Influence of sample temperature and environmental humidity on measurements of benzene in ambient air by transportable GC-PID

Abstract

Abstract. Calibration of in situ analysers of air pollutants is usually done with dry standards. In this paper, the influence of sample temperature and environmental humidity on benzene measurements by gas chromatography coupled with a photoionisation detector (GC-PID) is studied. Two reference gas mixtures (40 and 5 µg m −3 nominal concentration benzene in air) were subjected to two temperature cycles (20/5/20 • C and 20/35/20 • C) and measured with two identical GC-PIDs. The change in sample temperature did not produce any significant change in readings. Regarding ambient humidity, the chromatographs were calibrated for benzene with dry gases and subjected to measure reference standards with humidity (20 and 80 % at 20 • C). When measuring a concentration of 0.5 µg m −3 benzene in air, the levels of humidity tested did not produce any significant interference in measurements taken with any of the analysers. However, when measuring a concentration of 40 µg m −3 , biases in measurements of 18 and 21 % for each respective analyser were obtained when the relative humidity of the sample was 80 % at 20 • C. Further tests were carried out to study the nature of this interference. Results show that humidity interference depends on both the amount fractions of water vapour and benzene. If benzene concentrations in an area are close to its annual limit value (5 µg m −3 ), biases of 2.2 % can be expected when the absolute humidity is 8.6 g cm −3 -corresponding to a relative humidity of 50 % at 20 • C. This can be accounted for in the uncertainty budget of measurements with no need for corrections. If benzene concentrations are above the annual limit value, biases become higher. Thus, in these cases, actions should be taken to reduce the humidity interference, as an underestimation of benzene concentrations may cause a mismanagement of air quality in these situations.

Assessing the Effects of Atmospheric Properties on Energy Commodity Storage and Distribution: Focus on Correlation with Temperature and Wind Variations

“…From literature, gasoline contains elements of benzene which has been alleged to cause cancer and other carsogenic effects. Moreover, higher concentrations of benzene are more affected by ambient water vapour [14] and the major source of benzene in cities is gasoline, as it is one of its components as well as a product of its combustion [15]. Having noted the nexus between pollutant (filling station emission) and ambient variables, next consideration is the control, with understanding that a gasoline station deals on products in which elimination or reduction of the effects can be by change of attitude and regulatory policy.…”

Comparative Overview of Methods for the Detection of Airborne Electrolyte Components Released from Lithium‐Ion Batteries

“…The performance of GCs that were equipped with a PID was reported to be affected by temperature and humidity changes of the environment leading to a concentration bias of up to 47% to the reference concentration of benzene in a location with extreme humidity (30 g cm −3 absolute humidity). [ 113 ]…”

“…The performance of GCs that were equipped with a PID was reported to be affected by temperature and humidity changes of the environment leading to a concentration bias of up to 47% to the reference concentration of benzene in a location with extreme humidity (30 g cm À3 absolute humidity). [113] TCD: Thermal conductivity detectors use the differences in thermal conductivity to identify the analyte. They have the advantages of being rugged, safe (no flame required), low energy consuming, and fuel gas free.…”

“…The literature has shown that changes in humidity and temperature can influence the measurement and lead to an underestimation of the concentration of VOCs in air. [ 113 ] The high price, the constant supply of carrier gas (not for all systems), and the challenge to find the right configuration of the equipment for compounds not known a priori make the use of GC for air monitoring rather impractical for constant monitoring even in a known environment.…”