Shimadzu Scientific Instruments has published two application notes focused on the use of GC and HPLC instrumentation in the fuel-grade ethanol production laboratory
In the case of gas chromatography, GC analysis is used to determine the total amount of denaturant added to the final ethanol product prior to shipment, an analysis required in certain ethanol markets.
The denaturant, being a petroleum distillate product, can contain hundreds of different compounds.
The GC analysis for ASTM D5501 certification measures the amount of methanol, ethanol, and total amount of denaturant as area percents.
These area percents are corrected, per the ASTM method, to give corrected volume percentages for these materials.
HPLC is now a commonly used technique for monitoring the progress of the fermentation in the laboratory.
The HPLC system is typically used to profile the carbohydrate, alcohol, and organic acid content of the fermentation broth.
The analysis of the fermentation broth is intended to monitor the breakdown of the starch molecules into glucose, then the conversion into ethanol, following typical Krebs cycle dynamics.
The fermentation can go too far if the ethanol begins to be converted into acetic acid.
