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. 2024 Aug;416(20):4571-4580.
doi: 10.1007/s00216-024-05397-4. Epub 2024 Jun 21.

In situ growth of dual-responsive polymer as coating for open tubular capillary electrochromatographic separation of epimedins

Nasir Ali  1   2 , Liu Yutong  1   3 , Fuyi Wang  4   5 , Li Qi  6   7
Affiliations

In situ growth of dual-responsive polymer as coating for open tubular capillary electrochromatographic separation of epimedins

Nasir Ali et al. Anal Bioanal Chem. 2024 Aug.

Abstract

Recently, open tubular capillary electrochromatography (OT-CEC) has captured considerable interest; its efficient separation capability hinges on the interactions between analytes and polymer coatings. However, in situ growth of stimuli-responsive polymers as coatings has been rarely studied and is crucial for expanding the OT-CEC technique and its application. Herein, following poly(styrene-maleicanhydride) (PSM) chemically bonded onto the inner surface of the capillary, a dual pH/temperature stimuli-responsive block copolymer, P(SMN-COOH), was prepared by in situ polymerizing poly(N-isopropylacrylamide) carboxylic acid terminated [P(N-COOH)] in PSM. An OT-CEC protocol was first explored using the coated capillary for epimedins separation. As a proof of concept, the developed OT-CEC system facilitated hydrogen bonding and tuning the hydrophilic/hydrophobic interactions between the test analytes and the P(SMN-COOH) coating by varying buffer pH and environmental temperature. Four epimedins with similar chemical structures were baseline separated under 40 °C at pH 10.0, exhibiting dramatical improvement in separation efficiency in comparison to its performance under 25 °C at pH 4.0. In addition, the coated capillary showed good repeatability and reusability with relative standard deviations for migration time and peak area between 0.7 and 1.7% and between 2.9 and 4.6%, respectively, and no significant changes after six runs. This work introduces a paradigm for efficient OT-CEC separation of herbal medicines through adjusting the interactions between analytes and smart polymer coatings, addressing polymer coating design and OT-CEC challenges.

Keywords: Dual-responsive block copolymer; Epimedins; In situ polymerization; Open tubular capillary electrochromatography; Real herbal extracts.

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