Determination of carbamate residues in fruits and vegetables by matrix solid-phase dispersion and liquid chromatography-mass spectrometry
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Thirteen carbamates were analysed in orange, grape, onion and tomatoes by matrix solid-phase dispersion (MSPD) followed by liquid chromatography-mass spectrometry (LC-MS). Electrospray (ES) and atmospheric pressure chemical ionisation (APCI) were compared and both gave similar results in terms of sensitivity and structural information because at 20 V fragmentor voltages the fragmentation is minimal. The efficiency of different solid-phases (C-18, C-8, cyano, amine and phenyl) for the MSPD was compared. Mean recoveries using C-8 varied from 64 to 106% with relative standard deviations of 5-15% in the concentration range of 0.01-10 mg/kg. Matrix constituents did not interfere significantly with the ionisation process of carbamates. The limits of detection were typically in the 0.001-0.01 mg/kg range, which were between 10 and 100 times lower than the maximum residue levels (MRLs) established by the European Union (EU). The method was applied to residue detection in fruit and vegetable samples taken from Valencian markets, in which carbamates were detected at low concentrations.