Automated magnetic solid-phase extraction based on hydrophilic-lipophilic balanced materials for LC-MS/MS determination of macrolides in pork.

A fully automated method based on magnetic solid-phase extraction (MSPE) using commercial hydrophilic-lipophilic balanced magnetic particles (MHLB) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the simultaneous determination of nine macrolides in pork. Key parameters of the automated MSPE procedure, including elution solvent, adsorbent amount, and ultrasonic time, were systematically optimized, achieving complete elution with only 2 mL of methanol. Processing one sample consumed only 30 mg of MHLB and 3 mL of organic solvent, and the automated protocol enabled batch processing of up to 20 samples. The method showed good linearity (R² > 0.99), low limits of quantification (0.03-0.33 μg/kg), and satisfactory recoveries (77.8-90.0% with RSDs < 10.3%). Compared with conventional HLB cartridges (200 mg sorbent, 14 mL organic solvent, mandatory defatting), MHLB offered superior solvent economy, material efficiency, and operational simplicity, with better matrix effect tolerance and more consistent recoveries. This automated MHLB-LC-MS/MS approach provides a reliable, high-throughput, and more environmentally friendly alternative for monitoring macrolide residues in livestock products.