Íslenskar landbúnaðarrannsóknir - 01.09.1982, Síða 9

RESIDUE OF LINURON IN SOILS 7
tion into petroleum ether. The extract was
again evaporated to dryness and the linuron
residue hydrolysed in hydrochloric acid to
form 3,4—dichloroaniline. This aniline was
then measured by application of an auto-
mated diazotization and coupling proce-
dure (Friestad 1967, 1974, 1978).
Soil analysis
The procedure as described by Friestad
(1978) was followed closely. A preliminary
investigation of the soil extraction proce-
dure indicated that a 24 hour delay was
necessary after shaking a soil sample in
dichloromethane, before removal of an
aliquot for analysis. Higher recoveries of
linuron were obtained after a delay of 24
hours (mean recovery 78%) or 48 hours
(mean recovery 79%) than if the aliquot
was taken immediately (mean recovery
59%).
On the basis of these findings, each
sample was allowed to settle for 24 hours in
the dichloromethane extractant. After this
interval, an aliquot ofthe clear supernatent
was removed for clean-up by dimethyl
sulphoxide extraction. All evaporation of
solvents was performed in a water bath at
70°C.
Some minor changes were made to the
Autoanalyser module as presented by
Friestad (1974). In particular, it was
found to be beneficial to the flow pattern to
omit the Brij 35 from the sodium nitrite
reagent. The manifold flow diagram is
shown in figure 2.
In order to assess recovery of linuron
from soil the following experiment was
done on 4 test soil samples. One mg of
linuron, dissolved in 5-10 ml diluted
ethanol was pipetted over 100.00 g of each
ofthe undried, sieved test soils which were
Flow diagram of Autoanalyser module. FUðirit fyrir hina sjálfoirku efnagreiningu á linuron.