[Derivative-ratio derivative spectrum method for determining nitrate and nitrite radicals (NO3- and NO2-) in environmental water].

A derivative-ratio derivative spectrum method was devised for resolving the interference of two components in a two-component mixture measured in derivative spectrum method. The ratio derivative spectrum was obtained from the derivative absorption spectrum of the mixture divided by a derivative absorption spectrum of one of the components. The derivative of ratio derivative spectrum against wavelength resulted in the derivative-ratio derivative spectrum that was determined by the concentration of one component of the mixture. The results suggest that this method is better than ratio derivative spectrum method and it can be applied for determining nitrate and nitrite (NO3- and NO2-) in environment water samples. Being simple and stable, it can eliminate the influence of the interfering materials, giving a recovery rate of more than 96.7%.