Determination of Total Arsenic and its Species present in Foodstufs

To assess the risks associated with the consumption of arsenic-containing foodstuffs, the determination of total arsenic is not sufficient since the toxicity of arsenic is highly dependent on its chemical form. Inorganic species, such as arsenite (AsIII) and arsenate (AsV), are more toxic than monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) and therefore represent a higher potential health risk. Organic arsenic compounds, such as arsenobetaine (AsB), which is the major species found in seafood, are non-toxic and can be consumed without health concerns [1]. The present work aimed at analysing the total arsenic content and its species in fish, rice and baby food samples. Rice is of paramount importance since it is a staple food for many populations and the main contributed for arsenic exposure. Also rice is the dominant carbohydrate source to babies up to one year. Since infants have low body weight they are more exposed to arsenic toxicity than adults. Therefore rice varieties intended to be consumed by infants must be carefully monitored for arsenic content. Fish samples from different species (gilthead sea bream, meagre, salmon and oyster), were subjected to different cooking methods: boiling, grilling and roasting. Arsenic content was determined on both raw and cooked fish samples, by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). For all three matrices speciation studies were carried out by coupling a High Performance Liquid Chromatographer (HPLC) to an ICP-MS. To guaranty the quality of results samples were analyzed in duplicate and a reference material was used for total concentration determination and for speciation studies complying with metrological requirements. The obtained results for total arsenic in fish were between 710 µg.kg-1 and 5978 µg.kg-1. The lowest value was observed in the samples from raw meagre and the highest in grilled gilthead sea bream. Speciation studies revealed that, even though fish samples presented a high content of arsenic, more than 90% of the arsenic present was in the form of AsB. Apparently, the culinary treatment does not enhance the inter-conversion of species. Total arsenic content in rice and baby foods, were between 29 µg.kg-1 and 1143 µg.kg-1. The higher value was referred to the bran of the rice and the lowest to the baby foods. Speciation results showed that 80% of arsenic was present as inorganic and 20% as DMA in rice and rice baby foods.