Urea detection in milk by urease-assisted pH-sensitive carbon dots

Area of Science:

• Analytical Chemistry
• Materials Science
• Food Science

Background:

• Excessive urea in milk poses health risks and necessitates reliable detection methods.
• Traditional methods for urea detection in milk are often inconvenient and lack accuracy.
• Developing a sensitive and practical assay for milk urea is crucial for food quality control.

Purpose of the Study:

• To synthesize stable green light-emitting carbon dots (CDs) for use as a fluorescent probe.
• To establish a novel, convenient, and accurate method for detecting urea concentration in milk.
• To evaluate the performance of the developed carbon dot-based method for milk analysis.

Main Methods:

• Stable green light-emitting carbon dots (CDs) were synthesized using 3,5-diaminobenzoic acid via a one-step method.
• The fluorescence properties of CDs were characterized, including excitation and emission wavelengths.
• A detection strategy was developed based on the pH-dependent fluorescence quenching of CDs induced by urease-catalyzed urea hydrolysis.

Main Results:

• Synthesized CDs exhibited strong fluorescence with an optimal excitation wavelength of 390 nm and emission peak at 490 nm.
• The fluorescence intensity of CDs decreased with increasing pH (6-9), and was further quenched by ammonia produced from urea hydrolysis.
• The developed method demonstrated high sensitivity (LOD 6.27 mg/L) and a wide linear range (25-500 mg/L, R²=0.998) for urea detection in milk.

Conclusions:

• A novel, sensitive, and cost-effective fluorescent method for urea detection in milk was successfully established using carbon dots.
• The method offers advantages of simple operation, no pretreatment, safety, and low cost, making it suitable for routine food quality control.
• This carbon dot-based approach provides a valuable tool for ensuring the safety and quality of milk products.