Llorente-Mirandes 2011 — Total arsenic and arsenic speciation in six commercial edible seaweeds (Spain)

Llorente-Mirandes and colleagues determined total arsenic and water-soluble arsenic speciation (arsenosugars, methylated species, and inorganic arsenic) by LC-ICP-MS in six commercial edible seaweeds sold in Spain. Total arsenic ranged 5.8–56.8 mg As/kg dry weight; arsenosugars dominated (>90% of extracted arsenic in four of six species), and inorganic arsenic [As(III)+As(V)] was a small fraction, detected in only three of the six samples at 0.29–0.51 mg/kg and below detection in the two kombu species (Laminaria ochroleuca, L. saccharina) and nori. All six were below the French inorganic-arsenic seaweed limit (3 mg/kg dw). The certified reference material Sargassum fulvellum (a hijiki relative), run throughout, by contrast carried 69.9 mg/kg inorganic arsenic (69% of extracted As). The study refines the row picture: the kombu/Laminaria genus is not uniformly high-iAs — these European-market kombu species were low, in contrast to the elevated L. digitata reported elsewhere.

Key numbers

Total arsenic and inorganic arsenic in mg As/kg dry weight (Table 1; mean ± SD, n=3). Inorganic As = As(III) + As(V). Moisture 7–10%; all results dry mass.

Additional source-reported facts:

• Inorganic arsenic was detected in only three of six edible seaweeds: C. crispus 0.51 mg/kg (3% of extracted As), U. rigida 0.30 (14%), U. pinnatifida 0.29 (18%); not detected in P. purpurea, L. ochroleuca, or L. saccharina.
• All six samples were below the French inorganic-arsenic limit for edible seaweed (3 mg/kg dw); no sample approached the ANZ limit (1 mg/kg) either.
• Arsenosugars were the dominant arsenic compounds, accounting for 97.0% (C. crispus), 98.3% (P. purpurea), 99.0% (L. ochroleuca), and 98.5% (L. saccharina) of extracted arsenic.
• The CRM Sargassum fulvellum (NIES 9) had 69% of its extracted arsenic as inorganic As (69.9 mg/kg), consistent with the high-iAs pattern of the Sargassum/Hizikia group.
• Method detection limits (mg As/kg): As(III) 0.007, As(V) 0.017, inorganic-As components down to ~0.002; DMA 0.005, MA 0.007.
• Extraction efficiencies were generally high except U. pinnatifida (29%), so part of its arsenic was unextracted; the authors caution that checking inorganic arsenic alone may underestimate risk because much seaweed arsenic is in arsenosugar forms of uncertain toxicity, and that water may not extract tightly (protein-)bound As(III).

Methods (brief)

Six dried edible seaweeds (Galician coast, bought in Barcelona) were oven-dried (40 °C) and milled. Total arsenic was determined in triplicate by ICP-MS (Agilent 7500ce, He collision cell, Rh internal standard) after microwave digestion (Milestone Ethos, concentrated HNO3 + H2O2). Arsenic speciation used a water extraction (end-over-end shaking, 16 h, room temperature) suited to arsenosugars, with LC-ICP-MS on both anion-exchange (Hamilton PRP-X100) and cation-exchange (Zorbax-SCX300) columns; As measured at m/z 75 with m/z 77 monitored for ArCl interference. Arsenosugars lacking standards were quantified against the nearest-eluting standard (PO4-sug vs MA; SO4-/SO3-sug vs As(V); Gly-sug vs AC); an Fucus serratus extract was used to identify arsenosugar peaks. Quality control used CRM NIES 9 Sargassum fulvellum (certified total As 115 ± 9 mg/kg; measured 110.3 ± 0.7). Inorganic arsenic is reported as As(III) + As(V). All values dry mass.

Implications

• Certification (HMTc): a direct-evidence occurrence-and-speciation source for the Category 6 seaweed-kelp-foods row (iAs/tAs platform). Its key contribution is a within-genus refinement, internal to this paper: the kombu-marketed kelps Laminaria ochroleuca and Laminaria saccharina (Saccharina latissima) here had inorganic arsenic below detection and total arsenic ~52–57 mg/kg dominated by arsenosugars (this study did not include L. digitata). For the row’s clean/dirty structuring this argues the high-iAs concern is species-specific within the kelps rather than generic to all “kombu”, and that nori and most green/red edible seaweeds sit low. (The contrasting high inorganic arsenic of L. digitata and the Sargassum/Hizikia group is reported by other corpus sources; that cross-source comparison belongs to the Part 9 synthesis pass, not this single-source page.) All on the dry-mass basis.
• App: contributes to the seaweed ingredient contamination_profile for total and inorganic arsenic across the common edible-seaweed trade types (Irish moss, nori, sea lettuce, kombu, wakame).

Verification notes

• raw_handle MFK_llorente-mirandes2011 from the PDF filename; raw_path under “raw/Manual Fetch Kimi /June 8 Inorganic Arsenic Seaweed/“. DOI 10.1021/jf2040466 confirmed on the article header. Distinct from the existing corpus page llorente-mirandes2016-ias-food-analytical-review (a later analytical review by the same group) — this is the 2011 primary occurrence study.
• Evidence tier A: peer-reviewed primary speciation study, triplicate analysis, LC-ICP-MS with CRM (NIES 9) validation.
• Speciation: total As and inorganic As [As(III)+As(V)] reported and kept distinct (lifted to frontmatter as tAs, iAs); As(III) and As(V) components are tabulated separately in Key numbers. Organic species (DMA, MA, arsenobetaine, four arsenosugars) were measured and summarised in the body but NOT lifted to frontmatter — they are not HMI analyte-vocabulary tokens; recording any of them as iAs would be a speciation error and is avoided. <LOD values recorded as such, not as numbers.
• Units/basis preserved exactly (mg As/kg dry mass). Inorganic-As percentages (of extracted As) are the source’s own figures.
• sample_n=6 edible seaweed products; the CRM (S. fulvellum) is a method-validation reference, reported in Key numbers for context but not counted as a market sample.
• Brand firewall: not engaged. Products identified only by common trade name (Irish moss, nori, sea lettuce, kombu, wakame) and species; no commercial brand names.
• Jurisdiction ES (grown Galician coast, sold Barcelona); sampling_locations records the Galician coast origin; sampling year not stated.
• matrices [edible-seaweed, macroalgae, kelp, dry-weight] per corpus convention; kelp warranted (Laminaria ochroleuca, L. saccharina).
• Instrument/CRM/vendor names (Agilent, Milestone Ethos, Hamilton, Zorbax, NIES 9) retained in Methods as permitted scientific reporting.
• Audit subagent (2026-06-08, fresh-context) returned REVISE; Checks 1–4 clean (all Table 1 values, the iAs/tAs speciation labeling, and brand firewall verified exact — no arsenosugar/organic value mislabeled as iAs). One Check 5 ⚠️ applied: the Implications section had attributed the contrasting high-iAs of L. digitata to “(Ronan 2017, Taylor 2016)” as if established by this paper, which neither measured L. digitata nor cited those works; reworded so the within-genus refinement is presented as internal to this study and the cross-source L. digitata contrast is flagged as belonging to the Part 9 synthesis pass, not this source page. No numeric/speciation corrections needed.

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