Xw. Lou et al., Static subcritical water extraction combined with anion exchange disk sorption for determining chlorinated acid herbicides in soil, ANALYT CHEM, 72(3), 2000, pp. 481-488
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 chromatograph
ic (GC) analysis by placing the disk into a GC autosampler vial containing
1 mL of N,O-bis(trimethylsilyl)trifluoroacetamide derivatizing reagent. Wit
h the static SbWE/SAX disk extraction, nearly quantitative recoveries (typi
cally 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 bet
ween this method and EPA method 8151 for aged spiked soils. Detection limit
s 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 spectrometr
y, respectively. The method is fast and simple and uses a small amount of o
rganic solvent.