engleski

Validation of a method used for determination of 20 PCB congeners in air samples

Polychlorinated biphenyls (PCBs) determination require a highly sensitive and selective method because they are found in small quantities (measured in picogram and nanogram range) and are often extracted with other interfering compounds. Qualitative and quantitative PCB analysis, most often relies on high resolution gas chromatography with electron capture detector (HRGC-ECD). ECD is sufficiently sensitive to determine PCB congeners and they can be separated through appropriate stationary phases and in appropriate gas-chromatographic conditions. The aim of this study was to evaluate a method used in determining 20 PCB congeners in air samples. The congeners were extracted from polyurethane foam (PUF) and quartz fiber filter paper which were extracted with 5% diethyl-ether in n-hexane for 12 hrs in Soxhlet apparatus. Extracts were washed with concentrated sulphuric acid. Qualitative and quantitative analysis were performed using HRGC-ECD. PCB congeners were measured by the use of two capillary columns of 0.25 mm I.D. with 0.25 m stationary phase film thickness. One column was 30m long with SPB-1701 stationary phase (column 1) and the other 60m long with SPB-5 stationary phase (column 2). The column temperature programme started at 100 ^oC (column 2) and 110 ^oC (column 1) with ramp 4 ^oC/min to 240 ^oC, and kept at 240 ^oC for 50 min. The detector response was linear in the mass concentration range 0.5 – 10.1 ng/mL. The detection limit for all analysed compounds in the extract was 0.4 ng/mL and determination limit in the air was 0.5 pg/m^3. Recovery was determined by adding known amounts of analysed compounds to PUF and quartz fiber filter paper prior to extraction at three fortification levels: 0.93 – 1.40 ng, 4.65 – 7.00 ng, 18 – 21 ng, which equals to 0.93 – 1.40 pg/m^3, 4.65 – 7.00 pg/m^3, 18 – 21 pg/m^3, respectively, when the air sampling volume is 1000 m^3. Eight samples were analysed at each fortification level. Mean recoveries ranged from 55 % to 99 % depending on the compound. Reproducibility (expressed as relative standard deviation) ranged between 15 – 50 % (all three levels of added compounds are included).

Poliklorirani bifenili; kongeneri PCB-a; zrak; plinska kromatografija visokog razlučivanja

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