Investigation of matrix effects for some pesticides in waters by on-line solid-phase extraction-liquid chromatography coupled with triple quadrupole linear ion-trap mass spectrometry and the use of postcolumn introduction.

The effect of analytical conditions on on-line SPE-LC/MS/MS was investigated. Real matrix-induced signal suppression or enhancement due to the ionization process was simulated by using postcolumn introduction experiments. Results were compared with global matrix effects that occur during a routine analysis. Four pesticides were studied: carbendazim, fenuron, thiabendazole, and vamidothion. These compounds have different behaviors in terms of matrix effects. Good correlations were shown, demonstrating that the main matrix effect is due to the ionization step. Good results were also obtained for the RSD values (< 5% for routine analysis and < 35% for postcolumn introduction).