Abstract
The absolute quantification of five toxins involved in ciguatera fish poisoning (CFP) in the Pacific was carried out by quantitative 1H-NMR. The targeted toxins were ciguatoxin-1B (CTX1B), 52-epi-54-deoxyciguatoxin-1B (epideoxyCTX1B), ciguatoxin-3C (CTX3C), 51-hydroxyciguatoxin-3C (51OHCTX3C), and ciguatoxin-4A (CTX4A). We first calibrated the residual protons of pyridine-d5 using certified reference material, 1,4-BTMSB-d4, prepared the toxin solutions with the calibrated pyridin-d5, measured the 1H-NMR spectra, and quantified the toxin using the calibrated residual protons as the internal standard. The absolute quantification was carried out by comparing the signal intensities between the selected protons of the target toxin and the residual protons of the calibrated pyridine-d5. The proton signals residing on the ciguatoxins (CTXs) to be used for quantification were carefully selected for those that were well separated from adjacent signals including impurities and that exhibited an effective intensity. To quantify CTX1B and its congeners, the olefin protons in the side chain were judged appropriate for use. The quantification was achievable with nano-molar solutions. The probable errors for uncertainty, calculated on respective toxins, ranged between 3% and 16%. The contamination of the precious toxins with nonvolatile internal standards was thus avoided. After the evaporation of pyridine-d5, the calibrated CTXs were ready for use as the reference standard in the quantitative analysis of ciguatoxins by LC/MS.
Highlights
Ciguatera fish poisoning (CFP) refers to a peculiar form of neurologic poisoning resulting from the ingestion of fish inhabiting warm water regions
The CTX reference standard solution was dispensed in small aliquots into small glass vials, and the solvent was removed by a drying operation
To prevent the nonspecific adsorption of CTXs onto the glass wall surface, a very small amount of ethanol was added to each vial
Summary
Ciguatera fish poisoning (CFP) refers to a peculiar form of neurologic poisoning resulting from the ingestion of fish inhabiting warm water regions. In the Pacific, the causative toxins, named ciguatoxins (CTXs), are produced by microalgae, Gambierdiscus spp., and accumulate in various species of fish via the food chain [2]. Mouse bioassays [4] have been the routine practice to detect CTXs since early days but need to be substituted by other methods of higher sensitivity and specificity, not to mention the call to limit animal use for routine assays. We proposed using an LC/MS method as an alternative and successfully revealed the details of regional and species variations of toxin profiles in fish and causative algae [5]. The method is highly sensitive and produces accurate data, but we have to clear three hurdles to promote its wide use. The consensus on the regulation level is 0.01 ppb for ciguatoxin 1B or its
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
