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Refractometry and its uses in manufacturing process control

Process Refractometers

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Sean Herrington

Instrumentation engineer for the last 30 years specialising in process analytical Instrumentation and process control.

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Refractometry is a technique that involves the measurement of the refractive index of a substance. It is used in various industries such as food and beverage, pharmaceutical, and chemical manufacturing, to determine the concentration of a solution, the purity of a substance, and to monitor the quality of the manufacturing process. In this blog, we will discuss the basics of refractometry and its uses in manufacturing process control.

What is Refractometry?

Refractive index is a measure of how light bends when it passes through a substance. The refractive index of a substance is affected by the concentration of the substance in a solution. Refractometry measures the refractive index of a substance and uses it to determine the concentration of the substance in a solution.

In refractometry, a beam of light is passed through a sample of the substance, and the angle of refraction is measured. The angle of refraction is then used to calculate the refractive index of the substance with very high accuracy.

Types of refractometer

Here are just a few examples of the types of industrial process refractometers that are available. The choice of refractometer will depend on the specific application and the level of precision and automation required.

Traditional analog refractometers: These are the most basic type of refractometers that use a prism and a scale when held up to the light they measure refractive index by eye.
Digital refractometers like the Maselli UR24: These refractometers use digital technology typically a CCD to measure refractive index and display the results on a digital screen.
In-line refractometers like the Maselli UR32 or UR62: These are designed to be installed in a manufacturing process line to provide continuous monitoring of the process. They are commonly used in the food and beverage, chemical, and pharmaceutical industries.
Handheld refractometers like the JWII handheld refractometer: These are compact, portable, and easy-to-use refractometers that are ideal for field work or for spot-checking samples in a laboratory.
Abbe or benchtop refractometers like the Maselli LR05: These are high-precision refractometers that use a double prism system to measure the refractive index of a sample.
Polarimetric refractometers: These are used to measure the polarization angle of a sample and are commonly used in the sugar industry to measure sugar content.

Uses of Refractometry in Manufacturing Process Control

Refractometry is widely used in manufacturing process control for its ability to accurately measure the concentration of a substance in a solution. Here are a few examples of how refractometry is used in manufacturing process control:

Food and Beverage Industry

Refractometry is used in the food and beverage industry to determine the sugar content of fruits and vegetables typically using a benchtop refractometer like the Maselli LR05. This information is used to monitor the quality of the produce and to determine the appropriate time for harvest. In addition, refractometry is used to determine the sugar content of juices, wine, and beer, and an instrument like the Maselli UR24 can be fitted to the line and connected to the plant PLC for automatic process control which helps to ensure consistency in taste and quality while also improving product yield.

Pharmaceutical Industry

Refractometry is used in the pharmaceutical industry to determine the concentration of active ingredients in a drug. This information is crucial for ensuring that the drug is effective and safe for use. typically, a Maselli LR05 would be used in a laboratory to determine and record these parameters. Refractometry is also used to determine the purity of a drug, which helps to ensure that it meets regulatory requirements.

Chemical Industry

Refractometry is used in the chemical industry to monitor the concentration of chemicals in a solution. In this industry an in-line refractometer like the Maselli URX1 may be needed due to the hazardous working environment. For non-hazardous applications the Maselli UR24 is ideal This information is important for ensuring that the manufacturing process is efficient, and that the quality of the product meets specifications. Refractometry is also used to monitor the purity of chemicals, which is important for ensuring that they are safe to use.

Other Industries

Refractometry can be used in many other industries from mining and mineral, petrochemical, wood, paper, electronics, steel, textiles. This list is not exhaustive but provides a good overview of where a refractometer can be applied. The basic principle being any liquid process where process concentration of a binary liquid (or a liquid where only 2 components change) is of interest a refractometer could be applied very successfully.

Advantages of Refractometry in Manufacturing Process Control

Refractometry offers several advantages over other techniques for measuring the concentration of a substance in a solution.

Here are some key advantages of refractometry:

Non-destructive: Refractometry is a non-destructive technique, which means that the sample can be reused after measurement. This is particularly useful in industries where the cost of raw materials is high.

Rapid: Refractometry provides rapid results, which makes it useful for monitoring the manufacturing process in real-time. This allows for quick adjustments to be made to the process, which helps to improve efficiency and reduce waste.

Easy to use: Refractometers are easy to use and require minimal training. This makes them ideal for use in industries where operators may not have extensive technical knowledge.

Conclusion

Refractometry is a powerful tool for measuring the concentration of a substance in a solution. Its non-destructive nature, rapid results, and ease of use make it an ideal technique for use in manufacturing process control. Its applications in the food and beverage, pharmaceutical, and chemical industries are just a few examples of the many ways in which a refractometer is used to improve the quality and efficiency of manufacturing processes.

For more information on refractometers and their application in industry please feel free to contact us