Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: September 14, 2006
Publication Date: September 14, 2006
Citation: Trabue, S.L. 2007. Relative Humidity and its Effect on Sampling and Analysis of Agricultural Odorants in Air [abstract]. American Chemical Society Abstracts. American Chemical Society 232nd National Meeting. Abstract No. AGR085.
Source and ambient air sampling techniques used in agricultural air quality studies are seldom validated for the variability in the air matrix (temperature, dust levels, and relative humidity). In particular, relative humidity (RH) affects both field sampling and analysis of air samples. The objectives of this study were to determine the effect RH had on the recovery and analysis of agricultural odorants using various sorbent materials (Tenax, graphitized carbon, and carbon molecular sieves). Test atmospheres were generated at ambient temperatures (23 + 1.5 degrees C) and 25, 50, and 80% RH. Sorbent tubes were spiked with known concentrations of odorants and challenged with 2, 4, 8, 12 and 24 L of air at various RHs. Water sorption onto sorbent tubes was monitored gravimetrically. A custom designed sorbent tube containing carbopack X sorbent material performed best with quantitative recovery of all compounds at all RHs and sampling volumes tested. Tenax sorbent tubes gave quantitative results for all compounds except acetic acid, but after 8 L of air recovery of both propanoic and butanoic acid were below 70%. The sorbent tubes with carbon molecular sieve (CMS) material performed poorly at both 50 and 80% RH due to excessive sorption of water. Water sorption on CMS tubes ranged from 8-32 uL at 50% RH and 14-45 uL at 80% RH. At 25% RH, recovery of all compounds was excellent on CMS tubes due to little water sorption (less than 2.5 uL). Water management techniques such as heating sorbent tubes in excess of 10 degrees C above ambient temperatures and dry-purging of CMS tubes before analysis reduced the sorption of waster to less than 3 uL. Recovery of all compounds was greater than 86% using elevated temperatures during trapping, while recovery from dry purging was less than 85%. This study demonstrates that relative humidity and temperature has a dramatic effect on the detection and recovery efficiency of agricultural odorants.