Determination of herbicide residues by Laser Microprobe Mass Analysis (LAMMA)

Diffusion of herbicide residues and derived substances in ecosystems can arise from agrochemical treatments, depending on environmental interactions and the chemical characteristics of the parent molecules and their degradation products. As adsorption phenomena affect both herbicide residues and their metabolites, a complete extraction and identification of them is very difficult with traditional methods. Laser ablation could be an effective system of analysis of herbicides on solid surfaces (soil, leaves) especially in the presence of degraded residues and several by-products. Acifluorfen, a diphenylether herbicide, and rimsulfuron, a sulfonylurea herbicide, were irradiated with a Nd:YAG laser at 266 nm. The decomposition fragments were detected by using a time-of-flight mass spectrometer. This technique allows the identification of stable ions useful for a better determination of the analytes. Fragments derived from a decarboxylation reaction and cleavage of the ether function of acifluorfen were obtained. In the case of rimsulfuron, fragments deriving from the pyrimidine ring, such as 2-amino-4,6-dimethoxypyrimidine, were detected.