title: Determination of Acid Herbicides Using Modified QuEChERS with Fast Switching ESI(+)/ESI(-) LC-MS/MS.
abstract: A method for the determination of 35 acid herbicides in food matrices was developed, validated, and implemented. It utilizes a modified QuEChERS extraction procedure coupled with quantitation by liquid chromatography tandem mass spectrometry (LC-MS/MS). The acid herbicides analyzed are all organic carboxylic acids, including the older chlorophenoxy acid herbicides such as 2,4-dichlorophenoxyacetic acid (2,4-D), dicamba, 4-chlorophenoxyacetic acid (4-CPA), quinclorac, and many of the newer imidazolinone herbicides such as imazethapyr and imazaquin. In the procedure, 10 mL of water is added to 5 g of sample and then extracted with 1% formic acid in acetonitrile for 1 min. The acetonitrile phase is salted out of the extract by adding sodium chloride and magnesium sulfate, followed by centrifugation. The acetonitrile is diluted 1:1 with water to enable quantitation by LC-MS/MS using fast switching between positive and negative electrospray ionization modes. The average recoveries for all the compounds except aminocyclopyrachlor were 95% with a precision of 8%. The method detection limits for all residues were less than 10 ng/g, and the correlation coefficients for the calibration curves was greater than 0.99 for all but two compounds tested. The method was used successfully for the quantitation of acid herbicides in the FDA's total diet study. The procedure proved to be accurate, precise, linear, sensitive, and rugged.
authors.affiliation: U.S. Food and Drug Administration , 11510 West 80th Street, Lenexa, Kansas 66224, United States.
authors.forename: Chris
authors.initials: C
authors.lastname: Sack
authors.affiliation: U.S. Food and Drug Administration , 11510 West 80th Street, Lenexa, Kansas 66224, United States.
authors.forename: John
authors.initials: J
authors.lastname: Vonderbrink
authors.affiliation: U.S. Food and Drug Administration , 11510 West 80th Street, Lenexa, Kansas 66224, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Smoker
authors.affiliation: U.S. Food and Drug Administration , 11510 West 80th Street, Lenexa, Kansas 66224, United States.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Smith
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005506:Food Contamination / Q000032:analysis; D006540:Herbicides / Q000737:chemistry* / Q000302:isolation & purification*; D010573:Pesticide Residues / Q000737:chemistry* / Q000302:isolation & purification*; D052616:Solid Phase Extraction / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D006540:Herbicides; D010573:Pesticide Residues
keywords: LC-MS/MS; QuEChERS; acid herbicides; chlorophenoxy acid herbicides; imidazolinone herbicides