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Quality Assurance Analysis for Biofuels

ASTM International maintains approved written analytical procedures for assuring the quality of denatured fuel ethanol. These regulatory tests are intended to establish minimum quality specifications that all ethanol producers must meet to distribute fuel ethanol.

Determination of Chloride and Sulfate in Ethanol by Ion Chromatography

The National Institute of Standards and Technology (NIST) recently made recommendations for the minimum acceptable limit for contamination of ethanol with ions such as sulfate and chloride, with the goal of harmonizing US, European Union, and Brazilian standards for biofuels quality assurance. Excessive amounts of sulfate and chloride anions can clog automobile filters and fuel injector nozzles, negatively impacting engine performance. The NIST study recommends IC as the preferred analytical method for determining sulfate and chloride in ethanol, and also recommends lowering the regulated limit of chloride ion to more closely match the specification of 1 ppm adopted by Brazil.

As regulatory limits continue to decrease, powerful analytical techniques are required to detect trace levels of contaminants in complex matrices. Using the matrix elimination method with the Dionex ICS-5000 ICS, the system automatically re-concentrates chloride ions and eliminates interferences for detection limits as low as 1 ppm chloride in denatured ethanol and ethanol-gasoline blends.

In addition, using Dionex IonPac® AS24 or AS18 columns on the RFIC system provides accurate, reproducible results in even the most complex matrices.

The RFIC system method of direct injection of untreated samples (without sample preparation steps) is the simplest approach for determining inorganic anions in alcohol fuels, providing quantification of target anions with a single injection, fast analysis times, and minimal sample preparation.

The chromatogram below shows the results of a direct injection of an untreated methanol sample. Separation of chloride and sulfate at 5 mg/L each in methanol was obtained using the IonPac AS24 column and electrolytically generated potassium hydroxide eluent. The unique chemistry of this column allows fast run times (<12 min), and excellent retention time stability.

Benefits of the Dionex Solution for Biofuels Analysis

  • Short run times
  • Direct injection of samples
  • Enhanced separation of complex mixtures
  • Complete workflow solution
  • Innovative technology
  • The Chromeleon® Chromatography Data System provides comprehensive software tools

Alkali and Alkaline Earth Metals in Biodiesel Using Ion Chromatography

Recently, the ASTM adopted tougher standards for biodiesel blends, stipulating that a 6% blend may contain ≤0.3 ppm combined cations. The sensitivity range of ppb-to-ppm detection levels for ion chromatography is well-suited to the detection of inorganic cations, making this a simple application, with a wide linear dynamic range. As regulations become more stringent, your lab will have the analytical power required for the most demanding analyses.