Surface area expansion by flower-like nanoscale layered double hydroxides for high efficient stir bar sorptive extraction.

Enhancing the surface area of stationary phase is essential in chromatographic science. In this work, nanoscale NiAl-layered double hydroxides (NiAl-LDHs) with flower-like structure was used as a platform for supporting the stationary phase. Then strong hydrophobic p-naphtholbenzein molecule was immobilized onto the LDHs layer as sorbent for stir bar sorptive extraction (SBSE). The flower-like LDHs layer significantly increased the extraction efficiency through increasing the specific surface area and immobilized amounts of stationary phase. In addition, the LDHs can also provide anion exchange ability, which expanded the application of this stir bar for analysis of not only hydrophobic but also anionic analytes. For improving the workability, a poly(ether ether ketone) (PEEK) jacket stir bar with detachable dumbbell-shaped structure was employed. The PEEK jacket with high mechanical strength and dumbbell-shaped structure improved the durability of stir bar and the detectable design allowed elution to be realized with less solvent that enhanced the enrichment factor. The proposed stir bar showed good performance for the extraction of multiple analytes including flavonoids, non-steroid anti-inflammatory drugs and chlorophenoxy acids. By coupling with high performance liquid chromatography-ultraviolet detection (HPLC-UV), the SBSE-HPLC-UV method was applied for the extraction of three active components including bavachin, isobavachalcone and bavachinin in Psoralea corylifolia L. herb with low limit detection of 0.01–0.02 ng/mL.