The spectrophotometric determination of molybdenum-containing compounds in aqueous glucose solutions using pyrazine-2,3-dicarboxylic acid was investigated. Determination of the molybdenum complex with pyrazine-2,3-dicarboxylic acid was performed at (max) = 550nm. The light absorption of the deeply violet complex follows Lambert-Beer's law and can be measured with a molar absorptivity in the range of 4414-9020Lmol(-1)cm(-1). The presented method is very sensitive and shows good reproducibility for the extinction values.