Published:Journal of Chromatographic Science,
ISSN 0021-9665 Volume 45,
Number 3, March 2007, pp.131-139
Analysis of Some Chlorophenoxy Acids and Carbamate
Herbicides in Water and Soil as Amide Derivatives Using Gas Chromatography–Mass
Spectrometry
A.A. Salem
Department of Chemistry, Faculty of Science, United Arab Emirates
University, Al-Ain, UAE
A newly developed method for determining three phenoxy
acids and one carbamate herbicide in water and soil samples using
gas chromatography with mass spectrometric detection is developed.
Phenoxy acids are derivatized through a condensation reaction
with a suitable aromatic amine. 1,1-Carbonyldiimidazole is used
as a condensation reagent. Derivatization conditions are optimized
with respect to the amount of analyte, amine, solvent, and derivatization
reagent. The optimum derivatization yield is accomplished in acetonitrile.
4-Methoxy aniline is used as a derivatizing agent. Obtained derivatives
are stable indefinitely. Enhancement in sensitivity is achieved
by using the single-ion monitoring mass spectrometric mode. The
effectiveness of the developed method is tested by determining
investigated compounds in water and soil samples. Analytes are
concentrated from water samples using liquid-phase extraction
and solid-phase extraction. Soil samples are extracted using methanol.
Detection limits of 1.00, 50.00, 100.00, and 1.00 ng/mL are obtained
for 2-(1-methylethoxy)phenyl methylcarbamate (Baygon), 2-(3-chlorophenoxy)-propionic
acid (Cloprop), 2,4,5-trichlorophenoxyacetic acid, and 4-(2,4-dichlorophenoxy)butyric
acid, respectively. LPE for spiked water samples yields recoveries
in the range of 60.6–95.7%, with relative standard deviation
(RSD) values of 1.07–7.85% using single component calibration
curves. Recoveries of 44.8–275.5%, with RSD values ranging
from 1.43% to 8.61% were obtained using a mixed component calibration
curves. SPE from water samples and soil samples showed low recoveries.
The reason is attributed to the weak sorption capabilities of
soil and Al2O3.
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