Fig. 2.
EICs obtained from HILIC for (a) m/z 135.066 corresponding to 2-methyltetrols, (b) m/z 215.023 corresponding to methyltetrol sulfates from: (1) 10 μg mL−1 synthesized standard ((b1) 2-methyltetrol sulfates (dashed line) and 3-methyltetrol sulfates (solid line)); (2) laboratory-generated β-IEPOX SOA; (3) laboratory-generated δ-IEPOX SOA; (4) PM2.5 sample collected at Look Rock during 2013 SOAS campaign; (5) PM2.5 sample collected at Manaus in Nov. 2016. The laboratory-generated β-IEPOX SOA, δ-IEPOX SOA, Look Rock, and Manaus samples were diluted by a factor of 200, 100, 40, and 100, respectively. No significant peaks were observed beyond the shown periods of retention time.