Determination of halogenated solvents content in olive oil by two completely automated headspace techniques coupled to gas chromatography-mass spectrometry

Two different methods have been developed and compared for determining the halogenated solvents content of olive oils. The optimal parameters for isolation and preconcentration of relevant halogenated solvents (bromodichloromethane, dibromochloromethane, chloroform, bromoform, tetrachloroethene, trichloroethene, ethylenedichloride, and vinyl chloride) were established. These proposed procedures are completely automated and do not require reagents because both methods are based on headspace techniques, conventional headspace (HS) and headspace solid-phase microextraction (HS-SPME), both techniques on-line coupled to a gas chromatograph-mass spectrometer (GC-MS) operated in selected ion monitoring (SIM) mode. The methods were validated and compared their figures of merit. In general, both extraction techniques presented similar extraction efficiency at the studied concentrations. However, average relative standard deviation (R.S.D.) obtained at low concentration levels was slightly better for HS (8.6%) than for HS-SPME (11.8%) technique. It was due to the lower limits of detection (LOD) and quantification (LOQ) values obtained for HS, especially for the less volatile vinyl chloride, chloroform and ethylene dichloride compounds. Finally, the HS-GC-MS method was applied to the analysis of real olive oil and olive-pomace oil samples. None content of halogenated solvents was found above the LOD in the studied samples. The proposed methods are faster, simpler and easier than the official methods proposed by the European Union and the International Olive Oil Council.