Analysis of Imazethapyr in agricultural soils by ion exchange membranes and a canola bioassay
Szmigielska, A.M. and J.J. Schoenau . 1999. Communications in Soil Science and Plant Analysis 30:1831-1846
Abstract
Because imazethapyr residues in
soils may cause plant injury to certain rotational crops,
sensitive and reliable methods for imazethapyr monitoring
in soils are needed. In this study, imazethapyr
analysis was investigated using two newly developed
procedures: an anion exchange membrane extraction
followed by an HPLC-UV detection and a canola
bioassay. Nine soils in which no previous
application of imazethapyr had been made were collected
from farm fields in Saskatchewan, Canada. Soils
were spiked to yield imazethapyr concentrations in the
range of 0 - 80 μg kg-1 dry soil and were
subjected to analysis by the above procedures. In
the anion exchange membrane extraction, spiked soils were
shaken with the membrane strips; imazethapyr was then
eluted from the membranes with the KCL solution,
partitioned into dichloromethane and injected into the
HPLC. This method allowed for the extraction of the
ionized portion of imazethapyr from soils. In a
laboratory bioassay, pre-germinated canola were planted
in spiked soils and after five days of growth, root and
shoot growth inhibition was determined. The results
of both methods were dependent on soil type.
Generally, soils from depressions in the landscape
yielded low imazethapyr recovery by anion exchange
membrane extraction; these soils also showed low degree
of imazethapyr phytotoxicity to canola growth.
After imazethapyr field spraying, soils were sampled from
the field at different time intervals for up to one year
and analyzed in the lab by the above methods; also, after
one year, a field bioassay was performed. Using the
membrane extraction method, imazethapyr was detected only
in field samples collected one week after spraying.
The membrane extraction method, although very simple and
cost-efficient lacks sensitivity needed for the
imazethapyr presence in all field samples. However,
because crop growth inhibition was more severe in the
field than in the lab, a field bioassay may be the most
reliable means to assess injury potential for certain
sensitive rotational crops under field conditions.
