Arsenic speciation in freshwater fish: challenges and research needs

Feasible approaches for arsenic speciation analysis in foods for dietary exposure assessment: a review

Arsenic (As) occurs naturally in different forms and oxidation states. Amongst them, inorganic arsenic (iAs) is classified as both genotoxic and carcinogenic whilst other organic arsenic species are considered less toxic. As in rice is mainly present in the form of iAs which therefore poses a health risk to populations that consume rice as a staple food. In 2011, the Joint Food and Agriculture Organisation/World Health Organisation Expert Committee on Food Additives determined the iAs benchmark dose lower confidence limit for a 0.5% increased incidence of lung cancer in humans (BMDL0.5) which computed to be 3.0 μg/kg body weight (bw)/day. However, the European Food Safety Authority (EFSA) has recently lowered the BMDL0.5 of iAs to 0.06 μg iAs/kg bw per day based on a low risk of bias case-control/cohort study on skin cancer as a Reference Point (RP). Subsequently, EFSA established a BMDL10 of 18.2 mg monomethylarsenic (V) (MMA(V))/kg bw/day and 1.1 mg dimethylarsenic (V) (DMA(V))/kg bw/day as RPs with reference to studies on skin cancer and urinary bladder tumours in rats respectively. Therefore, As speciation is essential when conducting dietary exposure assessment. Recent studies showed thiolated counterparts of MMA and DMA were found in certain foodstuffs, especially grain. However, these thiolated As species were not recognised in acidic, basic or peroxide systems as they transformed to MMA and DMA in these extractants. Therefore, one of the objectives of this review was to assess whether published analytical methods are fit for As speciation analysis, especially for iAs, MMA and DMA, in foodstuffs. Besides, discussion was conducted on whether limits of detection are sufficiently low for dietary exposure assessment with respect to recently established RPs of iAs, MMA and DMA when an upper bound approach is applied. Moreover, possible future research gaps are identified based on current knowledge and existing literature.

Multimodal chemical speciation techniques based on simultaneous high resolution molecular/atomic mass spectrometry applied to online target/non-target analysis: A tutorial review

BACKGROUND

If identifying target species is challenging regarding chemical speciation, non-target species present even more significant difficulties. Thus, to improve the performance of the methods, multimodal online coupling involving atomic and molecular mass spectrometry (LC-ICP-MS-ESI-HRMS) is an advance in this direction. Then, this kind of coupling is highlighted in this Tutorial Review, as well as some references emphasizing its potentialities and possible limitations. Some crucial definitions of speciomics, chemical speciation, and others are also included.

RESULTS

The main parameters that influence the coupling of an inductively coupled plasma mass spectrometer with a high-resolution mass spectrometer through a chromatographic system are critically commented on, and a diversity of results is demonstrated by using a turtle liver (Caretta caretta) as a model sample. The parameters were discussed in detail in a step-by-step manner: ICP-MS/MS acquisition modes and instrumental parameters, HRMS acquisition modes and instrumental parameters, and data processing strategies (Full MS - Top N, All Ion Fragmentation - AIF, Parallel Reaction Monitoring - PRM). Additionally, this Tutorial Review also demonstrates a diversity of results through target and non-target analysis.

SIGNIFICANCE

Constituting a guide for those who are interested in a non-targeted analysis of molecular non-volatile/semi-volatile compounds, this Tutorial Review presents trans and multidisciplinary proposals for those communities involving chemistry, biochemistry, medicine, biology, environmental, pharmaceutical, food safety, and omics, among others, where metal (also metalloids or semi-metals and non-metals or heteroatoms) and molecular species are necessary for a good understanding of the studied system. This kind of coupling also allows the discovery of novel biological active elemental species in diverse matrices.

Risk assessment of complex organoarsenic species in food

The European Commission asked EFSA for a risk assessment on complex organoarsenic species in food. They are typically found in marine foods and comprise mainly arsenobetaine (AsB), arsenosugars and arsenolipids. For AsB, no reference point (RP) could be derived because of insufficient toxicity data. AsB did not show adverse effects in the two available repeat dose toxicity tests in rodents. It has not shown genotoxicity in in vitro assays. There is no indication of an association with adverse outcomes in human studies. The highest 95th percentile exposure for AsB was observed in 'Toddlers' with an estimate of 12.5 μg As/kg bw per day (AsB expressed as elemental arsenic). There is sufficient evidence to conclude that AsB at current dietary exposure levels does not raise a health concern. For glycerol arsenosugar (AsSugOH) a RP of 0.85 mg As/kg bw per day was derived based on the BMDL10 values for cognitive and motor function in mice. A margin of exposure (MOE) of ≥ 1000 would not raise a health concern. The highest 95th percentile estimate of exposure for AsSugOH (for adult consumers of red seaweed Nori/Laver) was 0.71 μg As/kg bw per day (AsSugOH expressed as elemental arsenic), which results in an MOE > 1000, not raising a health concern. Based on qualitative consideration of all identified uncertainties, it is regarded likely that the dietary exposures to AsB and AsSugOH do not raise a health concern. No conclusions could be drawn regarding other arsenosugars. No risk characterisation could be conducted for arsenolipids, due to the lack of data.

Switchable hydrophilicity solvent-assisted solidified floating organic drop microextraction for separation and determination of arsenic in water and fish samples

The aim of the current study was to separate and determine arsenic in water and fish samples using a novel and green solidified floating organic drop microextraction (SFODME), which is based on switchable hydrophilicity solvent (SHS)-assisted procedure followed by hydride generation atomic absorption spectrometry (HG-AAS). The 4-((2-hydroxyquinoline-7-yl)diazenyl)-N-(4-methylisoxazol-3-yl)benzene sulfonamide (HDNMBA) and tertiary amine (4-(2-aminoethyl)-N,N-dimethylbenzylamine (AADMBA) were used as ligand and SHS, respectively. The use of SHS promotes quantitative extraction of arsenic complexes into an extraction solvent (1-undecanol). Some factors that impact extraction recovery were studied. Under optimal conditions, the limit of detection (LOD) and limit of quantification (LOQ) were 0.005 μg L-1 and 0.015 μg L-1, respectively. The calibration graph was linear up to 900.0 μg L-1 arsenic, with the enrichment factor is 267. The proposed SHS-SFODME methodology for arsenic quantification in water and fish samples was successfully implemented. The environmental friendliness and safety of proposed method were approved by the Analytical Greenness Calculator (AGREE) and the Blue Applicability Grade Index (BAGI) tools.