COMPARISON OF SUPERCRITICAL-FLUID EXTRACTION (SFE), SOXHLET AND SHAKING METHODS FOR PENDIMETHALIN EXTRACTION FROM SOILS - EFFECT OF SOIL PROPERTIES AND WATER-CONTENT
L. Spack et al., COMPARISON OF SUPERCRITICAL-FLUID EXTRACTION (SFE), SOXHLET AND SHAKING METHODS FOR PENDIMETHALIN EXTRACTION FROM SOILS - EFFECT OF SOIL PROPERTIES AND WATER-CONTENT, Journal of contaminant hydrology, 33(1-2), 1998, pp. 171-185
Citations number
23
Categorie Soggetti
Water Resources","Environmental Sciences","Geosciences, Interdisciplinary
Supercritical fluid extraction with CO2 was applied to the analysis of
traces of pendimethalin, a herbicide of the dinitroanilines group, in
four different natural soils. The Supercritical Fluid Extraction (SFE
) method was compared with the classical Soxhlet and shaking methods i
n terms of ease to run, extraction efficiency, selectivity and reprodu
cibility. The influence of the physico-chemical properties of the soil
matrix on herbicide extraction was then evaluated with the SFE method
. The supercritical fluid extraction system used in the present study
was found to be much easier to run than the other two methods, less ti
me consuming and requires fewer operations as it was optimized for on-
line sample clean up. SFE is the most selective of the three tested me
thods as fewer co-extracts are obtained in the final samples. SFE with
CO2 is particularly powerful because pendimethalin is highly hydropho
bic. However, this makes pendimethalin a poor choice for a selectivity
study of SFE as it is very rapidly extracted at any CO2 density. Pend
imethalin extraction with supercritical CO2 was found to be almost com
plete with average recoveries of 96-99%, similarly to Soxhlet but with
a much lower standard deviation (8-10%). The performance of SFE was s
hown to be unaffected by soil parameters except soil water content. It
is demonstrated indeed that extraction efficiency is not linearly rel
ated to soil water content, and optimal recovery was found for water c
ontents ranging from 2 to 15% depending on the type of soil. Soil wate
r increases extraction efficiency because water acts as a modifier of
the supercritical fluid and increases the penetration of the fluid ins
ide the soil particles (clay swelling). In contrast to SFE and Soxhlet
, the efficiency of the shaking method appeared to be partial and stro
ngly dependent on soil properties. Although initial developments shoul
d be needed, the various benefits of SFE-CO2 make this method attracti
ve compared to traditional methods. (C) 1998 Elsevier Science B.V. All
rights reserved.