Screening for Volatile Fatty Acids in Agricultural Air Using Solid Phase Microextraction and Gas Chromatography - Mass Spectrometry

Abstract

Volatile fatty acids (VFAs) are a major component of odorous gases associated with agricultural sources. Because of typically low VFA air concentrations, conventional air sampling methods including sorbent tubes and vacuum canisters are often not sensitive enough to detect them. Solid phase microextraction (SPME) was used in this research because it is very sensitive, reusable, fast, and combines sampling and sample preparation, allowing for rapid detection of low concentrations of organics in air. This research focused on 7 VFAs: acetic, propionic, isobutyric, butyric, isovaleric, valeric, and hexanoic acids. Field experiments were conducted to test this method for air sampling of beef cattle feedyard, horse manure compost, and a swine operation in Texas. Rapid SPME samples were collected by exposing DVB/ Carboxen/PDMS 50/30 µm SPME fibers to air for 1 to 5 min. Sample preservation was accomplished by plugging of fiber assemblies with simple PTFE caps for transport to the laboratory for analysis on gas chromatograph- mass spectrometer (GC-MS). SPME DVB/Carboxen/PDMS 50/30 µm coating was very effective in detecting target VFAs and other gaseous components of agricultural odors. This coating was also very efficient in retaining major fraction of target VFAs.