Determining the refractive index and concentration as part of quality control or research and development tasks increasingly places greater demands on the measuring instruments used.
Requirements of harsh measuring conditions
Quality control in the sugar, chemical or fruit juice industries often takes place close to the production lines to reduce the distances covered. Instruments which are used here have to be particularly robust. Knocks, dust or water spray from cleaning with water hoses should not damage the instrument or influence the measurement results. In the chemical industry, measurements are also carried out on aggressive samples. The measuring instruments must be resistant to these chemicals and be easy to clean.
The refractive index may also be determined in fume hoods, in glove boxes or at-line, for example in the pharmaceutical industry or in research and development. Here there may be a risk to health requiring the instruments to be operated from a distance.
In the quality control of samples which contain pulp (e.g. fruit juice) or solid particles (such as in slurry production or in the sugar industry) measurement using conventional refractometers is disrupted by the particles settling on the measuring prism. In this case, conventional refractometers often fail to deliver stable and reproducible results.
To succeed here, measuring instruments need special properties:
- A robust, waterproof and resistant design for measurements at the production line and on aggressive samples
To guarantee high mechanical and chemical stability for measurements in such rough environments requires an instrument with a robust housing which is resistant to liquids, chemicals and dust. The optics and electronics are permanently protected from damage in a hermetically sealed instrument.
- Remote operation for measurements in fume hoods, glove boxes or at-line
Measurements under specially protected conditions (such as in the presence of toxic chemicals) require operation from a safe distance. This can be achieved by separating the measuring and operating unit. They remain connected via a cable. This means the operating unit can be positioned in a safe location. It is also possible to start the measurement via a push-button or foot-operated switch.
- Vertical positioning for samples containing particles
Measuring instruments should avoid errors caused by sedimentation of the sample on the measuring prism. A vertical positioning using a flow cell with filling funnel prevents this problem. Pulp and particles cannot disturb the measurement results.
Abbemat Heavy Duty: Measure when others fail.
Anton Paar has designed the new Abbemat 450 and 650 Heavy Duty refractometers to succeed in the described harsh conditions. They combine robust construction with very high precision (up to ±0.00002 nD) and are suitable for use under extreme measuring conditions:
- The stable housing allows highly precise refractive index and concentration determination in harsh environments
- The refractometers have a resistant measuring unit made of solid, anodized aluminum
- They are resistant to liquids and dust (IP68-certified)
- The waterproof measuring unit allows cleaning in production plants or brief immersion in water (up to 2 hours at a water depth of one meter)
- The remote control enables measurements under fume hoods, in glove boxes or at-line via a connecting cable (up to 5 meters)
- Hand-operated or foot-operated switch to start measurements
- Vertical positioning for reliable results on samples with pulp or particles
Anton Paar shows how unbelievably robust these new refractometers are under extreme conditions in a series of videos.