Polarimeters are precise optical instruments that measure purity and concentration through the optical activity exhibited in inorganic and organic compounds. Compounds are considered to be optically active if linearly polarized light is rotated when passing through them. This optical rotation in general means that the polarization of the direction of light is rotated at a specific angle proportionate to the concentration of the optically active substance being tested. Optical rotation is measured in degrees of angle. At point zero, a polarizer and analyzer are set in an angle of 90 degrees toward each other, which means that no light reaches the detector (0% transmission). When an optically active substance is then placed in the measuring tube, the transmission will rise as a result of the plane polarization. To measure the angle, the analyzer is rotated up to the point where the transmission of the detector is again at minimum. Polarimetry is a mature technique and today’s automatic instrumentation provides features and benefits that purely manual-optical systems do not. Busy labs processing multiple samples have the option of automated data capture, variable wavelength and temperature with circular polarimeters having 0.005 accuracy and 0.001 resolution. These instruments are suited for quality control, process control, and research for demanding applications in many industries including beverage, cosmetic, chemical, food, essential oils and pharmaceutical.
Which Polarimeter is Right for Your Lab?
With this overview, Reichert makes it easy to determine
which polarimeter suits your needs. Identify answers to the
steps below to determine the specific requirements of your
applications, in your industry, and with your budget. And then,
simply pick the appropriate Reichert polarimeter from the chart
on the back.
Selecting the Right Polarimeter
1 Measurement Range and Accuracy
Purchasing a new polarimeter is a major decision. Choose the model that offers the best measurement range and accuracy to meet present and future application needs. Be aware that many polarimeters offer a very limited measurement range that may limit readings. Also, most importantly, there are many polarimeters on the market that have a non-linear accuracy specification. In other words, within the limited measurement range of these instruments, the accuracy specification can degrade to different levels across that range.
Be sure the polarimeter has an accurate linear
response over the entire measurement range.
2 Measurement Response Time
In today’s labs, speed is critical - with fewer resources processing
more samples, technicians wait time must be minimized.
Reichert offers the fastest measurements for a given accuracy
3 Illumination Method
Polarimeters use different lamp sources for transmitting polarized light. Some models employ halogen lamps which have a short life span, generate heat, and require servicing while others have LED illumination. LED illumination does not require maintenance or generate heat and is environmentally friendly and energy efficient. All Reichert polarimeters feature LED illumination.
Operating costs are important to consider when evaluating instruments. Many companies offer expensive service plans. Reichert builds robust instruments that provide reliable service for decades without requiring repair contracts. Backed by longstanding knowledge in the analytical instruments industry, Reichert polarimeters are manufactured for reliability and longevity.
5 Sample Tube Lengths, Material Composition
Polarimetric applications utilize different sample tube lengths. Longer tube lengths provide greater accuracy. But sometimes shorter tube lengths are needed if samples are limited in quantity or very expensive. Tube lengths range from 10 to 200mm depending on the application. Material composition of tubes is also important. Many sample types work well with a stainless steel tube. Samples that are corrosive are better suited for glass. Reichert provides a wide range of tube lengths and materials to meet all needs.
When selecting a polarimeter, ensure the software features meet your needs. Reichert offers an intuitive, simple interface for quickly and accurately attaining measurements. The measurement screens are simplified and Reichert software provides custom scales and methods, and is compliant with 21CFR Part 11 compliance.