Speciation Analysis of Arsenics in Commercial Hijiki by High Performance Liquid Chromatography-tandem-mass Spectrometry and High Performance Liquid Chromatography-inductively Coupled Plasma Mass Spectrometry

Overview

Shimoda and colleagues measured total arsenic, water-extracted inorganic arsenic, and arsenosugar species in seven commercially available dried-hijiki products and two raw hijiki samples. The occurrence-relevant matrix is hijiki seaweed on a dry-weight basis, with source-region and production-system context retained from Table 1. Total arsenic, water-extracted total arsenic, inorganic arsenic, DMA, and individual arsenosugar peaks are kept separate below.

Key numbers

Table 1 identifies the nine hijiki samples:

Table 4 reports acid-digested total arsenic and water-extracted arsenic fractions in µg As/g dw; each sample solution was measured in triplicate and values are mean ± S.D. (n = 3). No unit conversion was performed.

Table 3 reports water-extracted arsenic compounds by HPLC-ICP-MS in µg As/g dw; values are means (n = 3). ND means not detected by HPLC-ICP-MS, and the AsSug 328 peak includes unresolved AsBe and AsSug 254 according to the table footnote.

Source-reported summary statements:

• Acid-digested total arsenic in the nine hijiki samples ranged from 37.1 to 118.6 µg As/g dw.
• Water-extracted total arsenic ranged from 18.4 to 81.0 µg As/g dw.
• The major water-extracted compound was arsenate in all samples (8.94 to 70.52 µg As/g dw in Table 3).
• Water-extracted arsenosugars represented 3.7 to 27.6% of acid-digested total arsenic.
• AsSug 408 was the major arsenosugar peak in the water extracts.
• The authors state that HPLC-MS/MS detected arsenosugars more sensitively than HPLC-ICP-MS, but HPLC-MS/MS could not detect inorganic arsenic; they therefore recommend combined HPLC-MS/MS and HPLC-ICP-MS for seaweed arsenic-speciation work.

Methods (brief)

Commercial dried-hijiki products and two raw hijiki samples were ground to powder. Total arsenic was measured by ICP-MS with dynamic reaction cell mode after acid digestion of 20 mg powdered sample with 0.5 ml HNO3 and 0.5 ml H2SO4 at 330 °C for 1 hr, dilution to 50 ml, and standard addition calibration; NIES CRM No. 18 urine was used to validate total arsenic, AsBe, and DMA measurements. Speciation extracts used 0.5 g powdered hijiki swollen with 20 ml ultra-pure water, ultrasonic disruption for 1 min, centrifugation at 3000 rpm for 15 min, and adjustment of supernatant to 50 ml. Arsenosugars, AsBe, DMA, and MMA were detected by HPLC-MS/MS with multiple reaction monitoring; arsenic species and water-extracted species totals were measured by HPLC-ICP-MS with PRP-X100 anion-exchange chromatography.

Implications

This source contributes primary occurrence evidence for hijiki seaweed with total arsenic and inorganic arsenic separated in the same samples. The commercial dried-hijiki products had acid-digested total arsenic from 37.1 ± 1.2 to 118.6 ± 11.3 µg As/g dw, while water-extracted inorganic arsenic ranged from 9.2 ± 0.4 to 71.3 ± 2.0 µg As/g dw across all nine samples. The raw and processed hijiki rows should remain on the source’s dry-weight basis, and total arsenic, arsenate/arsenite, DMA, and arsenosugar peaks should not be collapsed into a single arsenic species.

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 source page for DOI 10.1248/jhs.56.47, raw handle MFK_shimoda2010, title text, or cite key shimoda2010-commercial-hijiki-arsenic-speciation.
• Text was extracted to /tmp/hmi-seaweed-058.txt with pdftotext -layout; Tables 1-4, methods, Results/Discussion, and references were readable.
• J-STAGE lists DOI 10.1248/jhs.56.47 for this article, although the local PDF text does not print the DOI.
• All Key numbers were checked against /tmp/hmi-seaweed-058.txt, especially Table 1 sample descriptions, Table 3 water-extracted species values, and Table 4 total/water-extracted arsenic summary values.
• Units and bases are preserved as µg As/g dw, %, mgAs/l, µg/l, ml, min, and °C; no unit conversion was performed.
• Speciation check: acid-digested total arsenic, water-extracted total arsenic, As(III), As(V), DMA, and individual AsSug peaks are kept distinct. The page treats As(III)+As(V) as the source’s water-extracted iAs and does not substitute total As for iAs.
• Source-side consistency check: the abstract says W-iAs/A-TAs ranged from 24.5 to 60.1%, while Table 4 reports sample 9 as 23.9%; the table value was transcribed as printed and the discrepancy was not corrected.
• Brand firewall: consumer brands/stores are not named. Instrument, reagent, and reference-material vendors are retained only as scientific-method context.
• Missing-slug check: no missing product or ingredient slug blockers. Exact hijiki product forms, production systems, and source areas remain in Key numbers while frontmatter uses broad seaweed/kelp food routing.

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.