Analyzing Anions by Ion Chromatography

Anion analysis in food and beverage products

Weak-acid preservatives are anions that are widely used to prevent microbial spoilage of acidic foods and beverages, such as soda, fruit juice, soy sauce, jams, and other condiments. Inhibition by weak acids involves rapid diffusion of undissociated molecules through the plasma membrane, which liberates protons and acidifies the cytoplasm, preventing growth of microbes. Preservatives are more effective at low pH values where solutions contain increased concentrations of undissociated acids.

Anion analysis

Using a Thermo Scientific™ Reagent-Free™ ion chromatography (RFIC™) system simplifies weak-acid analysis, enabling full control of the hydroxide eluent concentration through Thermo Scientific™ Chromeleon™ Chromatography Data System (CDS) software. Samples only require a simple dilution prior to injection, and precision is significantly improved by avoiding manual preparation of eluents.

Regulatory information

  • FDA
    • Requires labeling of any food or beverage containing a sulfite concentration over 10 ppm.
    • Lists benzoate as a substance that is generally recognized as safe (GRAS), with a maximum permitted concentration of 0.1% in accordance with good manufacturing or feeding practices.
    • Requires infant formulas to have a minimum iodine concentration of 5μg/100 kcal and no more than 75μg/100 kcal.
  • European Union
    • Established a benzoate limit of 0.015% in soft drinks and up to 0.2% in other food products.

Example application notes

Application Note Sample IC Column
Rapid Determination of Phosphate and Citrate in Carbonated Soft Drinks Using a Reagent-Free™ Ion Chromatography System (AN 169) Soft drinks Dionex IonPac Fast Anion III Columns
Determination of Benzoate in Liquid Food Products by Reagent-Free Ion Chromatography (AN 165) Soy sauce Dionex IonPac AS18 Columns
Determination of Total and Free Sulfite in Foods and Beverages (AN 54) Wine Dionex IonPac ICE-AS1 Columns
Determination of Iodide and Iodate in Soy- and Milk-based Infant Formulas (AN 37) Milk and Infant Formula Dionex IonPac AS11 Columns