Which method is described as cheap but insensitive for urea determination?

• A. Direct Chemical/Fearon
• B. Indirect Enzymatic
• C. Colorimetric assay
• D. Mass spectrometry

Answer: (A)

In practice, methods for measuring urea vary in cost and sensitivity. The Feron method is a direct chemical colorimetric approach, which keeps expenses down by using simple reagents and a straightforward readout. That low-cost setup is its main advantage. But because the chemical reaction yields a relatively modest color change per unit of urea, the method has a higher limit of detection and broader, less precise response at low concentrations. Interferences from other substances in the sample can also affect accuracy, making it less reliable for detecting small amounts of urea.

In comparison, enzymatic approaches use urease or other enzymes, which can improve specificity and sensitivity but add cost and stability concerns. Mass spectrometry offers very high sensitivity and specificity but is expensive and less accessible. Colorimetric methods can be inexpensive and user-friendly, but the Feron method specifically trades off sensitivity for simplicity and cost, aligning with the description of being cheap but insensitive.