with acetone-diethyl ether
(25:75) and benzene respectively. The polychlorobiphenyls and the insecticides were
then determined by gas chromatography on the separate column eluates without
cross-interference.
Teichman et al [28] used a gas chromatograph containing a glass column packed
with 4% SE-30, 6% SP-4201 on Chromosorb W (100–120) mesh) or a glass column
packed with 4% SE-30, 6% QF-I on Chromosorb W (80–100 mesh). The operating
conditions were:
Model:
Column temperature
180
◦ –185
◦
Injector temperature
100
◦ –215
◦
Detector temperature
200
◦
Nitrogen gas flow rate
25 ml to 30 ml min
−1