Online extraction and determination of active components from Huangqi Chifeng Decoction based on a homemade monolithic adsorbent with a micron-tube structure

In this work, a monolithic block copolymer featuring a micron-tube structure was fabricated within a stainless steel tube (50 × 4.6 mm), using divinyltetramethyldisilane and <i>N</i>,<i>N</i>-diallylmelamine as the co-monomers, with the incorporation of doped lignin polymer. The prepared monolithic block copolymer was characterized by scanning electron microscopy, nitrogen adsorption-desorption method, mercury intrusion porosimetry, and infrared spectrometry, among other techniques. The results revealed a relatively uniform porous structure with micron-tubes and an enhanced specific surface area. The prepared composite block copolymer packed in the stainless steel tube served as a solid-phase extraction column for the online extraction and determination of prim-O-glucosylcimifugin, paeoniflorin, and calycosin-7-glucoside from the Chinese herbal medicine formula of Huangqi Chifeng Decoction. This was coupled online with a C18 analytical column and detected by high-performance liquid chromatography (HPLC). The solid-phase extraction adsorbent exhibited excellent selectivity for the target components. Compared to the porous structure achieved by particle accumulation, the micron-tube structure can enhance the efficiency contact sites between the components and the adsorbent surface, thereby improving the adsorption efficiency. The feasibility of the proposed method was confirmed through methodology validation, which demonstrated a relative standard deviation of no more than 2.0% and recoveries ranging from 95.5 to 100.7%.