Abstract: Samples (100 µL) in a carrier stream were mixed with an alkaline solution of K2SO8 and passed into a UV reactor where both inorganic and organic N-compounds were photo-oxidized to NO3-. Gases arising from the reaction were removed by debubbling and NO3- was measured at 226 nm. The calibration graph was rectilinear from 1 to 50 mg L-1 of N with a detection limit of 0.75 mg mL-1 and a coefficient of variation (n = 5) of 2%. Recoveries were 85%. Waste water was filtered (0.45 µm), diluted 1:25 and a portion (0.1 ml) of the solution was injected into a carrier stream (1.2 mL min-1) of Na2B4O7 - NaOH (pH 9) and mixed with a reagent stream (0.6 mL min-1) of 0.04 M K2S2O8 in a teflon coil (13 m x 0.5 mm). The mixture was exposed to UV light from a low pressure Hg lamp, the N compounds were converted to nitrate and gaseous by-products of the photolysis were removed in a debubbler before passing the solution to a flow-through UV detector operating at 226 nm. Calibration graphs were rectilinear up to 50 mg L-1 of nitrate, urea and aspartic acid and the detection limit was ~0.75 mg l-1. Coefficients of variation were 2% (n = 5). Interference was not present from the organic matrix.

Abstract: A review is presented, with 34 references, with emphasis on enzyme- and antibody-based flow injection analysis.