Research On Rapid Determination Of Tea Polyphenols In Health Care Products By Using The Test Paper

Tea polyphenol, also known as tea tan or tea tannin, occupies 30% of the tea's dry weight. It serves as one of major components for the tea's color, flavor and healthcare function, as well as one of major indicators for quality measurement. Although traditional testing methods for tea polyphenol are quite accurate, their economy, rapidity and convenience fail to meet requirements for real-time field test. For example, the traditional testing operation is fussy and complex, time and energy consuming, costly, and constrained by large-size laboratory instruments or professional operating technicians or less environmental-friendly reagents used. Thus a rapid and handy tea polyphenol testing method is badly needed for real-time field test. Regarding deficiencies in traditional testing methods for tea polyphenol, some research results are demonstrated as below:(1) Different blue-violet ligand ternary complexes are formed by reaction among ferrous ions, citrate ions and tea polyphenols; stable properties and color shade of ternary complexes are positively associated with the tea polyphenol concentration. On such a basis, ferrous citrate spectrophotometry is determined as the new method for measuring tea polyphenol content in healthcare products. Since the color of ferrous citrate based color reagent changes obviously after reaction with the tea polyphenol solution, and complexation reaction reaches the maximum dose within 5 minutes with the absorption peak of 545 nm, rapid test is available. After a series of optimal experiments, the tea polyphenol concentration within 0~100mg/L obeys Beer's law. Other parameters include the correlation coefficient R2=0.9997 with good linear dependence, the regression equation Y=0.00573+0.02885 X, the average recoveries of standard addition up to 99.12%, RSD<0.5, high precision and good stability. Experimental testing results of tea polyphenol content in healthcare products are consistent with high-performance liquid chromatography analysis results even with satisfactory accuracy, so the rapid test method is feasible for measuring tea polyphenol content in healthcare products.(2) Rapid test of tea polyphenol content in healthcare products with test paper is explored beforehand. Ferrous citrate is determined as the best color reagent and the slow color rendering of ferrous citrate test paper is settled. Chitosan is used to prevent color reagent spillover; the combined use of 3% chitosan and artificially added carbon dioxide milieu interne can protect color reagent from oxidization in the test process, which clears away obstacles for test paper preparation and functional application. Physical characterization of the test paper achieves expectant requirements of experimental design in mechanism and principle. Possible difficulties in test paper preparation have been roughly resolved and preparatory conditions for follow-up development of test paper application have been completed. It proves that the formal development of test paper is available.(3) Improve the production process of color reagent, explore best conditions for reaction between test paper and tea polyphenol, and establish the new method for tea polyphenol test with the ferrous citrate test paper. According to optimal experiments, ternary complexes formed by reaction between ferrous citrate and tea polyphenol can reach the stable maximum dose within 5 minutes under pH7~8, and color shade of test paper is positively associated with the tea polyphenol concentration in samples. Compared color reagent with standard colors, the tea polyphenol concentration is readable. Telling from the tea polyphenol concentration measuring in seven samples with the HPLC method, the method here can conduct semiquantitative analysis of tea polyphenol. As discovered from stability and interference experiments, test paper used in the method shows better stability and interference. Thus it can be seen that, the tea polyphenol test paper is featured with economical, simple and rapid, easy to carry, accurate and stable, which can be used in real-time rapid test of tea polyphenol content in healthcare product samples. Particularly, the tea polyphenol content test can provide necessary guidance for consumers buying tea polyphenol products to avoid blind purchase. It is predicted that, tea polyphenol test paper will have a broad prospect in application.