Amperometric ammonium ion and urea determination with enzyme-based probes

Area of Science:

• Biotechnology
• Analytical Chemistry
• Biosensors

Background:

• Ammonium and urea detection are crucial in clinical diagnostics and environmental monitoring.
• Existing potentiometric methods for ammonium detection suffer from ion interference and lower sensitivity.
• Enzyme-based biosensors offer a promising alternative for sensitive and selective analyte quantification.

Purpose of the Study:

• To develop and optimize amperometric enzyme probes for the detection of ammonium and urea.
• To evaluate the analytical performance and stability of the developed biosensors.
• To compare the performance of amperometric detection with existing potentiometric and spectrophotometric methods.

Main Methods:

• Assembly of amperometric enzyme probes using immobilized glutamate dehydrogenase (GLDH) and urease with platinum electrodes.
• Optimization of analytical parameters including pH, buffer, temperature, enzyme immobilization, cofactor concentration, and response time.
• Amperometric detection of ammonium and urea in standard solutions and saliva samples, with comparison to spectrophotometric analysis.

Main Results:

• Optimized probes demonstrated sensitive detection of ammonium (10(-5)-3 x 10(-4) mol l-1) and urea (10(-5)-3 x 10(-4) mol l-1).
• Enhanced reproducibility and stability were achieved using GLDH type III and NADH (10(-3) mol l-1).
• Amperometric detection showed improved sensitivity and no potassium ion interference, unlike potentiometric methods.

Conclusions:

• Amperometric enzyme probes provide a sensitive, stable, and interference-free method for ammonium and urea determination.
• Immobilized urease on nylon nets improved urea analysis.
• The developed biosensors show potential for reliable analysis in real-world samples like saliva.