Mixtures thermolabile

Cellulases can also be eliminated fiom a mixture with xylanases by selective thermal inactivation. Cellulases are more thermolabile than xylanases in tiie cdlulolytic systems of the fungus Y-94 (79), T. harzianum 20), and Tkermoascus aurantiacus (77), but not in the Trickoderma reesei system (Biely, P. and Vrsanska, M., Slovak Academy of Sciences, Bratislava, unpublished results). Since cellulase thoixud inactivation causes a significant loss of xylanase also, a more convenient way to eliminate cellulase activity is by selective chemical or biological inhibition or inactivation. There appear, however, to be no reports on the existence of natural inhibitors that would be specific for cellulases. Such inhibitors of amylases and pectinases are known to occur in plants (27). 

Introduction of the light-scattering detector has made the development of more efficient methods for the separation of natural complex mixtures of TG possible, including those of gradient elution. The evaporator temperature in the mass detector oven may influence the response of thermolabile compounds or compounds with low boiling points. Consequently, low tempera-... 

Photochemical activation of transition metal carbonyls has been used as a preparative tool for substitution of carbonyl ligands by donor molecules or unsaturated hydrocarbons for many years (7-6). The advantage of photochemical activation in comparison with thermal activation is the possibility of conducting reactions at fairly low temperatures. Hence even thermolabile products can be prepared and isolated by appropriate treatment of the reaction mixtures. However, due to the various activation modes of transition metal carbonyls by UV light, often more than one product is obtained, and chromatographic separation is necessary. Limitations are set primarily by the amount of substance which can be irradiated in solution at one time. 

Free radicals must be introduced into the system to start the reaction. There are many ways to accomplish this, but the most common method involves the use of a thermolabile compound, called an initiator, which decomposes to yield two free radicals at the temperature of the reaction mixture. Tiiat is,... 

The e do-adduct 21 from methoxycarbonylcarbene and cyclohexa-1,3-diene on treatment with Af-bromosuccinimide gave a mixture of thermolabile bromides which rearranged under the reaction conditions to produce methyl cyclohepta-2,4,6-trienecarboxylate (22). ... 

GC/MS with capillary columns has been the gold standard for more than 20 years, but LC/MS has become a complementary method due to the success in interface development with atmospheric pressure ionisation (API) for low molecular weight compounds and the appHcation to biopolymers. For many areas of analytical chemistry, LC/MS has become indispensible due to its advantages over GC/MS for polar and thermolabile analytes. A Hmiting factor for LC/MS has been the incompatibility between the hquid eluting from the LC and the mass spectrometer vacuum. This could be overcome in electrospray ionisation with the use of a nebuliser gas ( ion spray ) or additional heated drying gas ( turbo ion spray ) (70, 71]. Due to its high sensitivity and selectivity, APl-MS has become a standard tool for the stracture elucidation of analytes from complex mixtures. 

Nanostructure lipid carriers indicate lipid particles with a disperse phase made of a mixture of solid and liquid lipids. Owing to the decreased melting point of the lipid phase, such systems can be produced at lower temperatures, reducing the extent of degradation of the thermolabile compounds. "... 

Nanopure is suspensions homogenized in water-free media or water mixtures, i.e., the drug suspensions in the non-aqueous media were homogenized at 0 °C or even below the freezing point and hence are called deep-freeze homogenization. It can be used effectively for thermolabile substances in milder conditions... 

So if we use the basic theory of distillation and the methods that follow from it, the cost of separation of the mixtures of substances with close boiling temperatures can be decreased, and the problems of azeotropic and thermolabile mixtures separation may also be substantially overcome. On the whole, in this book, special attention will be paid to the problems mentioned above. 

There are two classes of mixtures that are not characterized by unlimited separability the azeotropic mixtures and the thermolabile ones. 

During the separation of thermolabile mixtures, for example, the petroleum, that is, mixtures to be separated at a high temperature at which detrimental chemical reactions take place, the problem is the maximum possible extraction of light components from these mixtures without the excess of specific temperature level. Vacuum separation in the presence of steam is used to decrease the temperature. 

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