Tedlar sample bag

Individual samples were prepared by injecting desired liquid volumes of 2-butanone, 2-hexanone, ethyl acetate and 4-methyl-2-pentanone (Sigma Aldrich, St Louis, MO) into each sample bag (SKC Tedlar^® Sample bag, SKC Inc., Eighty Four, PA) filled with 3 L of ultra high purity nitrogen (Airgas, Radnor, PA). These bags were maintained for more than 10 min at room temperature to equilibrate analytes into the gas phase to achieve the stock concentrations (1000 ppm). Serial dilution was performed from the stock concentration to achieve 100 ppm concentration of each chemical. Each gas phase chemical was sampled into a gas tight 1 mL glass syringe (Hamilton Co., Reno, NV) from the final concentration (100 ppm) and introduced separately into the inlet of the differential mobility spectrometer using a syringe pump with a dilution nitrogen gas flow. The final concentration of each chemical at the DMS cell inlet was 500 ppb. The bags with chemical mixtures were prepared by adding each new chemical to the bag followed by serial dilution. Therefore, the final concentration of each chemical in a mixture was ~ 500 ppb.

Desired volumes of 2-butanone, 2-propanone, ethanol, methanol and ethyl acetate (Sigma Aldrich, St Louis, MO) were individually sampled into 3 L sample bags (SKC Tedlar^® Sample bag, SKC Inc., PA.) and each sample bag was maintained for 10 minutes at room temperature for the sample to equilibrate into gas phase to achieve the stock concentrations (1000 ppm). Ultra-pure nitrogen (Air gas, Radnor, PA) was used as the dilution gas with water content in ultra pure N₂ around 1 ppm. Serial dilution was performed from the stock concentration and sampled into another sample bag to achieve 100 ppm. Each gas phase chemical was sampled into a gas tight 1 μL glass syringe (Hamilton Co., Reno, NV) from the stock concentration (100 ppm) and introduced separately into the inlet of the differential mobility spectrometer using a syringe pump with a dilution nitrogen gas flow to achieve the final concentration of 500 ppb.