Simultaneous Determination Of Five Phosphates In Dairy Products By Ion Chromatography

A simple and reliable analytical method was established for the quantitative determination of five phosphates (orthophosphate, pyrophosphate, trimetaphosphate, tripolyphosphate, and hexametaphosphate) in dairy products by ion chromatography (IC). The samples were deproteinized with 2% trifluoroacetic acid, defatted withn-hexane, and then purified on a C18 solid phase extraction cartridge. Five phosphates were separated on an IonPac(TM)AS11-HC analytical column (250 mm x 2 mm) and an IonPac(TM)AG11-HC guard column (50 mm x 2 mm) with gradient elution of 30-60 mmol/L NaOH, then detected by a suppressor type conductivity detector. The peak areas were linearly valuated with the concentration of the five compounds with good linear coefficients (not less than 0.9986). The limits of detection ranged from 0.1 mg/L to 0.6 mg/L. The average recoveries were within the range of 83.0-117.8% with the RSDs below 9.0%. The concentration of the five phosphates in the treated samples remained relatively stable within 48 h. The proposed procedure has been applied to the determination of the five analytes in several dairy product samples with satisfactory results.