Refractometry

What is refractometry used for?

Refractometry finds significant use in the food and drink industries, where it is used to perform quality control testing on sugars, oils, beverages, and many other products. It is also used in agriculture to analyze produce, particularly fruits, to ensure that they contain appropriate levels of various sugars.

Refractometry is also used to analyze the physical properties and purity of translucent solid materials, such as glasses and gemstones. One common use is determining the refractive index of plastics. This can help identify high-refractive-index polymers, which are needed for applications including anti-reflective coatings and image sensors.

How does refractometry work?

The principle of refractometry is based on a transparent or translucent material’s ability to refract and shift light, also known as its refractive index. The refractive index specifically acknowledges the degree to which a straight beam of light will bend upon entering a substance, and can be used to gather a lot of information about the substance.

Refractometers generally work by focusing a beam of light (either from natural external light or by producing its own light source) into a prism. The light passes through the prism, and into the sample to be tested. The device then measures the change in the angle that the beam is traveling at as it passes across the interface between the prism and the sample. This can be used to calculate the substance's refractive index, which offers information about its physical and chemical properties.

Several types of refractometers exist, though they all operate based on the same basic principle. Handheld refractometers are used for quick field analysis. These use sunlight as their light source and can be used to gather results outdoors without a power source. For more in-depth analysis, laboratory refractometers can provide more accurate data on a wider range of sample types.

Limitations of refractometry

In most refractometers, the change in the angle of the light is measured as it travels across the boundary between a prism and the sample. Generally, the substance will have a higher refractive index than the prism, making this a simple measurement. It may, however, be difficult to measure the refractive index if it is lower than that of the prism.

The refractive index of a material is also dependent on the temperature of the sample and the wavelength of light used. Under laboratory conditions, such variables can be effectively controlled, producing more accurate results. In the field, however, controlling them is much harder, which can lead to deviations in the results. Therefore, laboratory testing is preferable when accurate data is required.

Sample requirements and preparation

Refractometry can be performed on a variety of transparent and translucent media, including liquids, solutions, crystals, soft tissue, and gases. In most cases, only a small amount of liquid or solid is required for the analysis. In the case of handheld and digital refractometers, the device itself usually consists of a probe that can be directly inserted into a liquid sample.

Need a refractometric analysis?

Measurlabs offers high-quality refractometric analyses with a fast turnaround time and affordable pricing. If you have any questions about your sample or its suitability for the method, our experts are always happy to help. You can contact us through the form below or by emailing us at info@measurlabs.com.