BEVERAGE
ASIA PACIFIC FOOD INDUSTRY OCTOBER 2009
46
The
Great Divide
Liz West, NJ, US
The determination of inorganic anions and cations, as well as organic acids in non-alcoholic carbonated beverages is of importance from both health-related and manufacturing perspectives. By Jeff Rohrer, director corporate applications group, Dionex Corporate Organic acids such as citrate and malate, and inorganic anions such as phosphate are monitored due to their function as acidifiers or flavour enhancers. Chloride is monitored due to restrictions imposed by different countries, and many Group I and II metals are monitored for purposes of mass balance. As such, the content of these compounds needs to be monitored by the manufacturer to maintain product quality and to investigate possible patent infringements in competitive products. Ion chromatography (IC) is a well-established technique
for the determination of ions in solution. In order to do this, ion exchange or ion exclusion chromatography (ICE) is used with suppressed conductivity detection for the determination of inorganic anions, cations, and organic acids in several popular carbonated beverages. • Equipment Needs A chromatographic system consisting of: - Gradient pump - Chromatography module - Conductivity detector - Eluent organiser or degas module
- Autosampler - Peaknet chromatography workstation • Reagents & Standards - Deionized water (DI H2O), 17.8 MΩ-cm or better • Anion Analysis - Sodium hydroxide solution, 50% w/w (Fisher Scientific) - Methanol (EM Science) • Cation Analysis - M e t h a n e s u l f o n i c a c i d , >99% pure (Fluka ChemikaBioChemika) • Organic Acid Analysis - P e rc h l o r i c a c i d ( F l u k a Chemika-BioChemika) - Te t r a b u t y l a m m o n i u m hydroxide (Dionex, P/N 39602) Preparation Of Solutions & Reagents • 100 mM Sodium Hydroxide Weigh 992 grm (992 ml) of 17.8 MΩ deionized water into a one ltr eluent reservoir bottle. Vacuum degas the water for approximately 10 minutes. Tare the bottle on the balance and add eight grm (5.25 ml) of 50 percent sodium hydroxide directly to the bottle. Quickly transfer the eluent bottle to the instrument and pressurise it with helium.