Inorganic Arsenic Determination in Food: A Review of Analytical Proposals and Quality Assessment Over the Last Six Years.

Here we review recent developments in analytical proposals for the assessment of inorganic arsenic (iAs) content in food products. Interest in the determination of iAs in products for human consumption such as food commodities, wine, and seaweed among others is fueled by the wide recognition of its toxic effects on humans, even at low concentrations. Currently, the need for robust and reliable analytical methods is recognized by various international safety and health agencies, and by organizations in charge of establishing acceptable tolerance levels of iAs in food. This review summarizes the state of the art of analytical methods while highlighting tools for the assessment of quality assessment of the results, such as the production and evaluation of certified reference materials (CRMs) and the availability of specific proficiency testing (PT) programmes. Because the number of studies dedicated to the subject of this review has increased considerably over recent years, the sources consulted and cited here are limited to those from 2010 to the end of 2015.

Assessment of arsenic bioaccessibility in raw and cooked edible mushrooms by a PBET method.

The present study reports arsenic analysis in Lentinula edodes, Agaricus bisporus and Pleurotus ostreatus before and after being cooked. Furthermore, arsenic in raw and cooked mushroom was determined in the gastric and gastrointestinal bioaccessible fractions obtained after simulating human digestion by means of an in vitro physiologically based extraction test (PBET). Several certified reference materials (SRM 1568a, SRM 1570a, CRM 7503-a, BC211 and IPE-120) were analysed to evaluate the proposed methods. Total arsenic content was 1393, 181 and 335µgAskg(-1) for L. edodes, A. bisporus and P. ostreatus, respectively, and decreased by between 53% and 71% in boiled mushroom and less than 11% in griddled mushroom. High bioaccessibility was observed in raw, boiled and griddled mushroom, ranging from 74% to 89% and from 80% to 100% for gastric and gastrointestinal extracts, respectively, suggesting the need to consider the potential health risk of consumption of the mushrooms analysed.

Direct solid sample analysis with graphite furnace atomic absorption spectrometry­a fast and reliable screening procedure for the determination of inorganic arsenic in fish and seafood.

Direct solid sample analysis with graphite furnace atomic absorption spectrometry (SS-GF AAS) was investigated initially with the intention of developing a method for the determination of total As in fish and other seafood. A mixture of 0.1% Pd+0.06% Mg+0.06% Triton X-100 was used as the chemical modifier, added in solution over the solid samples, making possible the use of pyrolysis and atomization temperatures of 1200 °C and 2400 °C, respectively. The sample mass had to be limited to 0.25 mg, as the integrated absorbance did not increase further with increasing sample mass. Nevertheless, the recovery of As from several certified reference materials was of the order of 50% lower than the certified value. Strong molecular absorption due to the phosphorus monoxide molecule (PO) was observed with high-resolution continuum source AAS (HR CS AAS), which, however, did not cause any spectral interference. A microwave-assisted digestion with HNO3/H2O2 was also investigated to solve the problem; however, the results obtained for several certified reference materials were statistically not different from those found with direct SS-GF AAS. Accurate values were obtained using inductively coupled plasma mass spectrometry (ICP-MS) to analyze the digested samples, which suggested that organic As compounds are responsible for the low recoveries. HPLC-ICP-MS was used to determine the arsenobetaine (AB) concentration. Accurate results that were not different from the certified values were obtained when the AB concentration was added to the As concentration found by SS-GF AAS for most certified reference materials (CRM) and samples, suggesting that SS-GF AAS could be used as a fast screening procedure for inorganic As determination in fish and seafood.

Establishment of a method for determination of arsenic species in seafood by LC-ICP-MS.

An analytical method for determination of arsenic species (inorganic arsenic (iAs), methylarsonic acid (MA), dimethylarsinic acid (DMA), arsenobetaine (AB), trimethylarsine oxide (TMAO) and arsenocholine (AC)) in Brazilian and Spanish seafood samples is reported. This study was focused on extraction and quantification of inorganic arsenic (iAs), the most toxic form. Arsenic speciation was carried out via LC with both anionic and cationic exchange with ICP-MS detection (LC-ICP-MS). The detection limits (LODs), quantification limits (LOQs), precision and accuracy for arsenic species were established. The proposed method was evaluated using eight reference materials (RMs). Arsenobetaine was the main species found in all samples. The total and iAs concentration in 22 seafood samples and RMs ranged between 0.27-35.2 and 0.02-0.71 mg As kg(-1), respectively. Recoveries ranging from 100% to 106% for iAs, based on spikes, were achieved. The proposed method provides reliable iAs data for future risk assessment analysis.

Occurrence of inorganic arsenic in edible Shiitake (Lentinula edodes) products.

The present study reports arsenic speciation analysis in edible Shiitake (Lentinula edodes) products. The study focused on the extraction, and accurate quantification of inorganic arsenic (iAs), the most toxic form of arsenic, which was selectively separated and determined using anion exchange LC-ICPMS. A wide variety of edible Shiitake products (fresh mushrooms, food supplements, canned and dehydrated) were purchased and analysed. A cultivated Shiitake grown under controlled conditions was also analysed. The extraction method showed satisfactory extraction efficiencies (>90%) and column recoveries (>85%) for all samples. Arsenic speciation revealed that iAs was the major As compound up to 1.38 mg As kg(-1) dm (with a mean percentage of 84% of the total arsenic) and other organoarsenicals were found as minor species. Shiitake products had high proportions of iAs and therefore should not be ignored as potential contributors to dietary iAs exposure in populations with a high intake of Shiitake products.

A need for determination of arsenic species at low levels in cereal-based food and infant cereals. Validation of a method by IC-ICPMS.

The present study arose from the need to determine inorganic arsenic (iAs) at low levels in cereal-based food. Validated methods with a low limit of detection (LOD) are required to analyse these kinds of food. An analytical method for the determination of iAs, methylarsonic acid (MA) and dimethylarsinic acid (DMA) in cereal-based food and infant cereals is reported. The method was optimised and validated to achieve low LODs. Ion chromatography-inductively coupled plasma mass spectrometry (IC-ICPMS) was used for arsenic speciation. The main quality parameters were established. To expand the applicability of the method, different cereal products were analysed: bread, biscuits, breakfast cereals, wheat flour, corn snacks, pasta and infant cereals. The total and inorganic arsenic content of 29 cereal-based food samples ranged between 3.7-35.6 and 3.1-26.0 µg As kg(-1), respectively. The present method could be considered a valuable tool for assessing inorganic arsenic contents in cereal-based foods.

Determination of water-soluble arsenic compounds in commercial edible seaweed by LC-ICPMS.

This paper reports arsenic speciation in edible seaweed (from the Galician coast, northwestern Spain) produced for human consumption. Chondrus crispus , Porphyra purpurea , Ulva rigida , Laminaria ochroleuca , Laminaria saccharina , and Undaria pinnatifida were analyzed. The study focused on arsenosugars, the most frequently occurring arsenic species in algae. As(III) and As(V) were also determined in aqueous extracts. Total arsenic in the samples was determined by microwave digestion and inductively coupled plasma mass spectrometry (ICPMS). For arsenic speciation, a water extraction especially suitable for arsenosugars was used, and the arsenic species were analyzed by liquid chromatography with both anionic and cationic exchange and ICPMS detection (LC-ICPMS). The total arsenic content of the alga samples ranged from 5.8 to 56.8 mg As kg(-1). The mass budgets obtained in the extracts (column recovery × extraction efficiency) ranged from 38 to 92% except for U. pinnatifida (4%). The following compounds were detected in the extracts: arsenite (As(III)), arsenate (As(V)), methylarsonate (MA), dimethylarsinate (DMA), sulfonate sugar (SO(3)-sug), phosphate sugar (PO(4)-sug), arsenobetaine (AB), and glycerol sugar (Gly-sug). The highest concentrations corresponded to the arsenosugars.

Measurement of arsenic compounds in littoral zone algae from the Western Mediterranean Sea. Occurrence of arsenobetaine.

The determination of arsenic compounds in algae collected on the Catalan coast (Western Mediterranean) is reported. Ten algae species and the seagrass Posidonia oceanica were analyzed. Total arsenic in the samples was determined by microwave digestion and inductively coupled plasma mass spectrometry (ICPMS). Arsenic speciation in water extracts of samples was analyzed by liquid chromatography with both anionic and cationic exchange with ICPMS detection (LC-ICPMS). The total arsenic content of the algae samples ranged from 2.96 to 39.0mg As kg(-1). The following compounds were detected: arsenite (As(III)), arsenate (As(V)), methylarsonate (MA), dimethylarsinate (DMA), sulfonate sugar (SO3-sug), sulfate sugar (SO4-sug), phosphate sugar (PO4-sug), arsenobetaine (AB), arsenocholine (AC), trimethylarsine oxide (TMAO) and glycerol sugar (Gly-sug). The main arsenic species found were arsenosugars. Significant percentages of arsenobetaine (0.54 mg As kg(-1), 28% of the extractable arsenic and 0.39 mg As kg(-1), 18% of the extractable arsenic) were found in Ulva rigida and Enteromorpha compressa. These results are discussed in relation to the presence of epiphytes.