Comparison of chemical extraction and bioassay for measurement of metsulfuron in soil
Szmigielska, A.M., J.J. Schoenau and K.J. Greer . 1998. Weed Science 46:487-493
Abstract
A new extraction method for the
HPLC-UV determination of metsulfuron in soil was
developed and compared with NaHCO3 extraction
and a lentil bioassay technique. The new procedure
consisted of metsulfuron extraction using anion exchange
membranes followed by a dichloromethane concentration of
the membrane eluates. Three soils representing
different landscape positions were spiked with
metsulfuron to yield concentrations in the range of 0 to
40 μg kg-1 dry soil and were analyzed by the
above procedures. At a given spike rate, the
efficiency of the anion exchange membrane extraction was
highest for the soil from the upper slope position and
lowest for the soil from the lower slope position,
indicating that the amount of ion-exchangeable
sulfonylurea was affected by soil properties.
Similar trends in degree of root growth inhibition were
observed for lentil response to metsulfuron presence in
soil; percent root growth inhibition was related to
the landscape position as the amount of
membrane-extractable metsulfuron. The percent shoot
growth inhibition was not soil dependant and did not
differ among soils. The efficiency of NaHCO3
extraction for metsulfuron did not vary with soil
type; in the NaHCO3 method, because of
the buffered alkaline nature of the extraction,
differences in soil properties, particularly soil pH,
would have less effect on metsulfuron recovery.
Because of similar trends for the results of the membrane
extraction method and a lentil root bioassay, anion
exchange membrane extraction may provide useful
information on bioavailable fractions of sulfonylurea
herbicides in soil.
Key Words
Anion exchange membranes, phytotoxicity, landscape positions.
