Name:
KetoneGasWallPartition1

Instrument:
Gas Chromatograph - Flame Ionization Detector

Chamber:
Roger (Chamber 2)

Temperature (°C):
25

Relative humidity (%):
1

Volatile compound name or class:
2-ketones

Volatile compound source:

• Direct injection of commercial standards

Date of characterization experiment:
2020-02-22

Months since calibration:

Wall loss experiment description:
C7-C13 2-ketones were added to the chamber simultaneously over a period of 1.5 minutes, each with a concentration of 100 ppb in our chamber. A teflon-coated fan was run for 10 seconds to mix without increasing the gas-wall partitioning timescale. A 10 cm section of 0.47 cm I.D. Teflon tubing was passivated at a flow of 250 cm3 min-1, which resulted in passivation in <50 seconds. Gases were collected on Tenax adsorbent for 2 minutes each at times of 2, 5, 7, 13, 23, 45, 80, 120, 180, and 300 minutes after addition, where the time represents the midpoint of collection. Tenax adsorbent cartridges were thermally desorbed onto the GC-FID to monitor VOC concentrations.

Vapor loss calculation method:
Two parameters, gas-wall partitioning timescale and equivalent wall absorbing mass were determined. To determine the gas-wall partitioning timescale, the signal at time zero was determined by plotting the average signal over the experiment, and for VOCs that did not undergo gas-wall partitioning, the relationship was extrapolated for VOCs that did undergo gas wall partitioning. From there, each VOC time series was plotted such that the VOC signal at time zero was normalized to one. A single exponential function was fit to the first 90 minutes of the experiment, the resulting time constant was the gas-wall partitioning timescale. For the equivalent wall absorbing mass, the ratio of VOC in the gas-phase to VOC partitioned to the wall was plotted, and the slope multiplied by Mw, where Mw is the molar mass of the wall (200 g mol-1) gave the equivalent wall absorbing mass, relative to particles.

Parameterization developed:
Yes

Parameterization description:
t_w = 13 min C_w = 30 mg m-3 Two parameters, gas-wall partitioning timescale and equivalent wall absorbing mass were determined. To determine the gas-wall partitioning timescale, the signal at time zero was determined by plotting the average signal over the experiment, and for VOCs that did not undergo gas-wall partitioning, the relationship was extrapolated for VOCs that did undergo gas wall partitioning. From there, each VOC time series was plotted such that the VOC signal at time zero was normalized to one. A single exponential function was fit to the first 90 minutes of the experiment, the resulting time constant was the gas-wall partitioning timescale. For the equivalent wall absorbing mass, the ratio of VOC in the gas-phase to VOC partitioned to the wall was plotted, and the slope multiplied by Mw, where Mw is the molar mass of the wall (200 g mol-1) gave the equivalent wall absorbing mass, relative to particles.

Link to supplemental information:

Additional notes:

Characterization data file:
WallLoss_200222.csv