Micromass autospec ultima

p,p′-DDE levels were measured in stored serum samples using a Micromass Autospec Ultima (Waters, Milford, MA, USA) high-resolution gas chromatography coupled to a high resolution mass spectrometry (HRGC/HRMS) system based on the method by Sandau and colleagues (Barr et al., 2003 ) with some modifications. A more detailed description of the analysis in this sample has previously been presented (Salihovic et al., 2012 (link)).

For the identification of electrophysiologically active compounds in air entrainment samples, an Agilent 6890 N GC fitted with a capillary GC column (50 m × 0.32 mm i.d. HP‐1, 0.52 µm film thickness; J&W Scientific, Folsom, CA) and equipped with a cool on‐column injector was directly coupled to a mass spectrometer (Micromass Autospec Ultima; Waters, Milford, MA). Ionisation was by electron impact at 70 eV, 220 °C. The oven temperature was maintained at 30 °C for 5 min and then programmed at 5 °C min⁻¹ to 250 °C (hold time 21 min). Tentative identification by GC‐MS was confirmed by comparing retention indices of peaks with those of synthetic standards and by peak enhancement on GC by coinjection with authentic compounds,12 using an Agilent 6890A GC equipped with a cool on‐column injector, FID and a 50 m × 0.32 mm i.d. HP‐1 column (0.52 µm film thickness). The oven temperature was maintained at 30 °C for 2 min and then programmed at 10 °C min⁻¹ to 250 °C. The carrier gas was helium. Quantification of compounds was achieved using known amounts of a series of C7‐C22 alkanes as external standards, although it is appreciated that this results in very small discrepancies.