Spectrophotometric determination of nitrite after preconcentration on an SDS coated alumun column

Determination of traces of nitrite in water samples is of importance. In the present work sulfanilic acid, as the diazotizable and N-(1-naphtyl) ethylene diamine dihydrochloride, as the coupling agent, were added to nitrite sample to form the azo dye. The azo dye was collected on the sodium dodecyl sulphate coated alumina column and eluted with 7 mt HCL:CH3COOH (2:3). The absorbance of the effluent was measured spectrophotometrically at 553 nm. The calibration graph was linear in the range 0.4-24 ng mL(-1) and the preconcentration factor was 70. The detection limit (3 sigma) for 500 mt of sample solution was 0.173 ng mL(-1) and the relative standard deviation for six replicate determinations of 10 ng mL(-1) nitrite was calculated to be 0.36%. The interferences from various ions were investigated and the effects of interfering ions were removed by using the appropriate masking agents. The method has also been extended to the simultaneous determination of nitrite and nitrate by using cadmium-copper reductor column to convert nitrate to nitrite.