Íslenskar landbúnaðarrannsóknir - 01.09.1982, Blaðsíða 10

8 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
then spread out to an even depth of
approximately 0.5 cm on separate alumi-
nium trays. Each 100 g portion was mixed
well with the linuron solution and then
added to an additional 400.00 g of the same
test soil to give a final concentration of 2
mg/kg undried soil. The fortified soils were
then stored at 4°C for 2 weeks in airtight
plastic jars, before analysing in the same
way as the other soil samples. All soils were
air dried and dry matter recorded. After
sieving, residual dry matter was deter-
mined for each sample by drying 5—10 g at
100 °C overnight. This was followed by
ignition ofthe samples at 550 °C for 4 hours
to determine the content of organic matter
in the dry matter.
An interlaboratory comparison of
linuron quantification was made on eleven
soil samples in this study. Dried and sieved
samples were sent to the Agricultural
University of Norway in As, where Fries-
tad supervised the analysis.
Potato analysis
The method of extraction and clean-up of
potato samples was similar to that of
F riestad (1974) with the exception that the
petroleum ether extracts were passed
through a phase separating filter paper
(Whatman PS) containingabout 1 gram of
anhydrous sodium sulphate to remove the
remaining water phase.
In order to assess recovery of linuron
from potato samples, a stock linuron
standard (0.9 mg/ml) was diluted 1:1000
to give 0.9 jitg/ml. Five, 10, 15 and 20 ml of
this diluted standard were then pipetted
onto 100 g of potato tissue in a Waring
Blender. This is equivalent to a fortifica-
tion of 0.045, 0.090, 0.135 and 0.180 mg
linuron/kg potato. The samples were then
analysed according to the same procedure.
The potato sample used for these recovery
experiments was taken from a field known
never to have been treated with linuron.
Results
The series of dichloroaniline standards
which was always run during a period of
measurement, showed without exaption,
a straight line relationship obeying Beer’s
law (fig. 3).
FIGVRE3.
Standards of 3, 4-dichloroaniline (expressed as linuron). A typical
calibration line as used for soil measurements.
3. MYND.
Mæling á 3, 4-dichloroaniline stöölum (gefið upp sem linuron).
Dæmigerður staðalferill, eins og notaður var við mælingar á
jarðvegi.
Soil
The results of the recovery studies are
presented in table 2.
TABLE 2.
Recoveries of linuron from soil (average of 2
determinations).
2. TAFLA.
Heimta á linuron úr jarðvegi.
Soil type Recovery (%)
Jarðvegsgerð Heimta (%)
Loamy 1 83
Loamy 2 87
Sandy 1 74
Sandy 2 67