Ásta Heiðrún E. Pétursdóttir
Head of Public Health and Food Safety
Food safety and added value of Icelandic fishmeal - Determination of toxic and non ‐ toxic arsenic species in fish meal / Verðmæti og tryggi íslensks fiskimjöls - Kaupthing
There is a lot of arsenic in the ecosystem in organic compounds as well as in inorganic form and more than 50 natural chemical forms of arsenic have been found. Seafood naturally contains a high concentration of the total arsenic compared to, for example, agricultural products. However, most arsenic in seafood is bound in an organic form called arsenobetanide, which is considered safe. Other forms of arsenic in marine products are generally present in lower concentrations, including inorganic arsenic (arsenite and arsenate) which is toxic and rarely exceeds 3% of the total concentration of arsenic in fish and crustaceans. The morphology of arsenic in seafood is important because the bioavailability and toxicity of arsenic depend on its chemical form. Recently, the EFSA (European Food Safety Authority) called for information on inorganic and organic forms of arsenic in food and for chemical analysis methods to detect inorganic arsenic. This dissertation presents the results and evaluation of measurements of the total concentration in over 100 samples of Icelandic fishmeal. Among other things, it was examined whether there was a seasonal difference in the total concentration of arsenic. The samples were first decomposed by microwave and then measured on an ICP mass spectrometry (ICP-MS). To evaluate the chemical forms of arsenic present in the flour, a three-part distribution method was first developed. Emphasis was then placed on the analysis of toxic inorganic arsenic. The previously published alkali-alcohol extraction method, for the detection of inorganic arsenic, was adapted and the samples were measured by HPLC equipment connected to ICP-MS. Arsenobetanide was found to be the predominant form of arsenic in all cases. Inorganic arsenic was found to be less than four percent of the total concentration in twelve measured fishmeal samples. On the other hand, when another chemical analysis technique (HPLC-HGAFS) was applied to a sample of certified reference material, the concentration of inorganic arsenic was three times lower. The alkali-alcohol distribution method proved to give a convincing upper limit on the concentration of inorganic arsenic. The results also show that it is not enough to rely on one method when analyzing and quantifying arsenic forms. In addition, they demonstrate the need for a certified concentration of inorganic arsenic in standard materials to test the reliability of chemical analysis methods. The need for further development of chemical analysis methods in this field is urgent.
Arsenic is found in the biosphere in both organic and inorganic forms, and there have been recognized more than 50 naturally occurring arsenic species. Seafood products have naturally high concentration of total arsenic compared to eg agricultural produce. Arsenic is toxic to humans and animals and is known to be carcinogenic. The toxicity of the arsenic species varies severely and a large portion of the arsenic in seafood is present in the form of the organic compound arsenobetaine, which is considered non ‐ toxic. Other arsenic species are generally present in lower concentrations, including the most toxic inorganic arsenic species, arsenite, As (III) and arsenate, As (V), which usually do not exceed 3% of the total arsenic in fish and crustaceans. Existent European regulations on limits of arsenic in foodstuff and feed only take into account total arsenic concentration, not the toxic arsenic species. Recently the EFSA (European Food Safety Authority) stressed the need for more data on levels of organic and inorganic arsenic in different foodstuffs and the need for robust validated analytical methods for the determination of inorganic arsenic. In this thesis results from total arsenic concentration from over 100 samples of Icelandic fish meal are presented and evaluated. The samples were microwave digested and measured with inductively coupled plasma mass spectrometry (ICP ‐ MS). The samples were screened for a seasonal difference in the total arsenic concentration. To evaluate the arsenic species present in the meal a sequential method of extraction was developed. In addition, a special focus was on the determination of inorganic arsenic and a previously published method for an alkaline ‐ alcoholic extraction of the inorganic arsenic was modified and applied. For determination of arsenic species high pressure liquid chromatography (HPLC) was coupled to the ICP ‐ MS. The predominant arsenic species found in all samples was the non ‐ toxic arsenobetaine. Inorganic arsenic was not found to exceed 4% of total arsenic concentration in 12 samples of fish meal. However, a suspicion of co ‐ elution arose, and when another analytical instrument technique (Hydride generation atomic fluorescence spectroscopy (HPLC ‐ HG ‐ AFS)) was applied, concentration of inorganic arsenic was approximately three times lower in a certified reference material, TORT‐ 2. The alkaline ‐ alcoholic extraction method was found to give convincing upper limits of the inorganic arsenic concentration in fish meal samples. These results show the necessity of further method development and separate methods when identifying and quantifying species. This further stresses the need for a certified value of inorganic arsenic in a certified material to check the robustness of developed methods.