DIN ISO 3946:1986-12

This standard specifies a spectrophotometric method for the determination of the total phosphorus content of starch, including derivatives and by-products, in which the expected content, calculated as phosphorus (P), does not exceed 5 % (m/m). Destruction of the organic substances by digestion with a sulpho-nitric mixture and conversion of phosphates to ortho-phosphates. Formation, by means of a reducing agent, of a phosphomolybdate known as molybdenum blue. Spectrophotometric measurement of the intensity of the blue colour at a wavelength of 825 nm.