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CD 250™
Developed in cooperation with Quantum Northwest, Inc.
The CD 250™ is a temperature-controlled cuvette holder for circular dichroism measurements, compatible for use with the three Olis CD instruments (DSM 20, DSM 17 and DSM 1000).
- Rapid, precise Peltier control over a wide range of temperatures
- Carriages available for common cuvette types
- Variable speed magnetic stirring if needed
- Equilibrated nitrogen gas purge
- Optional remote computer control
- Built-in windows for stable thermal control
- Compact size
- TC 125 temperature-controller included
Description
The CD 250™ cuvette holder contains a thermoelectric cooler (Peltier device) for controlling the temperature. Cuvette carriages that optimally fit a variety of different cuvette types mount into the CD 250™. Four cuvette carriages are available:
a) Carriage for the Hellma 121.000 short path length CD cuvette
b) Carriage for a square (12.5 x 12.5 mm) cuvette
c) Carriage for a 10 mm path cylindrical cuvette
d) Carriage for the Olis Titrator cuvette
Other cuvette carriages can be designed on request. Windows at each side of the cuvette carriage enclose and control the environment around the cuvette, making it possible to precisely control the temperature of short path length cells. Nitrogen may be passed through a heat exchanger and directed within this chamber to speed equilibration and eliminate oxygen around the cuvette. Magnetic stirring may be used in square cuvettes or other cuvettes with adequate volume to hold a stir bar, thus minimizing temperature gradients in the sample.
Four Carriage Inserts
Temperature Range for Control
The normal full range of control for each of the temperature controllers is -55 °C to +105 °C ± 0.02 °C. If one specifies the extended temperature version available for the TLC 40, TLC 42, or TLC 50 (place a /E after the model number), then the full control range is -55 °C up to +150 °C ± 0.02 °C.
| approximate temperatures achievable under various conditions |
TLC 40 |
TLC 42 |
TLC 50 |
TLC 50F |
CD 150 |
CD 250 |
TURRET 400 |
FLASH 200 |
LC 600 |
| highest temperature /E option |
150 |
150 |
150 |
-- |
-- |
-- |
-- |
-- |
-- |
| normal highest temperature |
105 |
105 |
105 |
105 |
105 |
105 |
105 |
105 |
105 |
| in the open, no dry gas flow |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
| exposed but with dry gas flow |
-10 |
-10 |
-10 |
-10 |
-- |
-10 |
-10 |
-10 |
-10 |
| enclosed in dry environment, 0 degree circulating fluid |
-25 |
-25 |
-25 |
-25 |
-25 |
-25 |
-25 |
-25 |
-25 |
| with windows, cold circulating fluid, some added insulation |
-40 |
-40 |
-40 |
-- |
-- |
-40 |
-- |
-40 |
-- |
| with windows, very cold circulating fluid, lots of added insulation |
-55 |
-55 |
-55 |
-- |
-- |
-- |
-- |
-55 |
-- |
Achievable Temperatures
- highest temperature /E option – Special versions of the TLC 40, TLC 42, or TLC 50 can be made to operate above 105 °C. This requires special firmware in the microcomputer of the temperature controller and special changes that replace or isolate heat sensitive components under the cuvette. Temperatures up to 150 °C may be obtained, although the upper range of temperatures should not be used for extended periods of time. Operation substantially above boiling temperatures requires shutting down the cooling fluid circulation, limiting some features of control.
- normal highest temperature – All sample holders will heat to at least 105 °C. Unless the extended temperature option is installed, the controller limits operation to this temperature to prevent damage to internal components.
in the open, no dry gas flow – Unless special care is taken, operation at or below the dew point temperature of the room (estimated here to be 5 °C) will result in condensation on the cuvette windows.
- exposed but with dry gas flow – Most cuvette holders are provided with a dry gas purge option that greatly limits condensation when working in an exposed environment, permitting operation down to about -10 °C.
- enclosed in dry environment, 0 degree circulating fluid – When used inside of a spectrophotometer that can be purged with dry gas, no condensation will occur, and much lower temperatures may be reached. For a sample holder mounted in a spectrometer, simply providing dry gas flow to the holder will satisfactorily prevent condensation. Ice water is a convenient circulating fluid for most low temperature work.
- with windows, cold circulating fluid, some added insulation – Very cold operation requires the use of optical windows to thermally insulate the cuvette. We recommend the windowed jackets WJ-40, WJ-50 and WJ-200 on the TLC 40, TLC 50 and FLASH 200, respectively for this purpose. The CD 250 can also be provided with windows that mount directly on the sample holder. Very low temperatures also require the use chilled cooling fluid to remove heat from the Peltier unit. Typically one uses methanol or methanol-water mixtures within about 25 °C of the temperature you wish to achieve. Any additional insulation provided by the user (such as a layer of bubble wrap, for example) can speed temperature equilibration.
- with windows, very cold circulating fluid, lots of added insulation – We have only tested our sample holders down to -40 °C, but lower temperatures can be achieved with special care. Please contact us for suggestions on how to work at these very low temperatures.
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