KINETIC-SPECTROPHOTOMETRIC DETERMINATION OF PRIMARY AND SECONDARY-AMINES BY REACTION WITH 1-2-NAPHTHOQUINONE-4-SULFONATE

A kinetic-spectrophotometric method for the determination of primary and secondary amines is described. It is based on the coloured reaction of these amines with sodium 1,2 Naphthoquinone 4-sulphonate (NQS) in the presence of a non-ionic surfactant. For each determination the optimum conditions were studied and found to be as follows: pH 10.5, Carbonate-bicarbonate buffer 0.1M, Triton X-100 0.1%, Temperature 45 degrees C, and NQS 6.4x10(-3) M and interval of time 45-180s at wavelength 490 nm. The parameters used for the quantitative determinations are the reaction rate and the increase in the absorbance of the kinetic curves. This procedure has been applied to the determination of ephedrine and amphetamine in pharmaceutical samples.