Quantum chemical calculations resolved identification of methylnitrocatechols in atmospheric aerosols (CROSBI ID 240180)
Prilog u časopisu | izvorni znanstveni rad | međunarodna recenzija
Podaci o odgovornosti
Frka, Sanja ; Šala, Martin ; Kroflič, Ana ; Huš, Matej ; Čusak, Alen ; Grgić, Irena
engleski
Quantum chemical calculations resolved identification of methylnitrocatechols in atmospheric aerosols
Methylnitrocatechols (MNCs) are secondary organic aerosol (SOA) tracers and major contributors to atmospheric brown carbon ; however, their formation and aging processes in atmospheric waters are unknown. To investigate the importance of aqueous-phase electrophilic substitution of 3-methylcatechol with nitronium ion (NO 2 + ), we performed quantum calculations of their favorable pathways. The calculations predicted the formation of 3- methyl-5-nitrocatechol (3M5NC), 3-methyl-4- nitrocatechol (3M4NC), and a negligible amount of 3-methyl-6- nitro- catechol (3M6NC). MNCs in atmospheric PM 2 samples were further inspected by LC/( − )ESI-MS/MS using commercial as well as de novo synthesized authentic standards. We detected 3M5NC and, for the fi rst time, 3M4NC. In contrast to previous reports, 3M6NC was not observed. Agreement between calculated and observed 3M5NC/3M4NC ratios cannot unambiguously con fi rm the electrophilic mechanism as the exclusive formation pathway of MNCs in aerosol water. However, the examined nitration by NO 2 + is supported by (1) the absence of 3M6NC in the ambient aerosols analyzed and (2) the constant 3M5NC/3M4NC ratio in fi eld aerosol samples, which indicates their common formation pathway. The magnitude of error one could make by incorrectly identifying 3M4NC as 3M6NC in ambient aerosols was also assessed, suggesting the importance of evaluating the literature regarding MNCs with special care.
Atmospheric aerosols, Methylnitrocatechols, Brown carbon, SOA, LC/(−)ESI-MS/MS
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Podaci o izdanju
50 (11)
2016.
5526-5535
objavljeno
0013-936X
10.1021/acs.est.6b00823