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.
Doran
Gregory
G
CRC for Sustainable Rice Production, Farrer Centre, School of Agriculture, Charles Sturt University, Wagga Wagga 2678, NSW, Australia.
Helliwell
Stuart
S
Eberbach
Philip
P
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