ABSTRACT
The usefulness of the potassium tert-butoxide/dimethyl sulphoxide/ethyl iodide reaction with carbamate and phenylurea herbicides, and its application to phenoxy acids as a way to prevent hazards and toxicity of the sodium hydride/dimethyl sulphoxide/methyl iodide reaction was studied. Using factorial design optimization of this reaction was carried out. A solid-phase extraction method using dimethyl sulphoxide as eluent on-line with this reaction was developed to determine these herbicides in water samples by gas chromatography-mass spectrometry. Relative standard deviation values were lower than 10% for most of the herbicides in multicomponent trace determinations. Detection limits were in the 0.110-0.652 ng L(-1) concentration range. The validity of the method was confirmed by recovery studies from natural water samples.
Subject(s)
Butanols/chemistry , Carbamates/chemistry , Chromatography, Gas/methods , Dimethyl Sulfoxide/chemistry , Herbicides/chemistry , Carbamates/analysis , Herbicides/analysis , Molecular Structure , Pesticide Residues/analysis , Pesticide Residues/chemistry , Phenylurea Compounds/analysis , Phenylurea Compounds/chemistry , Reproducibility of Results , Water Pollutants, Chemical/analysis , Water Pollutants, Chemical/chemistryABSTRACT
A deep revision of the carbamate methyl derivatization reaction with sodium hydride/dimethyl sulfoxide/methyl iodide was carried out. Representative carbamates, R(1)-NH-COO-R(2), mainly N-methyl and N-aryl ones, have been studied in order to clarify which carbamates undergo this reaction. Two possible reaction routes are proposed; the route depends on the carbamate substituent (-OR(2) group) more than on the methyl or aryl groups joined to the NH moiety as literature indicates. The classification of carbamates in N-methyl and N-aryl is not suitable to predict the methylation pathway. A laboratory-made closed reactor allows handling the reagents involved, minimizing hazards and simplifying the procedure for rapid analysis.
Subject(s)
Carbamates/analysis , Chromatography, Gas/methods , Dimethyl Sulfoxide/chemistry , Hydrocarbons, Iodinated/chemistry , Carbamates/chemistry , Molecular Structure , Reproducibility of ResultsABSTRACT
An analytic method for the determination of phenoxy acid herbicides and 2,4-D esters in soil samples by GC-FID is described. The esterification reaction with MeOH and H(2)SO(4) as catalyst has been used, optimizing experimental variables by the 'Simplex method'. The recoveries in soil samples were between 76 and 97% with relative S.D.s between 4 and 7% (n=4) at level of concentration of 5 and 10 mug ml(-1) for phenoxy acids and 2,4-D esters, respectively.
