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2007.01

Monitor Antioxidants in Tea Extract

Using an Ultra Aqueous C18 HPLC Column and Unique® TOFMS

by Julie Kowalski, Ph.D., Innovations Chemist

• Use highly aqueous mobile phases without collapsing the stationary phase.

• Extract data for specific compounds and manually inspect spectra for other compounds.

• Simple sample preparation.

Much focus has been given to the health benefits of

foods and beverages that contain antioxidant com-

pounds. By reacting with free radical-forming

compounds before they can cause cell damage,

antioxidants protect the body against oxidative

stress.

Some foods and beverages naturally con-

tain antioxidants, but supplementing foodstuffs

has been on the rise due to demands by health

conscious consumers. Recently, green tea has been

successfully promoted as a health drink because it

contains antioxidant phenolic compounds.

Using LC/TOFMS, we show a straightforward

method for determining the presence of antioxi-

dant compounds in commercial tea formulations.

Samples were prepared by adding approximately

15g of dry tea product to 200mL of methanol

which was cooled to approximately 20°C. The

mixture was stirred for 5 minutes and decanted.

The tea product was rinsed with an additional

20mL of cooled methanol. The 200mL and 20mL

solutions were combined, then filtered through a

0.45µm syringe filter to capture particles. The fil-

tered solution was used directly for analysis.

We used a 150 x 2.1mm Ultra Aqueous C18 HPLC

column for the analysis and, because a tea extract

is a complex matrix, we used a gradient elution

and mobile phases with a high water content. The

Ultra Aqueous C18 stationary phase is ideal for

such an application: the phase is specifically

designed to prevent collapse of the C18 alkyl

chains in highly aqueous mobile phases.

Figure 1

A complex mix of tea extract components is best

separated on an Ultra Aqueous C18 column with a highly aqueous

mobile phase (total ion chromatograms of Table 1 compounds).

Figure 2

(-)-Epicatechin produced by infusion of a standard (A)

and spectrum of (-)-epicatechin created from an extracted ion

chromatogram (B).

LC_FF0425

LC_FF0425A

LC_FF0425B

For conditions see Figure 3.