The refractometer is an apparatus that measures the refraction index of the liquid measured. It is based in the principle of refraction: Light waves change of direction when they change from one medium to another. Depending on the composition of the medium, the angle will be different.

refracción Magapor

Left: schematic representation of the principle of refractometry; right: an example of refraction of the light

In the case of semen extenders, the osmolality is an important value to evaluate the correct reconstitution. The refractometry index, measured in degree brix, correlates with the osmolality.

The refractometer is a very inexpensive device, and it is quick and easy to use. It is a perfect tool to check in situ in the AI Stud proper dilution of the extender before it is used.


  1. Place a drop of laboratory water on the glass and cover it with the top
  2. Look through the refractometer (to a light source). Set the line to zero with the help of the screwdriver.
  3. Clean with a wet wipe.
  4. Place a drop of the sample to test (extender)
  5. Look through the refractometer (To a light source) and measure. The line will cross the scale on the value.
  6. Clean with a wet wipe after using.


Externally all the refractometers look alike, but they vary on some internal aspects. When buying a new one make sure that:

  • It is a refractometer with Automatic Temperature Compensation (ATC), since refraction index can vary with the temperature.
  • The scale it uses: Magapor recommends a scale 0-10°Brix to make a more precise measure. There are refractometers adapted for other uses with other scales and other units marked which can be less precise or less useful.