[Determination of phosphate, pyrophosphate, metaphosphate and total phosphorus in seafoods by ion chromatography]

A method for the determination of phosphate, pyrophosphate, metaphosphate and total phosphorus in seafoods by ion chromatography (IC) was developed. The samples for the determination of phosphate, pyrophosphate, metaphosphate were extracted by 100 mmol/L NaOH solution at room temperature; the samples for the determination of total phosphorus were digested by incineration at high temperature; and then solid phase extraction (SPE) column was used to eliminate the interferences. The separation was carried out on an IonPac AS11-HC analytical column (250 mm x 4 mm) and an IonPac AG11-HC guard column (50 mm x 4 mm) using 30 - 80 mmol/L KOH gradient elution at a flow rate of 1.0 mL/min at 35 degrees C, coupled with a suppressor-type conductivity detector. Under optimum conditions, the measurement could be completed within 20 min. The effects of pH value, organic solvent and coexisted ions were investigated. The linear range was 0.3 -60 mg/L, the detection limits were from 2.1 mg/kg to 2.3 mg/kg, and the relative standard deviations were from 1.6% to 2.6%. The method was applied to the determination of anions in fish and shrimps with the recoveries of 81.8% - 100.0%. The method offered high selectivity, sensitivity, and gave a satisfactory results for real sample analysis.