title: Selective pressurised liquid extraction of halogenated pesticides and polychlorinated biphenyls from pine needles.
abstract: Pine needles are an ideal matrix for the long-term monitoring of semi-volatile organic compounds in the atmosphere because they are naturally occurring and distributed worldwide. However, typical extraction methods result in the co-elution of matrix-interfering compounds and thus require time-consuming clean-up steps. A selective pressurised liquid extraction method (S-PLE) for extracting current-use pesticides, historic-use pesticides and polychlorinated biphenyls (PCBs) from pine needles that does not require additional clean-up steps was developed and validated. The selective extraction was achieved by packing the extraction vessel with a fat retainer, Florisil, down-stream of the pine needle matrix. A fat to fat-retainer ratio of 0.0057 (corresponding to 35 g of Florisil per 10 g of pine needle sample) was selected to minimise the co-elution of matrix-interfering compounds. Three 5-min extractions were performed using 25:75 (v/v) dichloromethane:n-hexane and a solvent flush of 150%. The mean recovery of spiked current-use pesticides, historic-use pesticides and PCBs using this method was 71%, 72%, and 84%, respectively. The method was validated by comparing target analyte concentrations measured in a pine needle sample using the optimised S-PLE method to those obtained using a conventional PLE method with external clean-up. The method detection limits and reproducibility were similar for the two methods; however, sample preparation time was 67% shorter when using the S-PLE method.
authors.affiliation: Department of Chemistry, University of Otago, Dunedin 9016, New Zealand.
authors.forename: Karen S
authors.initials: KS
authors.lastname: Lavin
authors.forename: Kimberly J
authors.initials: KJ
authors.lastname: Hageman
mesh_terms: D006586:Hexanes / Q000737:chemistry; D057230:Limit of Detection; D008055:Lipids / Q000737:chemistry; D059625:Liquid-Liquid Extraction / Q000379:methods*; D010575:Pesticides / Q000032:analysis / Q000302:isolation & purification*; D028223:Pinus / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry; D011078:Polychlorinated Biphenyls / Q000032:analysis / Q000302:isolation & purification*; D011312:Pressure; D015203:Reproducibility of Results
chemical_list: D006586:Hexanes; D008055:Lipids; D010575:Pesticides; C026385:n-hexane; D011078:Polychlorinated Biphenyls