l-Cysteine-modified magnetic microspheres for extraction and quantification of saxitoxin in rat plasma with liquid chromatography and tandem mass spectrometry.

Saxitoxin, which is one of the most typical paralytic shellfish poisoning toxins, ranks the highest intoxication rate of marine biological poisoning cases globally. Efficient clean-up and extraction of saxitoxin from complex biological matrices are imperative for the analysis and concentration monitoring of the toxin when correlative poisoning cases happen. Herein, l-cysteine-modified magnetic microspheres based on metal-organic coordination were synthesized by a facile approach and applied for magnetic solid-phase extraction of saxitoxin from rat plasma samples before liquid chromatography-tandem mass spectrometry detection. Parameters, including adsorbent amount, extraction time, desorption solution, and desorption time that could affect the extraction efficiency, were respectively investigated. The developed method demonstrated good linearity in the range of 5-300 ng/mL (R2  = 0.9985) with a limit of quantification of 5 ng/mL and a limit of detection of 0.5 ng/mL, acceptable accuracy. and precision of within-run and between-run.