Development of a compound-specific carbon isotope analysis method for 2-methyltetrols, biomarkers for secondary organic aerosols from atmospheric isoprene.
The stable carbon isotope compositions of 2-methyltetrols, biomarker compounds for secondary organic aerosols formed from isoprene in the atmosphere, have been determined by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). In this work, isoprene with various delta(13)C values was used to produce 2-methyltetrols via an oxidation reaction with hydrogen peroxide in sulfuric acid under direct sunlight. The target compounds with different stable carbon isotope compositions were then derivatized by methylboronic acid with a known delta(13)C value and measured by GC/C/IRMS. With delta(13)C values of 2-methyltetrols and methylboronic acid predetermined, isotopic fractionation is evaluated for the derivatization process. Through reduplicate delta(13)C measurements, the carbon isotope analysis achieved excellent reproducibility and high accuracy with an average error of <0.3 per thousand. The differences between the predicted and measured delta(13)C values range from -0.10 to 0.29 per thousand, indicating that the derivatization process does not introduce isotopic fractionation. The delta(13)C values of 2-methyltetrols could be calculated on the basis of the stoichiometric mass balance equation among 2-methyltetrols, methylboronic acid, and methylboronate derivatives. Preliminary tests of 2-methyltetrols in PM(2.5) aerosols at two forested sites were conducted and revealed significant differences in their isotope compositions, implying possible application of the method in helping us understand the primary emission, photochemical reaction, or removal processes of isoprene in the atmosphere.
Li
Qiang
Q
School of Stomatology, Tongji University, 200072 Shanghai, China.
Wang
Wu
W
Zhang
Hong-Wei
HW
Wang
Yang-Jun
YJ
Wang
Bing
B
Li
Li
L
Li
Huai-Jian
HJ
Wang
Bang-Jin
BJ
Zhan
Jie
J
Wu
Mei
M
Bi
Xin-Hui
XH
D000336:Aerosols / Q000737:chemistry; D001272:Atmosphere; D015415:Biomarkers / Q000032:analysis; D001896:Boron Compounds / Q000737:chemistry; D002070:Butadienes / Q000737:chemistry*; D002247:Carbon Isotopes / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D045782:Hemiterpenes / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D008027:Light; D010084:Oxidation-Reduction; D010420:Pentanes / Q000737:chemistry*; D013464:Sulfuric Acids / Q000737:chemistry
D000336:Aerosols; D015415:Biomarkers; D001896:Boron Compounds; D002070:Butadienes; D002247:Carbon Isotopes; D045782:Hemiterpenes; D010420:Pentanes; D013464:Sulfuric Acids; C005059:isoprene; C116999:methaneboronic acid; D006861:Hydrogen Peroxide; C033158:sulfuric acid