Slow heating method

No tandem MS experiment can be successful if the precursor ions fail to fragment (at the right time and place). The ion activation step is crucial to the experiment and ultimately defines what types of products result. Hence, the ion activation method that is appropriate for a specific application depends on the MS instrument configuration as well as on the analyzed compounds and the structural information that is wanted. Various, more or less complementary, ion activation methods have been developed during the history of tandem MS. Below we give brief descriptions of several of these approaches. A more detailed description of peptide fragmentation mles and nomenclature is provided in Chapter 2. An excellent review of ion activation methods for tandem mass spectrometry is written by Sleno and Volmer, see Reference 12, and for a more detailed review on slow heating methods in tandem MS, see Reference 13. 

BIRD. The first requirement is that since BIRD is a very slow-heating method the observation time has to be long (seconds or minutes). Second, the pressure has to be low (<10-6 torr) so that the risk of dissociation due to collisions with the background gas is negligible. There are close similarities between BIRD and another slow-heating method, IRMPD. 

S. A. McLuckey and D. E. Goeringer. Slow Heating Methods in Tandem Mass Spectrometry. J. Mass Spectrom., 32(1997) 461-474. 

McLuckey, S.A. Goeringer, D.E. Slow heating methods in tandem mass spectrometry. J. Mass Spectrom. 1997, 32,461-474. 

King, F. L. and Harrison, W. W. (1989) Collision-induced dissociation of polyatomic ions in glow discharge mass spectrometry. Irvt. J. Mass Spectrom. Ion Processes, 89,171-85. Mcluckey, S. A. and Goeringer, D. E. (1997) Slow heating methods in tand mass spectrometry. J. Mass Spectrom., 32,461-74. 

Two crystalline forms have been observed.One is formed by slow cooling from the melt and the other by slow heating of the amorphous polymer. The properties of the commercial products were therefore to some extent dependent on their heat history. Glass transition temperatures observed range from 7 to 32°C and depend on the time scale of the method of measurement. ... 

Measurements of melting curves can be used to obtain very accurate evaluations of the melting point of a compound when slow heating rates are used. The phase transition can also be monitored visually, with the operator marking the onset and completion of the melting process. This is most appropriately performed in conjunction with optical microscopy, thus yielding the combined method of thermomicroscopy or hot-stage microscopy [7]. 

Pyrolysis is a type of gasification that breaks down the biomass in oxygen deficient environments, at temperatures of up to 400°F. This process is used to produce charcoal. Since the temperature is lower than other gasification methods, the end products are different. The slow heating produces almost equal proportions of gas, liquid and charcoal, but the output mix can be adjusted by changing the input, the temperature, and the time in the reactor. The main gases produced are hydrogen and carbon... 

Cured Olixomer Properties. The T, of the cured specimen ms not obvious by DSC, however the T was observed at 383°C (Q maac) by dynamic mechanical testing of a torsion bar. The T obtained by this method has been driven up in temperature by the slow heating rate of 2°C/minute used in the test, the actual T is somewhat lower... 

Methods used to improve brick lifetime are the production of stable coatings in the burning zone, the control of ovality of the tyres and kiln alignment, avoidance of frequent kiln stoppages, and slow heating and cooling rates.62,69,70... 

During the initial stages of a fire, fire-retardant-treated wood contributes less heat than does untreated wood, especially from the flammable volatiles (8,26). This means that the spread of fire to nearby combustibles is slow. The fire tends to be confined to the primary source. In the ASTM E84 test for building materials, treated specimens produce about 75 percent less heat than untreated red oak. In a total combustion test, however, such as the National Bureau of Standards potential heat method (54), both treated and untreated wood release about the same total heat. 

Alternatively one can in principle derive both micropore and macropore diffusivities from measurements of the transient uptake rate for a particle (or assemblage of crystals) subjected to a step change in ambient sorbate pressure or concentration. The main problem with this approach is that the overall uptake rate may be controlled by several different processes, including both heat and extraparticle mass transfer as well as intraparticle or intracrystalline diffusion. The intrusion of such rate processes is not always obvious from a cursory examination of the experimental data, and the literature of the subject is replete with incorrect diffusivities (usually erroneously low values) obtained as a result of intrusion of such extraneous effects. Nevertheless, provided that intraparticle diffusion is sufficiently slow, the method offers a useful practical alternative to the Wicke-Kallen bach method. 

If molds are required to shape the plastisol into a finished product, they are generally light-weight low-cost molds of aluminum, electroformed nickel, or ceramic. Oven heating is slow but common. The major handicap is slow heat transfer, so overall production cycles may take 4-20 min. Several different methods are described below for converting plastisols into finished products. 

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