Dispersive solid‐phase extraction of alkaloids and polyphenols using borate hypercrosslinked polymers

In this study, a borate hyper-crosslinked polymer was synthesized by crosslinking 1-naphthalene boric acid and dimethoxymethane via the Friedel-Crafts reaction. The prepared polymer exhibits excellent adsorption performance toward alkaloids and polyphenols with maximum adsorption capacities ranging from 25.07 to 39.60 mg/g. Adsorption kinetics and isotherms model results indicated the adsorption was a monolayer and chemical process. Under the optimal extraction conditions, a sensitive method was established for the simultaneous quantification of alkaloids and polyphenols in green tea and Coptis chinensis by coupling with the proposed sorbent and ultra-high performance liquid chromatography detection. The proposed method exhibited a wide linear range of 5.0-5000.0 ng/ml with R2 ≥ 0.99, a low limit of detection (0.66-11.25 ng/ml), and satisfactory recoveries (81.2%-117.4%). This work provides a simple and convenient candidate for the sensitive determination of alkaloids and polyphenols in green tea and complex herbal products.