Quantifications of saxitoxin concentrations in bivalves by high performance liquid chromatography-tandem mass spectrometry with the purification of immunoaffinity column

In this study, saxitoxin (STX) immunoaffinity column (IAC) solid phase extraction (SPE) technology was used to extract and purify STX in bivalve aquatic products. By optimizing the conditions of sample pretreatment, the method of detecting STX in bivalve aquatic products had been established by high performance liquid chromatograph-tandem mass spectrometry (LC-MS/MS) based on the cleanup of SPE with immunoaffinity interaction mechanism. The phosphate buffer solution (PBS) was used to extract STX in bivalves. The sample was separated on a TSK-GEL Amide column (2.0 mm x 250 mm, 5 mu m) with water contained 2 mM ammonium formate-50 mM formic acid and 95% acetonitrile contained 2 mM ammonium formate-50 mM formic acid as mobile phase by gradient elution. STX had a good linearity in the range of 2.468 mu g/kg to 246.8 mu g/kg with the correlation coefficient of r greater than 0.999. The detection of limit (0.1 mu g/kg) was more sensitive, two orders of magnitude better than previous report (20 mu g/kg) in bivalve aquatic products. The recovery ranged from 79.3% to 102.9%. The method has a good selectivity with eliminating matrix effect thoroughly, no need for matrix matching, thus it can satisfy the requirements of trace STX detection in bivalve aquatic products.