# Ion mobility–mass spectrometry of palytoxin-like compounds produced by Ostreopsis cf. ovata

## TL;DR

This study uses ion mobility spectrometry to better identify and separate palytoxin-like compounds from a harmful microalgae species.

## Contribution

The first use of trapped ion mobility spectrometry and molecular dynamics to analyze palytoxin isomers and their ion mobility behavior.

## Key findings

- TIMS distinguished isomeric ions by detecting water loss from different toxin sites.
- DTIMS and TWIMS produced comparable CCS values for palytoxin analogues with less than 2% deviation.
- 102 CCS values were generated for toxin adducts and fragments, offering a reference for future toxin screening.

## Abstract

Palytoxin (PLTX) and its analogues from Ostreopsis cf. ovata are significant health concerns. They show potent vasoconstrictive properties, often causing seafood poisoning. PLTX analogues have chiral centers, resulting in many isomers, making their separation by liquid chromatography and identification/characterization by mass spectrometry challenging. This study explores for the first time the ion mobility spectrometry (IMS) behavior of these compounds to address these analytical challenges. Drift tube ion mobility spectrometry (DTIMS) and traveling wave ion mobility spectrometry (TWIMS) were used and compared. Additionally, trapped ion mobility spectrometry (TIMS) and molecular dynamics simulation were employed to explain unexpected results. TIMS provided higher resolution, distinguishing isomeric ions generated in the electrospray source by losing water molecules from different toxin sites. Computational studies offered theoretical insights into the ion mobility of triply charged calcium and sodium adduct ions, suggesting a folded conformation. DTCCSN2 (collisional cross section using DTIMS and nitrogen as buffer gas) values were obtained for PLTX (standard), ovatoxin-a, and ovatoxin-b from microalgae samples in Sant Andreu de Llavaneres (Barcelona, Spain). These values were comparable (ΔCCSs < 2%) to those measured with TWIMS calibrated using PLTX (standard). The study provides 102 CCS values from DTIMS and TWIMS data for adducts and fragment ions of PLTX analogues, which can be used as reference values in databases for toxin screening in complex samples.

The online version contains supplementary material available at 10.1007/s00216-025-06158-7.