Abstract
An FIA system was developed to analyze urea by monitoring ammonium ions generated by enzymatic degradation with a tubular ion-selective electrode containing nonactin on polyvinyl chloride (PVC) membrane. As an urease source, 120mg of the leguminous canavalia brasiliensis were immobilized in an enzymatic reactor with glutaraldehyde. Ammonium ions are converted to ammonia by an alkaline solution, 1mol l-1 NaOH, and permeates through a polytetrafluoroethylene membrane until the detector. The method can be used in an urea concentration range of 2.5×10-4 to 2.5×10-3mol 1-1(25.0°C). Analysis of 25μl commercial samples of fertilizers, showed a relative error of 0.2% with a high selectivity to the species present.
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