I am working on bio gas production through anaerobic digestion of wastes. I would like to quantify how much volatile fatty acids (i.e., Acetic acid, propoinic acid, Butyric acid, formic acid) present in the digested liquid. So please suggest protocol to quantify it using high pressure liquid chromatography.
volatile fatty acid should be done by GC because it is "volatile" but if your sample is aqueous, you may need HPLC based analysis so it is compatible with the sample. Check out my publication in my profile that I did long time ago with ion-exclusion chromatography with conductivity detector, of course new method should be available on internet.
Protocol Will change according to your sample. I hope your sample consists of water content. Filter your sample with 0.2 micron membrane filter. And go for HPLC with UV detector and Rezex™ ROA-Organic Acid H+ (8%), LC Column 300 x 7.8 mm, Ea (You can try different column too).
HPLC column Aminex HPX-87H column (Biorad, USA) maintained at 80°C with 0.005 M H2SO4 as a mobile phase with flow rate of 0.6 ml/min . Succinate, acetate, butyrate, propionate, lactate, formate, ethanol, acetone, propanol and butanol can be analysed using this column. I have personally used it for metabolite analysis during biogas production.
For this kind of analysis you can also used the Hi_Plex H from agilent at a tempertaure of 50°C, with 0.005 M H2SO4 as a mobile phase with flow rate of 0.3 ml/min
The protocol proposed by Mustafa Vohra - HPLC column Aminex HPX-87H column (Biorad, USA) maintained at 80°C with 0.005 M H2SO4 as a mobile phase with flow rate of 0.6 ml/min was originally published in R.T. Marsili, H. Ostapenko, R.E. Simmons, D.E. Green. High Performance Liquid Chromatographic Determination of Organic Acids in Dairy Products J. Food Sci., 46 (1981), 52-57. We have also used it successfully. Agilent has a similar application note http://www.chem.agilent.com/Library/applications/SI-01159.pdf
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