Studies On The Methods Of Determination Of Functional Components In Tea

This thesis has studied the analytical methods of determination of Functional Components of Tea. Four new determination methods of tea polyphenols and two new determination methods of caffeinum are reported. The methods have been applied to assay the samples and satisfactory results were obtained. It includes six parts as follows: Part 1: Review. A review of the published analytical methods for determination of tea polyphenols and caffeinum is given.Part 2: Indirect method of Atomic Absorption Spectroscopy to Determination of Tea Polyphenols. A new indirect method for determining tea polyphenols by atomic absorption Spectroscopy is studied. The basis is tea polyphenols could react with Pb2+ and lead to yellow precipitate .The precipitate is centrifuged to subside, the Pb2+ in supernatant is determined by AAS, and the concentration of tea polyphenols is obtained. The linear region is 3.0-25.0 u g?mL'1,RSD=l .3% and the recovery is 98.4-100% . When the method is applied to determine tea polyphenols, it can obtain good result.Part 3: Determination of Tea polyphenols by Ammonium molybdateSpectrophotometry.A new method for determining tea polyphenols by ammonium molybdate spectrophotometry was studied. The basis is tea polyphenols could react with ammonium molybdate and the yellow ester molybdate would be presented in sour solution. The linear region was 4.0-36 g mL-1, =2.1 X105 L- mol-1 ' cm-1, RSD =1.3% and the recovery is 100-105%. When the method is applied to determine tea polyphenols, it can obtain good result.Part 4: Determination of Tea Polyphenols by Differential Spectrophotometry. In the paper, a method for determining tea polyphenols by differential spectrophotometry was studied. The linear region was 2.0-12.0 g mL-1, e =1.97 X 105 L mol-1 cm-1,,RD=1.3% and the recovery is 97.5-102%. It can be successfully applied to the assay of tea polyphenols. Part 5: Determination of Tea Polyphenols in Tea Using Flow-injection Inhibitochemiluminesce. A novel flow injection methodasith inhibitory chemiluminescence system for the determination of tea polyphenols was presented. Tea polyphenols could inhibit the CL reaction of Luminol-HiCVKIC^ system in alkaline aqueous solution and the CL emission was inversely correlated with the tea polyphenols concentration. The linear range was 0.8 -2.4 u g mL-1 with a detection limit of 0.03 u g mL"1, the recovery was 102-105%, the sampling frequency was 240 times per hour. When the method is applied to determine tea polyphenols, it can obtain good result.IVPart 6: Determination of Caffeinum in Tea by O-phenylenediamine Spectrophotometry. A new method for determining caffeinum by o-phenylenediamine spectrophotometry was studied. The basis is caffeinum could react with o-phenylenediamine and the yellow light orange resultant would be presented in sour solution. The linear region was 4.0-25.0 u g mL-1, e =6.19 X 104, RSD=1.2% and the recovery was 100~105%.It can be successfully applied to the assay of caffeinum.