Determination of phenoxyacid herbicides in drinking water at the ppt-level by liquid chromatography and on-line selective preconcentration.
On-line precolumn sample handling using an anion-exchanger is applied to preconcentrate phenoxyacid herbicides in aqueous samples prior to their LC separation. Since direct percolation of large sample volumes through the ion-exchanger has to be avoided owing to the high content of inorganic anions in natural waters, a two-step preconcentration is carried out: phenoxyacids are concentrated in their neutral (acidic) form by percolation of natural samples at pH 1 first through a precolumn packed with the copolymer-based PRP-1 sorbent. Then, the PRP-1 precolumn is coupled on-line with a second one packed with the anion-exchanger and 3 ml of deionised water with 35% of acetonitrile allows the phenoxyacids to be desorbed from the PRP-1 sorbent and reconcentrated on the anion-exchanger in their ionic form. The content of the anion-exchanger is analysed on-line by coupling with a C18 analytical column and elution is made with a water-acetonitrile gradient. Detection limits in drinking water from a 500-ml sample are between 15 and 35 ng/l (ppt) and identity of phenoxyacids is reinforced by the fact that analytes are preconcentrated by the anion-exchanger. This methodology can be fully automated.
Coquart
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Ecole Supérieure de Physique et Chimie de Paris, Laboratoire de Chimie Analytique, France.
Hennion
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D015084:2,4-Dichlorophenoxyacetic Acid / Q000032:analysis; D008456:2-Methyl-4-chlorophenoxyacetic Acid / Q000031:analogs & derivatives / Q000032:analysis; D002853:Chromatography, Liquid / Q000379:methods*; D006540:Herbicides / Q000032:analysis*; D014881:Water Supply / Q000032:analysis*
D006540:Herbicides; D015084:2,4-Dichlorophenoxyacetic Acid; C008340:mecoprop; D008456:2-Methyl-4-chlorophenoxyacetic Acid