title: Selective enrichment of 17 pyrethroids from lyophilised agricultural samples.
abstract: The screening of agricultural samples to determine 17 synthetic pyrethroids was investigated. Samples were lyophilised without losses of the insecticides, and then extracted with n-hexane. A simple, continuous preconcentration-elution system was developed, which included a silica sorbent column (packed with 50 mg) and used an air stream to carry the eluent (ethyl acetate) which minimised the eluate volume thus increasing the preconcentration factor; so no evaporation step was required. Pyrethroids were determined by gas chromatography-electron capture detection (GC-ECD) by using a 5% phenylmethylpolysiloxane-coated fused-silica capillary column; gas chromatography-mass spectrometry was used to identify the pyrethroids detected by GC-ECD monitoring. Limits of detection varied between 0.1 and 0.8 ng/ml (except for piperonyl butoxide, 25 ng/ml) with linear ranges from 1 to 200 ng/ml; the precision of the method was high (3-6%). Recoveries of 17 insecticides from 14 different agricultural samples fortified at levels of 20-100 ng/g ranged from 66 to 102% (bifenthrin and deltamethrin were those providing the lowest values, 66-87%). Pyrethroids were detected in eight samples (from the 100 unfortified agricultural samples tested) at concentrations lower than the established maximum residue limits (MRLs).
authors: Analytical Chemistry Division, University of Córdoba, Spain.
authors: A
authors: A
authors: Columé
authors: S
authors: S
authors: Cárdenas
authors: M
authors: M
authors: Gallego
authors: M
authors: M
authors: Valcárcel
mesh_terms: D002849:Chromatography, Gas / Q000379:methods; D005612:Freeze Drying; D005638:Fruit / Q000737:chemistry*; D011722:Pyrethrins / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014675:Vegetables / Q000737:chemistry*
chemical_list: D011722:Pyrethrins