title: Isotope dilution determination of polycyclic aromatic hydrocarbons in olive pomace oil by gas chromatography-mass spectrometry.
abstract: A gas chromatographic (GC) method with mass spectrometry detection (MS) for the determination of eight polycyclic aromatic hydrocarbons (PAHs) in olive pomace oil has been developed. The oil was diluted with n-pentane and extracted by liquid-liquid partition with dimethyl sulphoxide (DMSO). After water addition and back-extraction with cyclohexane, a thin-layer chromatography on silica gel was performed as a further purification step. The PAHs spot was scraped off from the plate and the final extract was concentrated and analysed by GC-MS in full scan mode. The eight PAHs under investigation were determined in the presence of the corresponding labelled compounds added as internal standards to the sample at the beginning of the analytical process. The identified PAHs were then quantified by the isotope dilution methodology assuring the compensation of the concentration of each analyte for any variation in the sample preparation. The method precision was satisfactory with relative standard deviation (R.S.D.) values in the range 3.6-12.7% for all PAHs. The average recovery rates ranged from 69.0 to 97.5%. Accuracy was also calculated for benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene by analysing a certified reference material (CRM 458, coconut oil) with adequate results. All response curves exhibited a linear fit from 0.1 to 10 microg ml(-1) and the determination coefficients R2 were better than 0.9942. The limits of detection (0.1-0.4 microg kg(-1)) were acceptable when compared with the maximum permitted limit of 2 microg kg(-1) for each of the eight considered PAHs and 5 microg kg(-1) for the sum of the eight PAHs established by the Italian legislation. Measurement uncertainty was finally calculated identifying and quantifying the uncertainty components of the analytical process. The relative expanded uncertainties (Uc), expressed as percent values were in the range 8.5-11.4% thus appropriate for residues quantification in the range of concentrations considered in the present study.
authors.affiliation: Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Via Campo Boario, 64100 Teramo, Italy.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Diletti
authors.forename: Giampiero
authors.initials: G
authors.lastname: Scortichini
authors.forename: Rossana
authors.initials: R
authors.lastname: Scarpone
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Gatti
authors.forename: Luigi
authors.initials: L
authors.lastname: Torreti
authors.forename: Giacomo
authors.initials: G
authors.lastname: Migliorati
mesh_terms: D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D007554:Isotopes; D000069463:Olive Oil; D010938:Plant Oils / Q000737:chemistry*; D011083:Polycyclic Compounds / Q000032:analysis*; D012015:Reference Standards; D012680:Sensitivity and Specificity
chemical_list: D007554:Isotopes; D000069463:Olive Oil; D010938:Plant Oils; D011083:Polycyclic Compounds