Determination of Mono-, Di-, and Triphosphates and Citrate in Shrimp by Ion Chromatography

The polyphosphates typically used in foods such as shrimp are small, containing two or three phosphate units, and they are often hydrolyzed to orthophosphate before the food is eaten. Citric acid is sometimes added to shrimp as a preservative to maintain an acidic environment. Ion chromatography (IC) is commonly used to determine both large (>3 phosphates) and small polyphosphates, as well as citrate.

The goal of this work was to measure only the small polyphosphates, an IC method was developed that used an eluent generator. Thus, the analyst must only add deionized water to the system to prepare the eluents necessary for accurately measuring small polyphosphates and citrate in shrimp. Additionally, the sample pretreatment required for this analysis to maintain good chromatography and extend column lifetime has been automated so that it is done on-line using a Thermo Scientific Dionex InGuard cartridge.