Our plant is in the process of updating our plant Digesters.  We are hoping to test or monitor the VFA or VOA at the plant.  Is there much difference between Volatile Organic Acids and Volatile Fatty Acids?  Is it the same nine fatty acids listed in Standard Methods 5560 D?

We currently use the distillation method, 5560 C, anc are looking to possibly move to a chromatographic method.  I know that these acids can be tested using Ion Chromatography, but have not found an actual method cited.  

If we were to purchase a Chromatography system, I would rather perform this testing by Ion Chromatography since we could also test Nitrate and Nitrite which will be required.  

Thank you,

Patti

For most cases the VOA and VFA are the same. VFA came from steam distilled analysis and VOA came from colorimetric analysis. VFA is organic acids thru 6 carbon chain. VOA may contain C7 or C8 carbon chain organic acids as they will also react. Most samples only contain acetic, propronic, and butyric acids. Thus both methods will have the same result reported as acetic acid. Chromatigraphy methods will differentiate between these compounds.