Static subcritical water extraction combined with anion exchange disk sorption for determining chlorinated acid...

Static subcritical water extraction (SbWE) was coupled with collection on a strong anion exchange (SAX) disk for the determination of chlorinated acid herbicides and their esters in soil. With 100-150 degrees C water, esters were hydrolyzed into their acid form, and the herbicide acids extracted by subcritical water were trapped onto/into a SAX disk as the extraction cell was cooled. The trapped solutes were then derivatized for gas chromatographic (GC) analysis by placing the disk into a GC autosampler vial containing 1 mL of N,O-bis(trimethylsilyl)trifluoroacetamide derivatizing reagent. With the static SbWE/SAX disk extraction, nearly quantitative recoveries (typically over 80%) were obtained at 100 degrees C for 30 min in the extraction of herbicide acids and esters spiked on several different soils covering a range of organic content from 0.3 to 12%. Good agreements were reached between this method and EPA method 8151 for aged spiked soils. Detection limits of the static SbWE/SAX disk extraction were from 0.05 to 0.5 ppm and from 0.01 to 0.5 ppm using GC/electron capture detector and GC/mass spectrometry, respectively. The method is fast and simple and uses a small amount of organic solvent.