A multi-commuted flow injection system with a multi-channel propulsion unit placed before detection: spectrophotometric determination of ammonium

Sara M. Oliveira, Teresa I. M. S. Lopes, Ildikó V. Tóth, António O. S. S. Rangel*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)
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Abstract

A flow system with a multi-channel peristaltic pump placed before the solenoid valves is proposed to overcome some limitations attributed to multi-commuted flow injection systems: the negative pressure can lead to the formation of unwanted air bubbles and limits the use of devices for separation processes (gas diffusion, dialysis or ion-exchange). The proposed approach was applied to the colorimetric determination of ammonium nitrogen. In alkaline medium, ammonium is converted into ammonia, which diffuses over the membrane, causing a pH change and subsequently a colour change in the acceptor stream (bromothymol blue solution). The system allowed the re-circulation of the acceptor solution and was applied to ammonium determination in surface and tap water, providing relative standard deviations lower than 1.5%. A stopped flow approach in the acceptor stream was adopted to attain a low quantification limit (42 μg L-1) and a linear dynamic range of 50-1000 μg L-1 with a determination rate of 20 h-1.

Original languageEnglish
Pages (from-to)29-34
Number of pages6
JournalAnalytica Chimica Acta
Volume600
Issue number1-2 SPEC. ISS.
DOIs
Publication statusPublished - 26 Sep 2007

Keywords

  • Gas diffusion
  • Multi-commuted flow system
  • Spectrophotometry
  • Trace levels of ammonium
  • Waters

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