Multiresidue analysis and evaluation of the matrix effect on 20 pesticides in Brazilian maize ( Zea mays L.) flour.

Maize consists of a cereal widely used in the preparation of different food products. Brazil is one of the world's largest maize producers. Several types of pesticides have been applied in maize crop, which can lead to the contamination of the derived products. The present work aims at the validation of multiresidue method to analyze the matrix effect and level of pesticides in maize flour. Twenty residues were investigated in samples commercialized in the state of Ceara, Brazil. The method was satisfactorily validated, according to parameters recommended by European Union. About 55% of the pesticides had an intense negative matrix effect. Multiresidue analyzes showed the presence of traces of fenitrotion in 20% of maize flour samples. Detected levels were below maximum residue limits recommended for maize. The results indicate that maize products need continuous monitoring to ensure food security.