Nischwitz and Pergantis 2006 - commercial kelp arsenic speciation

Nischwitz and Pergantis analyzed 12 commercially available edible marine algal powders by ICP-MS total arsenic analysis and HPLC-ICP-MS / HPLC-ES-MS/MS arsenic-speciation methods. The products were kelp-style powders sold through United States and Canadian suppliers, with Ascophyllum, Laminaria, and Fucus materials represented. The occurrence-relevant results are total arsenic in the commercial powders and water-extractable arsenic species; total arsenic, arsenate, DMA, arsenobetaine, and arsenosugars are kept separate below.

Key numbers

Table 2 reports total arsenic in mg/kg for commercial powders (n = 2) and water-extraction efficiency for arsenic. The paper describes the powders as dry commercial algal powders; no unit conversion was performed.

Table 3 reports HPLC-ICP-MS quantitative results for arsenic species in deionized-water extracts of the 12 powders. All contents are µg of As/g referring to an extraction with deionized water (n = 2); nd means not detected.

Arsenate was detected only in the Laminaria-type samples KE7-KE10 (7.1 ± 0.9 to 15.2 ± 1.2 µg of As/g in extracts). The authors state that this difference is important for food production because of arsenate’s high acute toxicity and because Fucaceae and Laminariaceae differed in arsenate detection.

Table 6 standard-addition quantification for selected species in three representative powders reports values as µg of As/g in the commercial powder without further drying:

Speciation-identification findings:

• HPLC-ES-MS/MS quality-control tools provided evidence for 19 organoarsenic species in the algal extracts.
• The most frequently reported species detected were DMAsSugarGlycol, DMAsSugarPhosphate, DMAsSugarSulfonate, DMAsSugarSulfate, and DMA.
• The authors also detected DMThioAsSugarGlycol, DMThioAsSugarPhosphate, DMThioAsSugarSulfonate, DMThioAsSugarSulfate, and arsenobetaine, a group they had recently reported in algae.
• Five species were identified as not previously reported in marine algal extracts: TMAsSugarPhosphate, TMAsSugarSulfonate, TMA, DMAsSugarCarboxyl, and DMAsSugarAdenine.
• Figure 7 normalized peak-area comparisons indicated higher DMAsSugarSulfate, TMAsSugarSulfate, and DMAsSugarAdenine intensity in Ascophyllum/Fucus samples, while DMAsSugarPhosphate, DMAsSugarSulfonate, and DMAA were higher in Laminaria extracts.

Methods (brief)

Twelve commercial kelp powder samples were obtained from suppliers in the United States and Canada. Total arsenic was measured by ICP-MS after closed-vessel microwave digestion of 150-200 mg powder with 5 mL concentrated nitric acid, dilution to 50 mL, external calibration, and indium internal standard; Tuna CRM 627 was used for quality control (5.14 ± 0.12 mg/kg, certified 4.8 ± 0.3 mg/kg). Arsenic species were water-extracted from 0.25 g powder with 5 mL deionized water, shaken 30 min, centrifuged, re-extracted once, combined gravimetrically, and analyzed the same day or after frozen storage. Speciation used anion-exchange HPLC-ICP-MS, anion-exchange HPLC-ES-SRM, combined cation-anion HPLC-ES-SRM, product-ion spectra, and accurate-mass checks. Standard addition was used where standards and sufficient analyte concentrations were available.

Implications

This source contributes direct occurrence evidence for commercial kelp/algal powders and high-resolution organoarsenic speciation context. Total arsenic ranged from 25.2 ± 1.4 to 83.0 ± 2.9 mg/kg, but inorganic arsenate was detected only in the Laminaria-type extracts, so total arsenic must not be promoted to inorganic arsenic for the non-Laminaria powders. The page is routeable to seaweed/kelp foods and algae/seaweed supplements; downstream pooling should preserve the commercial-powder basis and the distinction between total As, arsenate, DMA, arsenobetaine, and arsenosugar species.

Wiki pages this source may touch

• seaweed-kelp-foods
• supplements-algae-seaweed-based
• seaweed
• arsenic-total
• arsenic-inorganic

Verification notes

• Identity checks before writing found no existing source page for DOI 10.1021/jf060971j, paper code JF060971J, raw handle MFK_nischwitz2006, title text, or cite key nischwitz2006-commercial-kelp-arsenic-speciation.
• Text was extracted to /tmp/hmi-seaweed-053.txt with pdftotext -layout; Tables 1-7, methods, Results/Discussion, and references were readable.
• All Key numbers were checked against /tmp/hmi-seaweed-053.txt, especially Table 2 total-As/extraction-efficiency rows, Table 3 HPLC-ICP-MS species rows, Table 6 standard-addition rows, and the Results text that arsenate was detected only in Laminaria samples.
• Units and bases are preserved as mg/kg, µg of As/g, commercial powder without further drying, extraction efficiency %, and ng of As/g; no unit conversion was performed.
• Speciation check: total arsenic, arsenate, DMA, arsenobetaine, TMA, and individual arsenosugar/thioarsenosugar species are kept distinct. Arsenate detections are treated as inorganic arsenic context only for the source-reported arsenate rows; total As is not substituted for iAs.
• Brand firewall: consumer suppliers/brands are not named. Instrument/reagent/reference-material vendors are retained only as scientific-method context.
• Missing-slug check: no missing product or ingredient slug blockers. Exact algal types and sample codes remain in Key numbers while frontmatter uses broad seaweed/kelp and algae/seaweed supplement routing.

Page history

The five most recent substantive edits to this page. 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.