Ma. Locke, SUPERCRITICAL CO2 FLUID EXTRACTION OF FLUOMETURON HERBICIDE FROM SOIL, Journal of agricultural and food chemistry, 41(7), 1993, pp. 1081-1084
Soil was treated with C-14-ring-labeled fluometuron [NN-dimethyl-N-[3-
(trifluoromethyl)phenyl]ureal (0.516 and 5.16 mumol g-1), air-dried, a
nd stored for 6 months at 5-degrees-C. The C-14 was then extracted fro
m soil with methanol by conventional extraction (twice with MeOH/H2O 8
0:20 v/v; 2:1 extract/soil v/w) and with CO2 using a supercritical flu
id extractor. Supercritical fluid extraction (SFE) method development
included adding modifiers and varying CO2 fluid density, extraction te
mperature, sample mass, and extraction time. Adding H2O to modify the
sample was the single most effective variable which improved recovery.
Extraction temperatures above 50-degrees-C lowered recovery, presumab
ly because of thermal instability of fluometuron. The optiMUM CO2 dens
ity at 50-degrees-C was 0.80 g mL-1. Static extraction times greater t
han 6 min and dynamic extraction times greater than 18 min did not sig
nificantly improve recovery. Recovery using optimum SFE conditions was
comparable to that obtained using conventional methods. Extraction of
aged field samples indicated that this technology can also be used to
extract some common fluometuron metabolites.