Standards Development
This document describes a method for the determination of inorganic arsenic in algae by anion-exchange HPLC-ICP-MS following water bath extraction. Inorganic arsenic consists of arsenite, As(III) and arsenate, As(V).
A representative test portion of the sample is treated with a diluted nitric acid and hydrogen peroxide solution in a heated water bath. Hereby the arsenic species are extracted into solution and As(III) is oxidised to As(V). The inorganic arsenic is selectively separated from other arsenic compounds using anion exchange HPLC (High Performance Liquid Chromatography) coupled on-line to the element-specific detector ICP-MS (Inductively Coupled Plasma Mass Spectrometry) for the determination of the mass fraction of inorganic arsenic.
External calibration with solvent matrix-matched standards is used for quantification of the amount of inorganic arsenic. The method is based on method EN16802: Inorganic arsenic in food of plant and marine origin by HPLC-ICPMS, but covers more algae species. The present AsSugar species in certain algae can cause As peaks which might overlap with the As peaks related to the inorganic As. The current method includes a gradient elution method with quality criteria to ensure a correct identification of the inorganic arsenic.
Algae are known to contain often high levels of arsenic (As). Different biologically relevant As species have been identified including: inorganic (Asi) compounds and organic compounds or more complex components such as arsenolipids (AsLipids) and arsenosugars (AsSugars), the latter known as abundant As compounds in algae. In general, Asi species are considered to be the most toxic arsenic species, and toxicological properties are the most documented for this species, whereas the toxicological effects of arsenosugars are less studied and they are hence often referred to as ‘potentially toxic arsenic compounds’.
Currently two CEN methods are published for the analysis of Asi in food (EN 16802:2016) and feed (EN 17374:2020) by highperformance-liquid-chromatography inductively-coupled-plasma-mass-spectrometry (HPLC-ICP-MS). However, in algae, the presence of AsSugars (particularly AsSug_408) makes a correct identification and quantification of Asi difficult. EN 16802:2016 and EN 17374:2020 have a risk of overestimation due to coelution for some algae due to the matrix containing arsenosugars.
Therefore, the purpose of the proposal is to develop a standard for an analytical method for the determination of inorganic arsenic in algae and algae products.
Note: in case the WI is based on documents from other organizations than ISO/IEC, please specify it here
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