Determination Of Catechins In Tea Research Articles

DETERMINATION OF CATECHINS IN TEA BY MICELLAR ELECTROKINETIC CHROMATOGRAPHY WITH A GRAPHENE OXIDE-COATED CAPILLARY

A novel approach was developed for the determination of four catechins, (-)-epigallocatechin gallate, (-)-epigallocatechin, (-)-gallocatechin gallate, and (-)-epicatechin, in tea by micellar electrokinetic chromatography (MEKC) using an acidic phosphate buffer (40 mM, 100 mM sodium dodecyl sulfate, and 30% methanol, pH 3.0). The linear dynamic ranges for the catechins were between 25 and 250 μg/mL, and the graphene oxide-coated capillary offered satisfactory accuracy, precision, and limits of detection. The developed method was employed for the determination of catechins in tea.

Alkyl imidazolium ionic liquid based sweeping-micellar electrokinetic chromatography for simultaneous determination of seven tea catechins in human plasma.

Determination of tea catechins in human plasma might provide a means of better evaluation of their benefits. The main difficulty in their analysis is the low catechins concentrations in plasma and their susceptible to oxidation during sample pretreatment. In the current work, a sweeping-micellar electrokinetic chromatography (sweeping-MEKC) by long alkyl chain ionic liquid was investigated for the simultaneous determination of seven principal naturally-occurring tea catechins in human plasma under acidic conditions after the intake of green tea beverage. The effects of type and concentration of three 1-tetradecyl-3-methylimidazolium ionic liquids, namely bromide, acetate and hydrogen sulfate salts were studied. The seven catechins were successfully separated within 5min by micellar running buffer of 5mmolL(-1) 1-tetradecyl-3-methylimidazolium bromide and 15mmolL(-1) phosphate buffer at pH 4.5 under optimal parameters of 50mbar injection for 150s, 10kV, 25°C and 200nm. To prevent the possibility of IL adsorption, an appropriate rinsing protocol was established. The method has analytical ranges from 0.5, 1, 0.5, 1, 2, 1 and 1 to 500ngmL(-1) for GC, C, EC, EGCG, GCG, ECG and EGC, respectively (r ranged from 0.995 to 0.999). The intraday precision and accuracy were 0.1-0.9% RSD (n=10) and 97-106% recovery, respectively. Limits of detections of analytes were ranged from 0.2 to 1.2ngmL(-1). The current sweeping-MEKC achieved sensitivity enhancement factor (SEF) up to 183-fold of analytes concentrations compared to other hitherto published CE reports that is suitable to find out the trace amounts of catechins in plasma.

High-performance liquid chromatography of aromatic compounds with photochemical decomposition and tris(2,2′-bipyridine)ruthenium(III) chemiluminescence detection

A novel high-performance liquid chromatographic method for the determination of aromatic compounds based on the on-line photochemical degradation and subsequent tris(2,2′-bipyridine)ruthenium(III) chemiluminescence detection has been developed. Chemiluminescence intensity depended upon the number of aromatic rings, UV irradiation time, and variety of substituted functional groups. One of the decomposition products of aromatic compounds by UV irradiation was identified as oxalic acid. As one application of this methodology, determination of catechins in tea has been shown. Calibration graphs, based on standard (−)-epicatechin and (−)-epigallocatechin gallate solutions, were linear over the range of 0.1–50 μM. The detection limits (signal-to-noise ratio = 3) were 0.8 pmol for (−)-epigallocatechin gallate and 1.2 pmol for (−)-epicatechin. The high-performance liquid chromatography–chemiluminescence (HPLC–CL) detection method with a post-column photochemical reactor can be applied to the sensitive and selective determination of catechins in tea.

Determination of catechins in tea leaves using high performance liquid chromatography with electrochemical detector

Determination of catechins in tea leaves using high performance liquid chromatography with electrochemical detector

HPLC determination of catechins in tea leaves and tea extracts using relative response factors

A simple high performance liquid chromatographic analysis of tea catechins using relative response factors has been developed. The separation system consisted of a C18 reversed-phase column, a gradient elution system of methanol/water and orthophosphoric acid, and a photodiode array detector. Relative response factors for catechins are given on different columns and relative to different references. It has been shown that the relative response factors for catechins are quite similar at 210 nm of detection under different analytical conditions (different columns, different elution systems, and different HPLC instruments). (+)-Catechin was selected as the reference compound for calculating the relative response factors of the catechins. Using this method, not every catechin is needed as a reference standard, making the method ideal for rapid, routine analysis, especially for those laboratories where catechin standards are not readily available. The method is applicable to all kinds of tea, tea extracts and some tea containing products. It is especially useful for the determination of (+)-gallocatechin and (+)-catechin, which often are regarded as being present below detectable limits when detected at 280 nm, and (−)-catechin gallate, which takes a long time to elute in isocratic systems.