Co is an essential element for life in
Co is an essential element for life in minute amounts . The human adult contains about 1.1mg Co with the daily requirement of 0.1μg/day. Co is a component of vitamin B12. Co induces erythropoietin and blocks iodine uptake by the thyroid, controls the transfer of enzymes like homocysteine methyltransferase in methionine metabolism . Contact dermatitis, cardiomyopathy, vision or hearing impairment, hypothyroidism and polycythemia, have been attributed to chronic of cobalt ions due to dietary supplements, occupation and medical devices (Co-containing implants). The knowledge of steady state Co concentrations in tissues in combination with the data on its adverse health effects in humans should help in the characterization of potential hazards associated with increased blood Co concentrations due to exposure to dietary supplements or cobalt‑chromium (Co-Cr) containing implants . Thus, the possibility to monitor Mn and Co ions can represent a helpful tool for clinical diagnostics, food industry and environmental control service. The analysis of the localization and distribution of essential and beneficial metals (including Mn and Co) in biological tissues and liquids (e.g. blood and urine) is a challenging task for medicine and other life sciences. Blood concentrations as well as urinary excretion rates of metallic ions are reliable biomarkers for systemic exposure to these compounds , , . Many instrument-based techniques have been applied for quantitative analysis of metal ions. Analytical methods such as high performance liquid chromatography (HPLC), gas chromatography, atomic (+)-Catechin hydrate sale and emission spectroscopy, mass spectrometry (MS) are currently and widely used , . The classical approaches of spectrophotometry and fluorometry, especially in combination with micro- and nanotechnologies , , , ,  are very popular too. Over the past years, the development and application of different MS imaging techniques for metals' analysis, including laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), has been rapidly growing in the life sciences in order to investigate the uptake and the transport of both essential and toxic metals in cells and tissues . Although the high-tech analytical techniques for detection of heavy and transition metals are highly sensitive and accurate, they are, however, time-consuming, expensive, require special skills and show limited capability for real-time measurements in biological samples. As an attractive choice to the mentioned above methods, the electrochemical analytical approaches are also extensively used for metal ions assay. Highly specific, sensitive, simple, fast and cheap biosensors based on electrochemical transducers (amperometric and conductometric electrodes, potentiometric pH-sensitive field effect transistors) and different biorecognition molecules as sensitive elements were developed for inhibitory analysis of heavy metals ions , . Different microbial cells , , enzymes , , , , DNA and antibodies , , , , , , as well as biomimics (molecularly imprinted polymers) ,  were used as bioelements. These analytical devices are promising tools for needs of health care, environmental control, biotechnology, agriculture and food industries. Improvement of their analytical characteristics (e.g. sensitivity, selectivity, stability etc.) may be achieved by using negatively or positively charged additional semi-permeable membranes, micro- and nanomaterials of different origin, genetically modified enzymes . Being rather simple, inexpensive, and portable, bio- and chemosensors are promising for real-time measuring for online and continuous analysis of natural samples for detection of metallic ions. The number of chemosensors, namely, based on platinum nanoparticles and 3,3,5,5-tetramethylbenzidine as chromogene with fiber optic detection  as well as based on gold clusters  and fluorescence graphene-based quantum dots , ,  were proposed in recent years.