Determination of 10 organic acid contents in tea using high performance liquid chromatography-diode array detector

Abstract

A high performance liquid chromatography (HPLC) was developed to simultaneously determine the content of 10 organic acids (oxalic acid, D/L-tartaric acid, formic acid, L-malic acid, ascorbic acid, lactic acid, acetic acid, citric acid, succinic acid and fumaric acid) in tea. The chromatographic conditions were optimized in the aspects of mobile phase composition, column temperature, flow rate and detection wavelength. The established HPLC method was methodologically assessed and applied to teas, which included maintaining TSKgel ODS-100V column (4.6 mm×250 mm, 5 μm) at 40 ℃, using 0.10% phosphoric acid-water solution (mobile phase A) and 50% acetonitrile-water solution (mobile phase B) with the gradient elution mode of 100% A (0 min)→100% A (12 min)→0% A (17 min)→0% A (25 min)→100% A (30 min)→100% A (33 min) with 2 min post-run at the flow rate of 1.0 mL/min, and detecting at the wavelengths of 210 and 245 nm for ascorbic acid, and 210 nm for other organic acids by diode array detector (DAD). The correlation coefficients of regression equations for all of the components were greater than 0.999 5, and the relative standard deviations (RSDs) of accuracy and repeatability were lower than 1%, and their RSDs of stability were lower than 4% (except ascorbic acid), as well as the recovery rate with the method of 97%-116%. It is appeared that the newly developed method can yield fine linear relationship, desirable precision, repeatability and separability for determinations of 10 organic acids in tea.