Pretreatment and preconcentration methods for hydroxylamine in environmental water samples using solid-phase extraction, followed by a spectrophotometric determination

Hydroxylamine has been determined by combining oxidation to nitrite with iodine and the usual Griess-Romijin method. This iodine oxidation technique, however, has been inapplicable to the determination of hydroxylamine in environmental water due to interferences from nitrite and salinity. We developed a pretreatment method for determining hydroxylamine in environmental water based on the above-mentioned technique. Nitrite in a water sample was converted to a red azo dye with sulfanilic acid (diazo component) and N-1-naphthyletylenediamine (coupling component); the azo dye was then removed using a Sep-Pak C-18 cartridge. We thus prepared a nitrite-free water sample. On the other hand, the interference from the salinity was solved by adding artificial seawater to sample to enhance the salinity to greater than 5parts per thousand. The salinity in a standard solution of hydroxylamine for a calibration curve was also prepared using the standard solution with > 5parts per thousand. In addition, the proposed method using a Sep-Pak C-18 cartridge was applicable to concentrate azo dye derived from hydroxylamine in water samples.