Extraction of fipronil and thiobencarb from anaerobic water samples using solid-phase extraction.
Anaerobic water samples containing levels of soluble Fe(II) may form insoluble Fe(III) particulates that could hinder subsequent extraction and analysis. Solid-phase extraction (SPE) cartridges could become blocked by this material, reducing the volume that can be processed. The ability of ascorbic acid to reduce these Fe(III) colloids and/or to prevent further oxidation of Fe(II) by dissolved oxygen during sampling was investigated and compared to sample stabilization with hydrochloric acid. Ascorbic acid (5%, w/v) proved the most effective treatment because it prevented 95% of the dissolved iron in the sample from precipitating during processing, compared to 40% in untreated samples. The effect of ascorbic acid addition on degradation of 2 rice pesticides, fipronil and thiobencarb, was investigated and compared to degradation rates in water. Pesticide reduction by ascorbic acid over a 3 h period was insignificant compared to the natural degradation occurring in deionized water. While this method was shown to increase sample processing time, it also allowed the processing of large-volume anaerobic water samples (150 mL) that were previously not extractable due to rapid obstruction of the SPE cartridge.
CRC for Sustainable Rice Production, Farrer Centre, School of Agriculture, Charles Sturt University, Wagga Wagga 2678, NSW, Australia.
Gregory
G
Doran
Stuart
S
Helliwell
Philip
P
Eberbach
D001205:Ascorbic Acid / Q000032:analysis; D002849:Chromatography, Gas; D003102:Colloids; D004305:Dose-Response Relationship, Drug; D006540:Herbicides / Q000032:analysis; D006851:Hydrochloric Acid / Q000032:analysis / Q000737:chemistry; D007306:Insecticides / Q000032:analysis; D007501:Iron / Q000032:analysis; D010100:Oxygen / Q000032:analysis / Q000737:chemistry; D010573:Pesticide Residues / Q000032:analysis; D010575:Pesticides / Q000032:analysis; D011720:Pyrazoles / Q000032:analysis*; D013859:Thiocarbamates / Q000032:analysis*; D013997:Time Factors; D014867:Water / Q000032:analysis*; D014874:Water Pollutants, Chemical
D003102:Colloids; D006540:Herbicides; D007306:Insecticides; D010573:Pesticide Residues; D010575:Pesticides; D011720:Pyrazoles; D013859:Thiocarbamates; D014874:Water Pollutants, Chemical; D014867:Water; C037925:benthiocarb; D007501:Iron; D001205:Ascorbic Acid; C082360:fipronil; D006851:Hydrochloric Acid; D010100:Oxygen