Arsenic speciation in edible alga samples by microwave-assisted extraction and high performance liquid chromatography coupled to atomic fluorescence spectrometry

Overview

García-Salgado et al. measured total arsenic and water-extractable arsenic species in 12 commercially available edible marine algae from France, Japan, and Spain. The study reports total arsenic by ICP-AES after microwave digestion and speciation by HPLC-(UV)-HG-AFS after microwave-assisted water extraction. Inorganic arsenic is reported as arsenate, As(V), with As(III) not detected in the alga extracts; total arsenic and As(V) are therefore kept separate throughout this page.

Key numbers

Table 2 reports total arsenic in µg g−1 on dry mass (mean ± SD, n = 3) after microwave digestion and ICP-AES:

Table 4 reports water-extractable arsenic species in µg g−1 arsenic on dry mass (mean ± SD, n = 3) by anion-exchange HPLC-(UV)-HG-AFS. The source labels arsenate as As(V); As(III), MMA, AsB, TMAO, and TETRA were not detected in any alga sample.

The CRM NIES No. 9 Sargassum fulvellum quality-control material returned total As 109 ± 2 µg g−1 by digestion against a certified value of 115 ± 9 µg g−1. In Table 4, the same CRM had total As extracted 107 ± 2, extraction efficiency 98 ± 2%, DMA 0.9 ± 0.1, As(V) 70 ± 1, Gly-sug 1.0 ± 0.2, PO4-sug 1.4 ± 0.2, SO3-sug n.d., SO4-sug 7 ± 2, and column recovery 75 ± 2%.

The abstract summarizes the occurrence range as total arsenic 23 to 126 µg g−1, glycerol and phosphate arsenosugars 0.11 and 22 µg g−1, sulfonate and sulfate arsenosugars 0.6-7.2 µg g−1 where detected, DMA <0.9 µg g−1, and As(V) up to 77 µg g−1.

Methods (brief)

Samples were dried commercial algae. Spain and Japan samples were purchased at local markets as dried products; three France samples were supplied by the Centre d’Etude et de Valorisation des Algues. Samples were ground with a tungsten carbide disc mill and stored in pre-cleaned polyethylene containers. Total arsenic was measured by ICP-AES after microwave digestion with nitric acid and hydrogen peroxide. Arsenic species were extracted from 200 mg algae with 8 mL deionized water by microwave-assisted extraction at 90°C for 5 min, repeated three times, then filtered and analyzed by HPLC-(UV)-HG-AFS using anion- and cation-exchange methods. The paper reports species LODs from Table 3, including anion-exchange As(III) 0.019 µg g−1 As, DMA 0.007 µg g−1 As, MMA 0.027 µg g−1 As, and As(V) 0.028 µg g−1 As.

Implications

This source is high-value seaweed arsenic-speciation evidence because it separates total arsenic from measured arsenate and arsenosugars in named edible algae. Brown algae had high total arsenic and many samples had measured As(V), while both Nori samples had no detected As(V). Downstream extraction should keep tAs, As(V), DMA, and arsenosugars as separate species and should not treat total arsenic as inorganic arsenic.

Wiki pages this source may touch

• Seaweed/kelp foods (nori, wakame, kombu, dulse — as food products)
• Seaweed
• Arsenic, Total
• Arsenic, Inorganic

Verification notes

• Identity checks before writing found no existing DOI, raw-handle, or cite-key page for 10.1016/j.aca.2011.12.001, MFK_10-1016-j-aca-2011-12-001, or garcia-salgado2012-edible-algae-arsenic-speciation.
• All Key numbers were rechecked against /tmp/hmi-seaweed-002.txt, extracted with pdftotext -layout, especially Tables 2, 3, and 4.
• Speciation check: total As from Table 2 is recorded as tAs. Table 4 arsenate is recorded as measured As(V) / inorganic arsenic context only; As(III) was not detected and no total-As value is promoted to iAs.
• Units and basis are preserved as µg g−1 dry mass, %, and µg g−1 As for LODs; no conversions were performed.
• Evidence tier A reflects peer-reviewed primary speciation data with named species, reported QA/QC CRM recovery, extraction efficiencies, column recoveries, and method LODs.
• Brand firewall: no sampled brands are reported. Instrument and CRM names are retained only as scientific method details.

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.