Autospec ultima

PCDD/Fs and PCBs were determined using a high-resolution gas chromatographer (Agilent 6890N, Wilmington, NC, USA) coupled with high-resolution mass spectrometer (AutoSpec Ultima, Waters Micromass, Wilmslow, UK) (HRGC/HRMS). Chromatographic separation was achieved on a DB-5MS fused silica capillary column (60 m × 0.25 mm i.d. × 0.25 μm, Agilent, USA). The mass spectrometer was operated in positive electron impact (EI⁺) and the targets were analyzed in voltage selective ion records (VSIR) mode at a mass resolution of above 10,000. The electron energy was 35 eV, and the ion source and transfer line were kept at 270 °C. Helium was used as the carrier gas at a flow rate of 1 mL min⁻¹. The injection port temperature was held at 270 °C and 1 μL of the sample was injected into the GC in splitless mode. The GC oven temperature was programmed as follows: for PCBs, the initial temperature was 120 °C, held for 1 min, and then increased to 150 °C at a rate of 30 °C min⁻¹, ramped to 300 °C at 2.5 °C min⁻¹ and held for 1 min; for PCDD/Fs, 150 °C for 3 min, 20 °C min⁻¹ to 230 °C and held for 18 min, increased to 235 °C at 5 °C min⁻¹ and held for 10 min, and finally 4 °C min⁻¹ to 330 °C and held for 3 min. Seventeen 2,3,7,8-substituted PCDD/F congeners, twelve dioxin-like PCB congeners, six indicator PCB congeners and six other PCB congeners were determined.

Serum concentrations of 6 PCB congeners (PCB118, PCB153, PCB138, PCB156, PCB170 and PCB180), DDE and HCB were determined by means of a Agilent 6890 gas chromatographer connected to a Waters Autospec Ultima high resolution mass spectrometer as described in an earlier study on the exposure data^{12 (link), 13 (link)}. Per subject we calculated a Z-Score_(POPs) as a representative of the internal exposure to the mixture of POPs. The Z-Score_(POPs) was defined as the sum of the Z-Scores for each compound: Z-Score_(compound) = (X − μ)/σ (where X represents the value of the subject, μ the mean and σ the standard deviation of the population)^{42 (link)}. Therefore, Z-Score_(POPs) = Z-Score_(PCB118) + Z-Score_(PCB153) + Z-Score_(PCB138) + Z-Score_(PCB156) + Z-Score_(PCB170) + Z-Score_(PCB180) + Z-Score_(HCB) + Z-Score_(DDE).