Bentley Instruments

Automated Urea Analysis

Measurement of milk urea or MUN.


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The ChemSpec 150 has been specifically designed for the determination of urea (or MUN) in milk. Accurate, compact, fast & reliable, the ChemSpec 150 is the system of choice for milk urea analysis.

  • Fully automated & compact
  • Capable of analyzing over 150 samples per hour
  • Very low cost per sample
  • Touchscreen operation
  • Enzymatic methodology
  • Colorimetric Measuring Principle

Technical overview & principle of operation
The ChemSpec 150 utilizes a modified Berthelot reaction to determine the level of urea in milk.

  • A small amount of milk is automatically dispensed in a well thermostated at 40°C. It is then split enzymatically with urease into ammonia and carbon dioxide.
  • After an incubation time, dye and activator solutions are added to form a green complex. The color intensity is proportional to the ammonia concentration which is directly proportional to the urea content in the milk.
  • The green color intensity is measured spectrophotometrically in a trans-reflectance cell.
  • The addition of a catalyst in the dye speeds up the reaction, intensifying the green color development, thus enhancing the sensitivity of the method.
  • The use of a highly precise sample dispenser allows the ChemSpec 150 to bypass a pre-dilution step. The milk is simply diluted in the chemicals used to generate the reactions. This dilution reduces the opacity of the medium, thus improving the spectrophotometric measurement and preventing interference from other milk components.
  • By alternating measurements of natural ammonia and converted ammonia, the ChemSpec implements a two-channel FIA. The difference signal from the two measurements allows the ChemSpec to precisely determine the urea concentration.
  • A carrousel incubator allows analysis overlap, yielding a capacity of 150 samples per hour.