Liquid-liquid microextraction methods based on ultrasound-assisted emulsification and single-drop coupled to gas chromatography-mass spectrometry for determining strobilurin and oxazole fungicides in juices and fruits

Two procedures are proposed based on ultrasound-assisted emulsification and single-drop liquid-liquid microextraction for the sensitive determination of seven strobilurin and six oxazole fungicides in fruits and juice samples. Both miniaturized techniques are coupled to gas chromatography with mass spectrometry in the selected ion monitoring mode, GC-MS(SIM). The procedures use low density organic solvents, and several factors influencing the emulsification, extraction and collection efficiency are optimized. The detection limits obtained at a signal-to-noise ratio of 3 are below the MRLs set by the European Commission. Enrichment factors are between 140-1140 for the first technique used and 80-1600 for the latter. The recoveries obtained for spiked samples are satisfactory for all compounds. The methods are validated according to the Commission Decision 2002/657/EC. Different fruit and juices are analyzed by the proposed method and none of the samples contained fungicide residues above the detection limits. (C) 2010 Elsevier B.V. All rights reserved.