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

• Ferrite nanospheres were creatively used as magnetic solid-phase extraction sorbents.
• CuFe2O4 nanospheres were first used for extraction of domoic acid from seawater.
• High ionic strength matrix did not interfere with extraction of domoic acid.
• The developed method was very simple, rapid and sensitive.

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 (MFe2O4; 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, CuFe2O4 magnetic nanospheres provided the best pretreatment performance, which were then characterized in detail. After further optimization of conditions, the developed method showed good linearity (r2 = 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.