Trace analysis of 2,4,5,TP and other acidic herbicides in wheat using multicolumn-HPLC

In continuation of our work dealing with multicolumn HPLC (MC-HPLC) techniques and their applicabilities for tracing a few compounds out of complex multicomponent matrices a residue analysis of the herbicides 2,4,5T and MCPA (phenoxyacids) in wheat is described. A simple plant extract with aqueous basic buffer is loaded in quantities of several 100 microliters onto a strong anion exchanger (column 1,C1) performing extraction of the acidic compounds, while the neutral and cationic substances are eluted thus attaining on-column trace enrichment. Via mobile phase selection (pH change) elution from C1 is possible, the fraction (zone-cut) containing the compounds of interest is transferred onto C2 (reversed phase, RP2 and RP18) on which peak compression is performed followed by (step)gradient elution. Detection limits in the lower ppb range are routinely obtained. A MC-HPLC chromatographic setup separation of eleven acidic herbicides in a formulation is also shown.