Determination of ariloxyphenoxypropionic acid herbicides in waters using different solid phase extraction procedures and Liquid Chromatography-Diode Array Detector.

For isolation and trace enrichment of aryloxyphenoxypropionic acid (ArPP) herbicides from drinking, spring, and ground water a sensitive, robust method is presented. A 1-2 1 volume of aqueous samples was passed through a disposable solid-phase extraction cartridge, packed with 500 mg of Carbograph-1 at a flow-rate of 100 ml/min. After washing, ArPPs are selectively eluted with 8 mi of dichloromethane-methanol (80:20, v/v) with 50 mmol/l formic acid and evaporated to dryness. The mixture was reconstituted with 250 mu l of water-acetonitrile (75:25, v/v) acidified with 0.1% trifluoroacetic acid and 100 mu l was injected into the high-performance liquid chromatography system. The ArPPs were separated via a binary gradient of water and a mixture of methanol-acetonitrile. Detection and confirmation were performed by diode array detection. Recovery of the six acid herbicides ranged between 90% and 98%. The limits of detection of ArPPs were 7-20 ng/l for drinking water and 16-36 ng/l for spring water. In terms of recovery and selectivity the effectiveness of Carbograph-1 cartridges was compared with that of LiChrolut-EN cartridges and polystyrene-divinylbenzene Empore disks. Relevant parameters such as pH and flow-rate for solid-phase extraction with divinylbenzene resins were optimized.