Evaluation of Phytic Acid Content of Some Tea and Nut Products by Reverse-Phase High Performance Liquid Chromatography/V
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Evaluation of Phytic Acid Content of Some Tea and Nut Products by Reverse-Phase High Performance Liquid Chromatography/ Visible Detector Kenan Dost 1 & Gülçin Karaca 1
Received: 27 May 2015 / Accepted: 16 September 2015 # Springer Science+Business Media New York 2015
Abstract 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.
Keywords Phytic acid . HPLC . Iron(III)-thiocyanate . Iron(III)-phytate . Nuts and teas
* Kenan Dost [email protected] Gülçin Karaca [email protected] 1
Department of Chemistry, Faculty of Science and Art, Celal Bayar University, Manisa, Turkey
Introduction Phytic acid is a natural plant product that is a primary storage form of phosphate in foodstuffs and can account for up to 60– 80 % of seed total phosphorus (Lopez et al. 2002). It originates in most cereal grains, legumes, nuts, oilseeds, tubers, pollen, spores and organic soils (Sanikommu et al. 2014). In cereals, phytic acid content ranges between 5 and 30 mg g−1; sometimes, it can reach up to 60 mg g−1 (Febles et al. 2002). Generally, in many plant species, 90 % of phytic acid is localized in the aleurone layer and only 10 % in the embryo. There are many factors such as genetics, environmental fluctuations, location, irrigation conditions, type of soils, year and fertilizer application that can affect the phytic acid content and phosphorus availability in cereal grains. Phytic acid is a six-carbon cyclic carbohydrate with a sixphosphate group attached to each carbon (Fig. 1). It has 12 replaceable protons that make it a strong polyionic acid with pKa values ranging from 1.9 to 9.5 (Evans et al. 1982). It accepts the sterically stable one phosphate at carbon two in the axial position and five phosphates in the equatorial position in the pH range of 0.5–9.0 and over pH 9.5 sterically hinder five phospha
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