Overview
Bralatei and colleagues developed and validated a field-deployable method for screening inorganic arsenic in seaweed, using HPLC-ICP-MS as the comparison method. The study analyzed 13 store-bought edible seaweeds and 34 Laminaria digitata kelp-related samples, reporting iAs concentrations on a dry-weight basis. Total arsenic was measured for context, but the routeable occurrence analyte in this source is inorganic arsenic.
Key numbers
The study analyzed 47 samples: 13 commercial edible seaweeds (3 Kombu, 4 Nori, 3 Wakame, and 3 Hijiki) plus 34 Laminaria digitata samples related to different parts of kelp collected from western Ireland.
Method validation and performance values:
| Finding | Source-reported value |
|---|---|
| Field-method recovery during optimization | 80-94% iAs recovery |
| Average reproducibility/error | +-19% |
| HPLC-ICP-MS comparison | slope 1.03, R2 = 0.70, no bias reported |
| Field-method observed LOQ | around 0.05 mg kg−1 (dry weight) |
| Field-method time | within 1 h |
| ERM-CD200 total As QC | 53 +- 2.6 mg kg−1, certified 55 +- 4 mg kg−1 |
| ERM-BCR-211 total As QC | 0.22 +- 0.016 mg kg−1, certified 0.26 +- 0.013 mg kg−1 |
| ERM-BCR-211 iAs QC | 0.11 mg kg−1, certified 0.124 +- 0.011 mg kg−1 |
For the 13 commercial edible seaweed samples, total As concentrations varied from 19 to 235 mg kg−1. HPLC-ICP-MS showed Hijiki samples with iAs concentrations 34-75 mg kg−1, while all other edible seaweed samples were below 1 mg kg−1. Field-method triplicates gave Hijiki iAs concentrations from 53 +- 7 to 76 +- 20 mg kg−1; the lowest field-method iAs concentration reported for the commercial set was 0.3 +- 0.01 mg kg−1.
For the 34 Irish Laminaria digitata kelp-related samples, HPLC-ICP-MS iAs ranged from 2.2-87 mg kg−1 with an average of 29 +- 19 mg kg−1. The field method gave 3-73 mg kg−1 with an average of 34 +- 18 mg kg−1. A paired Student’s t-test comparing average iAs by field method versus HPLC-ICP-MS reported p = 0.217.
Methods (brief)
Commercial edible seaweeds and Irish kelp samples were air-dried, milled, and analyzed for iAs by a field-deployable Gutzeit-style method: diluted HNO3 extraction, selective volatilization of iAs as arsine, and trapping on HgBr2-impregnated filter paper read by a Wagtech digital Arsenator. HPLC-ICP-MS used an Agilent 1100 HPLC with an Agilent 7500c ICP-MS, a Hamilton PRP-X100 anion-exchange column, carbonate buffer mobile phase, and rhodium internal standard. Total As was measured by ICP-MS after microwave digestion of 200 mg sample with 2 mL HNO3 (70%) and 1 mL H2O2 (30%).
Implications
This source provides edible seaweed and kelp iAs evidence with explicit analytical cross-validation against HPLC-ICP-MS. Hijiki and Irish kelp samples are high-iAs context for the seaweed-kelp foods category, while Nori, Wakame, and Kombu in the commercial set were below 1 mg kg−1 iAs in the main text. Total arsenic values should remain context only and not substitute for iAs.
Verification notes
- PDF text was extracted with
pdftotext -layout; main-text occurrence and method-validation values were checked in the extracted text. - DOI
10.1007/s00604-017-2151-1, raw handleMFK_bralatei2017, and cite-key checks found no existing source page before creation. - The detailed commercial-sample table is in the paper’s supplementary information; the source page uses only main-text ranges and examples available in the extracted PDF text.
- Speciation: the source’s routeable occurrence values are inorganic arsenic (
iAs). Total As is included in frontmatter and body only because the paper reports total As context for the same seaweed samples. - Units are preserved as
mg kg−1dry weight; no conversion was performed. - Brand firewall: commercial seaweed samples were purchased retail/online, but no brand names are attached to contamination values here.
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