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).

The CD 250™ cuvette holder contains a thermoelectric cooler 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


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

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.
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