Hundhammer, B.(PhD)Taddese, Tesfaye2018-06-262023-11-092018-06-262023-11-091999-06http://etd.aau.edu.et/handle/12345678/3485The membrane-stabilized water-nitrobenzene interface was used as an amperometric (or voltammetric) ammonium ion sensor for an indirect detection of urea. The ammonium ion was produced by the action of watermelon seeds and soy bean flour on urea in the aqueous phase (5 mmol/L Li2S04). The detection was based on the facilitated transfer of ammonium ions by DB[18JC-6. The organic phase contained 50 mmol/L DB[18JC-6 and 10 mmol/L EthVTPB. The performance of watermelon seeds and soy bean flour as soluble urease reagents is described. The problem caused by potassium indigenous to the tissues is discussed. The sensor was applied to the estimation of potassium in the seeds of some plantsenLiquid-Liquid InterfaceThesis