Accepted for presentation at the 2015 American Industrial Hygiene Conference and Exposition on Wednesday June 3, 2015 at SPCC: 355 C
Real-Time Detection of ppb Levels of Benzene in Industrial Atmospheres
Objective
The OSHA method
for benzene involves the collection on a charcoal tube and return to the lab,
for desorption with carbon disulfide and analysis by gas chromatography with a
flame ionization detector (GC-FID). While the PID is an ideal tool for
detecting low or sub ppm levels of benzene, it responds to all VOC’s, so the
measurement of benzene at or below 1 ppm is not very accurate. We propose to develop a hand held GC with a
PID to detect to detect low ppb of benzene in real time and “on site”.
Method
The hand held
GC weighs less than 3 pounds, is able to operate for >6 hours on a battery,is
easy to operate and has a small external tank for carrier gas (nitrogen) that
can be clipped onto a belt. The hand held GC stores the peak height and
concentration data. If a chromatogram is needed, up to 20 are stored in memory
and if more are needed, the 0-1 VDC analog output can be connected directly to
a PC with PeakWorks.
Results
A permeation tube was used
to generate ppb levels of benzene in air. A chromatogram of 500 ppb of benzene in
air is shown in the figure below. The detection limit for benzene is
approximately 5 ppb. The analysis time is 2 minutes presently but with some
optimization, it can be reduced to about 1 minute which would be ideal.
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Conclusions
The GC/PID method provides a very rapid and sensitive
technique for the analysis of benzene at
ppb levels. The precision of benzene for 5 samples at 1/10th of the
PEL was excellent at 5.8%. A special precolumn with back flushing removes
interferences.
Section: Real Time Detection Systems #RTDSC #RealTimeDetection
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