Kinetic–turbidimetric determination of phytic acid by sequential injection analysis Original Research Article

A sequential injection analysis method with kinetic–turbidimetric detection for the determination of phytic acid is described. The method is based on the diminution of the calcium oxalate crystallisation reaction rate in the presence of phytic acid. Such a crystallisation rate has been evaluated from the increase of turbidity with time. A linear calibration graph was obtained from 0.05 to 0.6 mg l−1 phytic acid and the relative standard deviation (n = 5) was 2.0% for a standard of 0.25 mg l−1 phytic acid. The method was applied to the determination of phytic acid in food samples (after purification by anion exchange chromatography) and compared with an indirect extraction–spectrophotometric determination based on the hydrolysis of phytic acid and determination of released phosphate.