Determination of total arsenic and hydrophilic arsenic species in seafood

Overview

Luvonga, Rimmer, Yu, and Lee measured total arsenic and hydrophilic arsenic species across seven seafood and seaweed study materials spanning microalgae, macroalgae, bivalve clam, crustaceans, and finfish. Total arsenic was determined by ICP-MS and speciation by HPLC-ICP-MS. The source reports spirulina and kelp on a dry-mass basis, while the other seafood materials are reported on an as-received basis.

Key numbers

Table 2 reports total arsenic and arsenic species in ng/g; spirulina and kelp are dry-mass values, and all other rows are as-received:

The abstract reports total arsenic ranging from 133 +/- 11 ng/g in aquacultured shrimp to 26,630 +/- 520 ng/g in kelp. The Results text identifies the highest total arsenic contents as kelp 26.63 +/- 0.52 ug/g, wild-caught shrimp 10.25 +/- 0.37 ug/g, and geoduck clam 3.73 +/- 0.11 ug/g; all other seafood samples had total arsenic below 0.60 ug/g.

Inorganic arsenic was detected only in spirulina and geoduck clam among the study materials. Acid extraction gave inorganic arsenic (iAs) 265 +/- 12 ng/g in spirulina and 201 +/- 16 ng/g in geoduck clam; water extraction gave iAs 254 +/- 3 ng/g in spirulina and 72 +/- 11 ng/g in geoduck clam. The source states that spirulina iAs accounts for about 56% of total arsenic, while geoduck clam iAs accounts for about 5% of total arsenic. Kelp had no detected iAs in this study, although SRM 3232 Kelp Powder contained iAs 79.2 +/- 0.4 ng/g.

Hydrophilic arsenicals accounted for between 10% and 95% of total arsenic in the study materials. AsB was absent in spirulina and kelp but accounted for 13% of total arsenic in geoduck clam, 8% in aquacultured shrimp, 92% in wild-caught shrimp, 79% in aquacultured salmon, and 47% in wild-caught salmon. The authors also established DMA as a decomposition byproduct of arsenosugars under acidic extraction conditions.

Methods (brief)

Spirulina powder and Atlantic kelp powder were packaged as powder materials; geoduck clam from Alaska, wild-caught brown shrimp from off Charleston, aquacultured white-leg shrimp from Alabama, wild-caught Coho salmon from off Alaska, and aquacultured Coho salmon from a Washington river-based facility were processed to edible portions and cryogenically homogenized. Total arsenic used ICP-MS after microwave digestion and standard addition. Inorganic arsenic used dilute nitric-acid extraction based on EN 16802:2016 with conversion to AsV. Other hydrophilic arsenicals used water extraction to preserve arsenosugar integrity, followed by HPLC-ICP-MS.

Implications

This source supplies primary arsenic-speciation occurrence evidence for seafood, shellfish, fish, kelp powder, and spirulina powder. It reinforces that total arsenic is not a reliable proxy for inorganic arsenic: wild-caught shrimp had high total arsenic dominated by AsB, kelp had high total arsenic dominated by arsenosugars with iAs not detected, and spirulina had lower total arsenic but a high iAs fraction. Downstream pooling should keep spirulina supplement evidence separate from kelp/seaweed foods and from fish or shellfish occurrence rows, and should preserve the dry-mass versus as-received basis distinctions.

Update history

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