Arsenic species in mushrooms, with a focus on analytical methods for their determination – A critical review

Highlights: • Comprehensive and critical review on arsenic speciation analysis in mushrooms. • Methodical overview of techniques for arsenic speciation analysis in mushrooms. • Summary of arsenic species that have been found in mushrooms so far. • Possible biotransformation of arsenic in mushrooms. • Reviewing arsenic hyperaccumulation in mushrooms. -- Abstract: Since the discovery of the "fish arsenic" arsenobetaine in a mushroom, arsenic species have been studied in all kinds of mushrooms, with very diverse results, for more than 20 years. Depending on the fungal species, inorganic arsenic, methylarsonic acid, dimethylarsinic acid, arsenobetaine and a couple of other arsenic-containing compounds have been detected in all kinds of concentrations in natural samples. A rule to predict the arsenic speciation of a new mushroom is yet to be found. Some research has been devoted to the question about the origin of the different arsenic species in mushrooms. It is still not clear whether mushrooms are able to transform arsenic by themselves or if they just take it up from the environment. For the determination of the arsenic species in mushrooms, high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry is used most of the times, but a few alternative approaches exist. This review will give an overview of these different techniques and critically discuss them. The arsenic species that have been found in mushrooms so far will be summarized, and the work that has been devoted to unraveling the origins of these compounds will be discussed in depth. The interesting phenomenon of arsenic hyperaccumulation by mushrooms will be reviewed as well.