The bachelor´s work provides a survey of information related to vitamin C, its properties, occurrence and symptoms of deficiency or its excess in human organism. The objective of this work is to determine the content of vitamin C in analysed food samples (fruit, vegetables and plant material), mathematically evaluate results obtained and compare them with the values of vitamin C given in literature. The first chapter describes vitamin C (L-ascorbic acid), its characteristics (nomenclature, history, structure, physical and chemical properties, stability, physiology, oxidation-reduction reactions, vitamin C as an antioxidant), its sources and occurrence (ruit, vegetables, drinks, food of animal origin, nutritional supplements and plants). Vitamin C as one of water-soluble vitamin is generally considered to be the basic antioxidant in human nutrition. Therefore, in one of the subchapters we have also focused on the intake and importance of vitamin C for human organism. The contents of the next chapter are materials and work methods used. Within the material we described sampling, treatment and sample processing (of fruit, vegetables and plant materials) before the analysis. We used three analytical methods to determine vitamin C: titration, chromatography (on filter paper and Whatmanne 40) and spectrophotometric method (on UV-VIS). The individual methods demonstrate the principles of determination, chemicals and instruments used, work procedures and chemical equations. In the following chapter we have evaluated the obtained results of analytical methods which were used and compared the contents of vitamin C in individual fruit, vegetable and plant material samples. In fruit samples in which we titrated vitamin C, the values of its concentration ranged from 3,29 mg (apple) to 122,20 mg (black currant) per 100 g, in the chromatographic assay ranged from 6,57 mg (apple) to 102,14 mg (black currant) per 100 g and in spectrophotometric assay ranged from 3,15 mg (apple) to 170,51 mg (black currant) per 100 g. In vegetable samples in which we titrated vitamin C its concentration ranged from 1,65 mg (cucumber) to 115,15 mg (red pepper) per 100 g, in the chromatographic assay they ranged from 8,76 mg (cucumber) to 116,73 mg (red pepper) per 100 g and finally, in spectrophotometric assay they ranged from 6,87 mg (cucumber) to 162,06 mg (red pepper) per 100 g. In samples of plant materials in which we titrated vitamin C, its concentrations ranged from 1,18 mg (beetroot - leaves) to 139,83 mg (parsley - leaves) per 100 g, in chromatographic assay concentrations ranged from 1,95 mg (beetroot - leaves) to 87,64 mg (parsley - leaves) per 100 g and in spectrophotometric assay ranged from 2,75 mg (beetroot - leaves) to 143,22 mg (parsley - leaves) per 100 g. Based on the obtained results from the analyses and their subsequent comparison with the values from literary resources, the most accurate method appears the spectrophotometric one. The results obtained are almost identical to the data from literature resources. Differences in the results could have occurred as the consequence of bad sampling, incorrect storage, inaccuracy in the measured data or the storage of the juice obtained over 10 hours at a room temperature. Vitamin C is both an essential antioxidant in human nutrition and cofactor of the enzyme-catalyzed reactions necessary for the proper functioning of the organs and thus, it is important to monitor its concentrations in food.