Carbohydrates mixtures

Hyperglycemia is the most common metabolic complication. A too rapid infuson of amino add-carbohydrate mixtures may result in hyperglycemia, glycosuria, mental confuson, and loss of consciousness Blood glucose levels may be obtained every 4 to 6 hours to monitor for hyperglycemia and guide the dosage of dextrose and insulin (if required). To minimize these complications the primary health care provider may decrease the rate of administration, reduce the dextrose concentration, or administer insulin. 

The Effect of Column Temperature on the Separation of a Carbohydrate Mixture... 

It should be possible to use the special properties of chiral structures for particular separation problems. According to Belinski and Tencer, one possible way in which nature solved the ribose problem could have involved an enantioselective and diastereoselective purification process acting on a mixture of biomolecules, which left ribose as the only molecule available for further reactions. The authors propose a theoretical mechanism in which a type of chromatographic process occurs at chiral mineral surfaces. This paper is likely to stimulate new experiments as well as the quest for as yet unknown surfaces which can separate racemic carbohydrate mixtures. The question arises, however, as to whether there were minerals present on the young Earth which are now unknown, as they no longer exist on the Earth of today (Belinski and Tencer, 2007). 

Difficulties are encountered in the qualitative and quantitative analysis of carbohydrate mixtures because of the structural and chemical similarity of many of these compounds, particularly with respect to the stereoisomers of a particular carbohydrate. As a consequence, many chemical methods of analysis are unable to differentiate between different carbohydrates. Analytical specificity may be improved by the preliminary separation of the components of the mixture using a chromatographic technique prior to quantitation and techniques such as gas-liquid and liquid chromatography are particularly useful. However, the availability of purified preparations of many enzymes primarily involved in carbohydrate metabolism has resulted in the development of many relatively simple methods of analysis which have the required specificity and high sensitivity and use less toxic reagents. 

Fermentation tests are based on the ability of yeast to oxidize the sugar to yield ethanol and carbon dioxide, although only the D-isomers are fermentable and only relatively few of these. Modem chromatographic techniques are, however, much more acceptable and paper and thin-layer techniques are useful for routine separation and semi-quantitation of carbohydrate mixtures, although GLC or HPLC techniques may be necessary for the more complex samples or for quantitative analysis. 

Several monophasic solvent systems are useful for the separation of carbohydrate mixtures, and in all those listed in Table 9.3 the smallest solute molecules have the fastest mobility. Thus pentoses have higher RF values than hexoses, followed by disaccharides and oligosaccharides. 

Separation and quantitation of carbohydrate mixtures may be achieved using HPLC, a method that does not necessitate the formation of a volatile derivative as in GLC. Both partition and ion-exchange techniques have been used with either ultraviolet or refractive index detectors. Partition chromatography is usually performed in the reverse phase mode using a chemically bonded stationary phase and acetonitrile (80 20) in 0.1 mol U1 acetic acid as the mobile phase. Anion- and cation-exchange resins have both been used. Carbohydrates... 

With the development of new liquid phases, interest in the separation of alditol acetates has revived, and this now may be considered the most widely used method for analyzing carbohydrate mixtures, provided that reduction does not introduce an ambiguity into the analysis also, it must be borne in mind that the multiplicity of peaks obtained by trimethylsilylation of a free sugar or of its methyl glycosides may serve a useful purpose in characterization. 

The intense absorption of water over most of the infrared spectrum restricts the regions where aqueous solutions of carbohydrates can be usefully studied. Absorbance subtraction makes it possible to eliminate water absorbance and magnify the remaining spectral features to the limit of the signal-to-noise ratio. Many other data-processing techniques, such as the ratio method,4 the least-squares refinement,5 and factor analysis,6 should be of benefit in the study of carbohydrate mixtures. 

Application of F.t.-i.r. spectroscopy to biological systems and carbohydrate mixtures or dilute solutions is of particular interest, because of the ease of analysis of data by use of such techniques as absorption subtraction or factor analysis. This is possible owing to the direct interfacing of the computer to the spectrometer, which allows arithmetic manipulation of the spectra in an imaginative way, as will be seen in the following Section. 

Schieberle, P. and Hofmann, T. 1998. Characterization of key odorants in dry-heated cyste-ine/carbohydrate mixtures-comparison with aqueous reaction systems. In Flavor Analysis. (C.J. Mussinan and J. Morello, eds.) American Chemical Society, Washington, D.C. 

Mazzoni, V., Bradesi, P., Tomi, F., and Casanova, J. (1995). Direct qualitative and quantitative analysis of carbohydrate mixtures using 13C NMR spectroscopy Application to honeys. Magn. Res on. Chem. 35, S81-S90. 

Fig. 4.3. High performance liquid chromatography (HPLC) of the monosaccharides obtained from a partially purified preparation of microbubble glycopeptide surfactant from forest soil. Following hydrolysis (in 2 N HC1 for 6 hr at 100°C) and filtration, the carbohydrate mixture was charged on a Bio-Rad HPX-87 cation exchange column. For comparison, part A shows the chromatogram (using the same HPLC column) of a standard solution, which contained 4 pg of each of three different monosaccharides (i.e., the last three peaks shown are glucose, xylose and fiicose, in the order of increasing retention times). Part B shows the chromatogram obtained from hydrolysis of the partially purified (see text) microbubble surfactant (approximately 30 pg). All other experimental conditions were identical in the two cases, i.e., water eluent, 0.5 ml/min flow rate, 85°C, refractive index detector attenuation -2x. (Taken from ref. 322.)...

To obtain a comprehensive analysis of carbohydrate mixtures from biological matrices that display a high degree of compositional and structural heterogeneity, a multidimensional approach is required. The combination into a so-called hyphenated system, of liquid chromatography (LC) or CE with MS provides the advantage of selective and efficient separation with the mass specificity, sensitivity, and structural information gained from MS. 

Despite the number of sheathless CE-ESI interfaces described, few have been used for the analysis of complex carbohydrate mixtures. Zamfir et al. described a sheathless on-line CE/ESI-MS interface consisting of a CE capillary with the terminus shaped into a copper-coated microsprayer.134,135 This was described as... 

Table 21.7 Energy Yields Obtained from Different Fat and Carbohydrate Mixtures...

Chromatographic Analysis of Carbohydrate Mixtures. Much effort has been devoted in recent years to devising methods for analyzing carbohydrate mixtures quantitatively and qualitatively in a single process (as is done for amino acid analysis). Four methods that offer most promise of this goal are described here. 

Microanalysis of Carbohydrate Mixtures by Isotopic, Enzymatic, and Colorimetric Methods... 

Obtain a numbered 1.5-ml microcentrifuge tube containing 1 ml of your unknown carbohydrate mixture. Record the number of your unknown solution in your notebook. This solution will be used on Day 1 and Day 2. 

From the known, differential complexing between boronic acids and polyhydroxy compounds, it follows that carbohydrate mixtures may be separated by column-chromatographic methods that exploit the differences. Nucleoside and nucleotide boronates have been separated on columns of anion-exchange resins,90 and sugars and alditols have been shown to be differentially retained on such resins in the sulfonated phenylboronic acid form,64 but perhaps the best uses of column chromatography in this connection have incorporated the resolving powers of insoluble polymers to which boronic acid groups have been covalently bonded. Such insoluble forms of boronates have been synthesized either by substitution of polysaccharide derivatives, or by polymerization of suitable arylboronic acids. 

Millqvist-Fureby A, Malmsien M, Bergenstahl B. Surface characterization of freeze-dried protein/carbohydrate mixtures. Int J Riarm 1999 191 103-14. 

The SMB technology was developed by UOP and its major field of application is in the area of binary separations. For example, SMB has been used in the chemical industry for several separations known as SORBEX processes [1-3], which include, among others, the PAREX process for p-xylene separation from a Cs aromatic fraction [4], the OLEX process for the separation of olefins from paraffins, the SAREX process to separate fructose from glucose [4] and the MOLEX process [5]. Simulated moving bed is being used particularly for separation of enantiomers from racemic mixtures or from the products of enantioselective synthesis [6,7]. It has been used for the production of fine chemicals, and petrochemical intermediates, such as Cg-hydrocarbons [8], food chemistry such as fatty acids [2], or certain sugars from carbohydrate mixtures [8] and protein desalination [9]. 

We present here coarse grain simulation results of two simple binary water-carbohydrate mixtures that shed light on the mechanism of water diffusion in the supercooled and glassy state, the coupling of water mobility in the glass to the sub-Tg dynamics of the matrix, and the effect of the internal modes of the saccharide on the decoupling of water motion from carbohydrate translation. 

Figure 60.2(a-d) shows the sorption isotherms for isomalt, maltitol syrup, and for the carbohydrate mixtures. The water content of isomalt increased with increasing arid water adsorption decreased with increasing temperature at the same... 

The maltitol syrup and carbohydrate mixtures sorption isotherms cross at the two different temperatures in the region between 0.3 and 0.4. Above this region, the water content was smaller at 308 K than at 298 K. A crossing of isotherms at two different temperatures was also observed by A3Tranci et al. (1990) in dried apricot, fig, and raisin. Analysis of variance showed that except for isomalt, the equilibrium water contents of the different products did not differ (p > 0.05) for each product at different temperatures. 

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