Laser desorption Fourier transform ion cyclotron resonance mass spectrometry of selected pesticides extracted on C18silica solid-phase extraction membranes

Laser desorption Fourier transform ion cyclotron resonance mass spectrometry was coupled with solid-phase extraction (SPE) on C18 silica membranes for the determination of selected pesticides in water. The desorption process for hydroxyatrazine was demonstrated to take place at the surface of the membrane. The method was further investigated using other model compounds, flumequine, isoproturon and flutriafol. These three pesticides have shown a different behaviour to hydroxyatrazine when extracted on SPE membranes. Among them, only flumequine was detected at 248 nm. The use of a 355 nm laser wavelength allowed the detection of all three compounds but under more vigorous conditions leading to significant fragmentation. The unexpected behaviour at 248 nm is not clearly explained by the respective UV absorptions of the molecules at the laser wavelength but would more likely depend on different interactions with the membrane.