Refractometry is an optical analytical technique used to establish the refractive index of transparent and translucent substances. The method provides information about the substance's chemical composition, purity, and physical properties and is commonly used as a quality control method.

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What is refractometry and how does it work?

Refractometry is an analytical technique that is used to measure 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.

There are several types of refractometers commonly used, though they all operate based on the same basic principle. 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 a lot of information about its physical and chemical properties.

Handheld refractometers exist 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 are used, as they can provide more accurate data on a wider range of sample types.

What is refractometry used for?

Refractometry is used across multiple industries to analyze various types of materials. It 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, to ensure that they have the correct chemical properties. It is also used in agriculture to analyze produce, particularly fruits, to ensure that they contain the correct levels of various sugars.

Refractometry is also commonly used to analyze the properties of translucent solid materials, such as glasses and gemstones. Through this, it can offer information about their physical properties, as well as their purity, making it an essential technique for quantitative analysis of these materials.

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. However, this can be difficult to measure accurately for materials with a refractive index lower than that of the prism. Therefore, refractometry is better suited for working with samples with a higher refractive index.

The refractive index of a material is also very dependent on the temperature of the sample and the wavelength of light used. Under laboratory conditions, this can be effectively controlled, producing more accurate results. In the field, however, this is much harder to control and can lead to deviations in the results gathered. Therefore, laboratory testing is preferable when accurate data is required, specifically for analyzing the physical and chemical properties of a substance.

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 fast results and affordable prices. 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

Suitable sample matrices

  • Liquids
  • Solutions
  • Crystals
  • Glasses

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Frequently asked questions

What is refractometry commonly used for?

Refractometry is commonly used to ensure that different materials have the correct chemical and physical properties. It is used, for example, in the food and drink industries for quality control on sugars, oils, beverages, and other products, in agriculture to measure the sugar content of fruits, and for analyzing the purity of gemstones and glasses.

What are the limitations of refractometry?

To get accurate results from the analysis, the material should have a higher refractive index than the prism used in the analysis. The results are also dependent on the temperature of the sample and the wavelength of the light used. Under laboratory conditions, these can be effectively controlled, but with handheld refractometers used in the field, this can significantly alter the results.

What kind of samples are suitable for refractometry?

Transparent and translucent media, like liquids, solutions, crystals, soft tissue, and gases are suitable for refractometric analyses.

What is Measurlabs?

Measurlabs offers a variety of laboratory analyses for product developers and quality managers. We perform some of the analyses in our own lab, but mostly we outsource them to carefully selected partner laboratories. This way we can send each sample to the lab that is best suited for the purpose, and offer high-quality analyses with more than a thousand different methods to our clients.

How does the service work?

When you contact us through our contact form or by email, one of our specialists will take ownership of your case and answer your query. You get an offer with all the necessary details about the analysis, and can send your samples to the indicated address. We will then take care of sending your samples to the correct laboratories and write a clear report on the results for you.

How do I send my samples?

Samples are usually delivered to our laboratory via courier. Contact us for further details before sending samples.