Temperature-time programme

Any suitable temperature-time programme may be used. In the method of Rogers the... 

EXAMPLE 4.10 Accelerated storage testing using temperature-time programme... 

North American modem ageing system (temperature-time programme) 7 days at 13°C (55-5 F) Yeast is removed from beer of2°P(SG1008)withno fermentable extract 6 days with temperature falling from 13°C slowly to 0°C (32°F). No secondary fermentation... 

Special features/comments on-line evaporation cleavage from support on the instrument, collection of products in custom block ( waste cube ) 4 zones with individually adjustable temperature and individually programmable temperature gradients temperature/time programs possible automated version available... 

In the electrothermal AAS system each step in the temperature programme of the graphite furnace must be optimized. Each stage requires different temperatures, times, and ramp-rates depending on the analyte and the sample matrix. 

A good example of the above statement are experiments with temperature-modulated dsc (TMDSC) on samples of hnear PE (112). Here a programmable temperature controller is set up in such a way that the temperature/time profile follows exactly the profile that in an off-line modulated dsc instrument is applied to the sample. By carefully assessing the correlation between the temperature profile and the influence this exerts on the invariant Q, as well as on the ciystalhnity derived from the waxs, it is possible to show that reversible melting and crystallization take place at the lamellar fold surface and not on the lateral surfaces of the crystallites (see Figs. 26a and 26b). 

The temperature rise time (TRT), i.e. the time required for the pyrolyser temperature to be increased from its initial to the final temperature, can be chosen in the range from several milliseconds to several minutes. Simultaneously, the temperature time profile (TTP), representing temperature as a function of time for a particular pyrolysis experiment, may be easily programmable. Pyrolysis may be carried out at a fast rate of temperature increase, e.g. 10 000 K s i in the case of flash pyrolysis, or the sample can be heated at a controlled rate over a temperature range in which pyrolysis occurs using a stepwise, linear or ballistic heating approach characterized by a total heating time (THT) of several minutes or even hours. 

Temperature programming was introduced in the early days of GC and is now a commonly practiced elution technique. It follows that the temperature programmer is an essential accessory to all contemporary gas chromatographs and also to many liquid chromatographs. The technique is used for the same reasons as flow programming, that is, to accelerate the elution rate of the late peaks that would otherwise take an inordinately long time to elute. The distribution coefficient of a solute is exponentially related to the reciprocal of the absolute temperature, and as the retention volume is directly related to the distribution coefficient, temperature will govern the elution rate of the solute. 

The use of stable, narrow-bore columns and fast oven temperature programmes result in analysis times of 5-15min, while maintaining the final resolution obtained with conventional GC approaches. Fast GC-MS (5-200 s) requires the matching of several technologies ... 

All gas chromatography parameters, including temperature programme rates and hold times, are controlled by the microprocessor and set through the CRT keyboard. Up to five sets of parameters can be stored on the computer disk for instant recall. 

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