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The main goal of this study is to develop a sampling and
analysis system for the atmospheric reduced sulfur compounds.
Atmospheric samples are cryogenically collected in a sampling
tube filled with Tenax TA adsorbent. Samples are pretreated on a
modified thermal desorber with a cryogenic/ thermal desorption
process, and on-line transferred to the capillary gas
chromatograph for sample separation and then detected with a
sulfur chemiluminescence detector(SCD). The analytical column is
30m x 0.32mm i.d., 4mm film thickness, Quadrex 007 series
capillary column, 28 sulfur samples in which boiling point
ranged from -63 ~ 200℃are separated within 35 minutes. In this
study, a flameless SCD and a flame ionization detector is
coupled in series for simultaneous detection of both sulfur and
hydrocarbon chromatograms. This configuration violates the limit
that the first detector in a series-coupled detectors system
should be a non-destructive ones. Using the n-alkylthiols as
the reference standards, the retention indices of twenty-six
volatile and semi-volatile sulfur compounds have been
established for sample identification. In a cryogenic sampling
method, peak splitting and retention time shift in chromatograms
caused by the water are serious problems. In this study, based
on the concept of the retention gap, a 0.53mm i.d deactivated
column is installed in front of the analytical column for
solving these problems. In a 1-L air sample with 80% relative
humidity collected at the room temperature, the relative
retention time shift can be controlled within 5% for H2S and CH3
SH and 1% for those compounds of which boiling points are
greater than C2H5SH. Another topic of this study is to separate
sulfur compounds in a short capillary column, shortened of
analysis time and optimized separation are achieved by using the
concept of best performance. The band broadening caused by the
extra-column effects and the relationship between instrumental
constant and column length are investigated. The H-u plot of any
column length can be predicted and theoretical shortest analysis
time can be calculated. Via the optimization process, the
analysis time of seven sulfur compounds is shortened from 12 to
2.6 min, and 22 sulfur compounds are separated within 11 minutes
using a temperature programming condition.
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