Sensitive determination of four camptothecins by solid-phase microextraction-HPLC based on a boronic acid contained polymer monolithic layer.

•A novel and high efficient boronic acid-based polymer monolithic layer for microextraction of CPTs was developed at the first time.•The limits of detection (LOD) were 0.05–0.2ngmL−1, which were lower than all papers reported.•The method has been applied in plasma samples, with good selectivity and good recoveries.