Laser Desorption Dynamics of Carbendazim on a Glass Surface

A study on the desorption of carbendazim (methyl-2-benzimidazolecarbamate, mass = 191 amu) from a glass surface (Pyrex) has been carried out using an experimental set-upbased on laser desorption and laser post-ionization followed by time-of-flight massspectrometry. After optimization of the experimental conditions a resolution of ca. 850was achieved at the mass of the pesticide (191 amu). All measured time-of-flight massspectra showed not only an excellent signal to noise ratio, but also the lack of significantmolecular fragmentation, except for a mass of 71 amu which was attributed to the lateralchain of the carbendazim. Neutral time-of-flight yields were measured for several desorptionenergies. Analysis of the corresponding velocity distributions suggests a thermalmechanism dominating the laser-induced desorption. Finally the capability of thepresent technique for analytical applications is also discussed.