“Reagentless” Flow Injection Determination of Ammonia and Urea Using Membrane Separation and Solid Phase Basification
✍ Scribed by James R. Akse; John O. Thompson; Richard L. Sauer; James E. Atwater
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 114 KB
- Volume
- 59
- Category
- Article
- ISSN
- 0026-265X
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✦ Synopsis
Flow injection analysis instrumentation and methodology for the determination of ammonia and ammonium ions in an aqueous solution are described. Using in-line solid phase basification beds containing crystalline media, the speciation of ammoniacal nitrogen is shifted toward the un-ionized form, which diffuses in the gas phase across a hydrophobic microporous hollow fiber membrane into a pure-water-containing analytical stream. The two streams flow in a countercurrent configuration on opposite sides of the membrane. The neutral pH of the analytical stream promotes the formation of ammonium cations, which are detected using specific conductance. The methodology provides a lower limit of detection of 10 g/L and a dynamic concentration range spanning three orders of magnitude using a 315-L sample injection volume. Using immobilized urease to enzymatically promote the hydrolysis of urea to produce ammonia and carbon dioxide, the technique has been extended to the determination of urea.