Evaluation of Phytic Acid Content of Some Tea and Nut Products by Reverse-Phase High Performance Liquid Chromatography/Visible Detector

Phytic acid contents of nine different types of nut and six different types of tea and steeped tea were analysed by reverse-phase high performance liquid chromatography with visible detector. The extraction method was based on hydrochloric acid extraction, and the analysis method was based on metal replacement reaction of phytic acid from coloured complex (iron(III)-thiocyanate), separation on CN column and monitoring the absorbance at 460 nm. The retention time for the monitored iron(III)-thiocyanate peak was achieved less than 3 min. The proposed HPLC/Vis procedure shows good linearity over the concentration range of 1-150 mg L-1 with a correlation coefficient value of 0.9938. The effectiveness of metal replacement reaction was presented in terms of relative standard deviation that was 0.62 and 0.88 % for 5 and 50 mg L-1 of phytic acid, respectively. Repeatability of the analytical method was ranging between 1.58-7.88 % (n = 10, for 50 mg L-1) and 0.98-4.63 % (n = 10, for 5 mg L-1) in terms of relative standard deviation. Accuracy of the method is good, ranging relative error between 4.52 and 8.00 % (n = 10, for 50 mg L-1). Phytic acid content is in the range of 1.54 to 9.74 mg g(-1) in nuts, 27.67 to 28.82 mg g(-1) in green teas, and 20.49 to 21.96 mg g(-1) in pocketed roasted teas.