JOURACA_SP_2017

Chlorination of Natural Organic Matter Components
and Preparation of Samples for High Resolution
Mass Spectral Analysis at the National Laboratory
in Tallahassee, Florida
Shahrzad Badri
Chlorination of Natural Organic
Matter Components and Preparation
of Samples for High Resolution
Mass Spectral Analysis at the
National Laboratory in Tallahassee,
Florida
Department of Chemistry
Chemistry
Natural organic matter (NOM), a
product of decomposing biological
matter, consists of numerous
compounds which contribute to
its complex chemical makeup. To
reduce this complexity, NOM is
frequently broken into fractions
before analysis. Fulvic acid (FA),
a component of NOM which dissolves
in acidic water, has been
successfully fractionated using
high performance liquid chromatography
(HPLC). Characterization
of fractions can be achieved
by UV-vis, mass spectrometry
(MS), and total organic carbon
(TOC) analysis. Mass spectrometry
is advantageous as it can accurately
quantify the masses of
compounds in a sample. Samples
in the gas phase are ionized and
separated according to their massto-charge
ratio which is plotted as
a spectrum. The mass spectrum of
a humic substance may contain
thousands of peaks, each peak
with its own unique mass, and the
use of software can substantially
simplify the process of assigning
formulas to peaks. The composiobserved.
Once peak assignments were made, van
Krevelen plots and Kendrick plots were used to graphically
represent the data. The van Krevelen plots indicated
that unchlorinated samples prepared by a ZipTip
had peaks with high H/C ratios and low O/C ratios but
unchlorinated unziptipped samples exhibited peaks
with both high H/C ratios and high O/C ratios. The
results are likely due to the non-polar stationary phase
in the C18 ZipTip attracting non-polar compounds that
tend to naturally have a lower abundance of electronegative
oxygen. Furthermore, ziptipped and chlorinated
samples exhibited some similarities in their plots
in terms of their peak distribution. However, the chlorinated
samples also displayed considerably less peaks
in the region around 5 O/C and 2 H/C suggesting that
chlorination may have possible altering effects on
SRFA. Kendrick plots also displayed a similar distribution
across all SRFA samples.
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