Polarimeter Sample Cells: Better By Design
Many Rudolph Polarimeter Cell designs offer significant advantages over traditional fused end glass cell designs as shown in Picture B. All glass, polarimeter cells are easily broken and often build up optically active residue on the inside of the glass ends. Also these cells do not have built in apertures so the light passing through the sample is easily affected by small air bubbles caught inside the cell as shown in Picture B. Rudolph does offer this style cell for those customers who prefer a fused glass end cell for use in their polarimeter or saccharimeter but doesn’t recommend them.
Rudolph Polarimeter Cells with built in apertures eliminate these problems because the stainless steel screw ends have apertures that are smaller than the internal diameter of the cell body to avoid the problem of the light being disturbed by small air bubbles along the surface of the cell. This design results in better optical rotation measurement stability (Figure 2).
As shown below, the screw caps have precision apertures which reduce the beam diameter to less than the internal diameter of the cell so that, when the cells are aligned with the beam, internal sidewall reflections and consequent depolarizing effects are minimized.
Polarimeter Samples Cells that are easy to clean
Another advantage over fused end cells is that screw caps, washers, and end plates are easily removed for cleaning the glass ends, sample cell interiors, or for replacement of the washers and end glass. To reassemble the cell requires following the configuration of Figure 2 and then applying finger tight pressure to the screw caps. As the screw caps are turned, the washers are compressed against the end glass creating a leak proof seal with the precision ground cell ends. Minimal screw cap pressure and the compressibility of the washer ensures a tight seal without causing stress induced birefringence in the glass end plates.
Sample Cell Selection
Cells That Meet Your Application
With over 50 cells to choose from, Rudolph Research Analytical has a cell to meet every application.
Rudolph Autopol™ Polarimeters Accept Sample Cells from 10mm to 200mm Long
Some polarimeters accept only special sample cells, with maximum lengths of 100mm. Rudolph’s Autopol™ accepts cells up to 200mm long. A 200mm sample cell offers twice the sensitivity when measuring the same solution in a 100mm cell. This additional optical path length is especially useful for solutions that have a small optical rotation. For precious samples and essential oils that have a large optical rotation, cells with only 0.05ml volumes and 10mm optical path lengths are available.
Type 40T TempTrol™
Type 40T TempTrol™ Polarimeter Sample Cells: These cells are constructed of stainless steel
and Delrin® and come with Luer® fittings at either end of the cell for easy filling with a plastic syringe or pipette.
The cells have removable metal collars that allow for easy cleaning and glass cell end replacement. All cells come with
Luer® lock and plug stoppers.
Type40T Ceramic Cell
For laboratories that work with strong acids and bases such as 6 Molar HCl,
the Ceramic Quartz Polarimeter Sample Cell
addresses the issues associated with corrosive samples. Rudolph’s exclusive design also incorporates
an improved sample flow through the cell to reduce cavitation and air bubbles. Available only from
Rudolph, the Ceramic Quartz Cell is available on all models and comes standard on the Autopol V PLUS
and Autopol VI, a Rudolph exclusive offering.
Access through gasketing in the top of the sample trough easily allows connection to a process stream (Figure 3). Readings can be downloaded via RS232 to a computer at fixed intervals or when prompted by an operator or an ASCI II command. Custom cells with special Swagelock® ferrules and fittings, and NEMA enclosures (as shown below) are available to allow connection to process streams.
Sample solutions are either poured, injected with a syringe or pipetted into the center well, side well or side tubulation. Air bubbles are released by tilting the cells side to side or to one side while filling. Flexible tipped pipettes capable of reaching from the center well to either end of the sample can be helpful in filling narrow bore center fill cells.
Micro Volumes for Chiral Detection After HPLC
If your application demands 1ml or less, Type 32 Cells offer less than 0.5ml volumes. These cells come standard with HPLC fittings which transform your polarimeter into a chiral detector when connected to a chiral column after HPLC (Picture D).
Pour In Sampling Capability
Rapid operation is achieved by using a Type 31 or 33 Flow Through Polarimeter Sample Cell as seen in Picture C. Once the sample cell is filled, each successive sample poured into the funnel will displace the previous sample through the drain tube. This method eliminates opening and closing the polarimeter or saccharimeter sample chamber door and interchanging sample cells. Measurements can be made about as rapidly as successive samples can be poured.
For sucrose or other high volume applications where the temperature coefficient is known, a 33 Cell can be used as in Picture C. This cell has a built-in temperature port which, when the temperature probe is inserted, automatically measures the sample temperature inside the cell and sends the temperature to the Autopol™ IV or Autopol™ 880 for correction to 20°C, 25°C or any customer specified temperature.
Two Sample Temperature Control Solutions
Patented TempTrol™ Technology Eliminates the Need for a Water Bath
TempTrol™ heating and cooling transfer surface in the measurement trough of the Autopol™ Polarimeter.
Temperature is selected via an easy to read and easy to operate, LCD Touch-Screen.
TempTrol™ cell with mating heating and cooling transfer surface.
Place the Rudolph TempTrol™ cell in your TempTrol™ equipped Autopol™ IV or V sample chamber to measure to within ±0.2°C of the USP, EP, JP, or BP specified temperature (normally 20°C or 25°C ±0.5°C)
Rudolph provides a temperature validation cell with every TempTrol™ system. The temperature validation cell along with an optional NIST traceable thermometer is designed to validate the temperature control performance of the polarimeter and cell to ±0.2°C.
Sample Temperature Control With Water Bath
As seen above, almost all Rudolph Research Analytical jacketed cells come standard with quick release fittings which allow cells to be easily removed from the polarimeter or saccharimeter sample chamber. Tubing is held in place by rubber gasketing on top of the trough and the door. Optional stopper (choose “S” after the cell part no.) for evaporative samples (Picture A).
Temperature control is obtained through the use of an external water bath and a jacketed cell (Figure 1).
How to use the Rudolph Research Polarimeter Cell FillStation®
For users who prefer not to hold the cell while working with highly acidic or basic samples, the Rudolph Cell Fill Station® should be used.
Filling a Rudolph Polarimeter cell is easy and you can be assured of an air bubble free sample cell. It is important to note that when using highly acidic or basic solution samples the cell should not be filled in the Polarimeter; doing so may allow spillage into the instrument which, over time, may damage the instrument.
The Rudolph Polarimeter Cell Fill Station® accessory is available for all Rudolph Autopol® Polarimeters and is included free of charge with Autopol® V, Autopol®V PLUS, and Autopol® VI Polarimeter Models.
How to Fill Cells Manually
When held at the correct angle and filled using the lower inlet port, the cell is filled with almost no possibility of leaving an air bubble in the cell. Filling from the lower inlet port forces any air bubbles up and out of the upper outlet port.
Rudolph cells are unlike other manufacturers’ cells as they are uniquely designed to keep small air bubbles out of the light path. Filling the cell is as simple as holding the cell at a slight upward angle and filling from the bottom inlet using a Luer Syringe. When the sample appears near the top outlet port, simply place the Luer cap on the upper port and then lower port. Your cell is now filled, capped and air bubble free. Cells must be clean and dry to ensure proper filling with minimum sample.