Automated Dispersive Solid-Phase Extraction Using Dissolvable Fe₃O₄‑Layered Double Hydroxide Core–Shell Microspheres as Sorbent

Automation of dispersive solid-phase extraction (d-SPE) presents significant challenges. Separation of the sorbent from the spent sample cannot be conducted without manual operations, including centrifugation, a widely used means of isolating a solid material from solution. In this work, we report an approach to d-SPE using dissolvable magnetic Fe₃O₄-layered double hydroxide core–shell microspheres as sorbent to enable automation of the integrative extraction and analytical processes. Through magnetic force, the sorbent, after extraction, was isolated from the sample and then dissolved by acid to release the analytes. Thus the customary analyte elution step in conventional SPE was unnecessary. The automated d-SPE step was coupled to high-performance liquid chromatography (HPLC) with photodiode array detection for determination of several pharmaceuticals and personal care products (PPCPs) [acetylsalicylic acid (ASA), 2,5-dihydroxybenzoic acid (DBA), 2-phenylphenol (PP), and fenoprofen (FP)] in aqueous samples. For the automated d-SPE process, experimental parameters such as agitation speed, temperature, time, and pH were optimized. The results showed that this method provided low limits of detection (between 0.021 and 0.042 μg/L), good linearity (<i>r</i>² ≥ 0.9956), and good repeatability of extractions (relative standard deviations ≤4.1%, <i>n</i> = 6). The optimized procedure was then applied to determination of PPCPs in a sewage sample and ASA and FP in drug preparations. This fully automated extraction–HPLC approach was demonstrated to be an efficient procedure for extraction and analysis of ASA, DBA, PP, and FP in these samples