Separation and determination of six catechins in tea by pressurized capillary electrochromatography

Abstract

An efficient pressurized capillary electrochromatography (pCEC) method has been successfully developed for the determination of six catechins in tea. The separation was performed on a reversed-phase EP-100-20/45-3-C18 capillary column (total length of 45 cm, effective length of 20 cm, diameter of 100 μm, ODS packing inside for 3 μm). The mobile phase ratio of organic phase, the concentration of phosphate buffer and sodium heptanesulfonate, separation voltage, and other experimental conditions were investigated and optimized. The mobile phase was 15 mM NaH₂PO₄ and 12 mM sodium heptanesulfonate (pH 3.0)/methanol (64:36) at a flow rate of 0.04 mL/min. Under optimal conditions including applied voltage of −4 kV and a UV detection wavelength of 230 nm, the six catechins in the tea were well separated. The calibration curves for the analytes had good linearity in the range of 8.02 μg/mL–202.13 μg/mL with a correlation coefficient of 0.9928–0.9997. The limits of detection (LOD) for the six catechins were 4.62 μg/mL–11.63 μg/mL (S/N = 3). The recoveries of the six catechins were 96.2%–108.4% with a relative standard deviation (RSD) between 0.78% and 4.51%. The method has been used for the determination of six catechins in tea samples with good results.

GRAPHICAL ABSTRACT

KEYWORDS:

• Catechin compound
• pressurized capillary electrochromatography (pCEC)
• Guangxi Liubao Tea
• Yunnan Pu'er Tea
• Hunan Anhua Dark Tea
• trace analysis

Disclosure statement

All authors declare no conflict of interest.

Additional information

Funding

This work was financially supported by Natural Science Foundation of Guangxi [Grant No. 2014GXNSFAA 118402, 2016GXNSFAA 380108]. We thank LetPub (www.letpub.com) for its linguistic assistance during the preparation of this manuscript.