[Study on the spectrophotometric determination of microamounts of iron with 1-(2-pyridylazo)-2-naphthol-6-sulphonic acid].

A new spectrophotometric method has been developed for the highly selective determination of Fe2+ with 1-(2-pyridylazo)-2-naphthol-6-sulphonic Acid. At pH 4.0, Fe2+ an be selectively determined at the wavelength of 760 nm. The calibration curve is liner in a concentration range of 0-10 micrograms/10 ml, relative coefficient is 0.9997, the apparent molar absorptivity is 1.57 x 104 L.mol-1.cm-1, RSD of within-run and between-day were 1.66% and 2.51%, the average rate of recovery 101.1%. The method has been applied to the direct determination of iron in milk powder, common coexistent substances don't interfere with the determination.