Determination of phytic acid in tea and some type of nuts by high performance liquid chromatography and UV-Vis

Phytic acid which exists in many natural products, and prevents to develop the calcium oxalate crystals (kidney stones) in kidney and urine by formation a complex with excess of calcium ions. Phytic acid also plays an antioxidant role to inhibit of iron-catalyzed oxidative reaction and formation of free radicals and reduce some cancers spices. The scope of this study, HPLC-Vis and UV-Vis methods were used for the determination of phytic acid in some type of nuts and tea leaves. Phytic acid does not have a characteristic absorption spectrum in UV Vis region, but it forms a stably complex with iron, therefore the determination of phytic acid was performed by measurement of the absorption of the ion(III)-5-sulfosalicylate complex in UV-Vis method and ion(III)-tiocyanide complex in HPLC method at 500 and 460 nm, respectively. Samples were treated with the iron-tiocyanide complex than directly injected into the HPLC system. Flow rate of the mobile phase, which was 30 % acetonitril/water consists of 0.1 M HNO3, was adjusted at 1 mL/min. The real retention time was 2.8 min. in these conditions. The level of phytic acid in nuts, tea leaves and cooked tea are ranged between 0.31 – 1.95, 4.09 – 5.76 and 5.30 – 5.96 mg/g, respectively. UV-Vis technique was used as a confirmation technique for the HPLC and both techniques were used in parallel. The results obtained for both techniques were in agreement with each other.