In situ derivatization-supercritical fluid extraction method for the determination of chlorophenoxy acid herbicides in soil samples

• Main Authors: Lopez-Avila, V. (Midwest Research Institute, Mountain View, CA.), Benedicto, J, Beckert, W.F
• Format: Book
• Language: English
• Published: Washington, D.C. (USA) American Chemical Society 1996
• Subjects: HERBICIDAS; HERBICIDE; SOL; SUELO
• ISBN: 0841234051; 9780841234055

This paper describes an in-situ derivatization/supercritical fluid extraction (SFE) procedure for 11 chlorophenoxy acid herbicides from a soil matrix. Soil samples (freshly spiked or spiked and weathered soils) are amended with pentafluorobenzyl bromide (PFBBr) and triethyl amine (TEA), prior to SFE, and are pressurized (static) with supercritical carbon dioxide at 400 atm/100 degrees C for 60 min. During this time, the acids are converted to their corresponding PFB esters, which are very soluble in carbon dioxide, and thus, easily extracted from the soil matrix. During a 30-min dynamic extraction, the esters are collected in acetone or on a C18-bonded silica trap and subsequently rinsed off the trap with acetone. The acetone extract is subjected to silica chromatography to remove the excess reagents and analyzed by gas chromatography with electron capture detection. Single-laboratory data and some results of a collaborative study are presented here