Adding to our series on gas chromatography techniques of characterizing biofuels and ion chromatography analysis of fuel-grade butanol, here we present an HPLC method with charged aerosol detection (CAD) to determine acylated and free glycerols in biodiesel including in process, finished product, and petroleum mixed samples!
Biodiesel is a clean and renewable fuel that can be used in current diesel engines and oil burners without any or significant modifications to the engines or burners. It made from a wide range of natural oils, such as virgin and waste cooking oils, algal oils, and animal fats.
From these oils, biodiesel is produced through hydrolysis-esterification of the oils, which produces the biodiesel fuel, but also produces harmful impurities, such as unreacted acylated and free glycerols, which must be removed to avoid damaging the fuel systems. The determination of total glycerols (acylated and free glycerols) in biodiesel is challenging: these impurities do not possess chromophores precluding the use of ultraviolet or fluorescent HPLC detectors, and the analytes are also not volatile requiring derivatization for determination by gas chromatography (GC), which is the current industry standard technique, ASTM D6854.
The poster, Single Method for the Direct Determination of Total Glycerols in All Biodiesels Using Liquid Chromatography and Charged Aerosol Detection, (downloadable PDF), describes an update to a previous work and demonstrates an increased scope in samples and the quantification of total glycerols in all biodiesel samples. This method is simpler than the current GC technique by using typical HPLC conditions and simple sample dilution offering the following advantages:
- No sample preparation is required beyond dilution (no extractions, no derivatizations, no internal standards).
- Measures triacylglycerols, diacylglycerols, monoacylglycerols, and free glycerol in a single analysis.
- Peaks are grouped together for easy identification and quantitation. The quantitation is greatly improved for the grouped analytes by using our charged aerosol detector (Thermo Scientific Dionex Corona ultra RS detector).
- Can be used for in-process samples (process optimization), wet biodiesel (glycerols washing process), B100, and mixed petroleum biodiesel fuels (B2, B5, B10, B20). In comparison, the GC method can only be used on dry B100 biodiesel.
- Can be used for coconut and palm oil based biodiesels, where as the GC method cannot be used for these biodiesels due to overlapping peaks.
- Meets and exceeds ASTM glycerol specifications.
Don’t forget to let us know of any specific applications for biofuels that you are interested in the comments box below. Our applications lab would be pleased to consider your request!