Preparation of a Particle-Loaded Membrane for Trace
Gas Sampling
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Abstract
A divinylbenzene (DVB) particle-loaded
membrane with high extraction
capacity was prepared using the bar coating method. The prepared membrane
was evaluated in terms of morphology, effect of particle ratio, and
membrane size on extraction efficiency, as well as linear calibration
curve and limit of detection. The SEM (scanning electron microscope)
images showed that the DVB particles were uniformly distributed in
the PDMS base, ensuring the repeatability of the membranes. The extraction
amount was quantified by gas chromatography–mass spectrometry
coupled with a thermal desorption unit. Results showed that the extraction
efficiency of the prepared membrane increased about 2 orders of magnitude
for benzene sampling as the particle ratio increased from 0% to 30%,
and the extraction amount was linearly proportional to the size of
the membrane. A comparison with a pure PDMS membrane and DVB/PDMS
fiber for outdoor air sampling showed that the extraction efficiency
of the DVB/PDMS membrane was significantly enhanced, especially for
volatile and polar compounds. The limit of detection was about 0.03
ng/mL for benzene in air, and the linear dynamic range extended to
100 ng/mL. An equilibrium calibration method was proposed for low-level
air pollutant sampling using this high capacity membrane, and a displacement
effect was not observed. To demonstrate the power of the technique,
the developed approach was applied to monitor both spot and time weighted
average (TWA) concentrations of benzene in outdoor air. A high spot
concentration of benzene was observed in morning and afternoon rush
hours, with TWA concentrations of 10.7 ng/L measured over the 11-h
monitoring period