Sample water removal method in volatile organic compound analysis based on diffusion through poly(vinyl fluoride)...

Area of Science:

• Environmental Chemistry
• Analytical Chemistry

Background:

• Humidity during air sampling or storage negatively impacts volatile organic compound (VOC) analysis, leading to unreliable results.
• Water vapor can interfere with the detection and quantification of VOCs, particularly when using water-sensitive analytical techniques or adsorbents.

Purpose of the Study:

• To compare the water vapor diffusion capacities of different film materials: poly(vinyl fluoride) (Tedlar), fluoroethylene propylene (Teflon), and Flex foil.
• To introduce and evaluate a novel sample water removal (SWR) method for moderately polluted atmospheres using Tedlar film's diffusion properties.

Main Methods:

• Diffusion capacities of Tedlar, Teflon, and Flex foil were assessed for water vapor transmission.
• A pretreatment method involved placing air samples containing ten VOCs (500 ppbv each) in a 70% relative humidity atmosphere within Tedlar bags.
• These Tedlar bags were then placed in a chamber flushed with dry air (<5% relative humidity) to facilitate water removal.

Main Results:

• Tedlar film demonstrated effective water vapor diffusion, allowing humidity removal from the air samples.
• After a few hours in the dry air stream, samples in Tedlar bags achieved a relative humidity below 5%.
• Crucially, the SWR method using Tedlar bags did not result in significant loss of the target VOCs.

Conclusions:

• The developed sample water removal (SWR) method effectively reduces humidity in air samples using Tedlar film.
• This technique is a promising pretreatment step for air sampling, especially when employing water-sensitive adsorbents for VOC analysis.
• The SWR method enhances the reliability of VOC analysis by mitigating humidity-induced interferences.