Ferrite nanospheres-based magnetic solid-phase extraction for determination of domoic acid in seawater samples using high-performance liquid chromatography with tandem mass spectrometry

A simple, rapid and sensitive method for determination of trace levels of domoic acid (DA) in seawater was developed, based on a magnetic solid-phase extraction (MSPE) followed by high-performance liquid chromatography with tandem mass spectrometry (HPLC–MS/MS). Five kinds of ferrite magnetic nanospheres (MFe 2 O 4 ; M   =   Fe, Co, Ni, Cu and Zn) were prepared and first used as sorbents for MSPE of DA and removal of salt interference. Under the same extraction and elution conditions, CuFe 2 O 4 magnetic nanospheres provided the best pretreatment performance, which were then characterized in detail. After further optimization of conditions, the developed method showed good linearity (r 2   =   0.9991) with the range of 5–1000   pg   mL −1 , low limit of detection (2.5   pg   mL −1 ; S/N   =   3:1), low limit of quantification (5.0   pg   mL −1 ; S/N   =   10:1), and good recoveries (86.0–98.1%) with acceptable repeatability (RSD   ≤   6.5%; n   =   3) in seawater samples. The results demonstrated that the ferrite magnetic nanospheres are promising sorbents for efficient extraction of highly polar analytes from high ionic strength solutions.