Biodiesel: Testing for Chloride and Sulfate Contamination

Despite passing through several purification steps following fermentation, bulk biodiesel may contain the dissolved salts chloride and sulfate. Because of their ability to damage modern engines, determining chloride and sulfate levels in biodiesel-based fuels is an important quality criterion. A standard method for detection of these analytes is ion chromatography (IC) configured with a conductivity detector. However, it lacks the capability to definitively identify the compounds.

An alternative method involves LC-MS. This is accomplished by post-column reaction with a di-/tri-cationic solution. This reaction causes positively charged adducts to be formed between the cationic reagents and the anionic chloride and sulfate. These adducts are detectable by the MS in the highly sensitive positive ESI mode. Advantages over IC methods are:
  • Definitive identification of analytes by their mass and spectra.
  • Easier sample preparation for complex matrices like biofuels.

Technical Article:
Detection of Chloride and Sulfate with Dication and Trication Solutions