Thermostatically controlled oven

The gas chromatograph comprises an oven with sufficient volume to hold one or two columns easily and which can heat up to more than 400 °C. A weak thermal inertia permits a rapid but controlled temperature climb (gradient able to attain 100 °C/min). The temperature must be controlled to within 0.1 °C in order to get reproducible separations in isothermal or temperature programmed modes. By installation of a cryogenic valve fed with N2 or CO2 in the liquid state, the oven can be regulated at low temperature. 

Although the performance of packed columns is more modest than capillary columns, they are still usually employed for many routine analyses. Easy to manufacture and with a large choice of stationary phases available, they are not however, well adapted to trace analyses. 

They are usually made of the highest purity fused silica obtained by the combustion of tetrachlorosilane (SiCl4) in an oxygen-rich atmosphere. The internal diameter of 

For packed columns, for which impregnation techniques are very simple, over 100 

Each of these phases can be used between a minimum temperature beneath which concentration equilibria are too slow to occur, and a maximum temperature above which degradation of the polymer occurs. This high limit depends on the film thickness and the nature of the polymer. 

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The column is enclosed in a thermostatically controlled oven so that its temperature is held constant to within 0.5 °C, thus ensuring reproducible conditions. The operating temperature may range from ambient to over 400 °C and for isothermal operation is kept constant during the separation process. 

To ensure operation under reproducible conditions, the column is enclosed in a thermostatically controlled oven whose temperature can be held constant to within 0.1°C. Operating temperatures range from ambient to over 400°C and may remain constant during a separation - isothermal operation - or automatically increased at a predetermined rate to speed the elution process - temperature programming (p. 106). The latter is a form of gradient elution. Rapid temperature equili-... 

The beaker containing the solvent is equilibrated in a thermostatically controlled oven at 95 C for about 15 minutes. 

Berkhout Stability Test, designed in the artillery laboratory at Hembrug,Holland, consists in heating samples of NC or propints in weighing bottles at 95°, 105° or 110° and noting the loss of wt in a definite period(such as 72 hrs), as well as the time required for evoln of red fumes. The heating is conducted in a specially designed thermostatically controlled oven. Two models of such ovens are described in Ref 1 (Compare with Jacque Test and with Sy Test) Refs 1)J.D.Berkhout,SS 17,33 4(1922) CA 16, 2602(1922) 2)Reilly(1938),85... 

The sample is carried through the column (3) by the carrier gas/mobile phase. The column is enclosed in a thermostatically controlled oven (4). Depending on how firmly each component of the sample sticks to the stationary phase - i.e. its affinity for the stationary phase - the mobile phase carries it through the column more or less quickly. Components that stick least tightly to the stationary phase move fastest, while those that are held more firmly move through more slowly. The time taken for a component of a mixture to pass through the column is known as its retention time. The retention time of a substance depends on how its vapour is distributed between the mobile and stationary phases. 

To ensure operatjdn under reproducible conditions, the column is cndqsed in a thermostatically controlled oven whose temperature can be held Constant to wjtpin ().1°C. Operating temperatures range from... 

The flask is kept at the temperature of 40°C (104°F) for 40 days, extra dew being added as necessary. Later, the temperature is raised until a dry ash is obtained. This is then put into long test tubes, together with about 2.5 grams of powdered gold and some dew, and the tubes are sealed with a rubber stopper. Barbault has a thermostatically controlled oven maintained at a temperature between 150° and 200°C (302° and 392°F)— that is, substantially above the boiling point of water—and 12 test tubes are inserted partway into this oven so that the contents... 

The SFC systems are grouped into two categories analytical SFC for chemical analysis and preparative SFC for scale-up chemical synthesis and purification. On a fundamental level, the instrumentation for SFC consists of the following (1) a fluid delivery system with high-pressure pumps to transport the sample in a mobile phase and to control the pressure (2) the column in a thermostat-controlled oven where the separation process occurs (3) a restrictor to maintain the high pressure in the column (4) a detection system and (5) a computer to control the system as well as to record the results (see Figure 9.5 as an example). In SFC the mobile phase... 

A gas chromatograph is composed of several components within a special frame. These components include the injector, the column and the detector, associated with a thermostatically controlled oven that enables the column to attain high temperatures (Figure 2.1). The mobile phase that transports the analytes through the column is a gas referred to as the carrier gas. The carrier gas flow, which is precisely controlled, enables reproducibility of the retention times. 

All crystallizations were carried out in sealed polypropylene tubes of 30-40-ml capacity. Glass was avoided purposely in all our experiments since it is attacked readily by the reactants used and the crystals nucleate mostly on the glass walls. In particular, we have noted that reproducibility of Li,Na-zeolite crystallizations is exceedingly poor when carried out in borosilicate glass even at relatively low temperatures. The polypropylene tubes containing the reactants were rotated slowly (about 8 revolutions per minute) at 100°C in thermostatically controlled ovens. 

Aging is carried out in thermostatically controlled ovens, which may be of the usual cabinet type or consist of a number of cells in a heated block. For plastics, relatively little consideration appears to have been given to details of the oven other than control of temperature, but for rubbers other factors that can influence results are carefully specified, and it would seem reasonable to suppose that these could be significant for plastics also. 

The solutes chosen were (S) and (R) 4-benzyl-2-oxazolidinone. The apparatus consisted of an LC pump, a 1 pi internal loop sample valve and the column was situated in a thermostatically controlled oven. The oven could be operated at temperatures between 5°C and 85°C with a precision of 0.2°C. The mobile phase was passed through a preheater, consisting of 1 m length of coiled stainless steel tube, 0.010 in. ID., situated in the thermostat, between the sample valve and the column. The column outlet was connected directly to a UV detector operating at 220 nm. The eluent from the detector was passed to a 50 ml Grade A burette and the retention volumes were measured directly in ml of mobile phase. The burette was read with an accuracy of 0.02 ml. The output of the detector was displayed on a digital meter and an electronic recorder/integrator. 

A new sample handling accessory with which films of constant thicknesses can be prepared has been introduced by Phillips Analytical. The plastic film press contains a thermostatically controlled oven unit that is calibrated up to 300 °C. It also contains a cooling facility which may be connected to a low-pressure compressed air supply to cool the prepared films rapidly. Reproducible thickness is ensured by using a set of brass dies that can be heated and cooled quickly. The dies can produce films of 20, 50, 100, 200, and 500 pm thickness. 

A thermostatically controlled oven at 60 °C capable of being evacuated in less than 2 kPA was used. 

The column is enclosed in a thermostatically-controlled oven that is maintained at a steady temperature or programmed to increase progressively during a separation. 

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