Method optimization using fractional factorial design for arsenic speciation in marine samples

Marine organisms from lower trophic levels, such as marine algae, blue mussels, and mesopelagic organisms, are recently being considered as novel feed ingredients in aquaculture production. Within the European Union, maximum limits are established for undesirables in feed and feed ingredients, including heavy metals and arsenic (Directive 2002/32 EC and amendments). Arsenic is a trace element that is known for its complex chemical nature, with over 100 naturally occurring species identified in the marine environment [1]. Inorganic arsenic is classified as carcinogenic substance by the International Agency for Cancer Research (IARC), while the organic compound arsenobetaine is considered non-toxic to both human and animal [2]. The European Food Safety Authority Panel on Contaminants in the Food Chain highlighted the need for arsenic speciation indifferent foodstuffs to prevent overestimation of health effects related to dietary arsenic exposure. Arsenic speciation requires extraction under mild conditions to preserve the original chemical properties of the species. As a single extraction procedure for all foodstuffs is not possible, a targeted sample preparation is recommended [3]. In the present study, a fractional factorial design was applied to optimize the extraction of water-soluble arsenic species in blue mussels. The experimental procedure was performed according to 27-3 fractional factorial design (16 experiments). The tested factors were sample amount, type of extraction solution, amount of extraction solution, addition of hydrogen peroxide, extraction temperature, extraction time, and use of ultrasonication. Analysis of variance (ANOVA) was used to test for the statistical significance of main effects at a confidence level of 95%. The optimum extraction condition was evaluated based on arsenic recoveries in the extracts and the stability of arsenic species. Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the total arsenic, whereas arsenic speciation was carried out via high performance liquid chromatography with both anionic and cationic exchange coupled to ICP-MS detection (HPLC-ICP-MS). The optimised extraction and chromatographic conditions were applied to certified Reference materials and different marine samples. The proposed method is hereby shown useful for the determination of arsenic species in marine samples.