Which statement about refractometers is correct?

Which statement about refractometers is correct?

• A. It measures the refractive index of a solution
• B. It measures the pH of plasma
• C. It measures the refractive index of a solution and can be used to estimate protein concentration in plasma
• D. It measures viscosity of a solution

Answer: (C)

Refractometers determine how much light bends as it passes through a liquid, giving the refractive index of the sample. In plasma, the refractive index rises with protein and other solutes, so the reading can be calibrated to estimate total protein concentration. This dual capability—measuring refractive index and using that value to infer protein concentration in plasma—is why the statement is correct. Refractometers don’t measure pH or viscosity, which are determined by separate methods.

Refractometers determine how much light bends as it passes through a liquid, giving the refractive index of the sample. In plasma, the refractive index rises with protein and other solutes, so the reading can be calibrated to estimate total protein concentration. This dual capability—measuring refractive index and using that value to infer protein concentration in plasma—is why the statement is correct. Refractometers don’t measure pH or viscosity, which are determined by separate methods.