394 silver nitrate silica gel column (1 g 10% w/w). GPC- cleaned-up samples (after solvent exchange to n-hexane) were loaded on the columns and eluted with 30 ml of dichloromethane:n-hexane mixture (2:98 V/V). Subse- quently only second silver nitrate column was eluted with 25 ml of a dichloromethane:n-hexane mixture (50:50 V/V). First fraction contained PCBs and the second PBDEs. PCB fraction was subsequently fractionated using short (10 9 100 mm) Florisil column containing 2 g of activated Florisil. PCB fraction was evaporated to dryness and quantitatively transferred on the top of Florisil column with 2 9 1 ml portions of n-hexane. Florisil column was ﬁrst eluted with 30 ml of dichloromethane:n-hexane mixture (0.5:99.5) (fraction containing ortho-substituted PCBs) and then with 25 ml of 50% dichloromethane : n-hexane mix- ture (fraction containing non-ortho substituted PCBs). PCB fractions were evaporated to dryness, spiked with injection standards, re-dissolved in 1 ml of n-hexane and submitted for GC/MS/MS analysis. GC/MS method used for PCB analysis was based on those reported previously [14] with modiﬁcation of sample introduction technique. Inject-ions were made into cold (60 C) PTV injector bafﬂe liner. A total of 40 ll of puriﬁed and concentrated extract was introduced into the PTV injector (10 ll s-1) working in the solvent split mode (with split valve set 200 ml min-1). After 1 min, the split valve was closed and the injector temperature was ramped to 280 C and held for 2 min. Next, the injector temperature was increased to 320 C (10 min hold) and the split valve was opened with ﬂow rate set to 100 ml min-1 to eliminate any residual high boiling contaminants out of the injector system. The PBDE fraction was re-dissolved in n-hexane, spiked with injection standards and concentrated to an approxi- mate volume of 100 ll under a gentle stream of nitrogen. The sample was introduced into GC/MS using the standard purged-splitless injection technique into a straight glass liner (2 mm ID). Injector was operated at 320 C and helium pressure of 480 kPa was applied. A total of 6 ll of puriﬁed and concentrated extract was introduced into the PTV injector (10 ll s-1). Splitless time was set to 2 min. The carrier gas ﬂow rate (not including initial ramp due to purged injection) was programmed starting from 1.5 ml min-1 (50 min hold), to 2.5 ml min-1 (40 min hold) and subsequently to 1.5 ml min-1. Data Analysis Results are given as a mean value of two parallel deter- minations (±one standard deviation, if given) of the composite laboratory sample (prepared from three different oils mixed at equal proportions). TEQs for individual PCBs were calculated using WHO 1998 published factors [16]. For each sample total TEQ value was calculated as the sum 123 J Am Oil Chem Soc (2012) 89:389–400 of individual TEQs of all dl-PCBs. Lower-bound, medium- bound, and upper-bound results have been reported in line with Commission Regulation 1883/2006 [17]. Data in Table 8 were also calculated using the revised TEF 2005 values [18]. Results and Discussion There is scarcely any literature data concerning the pres- ence of chemical contaminants in cold-pressed vegetable oils. The present study revealed that pesticides, PAHs, PCBs and PBDEs were present in the cold pressed oils at varying concentration levels. Pesticides Concentrations of pesticide residues found in the studied cold-pressed vegetable oil samples are given in Table 4. The results are quite surprising. Five out of 8 of the com- posite oil samples studied showed detectable amounts of pesticide residues. Mostly organophosphorus insecticide residues (Pirimiphos methyl, Chlorpyrifos methyl, DDVP) were found. DDT isomers and Triﬂuralin herbicide were determined in pumpkinseed oil. DDT is on the Stockholm persistent organic pollutant (POP) list and its presence in oil samples is most likely related to the environmental POPs background level. The highest total concentration of pesticides was found in the Linaire oil sample, with pir- imiphos methyl concentration at the 1.170 mg kg-1 level. European Union legislation does not recognize any maxi- mum residue levels (MRLs) for the determined compound/ investigated oil combinations. Nevertheless, the concen- trations are very high when compared to MRLs deﬁned for oil seeds (0.05 mg kg-1 for sum of DDT isomers, 0.05 mg kg-1 for pirimiphos methyl, 0.01 mg kg-1 for DDVP, 0.1 mg kg-1 for triﬂuralin, 0.05 mg kg-1 for chlorpyrifos methyl). Those MRLs were exceeded in the majority of the tested samples. A typical chromatogram of a vegetable oil sample is shown in Fig. 1. Pesticide residue levels found in the oil samples are probably among the most unexpected results. Organophosphorus (OPPs) insecticides are commonly used in agriculture for protec- tion of oily plants. Most probably this fact is responsible for the presence of those compounds in cold-pressed veg- etable oils. Most of OPPs are fat-soluble and might be easily stored in oil seeds. What’s more, fats—as energy reserves for oil seeds—may be not subject to metabolic pathways that could affect OPPs. This hypothesis might also explain the very high concentrations of OPPs deter- mined in the samples. Persistence of organophosphorus insecticides in vegetable oils was also reported previously [19]. Due to speciﬁc ﬂavors and other characteristics of