J Am Oil Chem Soc (2012) 89:389–400 connected via a heated transfer line with a Polaris Q low- resolution ion-trap mass spectrometer (Austin, TX, USA) was equipped with a Programmable Temperature Vapor- izer (PTV)-based injector and TriPlus Autosampler (Austin, TX, USA). All separations were made on 60 m 9 0.25 mm 9 0.25 mm Zb-5 MS 5%-Phenyl-Arylene-fused- silica capillary column (Phenomenex, Torrance, CA, USA) connected via a Vu2 Union connector (Restek, Bellefonte, PA, USA) to a 5 m 9 0.25 mm 9 0.25 mm guard column/ retention gap (Restek). Helium was used as a carrier gas at a constant ﬂow rates of 1 ml min-1. The GC’s oven pro- gram was as follows: initial 40 C (1 min hold)— 180 C at 25 C min-1—215 C at 2 C min-1 (1 min hold)— 255 C at 5 C min-1 (0.5 min hold)— ﬁnal 280 C at 25 C min-1 (20 min hold). Spectrometer mass calibration was tuned against perﬂuorotributylamine (FC-43) in electron-impact positive ionization mode according to the manufacturer’s recommendations. Pesticide residues in oil samples were determined using slightly modiﬁed method proposed in our previous study [12]. Brieﬂy, oil samples were extracted with acetonitrile : water mixture (1:5), cleaned up on a double layer SPE cartridges, evaporated to dryness and analyzed with gas chromatography ion trap mass spec- trometry. Neither recovery of pesticides from the analyzed spiked samples, relative recovery standard deviations, nor limits of quantiﬁcation for individual pesticides were sig- niﬁcantly different than those reported previously. Recov- ery of the analyzed pesticides from the fortiﬁed oil samples was within the 70–120% range, recovery relative standard deviation was below 20% in most cases. Pesticide recovery data are given in Table 1. Detailed analytical parameters including ionization and data acquisition methods used for pesticide determination were given previously [12]. Determination of PAHs Determinations of PAHs were conducted on a Shimadzu (Duisburg, Germany) Prominence chromatographic system equipped with an auto injector, degasser and a FLD detector was used in this study. Analysis were performed on a Pin- nacle II PAH (Restek), 4 lm, 150 mm 9 3.2 mm column operated at a ﬂow rate of 300 ll min-1. Following gradient mobile phase (A: Acetonitrile B: water) was used for separations: initial A:B 50:50—5–20 min A:B 75:25— 20–30 min A:B 78:22—30–60 min A:B 100:0—60–70 min A:B 50:50. Samples were introduced via a 10-ll loop type auto injector. PAHs were determined according to modiﬁed method proposed by Larsson et al. [13]. Brieﬂy, 10 g of oil sample was placed in a separatory funnel, dissolved in 20 ml of cyclohexane and triple-extracted with 10-ml portions of dimethylsulfoxide (DMSO). Combined DMSO extracts were mixed with 60 ml of water and re-extracted with 50 ml of petroleum ether. Petroleum phase was evaporated to 393 dryness with rotary evaporator operated at 30 C. Subse- quently dry residues were quantitatively transferred with a 3 9 1 ml portions of cyclohexane on the SPE silica gel (5 g) cartridge, pre-conditioned with 20 ml of cyclohexane. The cartridge was ﬁrst washed with 15 ml of cyclohexane and with 10 ml of dichloromethane:cyclohexane mixture (5:95 V/V). PAHs were eluted with 15 ml of dichloro- methane:cyclohexane mixture (50:50 V/V). The PAH fraction was rotary evaporated to dryness, re-dissolved in 500 ll of acetonitrile and submitted to HPLC analysis. Determination of PCBs and PBDEs Determinations were performed on the same instrument/ conﬁguration as used for pesticide residue analysis. Helium was used as the carrier gas at a constant ﬂow rate of 1 ml min-1 in PCB analysis and programmed ﬂow from 1.5 to 2.5 ml min-1 for PBDE analysis. The GC’s oven program in PCB analysis was as follows: initial 100 C (3 min hold)— 180 C at 10 C min-1—200 C at 1.7 C min-1 (2 min hold)—240 C at 1.8 C min-1 (8 min hold)—ﬁnal 280 C at 50 C min-1 (15 min hold), and for PBDE initial 80–180 C at 3 C min-1 (20 min hold)— 300 C at 5OC min-1 (21 min hold)—310 C at 10 C min-1 (41 min hold). To obtain the required sensitivity, the multiplier voltage was manually set to 1700 V, and auto- matic gain control to 15. Detailed analytical parameters including ionization and data acquisition methods used for PCB determination were given previously [14]. In the case of PBDE analysis the mass spectrometer was operated in the MS/MS mode. Helium was used as the ion- trap dumping gas (ﬂow 1.7 ml min-1 and 2.5 ml min-1 for BDE 209) analysis were conducted at 31 eV electron energy and 250 mA emission current. [M-79Br81Br]? ions were used as an MS/MS precursor ion for all studied PBDEs. [M-(279Br)81Br]?, [M-79Br(281Br)]?, [M-(279Br)81Br-2CH2]? and [M-79Br(281Br)-2CH2]? peaks were monitored in MS/ MS spectra for quantitative purposes. Determination of BDE 209 required separate ion optic lens optimization against m/z 614 of FC43 mass spectra. Ion source temperature was set to 300 C, isolation time 20 ms, excitation time 30 ms. Excitation energies required for sufﬁcient CID yield were in the 3.3–5.5 V range for tri- to deca- BDE. Xcalibur version 1.2 software was used for data acquisition and analysis. Analytical method used to determine PCBs and PBDEs was based on procedures described in our previous study [13] with some major modiﬁcations based on results of Hanxia et al. [15]. Brieﬂy, samples were spiked with 13C12 PCB recovery standards, dialyzed through LDPE semi- permeable membrane and cleaned with gel permeation chromatography as described previously. Subsequent cleanup was performed on a multilayer silica-gel-based chromatography column connected in series with short 123