Development of a solid-phase extraction method for phenoxy acids and bentazone in water and comparison to a liquid-liquid extraction method

A rapid solid-phase extraction (SPE) method was developed for the determina tion of bentazone and the phenoxy acids 2,4-D, dichlorprop, MCPA, and mecop rop in Norwegian environmental water samples. Cartridges with a high-capaci ty cross-linked polystyrene-based polymer were used for offline preconcentr ation. The effects of elution solvent, elution volume, sample volume, sorbe nt mass, pH, and flow rate on the recoveries of the pesticides were investi gated using HPLC. Average recovery of > 90% was achieved with 500 mg sorben ts using 2 mi of methanol with 5% NH3 as elution solvent. The recoveries we re independent of sample pH in the tested range of pH 1-7. Using a sample v olume of 200 mi, the limits of determination for the phenoxy acids and bent azone are 0.02 mug/L. Sample volumes up to 2000 mi at a flow rate of 60 mL/ min could be handled without any loss of analytes, which makes it possible to lower the limits of determination. The SPE method was compared to a rout inely used liquid-liquid extraction method. Three different water matrices spiked at 1.0 and 0.05 mug/L were extracted, and the quantification was per formed by CC-MS. Both methods permitted the determination of phenoxy acids and bentazone in distilled water, creek water, and well water down to a lev el of 0.05 mug/L with recoveries >80% for 200 mi samples. Important advanta ges of the SPE method compared to the liquid-liquid extraction method were the short extraction times, lack of emulsions, use of disposable equipment, and reduced consumption of organic solvents.