Miniaturized measurement system for ammonia in air

B.H. Timmer, K.M. van Delft, R.P. Otjes, Wouter Olthuis, Albert van den Berg

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    The development of a miniaturized ammonia sensor made using microsystem technology is described. Gas is sampled in a sampler comprising two opposite channels separated by a gas permeable, water repellent polypropylene membrane. Subsequently, the acid sample solution is pumped into a selector where an alkaline solution is added to ionize all sampled ambient acid gasses, resulting in an enhanced selectivity. In the selector, the ammonia can diffuse through a second membrane into a purified water stream where an electrolyte conductivity sensor quantifies the resulting ammonium concentration. The realized system is shown to be selective enough not to be influenced by normal ambient carbon dioxide concentrations. Experiments with a gas flow of 3 ml/min, containing ammonia concentrations ranging from 9.8 to 0.3 ppm in a nitrogen carrier flow, into a 15 μl/min sample solution flow and finally into a 5 μl/min purified water stream have been carried out and show that the system is sensitive to ammonia concentration below 1 ppm.
    Original languageUndefined
    Pages (from-to)137-143
    Number of pages7
    JournalAnalytica chimica acta
    Issue number1
    Publication statusPublished - 2004


    • Gaseous ammonia sensor
    • METIS-219020
    • Micro-fluidics
    • IR-47960

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