Extraction of glyphosate herbicide from soil and clay minerals and determination of residues in soils

Abstract

Extraction of the herbicide glyphosate [N-(phosphonomethyl)glycine] from clay minerals and two soils was studied by a batch equilibrium technique. Experiments showed that, for most of the sorbent/solvent systems studied, the amount of herbicide extracted increased as pH increased, suggesting that sorption occurs through ion exchange and hydrogen bonding. Alkaline solutions of kaolinite, iron oxide, and two Calvin silt loam soil samples showed resorption of glyphosate after an initial desorption step. Determination of glyphosate residues in soils was performed by derivatization of soil extracts with 9-fluorenylmethyl chloroformate and analysis by HPLC with fluorometric detection. Glyphosate was successfully recovered from sandy soils at 0.5 ppm by triplicate extraction with 0.

Adsorption of glyphosate in chilean soils and its relationship with unoccupied phosphate binding sites

“…As clay content is also a factor that has been reported affecting glyphosate adsorption, it can be thought that adsorption should be higher in the case of Chicureo soil that has a higher clay content than Clarillo soil. However, it seems like clay type is more important than its percent content (Sprankle et al, 1975a;McConnell & Hossner, 1985;Glass, 1987;Miles & Moye, 1988). The predominant clay type found in Chicureo soil is montmorillonite (2:1 form) while in the Clarillo soil, due to its more recent formation, there is a mixture of 2:1 and 1:1 (kaolinite) clays and probably, some alophan.…”

“…Ion exchange and hydrogen bonding can explain glyphosate soil adsorption (Miles & Moye, 1988). However, glyphosate soil adsorption could be also variable and, in some cases, not as high as supposed.…”

Comportamento do glifosato no solo e deslocamento miscível de atrazina

“…Essa interação está relacionada aos valores de K ow da molécula e é de fundamental importância para a sorção de pesticidas hidrofóbicos não iônicos (Koskinen & Harper, 1990;Prata et al, 2000a (Jonge et al, 2001). A relação entre as altas taxas de sorção do glifosato e a capacidade dos solos em adsorver fosfatos foi apontada por vários autores (Hance et al, 1976;Glass, 1987;Miles & Moye, 1988;Gerritse et al, 1996;Jonge et al, 2001). Jonge et al (2001) mostraram ter havido adsorção competitiva entre o glifosato e o P inorgânico, mas, entretanto, embora observado um decréscimo nos valores de K f (coeficiente de Freundlich para sorção) do herbicida, os valores ainda continuavam muito elevados.…”

“…O comportamento do glifosato no solo tem sido tema de várias pesquisas (Nomura & Hilton, 1977;Glass, 1987;Miles & Moye, 1988;Gerritse et al, 1996;Cheah et al, 1997;Prata et al, 2000b;Jonge et al 2001). De forma geral, essas pesquisas caracterizam o herbicida pela sua elevada capacidade de sorção, a qual impede sua degradação na solução do solo.…”

Métodos de extração e determinação do herbicida glifosato: breve revisão

“…A etapa de derivação do glifosato pode ser efetuada de forma direta em amostras de solo com FMOC-Cl em acetona por 20 min 10 . Os derivados obtidos foram posteriormente extraídos em acetato de etila ou éter, realizando separação cromatográfica em coluna de NH 2 e eluindo com tampão KH 2 PO 4 (pH 6) e acetonitrila.…”