Capillary electrophoresis–tandem mass spectrometry for multiclass analysis of polar marine toxins
Polar marine toxins are more challenging to analyze by mass spectrometry-based methods than lipophilic marine toxins, which are now routinely measured in shellfish by multiclass reversed-phase liquid chromatography–tandem mass spectrometry (MS/MS) methods. Capillary electrophoresis (CE)–MS/MS is a technique that is well suited for the analysis of polar marine toxins, and has the potential of providing very high resolution separation. Here, we present a CE–MS/MS method developed, with use of a custom-built interface, for the sensitive multiclass analysis of paralytic shellfish toxins, tetrodotoxins, and domoic acid in seafood. A novel, highly acidic background electrolyte (5 M formic acid) was designed to maximize protonation of analytes and to allow a high degree of sample stacking to improve the limits of detection. The method was applied to a wide range of regulated and less common toxin analogues, and exhibited a high degree of selectivity between toxin isomers and matrix interference. The limits of detection in mussel tissue were 0.0052 mg/kg for tetrodotoxins, 0.160 mg/kg for domoic acid, and between 0.0018 and 0.120 mg/kg for paralytic shellfish toxins, all of which showed good linearity. Minimal ionization suppression was observed when the response from neat and mussel-matrix-matched standards was corrected with multiple internal standards. Analysis of shellfish matrix reference materials and spiked samples demonstrated good accuracy and precision. Finally, the method was transferred to a commercial CE–MS/MS system to demonstrate its widespread applicability for use in both R & D and routine regulatory settings. The approach of using a highly acidic background electrolyte is of broad interest, and can be considered generally applicable to simultaneous analysis of other classes of small, polar molecules with differing pKa values.
KeywordsBiotoxins Tetrodotoxin Paralytic shellfish poisoning Domoic acid Harmful algal bloom Capillary electrophoresis
The authors thank Michael Boundy from the Cawthron Institute and Aifeng Li from Ocean University of China for generously providing the sea slug and pufferfish tissue, respectively. Thanks are due to Jean-Francois Roy, Sylvie Larocque, and Dat Phan of Agilent Technologies for arranging access to the commercial capillary electrophoresis–tandem mass spectrometry system and for technical assistance with the related experiments.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no competing interests.
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