Many Americans have started using ethanol fuel as an affordable and environmentally-friendly alternative to regular gasoline. The highly publicized E85 fuel is a blend of 85% ethanol and 15% gasoline and can only be used in specially designed vehicles known as “Flex-Fuel”. However, did you know that even if your car isn’t flex-fuel, you may be using ethanol? In fact, 95% of all automotive gasoline sold is blended with 10% ethanol, known as E10, and can be used by any normal gas powered car. Most states don’t require E10 manufacturers to label gasoline used with ethanol, so you may be pumping ethanol into your car without even realizing it!
Needless to say, ethanol production has become a very important industry in the United States. One glaring complaint against ethanol is that there are many variations in fuel samples. The precise composition of ethanol varies between seasons, states and even gas stations. This variation often becomes apparent to consumers when they notice fluctuations in their gas mileage. This is because some variations of ethanol burn more efficiently than others. Ethanol manufacturers can get away with this because there’s no national standard or “recipe” for blended regular gasoline and there are different regional standards for the production of E85.
Ethanol can be contaminated with chlorides and sulfates which can cause corrosion within the engine. Denatured fuel ethanol is required to have <4mg/L sulfate and <40mg/L chloride as specified by ASTM D4806. The materials testing method ion chromatography (IC) can be used to determine the presence and quantify the amount of corrosive anions such as chlorides and sulfates in fuel ethanol.
To analyze the sulfate and chloride in denatured fuel ethanol, the IC analysis process is as follows:
- Sample preparation – The sample or components of interest must be suspended in solution.
- Feed injection – The sample is injected into the carrier fluid in a column with an ion-exchange resin. The resin’s surface layer has limited ion-exchange sites that attract inorganic anions.
- Separation – Ionic separation of the sample takes place.
- Exiting of components – The components exit (elude) from the column, beginning with those least bound to the stationary phase.
- Detection – The eluded components are analyzed by measuring the change in conductivity, UV absorbance or refractive index of the eluent as the separated ionic species pass through the detector.
- Chromatogram – A chromatogram is produced that plots the peaks representing sample components.
The results of IC analysis can be used qualitatively to identify unknown anions or cations in the sample or quantitatively to measure the concentration of a known anion or cation within the sample. In the case of ethanol analysis, the levels of chloride and sulfate contaminants can be determined. This information could help a fuel producer measure the quality of their product or help a distributor determine if they’re buying a good product or not.
In addition to analyzing fuel ethanol, IC analysis is a reliable testing method used for measuring emissions, food additive identification, cleanliness testing, and other applications.