Many studies have shown that green tea is rich in polyphenolic compounds which include flavanoids and phenolic acids. Flavonoids containing quercetin, kaempferol and rutin were found in green tea. Quercetin and kaempferol have the pharmacological effects of free radical scavengers, reduction of elevated blood pressure, anticancer and antioxidant properties. Chitosan is the second abundant natural polymer after cellulose. The presence of reactive groups including OH and terminal NH2 in chitosan chain could serve chelation sites. Therefore, chitosan has the ability to efficiently remove heavy metal ions(Cu 2+) and acid dyes.

Researchers from the Key Laboratory of Chemistry of Northwestern Plant Resources of the Chinese Academy of Sciences, have developed a new solid-phase extraction mode for magnetic retrieval of chitosan. The mode is combined with high-performance liquid chromatography-diode array detection for the pre-concentration and determination of flavonoids in green tea beverage samples.

In this mode, chitosan was directly put into acidic sample solution as sorbents for the extraction of target analytes. A great deal of undissolved chitosan in the sample solution plays an important role for extraction. After completing the extraction process, Fe3O4 nanoparticles acting as carrier were added to retrieve chitosan from sample solution. Good reproducibilities and satisfactory recoveries were obtained.

The proposed method possesses the advantages of fastness, simplicity, low cost, ease of operation and environmental benignity.

The work has received support from the National Natural Science Foundation of China. The findings have been published in Analyst (Analyst, 2012, 137, 910–916).

Analyst Paper

The experimental process of magnetic retrieval of chitosan solid phase extraction method. (Image by SHI Yanping et al.)