Sadee et al. 2024 — Arsenic speciation in marine organisms: a review of occurrence and analytical methods
This review synthesizes the literature on arsenic occurrence and speciation in marine organisms — including fish, shellfish, and algae — with a focus on analytical methods for distinguishing inorganic arsenic (iAs) from the dominant organoarsenical species (arsenobetaine, arsenosugars, arsenocholine, DMA, MMA) characteristic of marine food matrices. The review compiles reported concentration ranges for total arsenic (tAs) and iAs across marine taxa and geographic regions, demonstrating that total arsenic in marine organisms is typically high (often hundreds to thousands of µg/kg ww) but that the fraction as iAs is generally small (commonly below 1–10% of tAs), with the remainder consisting of low-toxicity organic arsenicals. Analytical advances covered include HPLC-ICP-MS, HPLC-ICP-OES, and hydride-generation atomic absorption spectrometry for speciated arsenic determination. The review is directly relevant to regulatory discussions about applying iAs limits to seafood matrices where tAs is dominated by organoarsenic compounds.
Key numbers
The review is a secondary compilation; exact occurrence values vary widely by species, geography, and matrix:
- Total arsenic in marine fish: typically 100–2,500 µg/kg ww depending on species and tissue.
- Inorganic arsenic (iAs) fraction in marine fish: typically 1–5% of tAs, corresponding to approximately 1–50 µg/kg ww in muscle tissue; higher proportions in some bivalves.
- Seaweed and algae: tAs can reach 10,000–100,000 µg/kg dw, but speciation varies substantially by species; hijiki seaweed is notable for elevated iAs proportions.
- Shellfish (bivalves, crustaceans): tAs intermediate; iAs fractions higher than in fish muscle, with some mollusks at 10–30% iAs of tAs.
- HPLC-ICP-MS is the gold-standard method for speciation; the review documents LODs in the range of 0.1–2 µg/L for individual species.
Methods (brief)
Review methodology: systematic literature survey covering peer-reviewed publications on arsenic speciation in marine biota. Analytical techniques reviewed include HPLC-ICP-MS (most prevalent), HPLC-ICP-OES, HG-AAS, and electrochemical methods. The review distinguishes iAs from organoarsenicals by chromatographic separation; studies using ICP-MS without HPLC separation report tAs only and are discussed separately.
Implications
Certification: Establishes the critical principle that tAs in seafood is not a valid proxy for iAs; regulatory limits for iAs in seafood must rely on HPLC-speciated measurements. Relevant to HMT&C analyte selection and to certification of seafood-containing products. Courses: Essential teaching resource for the iAs vs. tAs distinction in marine matrices; the review explains why arsenobetaine dominates and why the toxicological risk from seafood arsenic differs categorically from arsenic in rice. App: Supports the app’s need to distinguish matrix type when estimating arsenic risk from ingredient lists; seafood entries should use tAs occurrence data with a note that iAs fraction is typically small. Microbiome: Not directly addressed; arsenic speciation literature notes that gut microbiota can demethylate organoarsenicals to produce some iAs in vivo, but this is not the review’s focus.