Investigation of the herbicide glyphosate and the plant growth regulators chlormequat and mepiquat in cereals produced in Denmark.

2001 
An LC-MS/MS method for analysing glyphosate and aminomethylphosphonic acid (AMPA) in cereals was developed. The method is based on extraction with water and detection of the ions from the fragmentation m/z 170→88 (glyphosate) and m/z 112→30 (AMPA) using electrospray interface in the positive mode. Investigation from the harvests of 1998 and 1999 showed residues of glyphosate and/or its degradation product AMPA in more than half of the cereal samples produced in Denmark. The average concentration of glyphosate in 46 samples from the 1999 harvest was 0.11 mg/kg compared with 0.08 mg/kg for the 1998 harvest (n = 49). Thus, the figures were well below the maximum residue limit (MRL) and no violations were observed. The plant growth regulators chlormequat and/or mepiquat were investigated in cereals from the Danish harvest of 1999 where 83% of the samples contained chlormequat (n = 46) compared with 87% of the samples from the 1997 harvest (n = 52). The average concentration of chlormequat in 1999 was 0.32 mg/kg compared with 0.23 mg/kg in 1997. At 2.9 mg/kg, one sample of wheat bran was exceeding the MRL of 2 mg/kg for wheat. The intakes of the pesticides through the diet of cereals were estimated to comprise 0.04% of the acceptable daily intake (ADI) for glyphosate and 1% of the ADI for chlormequat for an adult Dane. Le glyphosate inhibe la production de quelques acides amines essentiels pour la croissance des plantes. Son metabolite majoritaire dans la plante et le sol est l'acide aminomethylphosphonique (AMPA). Les regulateurs de croissance chlormequat et mepiquat sont aussi tres utilises au Danemark. Le chlormequat raccourcit et renforce la tige, prevenant les cereales de la verse. Cette etude a pour but de determiner les teneurs en glyphosate, AMPA, chlormequat et mepiquat dans des cereales produites au Danemark (98/99). Les resultats montrent des residus glyphosate et/ou ses produits de degradation dans plus de la moitie des echantillons, des regulateurs de croissance dans environ 85% des echantillons. Cela represente un apport alimentaire de pesticide de 0,04% de l'apport journalier acceptable pour le glyphosate et 1% pour le chlormequat.
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