Stability of Sulfur Compounds in Whole Air Sampling

Air Methods, Monitoring, and Technology - Session 2
Oral Presentation

Prepared by
1 - Markes International, Inc., 2355 Gold Meadow Way, Gold River, Gold River, Sacramento, CALIFORNIA, 95670, United States
2 - Markes International Ltd, Gwaun Elai Medi-Science Campus, Llantristant, No State Available, CF72 8XL, United Kingdom
3 - Markes International, Gwaun Elai Medi-Science Campus, Llantrisant, Llantrisant, CF72 8XL, United Kingdom


Contact Information: jason.hoisington@restek.com; 814-353-1300


ABSTRACT

Volatile sulfur compounds in ambient air can be a major source of odors near industrial and agricultural areas, and present significant challenges for collection and analysis. Sulfur compounds such as hydrogen sulfide, methyl mercaptan, and ethyl mercaptan show higher reactivity in ambient air samples when compared to dry lab standards, and can break down in air canisters and sorbent tubes. This presents difficulties in collecting accurate measurements, as samples must be rushed to laboratories or analyzed on site to guarantee good data. Surface deactivations such as fused silica lined (FSL) canisters have historically been used to extend the lifetime of reactive sulfurs in whole air samples, but the stability of some sulfur compounds is still limited.
This presentation investigates the effects of increasing humidity on the stability and repeatability of 6 sulfur compounds (hydrogen sulfide, carbonyl sulfide, methyl mercaptan, ethyl mercaptan, dimethyl sulfide, and dimethyl disulfide) in ambient air using GC/FPD. The differences between standard electro polished air canisters and fused silica lined canisters is also explored. Methods for drying air during sampling are also investigated, and a sampling method is proposed that limits the loss of sulfur compounds due to drying and extends sample shelf life by reducing the humidity of the collected air.