Arsenolipids are a group of organic lipophilic arsenic compounds that are present in the marine food web, in fish in particular^1,2. Even so, studies on their metabolism, origin, abundance, and toxicity are still limited. Based on their chemical structure, arsenolipids (AsLps) range from arsenic-containing hydrocarbons (AsHC) and arsenic-containing fatty acids (AsFA), to the more structurally complex arsenic-containing triacyglycerides (AsTAGs). AsLps can occur at high levels in edible fish, often constituting as much as 20% of their total arsenic content or even more in fatty fish such as sashimi tuna¹. As the toxicity of arsenicals relates to their chemical form, knowledge of the speciation of AsLps in marine seafood is vital for health risk assessments³.

So far, our knowledge concerning the abundance and identity of these compounds is limited, especially compared to what we know about the water-soluble arsenic compounds present in marine organisms. This knowledge gap is partly due to the challenges involved in isolating trace amounts of AsLps from their lipid matrix in order to use them as standards, and the lack of routine analytical methods for the determination of AsLps in samples such as marine fish. To overcome these difficulties a few recent studies have reported on the synthetic preparation of AsLp standards and the preliminary characterization of the AsLps present in a few reference materials¹. However, AsLps are still not commercially available, and reference materials require more detailed characterization of their AsLp content.

In this presentation we will be discussing the development and application of a range of advanced analytical techniques for the determination (partial structural characterization and quantitation) of AsLp species in a tuna fish certified reference material (CRM) BCR 627. More specifically, we will be demonstrating the use of gradient elution HPLC – inductively coupled plasma mass spectrometry (ICP-MS), in combination with HPLC - electrospray ionization high resolution MS with a single AsLp standard in order to determine AsLps in the widely utilized BCR 627. We will be presenting data to confirm the presence of several already reported AsLp species in BCR 627, and propose the identity of some unknown AsLp species. Data processing workflows using freeware software packages will be presented for both targeted and non-targeted AsLp determination. This combination of techniques, materials and workflows may prove vital in enabling more widespread capabilities for AsLp determination in seafood, and thus facilitate the start of a new era in the study of such compounds.

References
[1] M. Stiboller, F.P. Freitas, K.A. Francesconi, T. Schwerdtle, A.J.A. Nogueira, G. Raber, J. Anal. At. Spectrom., 2019, 34, 2440.
[2] K.O. Amayo, A. Petursdottir, C. Newcombe, H. Gunnlaugsdottir, A. Raab, E.M. Krupp, et al. Analytical Chemistry, 2011, 83, 3589.
[3] J. Bornhorst, et al. Metallomics, 2020, 12, 794.