MolybdatVerfahren

The MolybdatVerfahren, often translated as the Molybdate Process, is a method used in analytical chemistry for the quantitative determination of phosphate ions. It relies on the formation of a heteropoly acid complex between phosphate and molybdate ions in an acidic solution. When phosphate is present, it reacts with ammonium molybdate in the presence of nitric acid to form phosphomolybdic acid. This complex is typically yellow. The intensity of this yellow color is directly proportional to the concentration of phosphate in the sample. This colorimetric relationship allows for the quantification of phosphate using spectrophotometry, where the absorbance of the solution at a specific wavelength (usually around 400-450 nm) is measured and compared to a calibration curve prepared from known phosphate standards. Various modifications of the MolybdatVerfahren exist, often involving reduction of the phosphomolybdic acid complex to a more intensely colored blue species, further enhancing sensitivity. This blue reduction product, often formed using reducing agents like stannous chloride or ascorbic acid, allows for the detection of even very low phosphate concentrations. The MolybdatVerfahren is widely applied in environmental analysis, water quality monitoring, and biological sample analysis due to its relatively simple procedure and good sensitivity. Care must be taken to control reaction conditions, such as pH and temperature, to ensure accurate and reproducible results.