A SPECTROPHOTOMETRIC METHOD FOR THE DETER MINATION OF NITRITES IN WASTE-WATERS, BY STOPPED-FLOW INJECTION-ANALYSIS

Recently, flow injection analysis (FIA), which is more rapid, sensitiv e and precise than the usual batch procedures, has been used to determ ine nitrite in waste waters. This paper describes a spectrophotometric method for the determination of nitrite in waste waters by stopped-fl ow injection analysis. The method is based on the diazotisation of nit rite with sulphanilic acid, the product being coupled with alpha-napht hylamine to form a highly coloured azo dye, which is measured at 520 n m. The determination of nitrite is reported by using two procedures. N itrile in waste water was determined by using the proposed FIA method and the results were compared with those obtained by standard method. A calibration run was obtained from 0-4 ppm NO2- by the proposed first procedure respectively 4-32 ppm NO2- by the proposed second procedure . The detection Limit was about 0.5 ppm NO2- for the first procedure, and 4 ppm NO2 for second procedure. The sampling rate was 40 h(-1). Th e interference of other ions commonly present in waste waters was also studied.