Sequential injection analysis as a tool for in situ monitoring of Fe(II), Fe(III), NO3- and NO2- in natural and waste waters

This paper presents a sequential injection analysis (SIA) system for sequen tial monitoring of Fe(II) and Fe(III), or NO3- and NO2- with typical concen trations of natural and waste waters. Determination of nitrite was based on the Griess-Ilosvay reaction, while the Fe(II) determination was based on t he reaction with 1,10-phenantroline. Determination of Fe(III) and NO3- were performed after their reduction, respectively, in Jones and copperized cad mium columns, using forward and reversal flow directions. Tangential filtra tion permitted the application of the methodology for determination of diss olved species in aquatic suspensions containing particulate matter and sedi ments. The stability of the analytical curves was verified over periods of 4-5 days. Quantification limits for NO2- and NO3- were 0.01 and 0.02 mg l(- 1) N, respectively. For Fe(II) and Fe(III) the quantification limits were 0 .05 and 0.1 mg l(-1), respectively, with a sampling frequency of 20 h(-1). The influence of sulphides and natural organic matter on the performance of the reducing columns were evaluated, as well as the use of regeneration so lutions. (C) 2001 Elsevier Science B.V. All rights reserved.