Development of a sequential injection gas diffusion system for the determination of ammonium in transitional and coastal waters

Ricardo Alves Segundo, Raquel Beatriz Ribeiro Mesquita, Maria Teresa Soares Oliveira Barbosa Ferreira, Catarina Fernanda Carvalho Pinheiro Teixeira, Adriano Agostinho Bordalo, António Osmaro Santos Silva Rangel*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)
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Abstract

This work describes the development of a sequential injection system for the ammonium determination in transitional and coastal waters with a wide salinity range. Estuarine waters are rather complex matrices as their characteristics change considerably along the salinity gradient, as well as the ammonium levels. The developed system effectively solves these issues by converting ammonium into ammonia and using a gas diffusion unit (GDU) for matrix removal. The ammonium determination in a wide quantification range (0.1-5.0 mg L-1) was obtained with small changes in the protocol sequence and was applied, not only to estuarine samples, but also well water samples (low salinity) and coastal waters (higher salinity). Spectrophotometry was the chosen detection system to measure the absorbance change in the bromothymol blue acid base indicator caused by the diffusion of ammonia through the GDU. Additionally, the developed system used a green chemistry approach, as there was no indicator reagent consumption per determination, still maintaining a good precision (relative standard deviation lower than 2%) and a low detection limit, 27 μg L-1 (1.5 μM).

Original languageEnglish
Pages (from-to)2049-2055
Number of pages7
JournalAnalytical Methods
Volume3
Issue number9
DOIs
Publication statusPublished - 1 Sept 2011

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