Elution, chromatography conditions

Elution Chromatography The components of the mobile phase supphed to the cohimn ter feed introduction have less affinity for the stationary phase than any of the feed solutes. Under trace conditions, the feed solutes travel through the cohimn as bands or zones at different velocities that depend only on the composition of the mobile phase and the operating temperature and that exit from the cohimn at different times. 

TABLE 16-14 Expressions for Predictions of Chromatographic Peak Properties in Linear Gradient Elution Chromatography under Trace Conditions with a Small Feed Injection and Inlet Gradient Described by op = opo + pt (Adapted from Refs. A and B). 

In the laboratory conducted portion of the organic analysis, a seven step liquid elution chromatography separation on silica gel forms the central part of the scheme. It is an analytical step (in that behavior of a given class of compounds is predictable) as well as a separation step (since the fractions may be further analyzed much more readily than the original mixture). The behavior of selected classes of compounds with respect to the chromatographic conditions employed is shown in Figure 4. 

Purified zones of analytes can be obtained under favorable conditions in a far more efficient way than can be attained using overloaded elution chromatography. 

Currently, the best way of preserving the native conformation under the conditions of elution chromatography is hydrophobic interaction chromatography with minimized adsorption forces. These can be adjusted by selecting the appropriate stationary phase, e.g., from a series of alkylated agarose gels with various alkyl chain lengths. 

Cyclohexene is oxidized very slowly in the presence of TS-1 little if any epoxide could be obtained under conditions of rapid oxidation of 1- and 2-alkenes to the corresponding epoxides. This low reactivity has been ascribed to the molecular dimensions of cyclohexene, which cannot enter the channel system of TS-1. Evidence for this suggestion was obtained by elution chromatography when TS-1 was loaded in a chromatographic column and a mixture of cyclohexene and 2-hexene injected, the retention time for cyclohexene was much less than that of linear 2-hexenes, despite the higher boiling point of cyclohexene (Tatsumi et al., 1990a). 

Elution chromatography may be subclassified according to the continuity of the mobile phase. Isocratic elution is the term used when the sample is introduced onto the column and eluted from it under the same set of mobile phase conditions. Isocratic elution is the most common way... 

Figure 2.18 Wheat germ lectin isolation using A -acetyl-o-glucosamine as the ligand. Chromatography conditions column, Waters API glass column, 100 x 10 mm I.D. flow rate, 1 ml/min detection, UV absorbance at 280 nm. The sample was 1 ml of crude wheat germ preparation 1.2 mg/ml of lectin was eluted from a crude preparation with 6.8 mg/ml total protein. (Reprinted from Ref. 64 with permission.)...

Cation exchange elution chromatography has been used as our separation method for Am and Cm. The separation conditions have been studied in detail. They involved the dependence of elution solution pH, temperature of the column and resin cross-linking on resolution. When cross-linking of the resin equals 4 per cent and column temperature equals 50° to 75°C, resolution is optimized. 

This model assumes the absence of any disturbance of the acetonitrile adsorption equilibrium by the analyte. This assumption limits the application of this model toward very low analyte concentrations—typical conditions for linear elution chromatography. 

To analyze potential interference of amino acids in monosaccharide analysis, each of the 20 amino acids (10 /xg each, each injected separately) was subjected to the chromatography conditions used for separating, detecting, and quantifying monosaccharides. In addition to PAD detection, we monitored UV detection at 215 nm after the electrochemical detector to verify amino acid electrochemical detection. Ten amino acids (R, K, Q, V, N, A, I, L, T and C) eluted between 2 and 25 min and were both PAD and UV active. Of these ten, two amino acids could potentially interfere with monosaccharide analysis. Glutamine was found to elute as a shoulder on mannose. However, acid hydrolysis conditions used to release monosaccharides from glycoproteins likely would oxidize glutamine. 

EFFECTS ON CHROMATOGRAPHIC SEPARATION INDUCED BY CHANGING OPERATION CONDITIONS AND (OR) OE GRADIENT PARAMETERS IN GRADIENT-ELUTION CHROMATOGRAPHY BY A FACTOR / AT CONSTANT OTHER OPERATION CONDITIONS... 

Solid phase extraction. With the availability of pre-prepared cartridges of silica-based adsorbents, the use of solid phase extraction has increased in the last few years although the technique has been in use for many years for the isolation of many biochemicals, e.g. amino acids, catecholamines. In essence it is a version of chromatography conditions for the selective adsorption of the analytes (column, solvent, pH, etc.) are chosen, the sample is applied to a column, washed and the analytes selectively eluted with appropriate solvents. Since the columns are disposable there is no need to worry about protein contamination or infection. The adsorbents available cover an even wider range than HPLC materials since they are not required to withstand high back pressures. It is possible... 

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