Sorption-catalytic determination of imazapyr on a copper-containing sorbent

Sorption of copper on filter-paper with chemically attached hexamethylenedi amino-groups (HMDA-filter) allows to obtain the sorbent (Clu/HMDA-filter) s table in respect to desorption of copper. A nitrogen-containing herbicide i mazapyr (imaz) is retained on Cu/HMDA-filters at pH 5.5-7.0 forming a relat ively stable complex. Imazapyr is determined directly on the sorbent by its activating effect in the oxidation of hydroquinone with H2O2 catalyzed by Cu(II) with the formation of a product absorbing at 490 nm. The copper ions serve both to preconcentrate imazapyr and to catalyze the indicator reacti on. The use of 1-muL sample aliquots pipetted onto the Cu/HMDA-filters allo ws to determine 1 x 10(-3) -0.03 mu mol of imazapyr, whereas preconcentrati on of the analyte by pumping of its solution through the same sorbent expan ds the linear range to 1 x 10(-4) -1 x 10(-1) mu mol of imazapyr. When the indicator reaction is carried out in solution, the range of activating acti on of imazapyr is narrower (0.06-0.1 mu mol a for a solution volume of 10 m L). The determination is selective: 5-100-fold amounts of amines, aminoacid s, carboxylic acid derivatives and other model compounds do not interfere. Soil extracts and carrot juice samples spiked with imazapyr have been analy zed.