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19.
A Critical Evaluation of Anion Exchange Chromatography for the
Separation of Water Soluble Organic Carbon
Hui
Chang, Pierre Herckes, Jeffrey L. Collett, Jr.
Colorado
State University, Department of Atmospheric Science, Fort Collins
CO 80523
Anion exchange chromatography has been used in several
recent studies to fractionate water soluble organic carbon (WSOC)
from aerosol and fog samples into neutral/basic, mono/dicarboxylic
acid and polyacidic fractions. Detection of the fractions was
made by UV absorption or by offline Total Organic Carbon (TOC)
measurements. We have recently tested this technique with artificial
solutions and applied the method to different types of ambient
samples: WSOC in aerosol samples from Fort Collins (CO), Fresno
(CA) and Yosemite NP (CA) and fog samples from Fresno (CA).
The results obtained for the ambient samples are
very similar to published studies. Tests of the separation method,
however, suggest that the characterized “fractions”
are not as easy to define as commonly reported. Various test organic
compounds eluted in fractions other than expected based on their
molecular structures. Phenol and benzaldehyde, for example, were
observed to elute in the mono/dicarboxylic acid fraction. We will
detail our observations and discuss their potential impact on
interpreting results from this increasingly popular separation
technique.
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