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Human exposure to mycotoxins is almost inevitable as mycotoxins are naturally occurring contaminants of large portion of food and feed. Depending on the type of mycotoxins, inter-individual mycotoxin adsorption, bioaccumulation, distribution, metabolism and excretion, can cause serious adverse health effects. Therefore, continuous biomonitoring studies of population exposure to mycotoxins are needed. Here we describe a multi-analyte approach for the detection and quantification of 20 mycotoxins in human serum using ultra-performance liquid chromatography-electrospray/tandem mass spectrometry operated in targeted multiple reaction monitoring mode. The validated method was used to assess occurrence of mycotoxins in serum samples of 46 residents of Qatar. Mycotoxins that were detected with high incidence were HT-2 toxin (13.0%), sterigmatocystin (10.9%) and 3-acetyldeoxynivalenol (6.5%). Also, co-exposure to several mycotoxins was noticed in the analysed samples. Our results show that strict food quality control is needed to remove mycotoxin contaminated food from the market in order to minimise human exposure to mycotoxins.

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Oxidation of water on an illuminated TiOs electrode was investigated using a rotating ring-disk electrode, focusing on the role of the reducing agent, SO~-, added in solution. The TiO2 disk was illuminated with a chopped-light source, and the corresponding ring response at the Pt-ring, AI~ = I~ (light) -I~ (dark), was recorded. Although oxidation products were expected to be produced on the disk surface and carried to the ring electrode, AIR was found to be negative in dilute Na2SO3 solution even at large negative potentials, e.g., -0.8 V vs. SCE. This phenomenon was observed in neutral and basic solutions. It is proposed that SO~* radical is formed at an illuminated TiOs-disk and subsequently initiates a homogeneous free-radical chain oxidation of sulfite ion. This chain reaction consumes oxygen to be supplied from the solution via the disk to the ring, reducing the ring current associated with the reduction of oxygen. As a result, the ring current is lower under illumination than in the dark.