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Abstract

2-Oxoglutaric acid reacts with 3-methyl-2-benzothiazoline hydrazone in acid solutions in the presence of FeCl₃ to give a stady yellow colour. The method enables the substance to be determined in concentrations as low as 15 μmol l^-1 with an accuracy of about 10%. The analysis can be performed in the presence of some additional natural or synthetic 2-oxo acids. The applicability of the method was tested in the determination of the activity of some enzymes involved in the metabolism of 2-oxoglutaric acid. Glutamic acid can be determined after its prior nonenzymatic transamination. A number of 2-oxo acids including 2-oxoglutaric acid can be determined photometrically with a high sensitivity by reaction with 3-methyl-2-benzothiazolinone hydrazone in conditions favouring the formation of blue tetra-aza-pentamethinecyanine dyes. The molar absorptivities largely lay within the region of (2-4.5) . 10⁴ l mol^-1cm^-1.