Spectrophotometric determination of hydroxylamine and its derivatives in pharmaceutical formulations

A sensitive spectrophotometric method for determination of hydroxylamine has been described. The method was based on the oxidation of hydroxylamine to nitrite with an excess of bromine solution under acidic conditions. The formed nitrite was determined based on the diazo-coupling reaction between p-nitroaniline and N-( 1 -naphthyl)-ethylenediammine dihydrochloride (NEDA). The method obeyed Beer's law in the concentration range 0-10 μg of hydroxylamine in an overall aqueous volume of 25 mL at 545 nm; the developed color was stable for 3 h. Relative standard deviation was 2.5% (n = 10) for 6 μg of hydroxylamine. Molar absorptivity was 5.5 × 10 4 L mol- 1 cm -1 and correlation coefficient was 0.998. Interferences due to various foreign ions were studied and the method was applied to determination of hydroxylamine and its derivatives after hydrolysis in drug formulations. The results obtained by the proposed method, by Verma-Gupta's method, and in recovery studies were consistent.