Determination of different arsenic species in food-grade spirulina powder by ion chromatography combined with inductively coupled plasma mass spectrometry

Overview

Li and colleagues developed a two-step microwave-assisted extraction and IC-ICP-MS method for arsenic speciation in food-grade spirulina powder. They then applied the method to seven spirulina powder samples from Chinese production sites, reporting arsenite, arsenate, DMA(V), MMA(V), five unknown organic arsenic species, species sum, total arsenic, and recovery. Spirulina is handled here as an algae/cyanobacteria supplement powder; the taxonomy snapshot has no exact Spirulina ingredient slug.

Key numbers

Table 1 reports arsenic species in spirulina powder as ng g-1 (Average±SD, n=3). No unit conversion was performed. The source reports As(III) and As(V) separately; this page does not calculate a combined inorganic arsenic (iAs) value.

Table 1 footnotes state that - means not detected. As(III) was extracted with Milli-Q water under the optimized MAE temperature and time; As(V) was reported after subtracting the concentration obtained by Milli-Q-water extraction; total arsenic (As) was from digestion with HNO3-H2O2 (5:1, v/v); recovery was calculated as (species sum/total As) × 100.

The abstract and results summarize the same dataset as follows:

• As(V) was detected in all seven spirulina samples at 170-394 ng g-1, accounting for 8-100% of species sum.
• As(III) was detected in five provinces except Hainan and Guangxi at 28-147 ng g-1, accounting for 2-13% of species sum.
• DMA(V) was detected in six provinces except Guangxi at 32-839 ng g-1, accounting for 7-24% of species sum.
• MMA(V) was detected only in the Yunnan sample at 67±3 ng g-1.
• Five unknown organic arsenic compounds were detected except in the Guangxi sample; the results text reports their range as 38-2196 ng g-1, accounting for 9-62% of species sum.
• The concluding remarks state that spirulina powder samples had total arsenic in the range 0.33-3.38 µg g-1 and that extraction recovered >96% of arsenic.

Method-performance values reported by the source:

• Yunnan spirulina extracted-As species sum was (3527±71) ng g-1; digested total As was (3384±68) ng g-1; extraction recovery was (104±2)%.
• Instrumental detection limits were 5.00-10.0 ng L-1 for As(III), DMA(V), MMA(V), and As(V).
• Method detection limits in spirulina samples were 0.1, 0.1, 0.2, and 0.2 ng g-1 for As(III), DMA(V), MMA(V), and As(V), respectively.
• Spiked extraction recovery for As(III) in the Yunnan spirulina sample was (105±1)%.

Methods (brief)

Food-grade spirulina powder samples were purchased from production sites in Inner Mongolia, Zhejiang, Fujian, Hainan, Guangxi, Jiangsu, and Yunnan, China. About 500 g was purchased at each site, sifted through 100 mesh, stored in valve bags, and kept in a desiccator.

For most arsenic species, about 0.04 g spirulina powder was extracted in 12.0 mL H2O2/H2O (1:5, v/v) in sealed PFA jars and PEEK cans using an ETHOS UP microwave extractor at 100°C for 20.0 min. Extracts were weighed, filtered through 0.22 µm polypropylene membranes, and analyzed by IC-ICP-MS with 80 ng mL-1 74Ge as internal standard. As(III) was extracted and analyzed by the same procedure using Milli-Q water instead of H2O2/H2O because the authors state that As(III) is oxidized to As(V) during the peroxide extraction. The IC-ICP-MS system used a Dionex ICS-1100 IC and NexION 300X ICP-MS with an IonPac AS23 anion-exchange column; a cation-exchange column was used to verify species in concentrated Yunnan spirulina extract.

Implications

This source adds a primary arsenic-speciation dataset for food-grade spirulina powder from China. It is routeable to algae/seaweed-based supplement and dietary-supplement powder rows, but the source metadata leaves ingredients: [] because the closed vocabulary has no exact Spirulina/cyanobacteria ingredient slug. As(III) and As(V) are kept as source-reported species and are not collapsed into a hand-calculated iAs total.

Related evidence

• Ingredient class — algae/seaweed-based
• Dietary Supplements
• Oral solids: powders (bulk tubs, sachets, stick packs)
• Arsenic, Total
• Arsenic, Inorganic

Update history

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