In this work a study of several variables that affect the matrix effects (ME) was performed. The choice was given among four extraction solvents and four different clean-up methods which were compared in order to find the method that produces least ME and gives the highest response for 18 compounds. Variability of ME under identical chromatographic conditions for five fruits was also studied. Finally we evaluated different analyte/matrix ratios to assess the ME. The results showed that the significantly better responses (P < 0.05) were achieved by using the mixture of three absorbents and the use of only Graphitized Carbon Black causes greater suppression of ionization. From the five matrices tested it was found that grapes and tomatoes extract induced a larger ME, meanwhile the use of apple and mango matrices gave responses more like matrix-free standards. Finally, a negative correlation between the suppression of ionization and the compound/matrix ratio was found.
pesticides; mass spectrometry; liquid chromatography; matrix effect
