This title of this paper could just have well have been, "A Stinky Day in the Life of an Analytical Chemist!", as the samples and analytes are exceptionally malodorous. But after all the jokes subside, this turns out to be a great example of the significant impact that can be made by applying advancements in analytical chemistry to traditional methods. Short Chain Fatty Acids (SCFA's) maybe best known for their unpleasant odors, but they may also be key indicators of serious human digestive disorders such as colorectal cancer and celiac disease. Challenges include extracting the water-soluble analytes from the matrix, and then preparing the analytes for GC analytes. Methods currently exist, but they involve extensive sample preparation steps including pH adjustments, water extraction, liquid-liquid ether extraction before GC analysis. The excessive sample manipulation leads to decreased precision and sacrifices detection limit. This new method is almost “dilute and shoot”, as there is just one step before GC injection: water extraction. Historically, GC operators have been taught not to inject water directly onto a GC due to its excessive expansion coefficient (1200x). We were also cautioned against attempting to analyze free fatty acids without derivatization, due to excessive tailing caused by adsopriton of the acids. While those may have been true in the past, modern GC's can handle direct water injections and the analysis of free fatty acids...if the conditions are set correctly! This new method employees a pressure-pulsed injection in order to decrease the volume of water vapor injected into the GC. By doubling the pressure during the injection process, the 1200 uL of water vapor is squeezed down to 600 uL. eliminating the overload of the 1000 uL liner. The tailing issue was eliminated by choosing deactivated liners and a stationary phase (DB-FFAP) designed to produce excellent peak shapes for free fatty acids. These Free Fatty Acid Profile (FFAP) columns start with a poly ethylene glycol stationary phase, which is then derivatized with terephthalic acid to form a very polar surface with low adsorption characteristics. The resultant method is faster, more precise and more sensitive...and much easier on the analyst!

Disease detection by GC-FID: Determination of short chain fatty acids (SCFA) in human fecal samples

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.