Organic (methyl-, ethyl-, phenyl-) and total mercury (Hg) in fungal biomass: The influence of species, substrates, source proximity and analytics on reported occurrences.

Mercury occurs in inorganic and organic forms in abiotic and biotic environments, food and humans. Diet is a primary pathway to chronic exposure and the Hg content of food is regulated, including the three most cultivated edible fungi. The reliable determination of total Hg and organo-Hg compounds in fungi is therefore crucial from the regulatory and human exposure viewpoint. So far, no fungal species have been identified that exhibit mercury hyperaccumulation. Chronologically, external fungal biomass decomposition, elementary Hg0 vapour generation and cold vapour-atomic absorption spectroscopy measurement was the first popular instrument technique used to measure Hg in mushrooms. In more recent time, chemical vapour generation - atomic fluorescence spectrometry is getting more popular. Radiochemical analysis, instrumental neutron activation analysis, electrothermal atomic absorption spectrometry and electrochemical techniques (anodic stripping voltammetry, differential pulsed anodic stripping voltammetry and potentiometry) were occasionally used. More recently and going forward, ICP-MS technique that allow precise measurement of multiple elements including Hg simultaneously are likely to most widely used. For speciation studies of Hg in fungal biomass, CV-AAS and a variation of the instrumental couplings of gas- and liquid chromatography (combined with chemical vapor generation) and non-chromatographic separations with various detectors have been used. From the use of L-cysteine as a complexing agent to the quantitative capture and determination of MeHg in various matrices, a number of applications, modifications and updates to the methodology have been introduced since then. L-cysteine has the potential to capture MeHg, EtHg and PhHg or possibly any organo-Hg compound in a sample extract.