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A method for estimation of urea using ammonia electrode and its applicability to milk samples
Rajan Sharma1, Yudhishthir S Rajput, Sumandeep Kaur
1Department of Dairy Chemistry, National Dairy Research Institute, Karnal-132 001, India.
The Journal of Dairy Research
|July 23, 2008
Summary
This study presents a simple, fast ammonia electrode method for estimating urea in milk. The method accurately quantifies urea, showing comparable results to standard enzymatic techniques.
Area of Science:
- Analytical Chemistry
- Biochemistry
Background:
- Accurate quantification of urea in milk is crucial for dairy quality control.
- Existing methods for urea estimation can be time-consuming or prone to interference.
Purpose of the Study:
- To develop and validate a simple, rapid, and reliable method for urea estimation in milk using an ammonia electrode.
- To assess the method's accuracy, precision, and potential interferences.
Main Methods:
- Urea in milk is enzymatically degraded to ammonium ions using urease at neutral pH.
- Ammonium ions are converted to ammonia at alkaline pH for detection by an ammonia electrode.
- Electrode response is measured and correlated with urea concentration via a logarithmic relationship.
Main Results:
- A linear inverse relationship was observed between the logarithm of ammonia/urea concentration and electrode response.
- The method demonstrated good repeatability (1.77% CV at 8.92 mm-urea) and quantitative recovery (95-100%) in spiked milk samples.
- Preservatives sodium azide did not interfere, but Bronopol at 0.5 g/l led to lower urea values.
- Results were comparable to a standard enzymatic method, with minimal interference from other milk constituents.
Conclusions:
- The ammonia electrode method provides a simple, fast, and accurate means for estimating urea in milk.
- This method is robust and suitable for routine dairy analysis, offering an alternative to conventional enzymatic assays.
- Care should be taken when using Bronopol as a preservative, as it may affect urea measurements.
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