For the organic extracts of grape the same behaviour is observed, but there is less variation in absorbance related to pH, since this extract has a lighter colour than the tomato extract. For the pineapple extracts this difference is quite small, since the extract obtained is very limpid. Based on these results we can conclude that the pH affects the extraction of the co-extractives of the samples, showing that the pineapple, tomato and grape matrices that have low pH values, presented higher matrix effects. The chemometric analysis using PCA proved to be a useful tool in studying the effect of co-extractives of seven matrices in chromatographic response of eleven pesticides.

The co-extractives of the tomato, grape and pineapple matrices caused a positive matrix effect in the analysis of the pesticides and selleck kinase inhibitor were grouped. The apple, potato and water matrices caused small matrix effect. The soil matrix caused a negative matrix effect for most pesticides and was well separated from other matrices by principal component analysis. The influence of pH on the matrix effect was also evaluated. Organic extracts obtained from water samples with low pH led to a reduction in the chromatographic response of pesticides. The reduction was of the same order of magnitude

of pure water samples, showing that the pH of the samples does not directly influence the matrix effect. However, by increasing the pH of the more acidic samples, less co-extractives are extracted to the organic phase. Thus it was concluded that pH influence the matrix effect beta-catenin mutation favoring or not the extraction of the co-extractives of the samples not interfering directly in the properties of pesticides. We thank the Brazilian Agencies: Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) and Coordenação de Aperfeiçoamento Carnitine palmitoyltransferase II de Pessoal de Nível Superior (CAPES) for their financial support. “
“Original from the east, Mangifera

indica is an exotic tree that was very well adapted in Brazil. It is considered one of the best tropical fruit, popularly known as mango. Ethnobotanical studies indicate that M. indica is widely used in Brazil to treat back ache and bronchitis ( Albuquerque et al., 2007). The use of medicinal plants is a direct consequence of ancient habits involving the search of natural healing against sickness and pathologies. These plants have active substances in their composition with high therapeutic potential. The essential oils, like some of those substances, are extremely powerful. The solid phase microextraction (SPME) is an efficient technique used on the extraction of volatile oils. Introduced by Arthur and Pawliszyn (1990), it is a solvent-free sample preparation technique for the extraction of volatile and semi volatile compounds ( Bicchi et al., 2007 and Cavalli et al., 2003).