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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


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.