Fig. 4.

Extracted ion chromatograms (m/z 41) illustrate detection of N,N-dimethyltetradecylamine and bis-2-ethylhexyl phthalate using GC × GC-TOF-MS in high DRO samples (1 and 2) and no detection in low DRO samples (3 and 4). Mass spectra of samples 1, 2, and the bis-2-ethylhexyl phthalate standard are given in the ESI (Fig. S5^†). N,N-dimethyltetradecanamine identification was also confirmed with an authentic standard. These signals were absent in 14 field and lab blanks, and absent in two field blanks collected at the same time and two lab blanks extracted on the same date as samples 1 and 2 (Fig. S5^†). The z-axis is scaled automatically to the highest intensity peak. The color map indicates the extracted ion intensity (where the maximum height is colored red) and the small peaks (colored royal blue) are close to the baseline intensity due to their small abundance.