Abstract:Single laboratory validation of a method for arsenic speciation analysis in seafood and seaweed is presented. The method is based on stepwise extraction of water-soluble and non-polar arsenic with hot water and a mixture of dichloromethane and methanol, respectively. While the water-soluble arsenicals were speciated by anion and cation exchange liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS), the non-polar arsenicals were collectively determined by ICP-MS after digestion in acid.… Show more
“…4b). Quantification of AsSugars in CRM Hijiki 7405a has been reported by Wolle et al [27], showing good agreement with the quantification here, ESM Table S6, although double concentration of AsSugarSO 3 was found here compared to Wolle et al, where this higher concentration may possibly be attributed to co-elution of other water-soluble species.Fig. 4AsSugars, other As trace peaks not shown, full quantification in ESM Tables S4 and S5.…”
Section: Resultssupporting
confidence: 86%
“…The amount of arsenic in the hexane fraction seemed more arbitrary than in the other fractions, ranging from very little non-polar As present to up to 1 mg kg −1 . CRM Hijiki has been reported before with reasonable agreement with the totAs for the MeOH/DCM phase at 6.24 mg kg −1 [20] and 3.8 mg kg −1 [27] compared to 7.9 mg kg −1 here on average, Table 1. The lower value reported by Wolle et al [27] for the MeOH/DCM phase is likely due to a water extraction prior to the MeOH/DCM as reported in Pétursdóttir [19] and also speculated by Wolle et al [27].…”
Section: Resultssupporting
confidence: 80%
“…CRM Hijiki has been reported before with reasonable agreement with the totAs for the MeOH/DCM phase at 6.24 mg kg −1 [20] and 3.8 mg kg −1 [27] compared to 7.9 mg kg −1 here on average, Table 1. The lower value reported by Wolle et al [27] for the MeOH/DCM phase is likely due to a water extraction prior to the MeOH/DCM as reported in Pétursdóttir [19] and also speculated by Wolle et al [27]. The totAs for the hexane fraction [20] was higher than found here, or 0.97 mg kg −1 compared to 0.1 mg kg −1 .…”
Section: Resultssupporting
confidence: 80%
“…The totAs for the hexane fraction [20] was higher than found here, or 0.97 mg kg −1 compared to 0.1 mg kg −1 . Total As of water-soluble fraction of hijiki was in good agreement at 22.6 mg kg −1 [27] compared to 20 ± 2 mg kg −1 found here, Table 1.…”
Brown macroalgae
Saccharina latissima
(30–40 individuals) and
Alaria esculenta
(15–20 individuals) were collected from natural populations in winter in Iceland. The algal thalli were sectioned into different parts (e.g. holdfast, stipe, old frond, young frond and sori-containing frond sections) that differed in age and biological function. The work elucidated that arsenic (As) was not uniformly distributed within the two brown macroalgal species, with lower levels of total As were found in the stipe/midrib compared to other thallus parts. The arsenosugars mirrored the total arsenic in the seaweed mainly due to AsSugSO
3
being the most abundant As species. However, arsenic speciation using parallel HPLC-ICP-MS/ESI-MS elucidated that the arsenic-containing lipids (AsL) had a different distribution where the arsenosugarphospholipids (AsPL) differed by approximately a factor of 4 between the sections containing the lowest and highest concentrations of AsPLs. When placing the sections in order of metabolic activity and an estimate of tissue age, there appeared to be a relationship between the activity and AsPLs, with lower levels of AsPLs in oldest parts. This is the first time such a relationship has been shown for AsLs. Hence, by applying sophisticated analytical techniques, it was possible to gain a deeper understanding of arsenolipids in seaweed.
Electronic supplementary material
The online version of this article (10.1007/s00216-019-01907-x) contains supplementary material, which is available to authorized users.
“…4b). Quantification of AsSugars in CRM Hijiki 7405a has been reported by Wolle et al [27], showing good agreement with the quantification here, ESM Table S6, although double concentration of AsSugarSO 3 was found here compared to Wolle et al, where this higher concentration may possibly be attributed to co-elution of other water-soluble species.Fig. 4AsSugars, other As trace peaks not shown, full quantification in ESM Tables S4 and S5.…”
Section: Resultssupporting
confidence: 86%
“…The amount of arsenic in the hexane fraction seemed more arbitrary than in the other fractions, ranging from very little non-polar As present to up to 1 mg kg −1 . CRM Hijiki has been reported before with reasonable agreement with the totAs for the MeOH/DCM phase at 6.24 mg kg −1 [20] and 3.8 mg kg −1 [27] compared to 7.9 mg kg −1 here on average, Table 1. The lower value reported by Wolle et al [27] for the MeOH/DCM phase is likely due to a water extraction prior to the MeOH/DCM as reported in Pétursdóttir [19] and also speculated by Wolle et al [27].…”
Section: Resultssupporting
confidence: 80%
“…CRM Hijiki has been reported before with reasonable agreement with the totAs for the MeOH/DCM phase at 6.24 mg kg −1 [20] and 3.8 mg kg −1 [27] compared to 7.9 mg kg −1 here on average, Table 1. The lower value reported by Wolle et al [27] for the MeOH/DCM phase is likely due to a water extraction prior to the MeOH/DCM as reported in Pétursdóttir [19] and also speculated by Wolle et al [27]. The totAs for the hexane fraction [20] was higher than found here, or 0.97 mg kg −1 compared to 0.1 mg kg −1 .…”
Section: Resultssupporting
confidence: 80%
“…The totAs for the hexane fraction [20] was higher than found here, or 0.97 mg kg −1 compared to 0.1 mg kg −1 . Total As of water-soluble fraction of hijiki was in good agreement at 22.6 mg kg −1 [27] compared to 20 ± 2 mg kg −1 found here, Table 1.…”
Brown macroalgae
Saccharina latissima
(30–40 individuals) and
Alaria esculenta
(15–20 individuals) were collected from natural populations in winter in Iceland. The algal thalli were sectioned into different parts (e.g. holdfast, stipe, old frond, young frond and sori-containing frond sections) that differed in age and biological function. The work elucidated that arsenic (As) was not uniformly distributed within the two brown macroalgal species, with lower levels of total As were found in the stipe/midrib compared to other thallus parts. The arsenosugars mirrored the total arsenic in the seaweed mainly due to AsSugSO
3
being the most abundant As species. However, arsenic speciation using parallel HPLC-ICP-MS/ESI-MS elucidated that the arsenic-containing lipids (AsL) had a different distribution where the arsenosugarphospholipids (AsPL) differed by approximately a factor of 4 between the sections containing the lowest and highest concentrations of AsPLs. When placing the sections in order of metabolic activity and an estimate of tissue age, there appeared to be a relationship between the activity and AsPLs, with lower levels of AsPLs in oldest parts. This is the first time such a relationship has been shown for AsLs. Hence, by applying sophisticated analytical techniques, it was possible to gain a deeper understanding of arsenolipids in seaweed.
Electronic supplementary material
The online version of this article (10.1007/s00216-019-01907-x) contains supplementary material, which is available to authorized users.
“…27 To compensate for the lack of a suitable CRM for arsenosugars, other strategies, including an addition-recovery test, a standard addition method, and/or multiple analysis methods, are carried out to support the accuracy of the results. 28,29 But without a CRM, it is difficult to confirm the accuracy of independent results or to compare them with other results.…”
An inter-laboratory study was carried out to characterize a candidate hijiki seaweed for its concentrations of total arsenic and water-soluble arsenic compounds, particularly arsenosugar compounds. The candidate material, a dried hijiki seaweed powder, was analyzed by individual techniques in two laboratories. The water-soluble arsenic compounds were separated by anion exchange, and reversed-phase columns, and As(V), DMA and four kinds of arsenosugars, namely glycerol (-OH), phosphate (-PO4), sulfonate (-SO3), and sulfate (-SO4) types were detected by HPLC-ICP-MS. The methods applied were validated by analyzing a second sample, the NMIJ CRM 7405-a hijiki seaweed, which is certified for both total arsenic and As(V). Techniques for the inter-laboratory study, extraction efficiencies under different extraction conditions, some chromatographic techniques and sequential extraction were investigated. The results from the two laboratories for the candidate hijiki material showed good agreement within the measurement uncertainties for total and water-soluble arsenic compounds.
Arsenic can accumulate in freshwater biota, sometimes reaching potentially harmful levels. However, the toxicity of arsenic strongly depends on which arsenic species are present. Although organic species are considered less harmful than inorganic ones, they have not been extensively studied in freshwater environments and drivers of variation in arsenic speciation among sites and taxa remain unclear. We assessed concentrations of two organic arsenic species, arsenobetaine (AsB) and dimethylarsinic acid (DMA), in fish and invertebrates from three lakes near Sudbury, Ontario, Canada—a region with widespread mining impacts. Both AsB and DMA were detected in most samples (n = 212), varying across a wide range of concentrations (<0.001–30.144 and <0.006–5.262 mg/kg dry wt., respectively). The lake with the most severe mining impacts typically had the highest concentrations ([]) of AsB and DMA. In contrast, the percentage of total arsenic made up by AsB (%AsB) and DMA (%DMA) did not vary significantly between lakes. Arsenic speciation in fish muscle varied with fish size, selenium concentrations, and trophic elevation (inferred from nitrogen stable isotope ratios, δ15N), but relationships with dietary carbon source (inferred from carbon stable isotope ratios, δ13C) were more varied. Within all 3 lake food webs, [AsB] and [DMA] typically underwent biodilution, decreasing with trophic elevation (i.e., δ15N). Although the aforementioned factors explained some variation in arsenic speciation, there remains considerable unexplained variation. Further studies on arsenic speciation in freshwater biota should target a wider diversity of taxa to better understand drivers of variation in arsenic speciation. Additionally, work emphasizing the percentage of inorganic arsenic and other organic arsenic species is needed to improve environmental and human health risk assessments.
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