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 determination of bentazone and the phenoxy acids 2,4-D, dichlorprop, MCPA, and mecoprop in Norwegian environmental water samples. Cartridges with a high-capacity cross-linked polystyrene-based polymer were used for off-line preconcentration. The effects of elution solvent, elution volume, sample volume, sorbent mass, pH, and flow rate on the recoveries of the pesticides were investigated using HPLC. Average recovery of >90% was achieved with 500 mg sorbents using 2 mL of methanol with 5% NH3 as elution solvent. The recoveries were independent of sample pH in the tested range of pH 1-7. Using a sample volume of 200 mL, the limits of determination for the phenoxy acids and bentazone are 0.02 microg/L. Sample volumes up to 2000 mL 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 routinely used liquid-liquid extraction method. Three different water matrices spiked at 1.0 and 0.05 microg/L were extracted, and the quantification was performed by GC-MS. Both methods permitted the determination of phenoxy acids and bentazone in distilled water, creek water, and well water down to a level of 0.05 microg/L with recoveries >80% for 200 mL samples. Important advantages 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.
Thorstensen
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CW
The Norwegian Crop Research Institute, Plant Protection Centre, Department of Plant Pathology, Hogskoleveien 7, 1432 As, Norway. christian.thorstensen@planteforsk.no
Lode
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Christiansen
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D001581:Benzothiadiazines / Q000032:analysis*; D002853:Chromatography, Liquid / Q000379:methods; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006016:Glycolates / Q000032:analysis*; D006540:Herbicides / Q000032:analysis*; D010573:Pesticide Residues / Q000032:analysis*; D014867:Water / Q000737:chemistry*
D001581:Benzothiadiazines; D006016:Glycolates; D006540:Herbicides; D010573:Pesticide Residues; D014867:Water; C002003:bentazone