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	CD 250™	temperature specs
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	Temperature-Controlled Cuvette Holder for Circular Dichroism The CD 250 is a cuvette holder that provides precision temperature control for circular dichroism measurements. To accommodate the several kinds of commonly used CD cuvettes, the CD 250 has a body that supports different cuvette carriage for different CD cells. Optional low-strain, fused silica windows may be purchased to enclose a CD cell for better temperature control. Features include variable speed magnetic stirring and dry gas purge to minimize condensation on the cuvette surfaces when working at low temperature. It is provided with a matched and calibrated TC 125 Temperature Controller.

	CD 250™ Temperature-Controlled Cuvette Holder	Breakaway view of a CD 250™

	• 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 • Optional built-in windows for stable thermal control • Compact size to fit most CD spectrometers • TC 125 temperature-controller included
	Description
	Since there are several kinds of CD cuvettes that are commonly used, the CD 250 controls the temperature of a metal cuvette carriage that holds the cuvette. The carriage screws down firmly into a temperature-controlled base. Optional 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 cuvette. The temperature of the CD 250 tower is controlled by a thermoelectric cooler (TEC), a device using the Peltier principle. The TEC pumps heat into or out of the tower. For heat removal, a small flow of water passes through a heat exchanger under the TEC. The CD 250 includes a matched and calibrated TLC 125 Temperature Controller.
	Cuvette Size and Types
	Cuvette carriages that optimally fit a variety of different cuvette types mount into the CD 250. For example: a) Carriage for the Hellma 121.000 short path length CD cuvette b) Carriage for a square, 10 x 10 mm path length, 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. Unlike Quantum Northwest’s other cuvette holders, the standard carriage for the square cuvette uses a z-height of 15 mm.

	Special Options
	SER 2.3, Serial Control	Optional software, the SER 2.3 package, is available to operate the controller remotely from your computer, allowing complex functionality.
	BATH 100, Water Circulating Pump	The TLC 40 requires a small flow of water to pass through the heat exchanger below the TEC. To provide such a flow, you may purchase the optional BATH 100, which consists of a submersible pump, a plastic bucket and the necessary tubing and fittings.
	Mounting Requirements
	As you can see in the page on Aftermarket Cuvette Holders, Quantum Northwest has the necessary knowledge to make versions of the CD 250 for several commercial circular dichroism instruments. If you do not find your instrument in the list, please contact us anyway. With a little help on dimensions and the configuration of your spectrometer sample compartment, we can usually make a custom cuvette holder for a price comparable to that of one of our normal products. We are happy to do this, because it helps us learn about different instruments. To make a version of the CD 250 for a spectrophotometer, we must know some basic information about the floor plate of the sample compartment and how we must make a base plate that will mount in place. We also must know the height of the optical center line above the floor of the sample compartment. An easy way to determine this basic information for a new spectrophotometer is to measure an existing non-regulated cuvette holder. Utilities for the cuvette holder include two tubes for water (or other coolant), one tube for dry gas, and an electrical cable. These must pass out of the sample compartment in a manner that does not disrupt the measurement. Suitable methods for getting the utilities out of the sample compartment have been found for most common spectrophotometers, but we may require assistance and suggestions for new instruments.
	Performance
	Using a 10 x 10 mm path length square cuvette, the CD 250 has temperature performance very similar to that of the TLC 50. The temperature of the holder changes rapidly and may be maintained at ±0.02 °C. However, when working with short path length cylindrical cells, where the thermal path from the sample holder to the sample is long, equilibration with be relatively slow.
	Availability
	You will need to specify the spectrometer in which the CD 250 will be used. You will also need to tell us if you want a special option such as a different z-height or a high temperature option. Tell us if you would like a BATH 100 water circulator and the SER 2.3 software package. Most configurations of the CD 250 can be shipped in two to three weeks. New configurations require getting necessary dimensions and preparing designs will, of course, also require additional time for design. Please contact us with your questions or to request a quotation.

we provide temperature-controlled cuvette holders and photoacoustic instrumentation