Solvent columns

In-column solvents Column size (mm) Theoretical plate number Exclusion limit Poiystyrene PEG Particle size (/urn) Pore size (A) Flow Rate (ml/min) Maximum pressure (kgf/cm ) Maximum temperature (°C)... 

FIGURE 13.57 NOTE The importance of Solvent/column interaction using Jordi DVB columns cannot be over emphasized. We have found that a SOySO mbc of MeOH/ACN for the strong solvent Is adequate for many reverse phase separations and is better than either alone. We have now observed that the use of THF/ACN as strong solvent is often better than MeOH/ACN. In general Lewis bases (electron donor solvents) deactivate the aromatic rings and often dramatically increase column efficiencies. 

Our most recent work with B megapotamica has been with the isolation of large quantities of baccharinoids from a 1800 Kg collection. The workup of the crude extract (ca. 30 Kg of black tarry material) of this plant material was conducted by Dr. Fred Boettner of Polyscience, Inc. This near Herculean task required tremendous quantities of solvents, column packings and time to complete. An outline of the fractionation scheme is presented in Figure 2. Fractions F6-F11 contain a large number of baccharinoids. To date, we have characterized over twenty macrocyclic trichothecenes found in B mega-... 

Cool on-column >250 pm column (i.d.) 1 ppm (FID) Reduced thermal degradation and discrimination Wide range of analyte concentrations High sample capacity (LVI) Autosamplers Direct quantification Excellent precision Control of operational conditions (initial oven temperature) Optimisation required Not applicable for polar solvents Column contamination by dirty matrices Poor long term stability... 

Traditionally, HPLC, GC-MS, or LC-MS methods were used to monitor the clearance of small-molecule impurities. These analytical techniques often require unique solvents, columns, methods, reagents, detectors, and buffers for each analyte to be quantified. The NMR method, albeit not the most sensitive technique, normally does not have these problems. In this chapter, some examples will be used to demonstrate that NMR is a fast, generic, and reliable analytical technique for solving analytical problems encountered in the development of biopharmaceutical products. The NMR techniques described here require minimal sample handling and use simple standard NMR methods. They can easily be implemented and used for process development and validation purposes. 

Fig. 17. FTD chromatograms of poly-(diethylene glycol adipate), M = 560, f = 1.63, obtained at critical conditions in different binary solvents. (Column Si-100, u = 1 ml/min, volume of the sample 10 pi, refractometer, l = 24 °C)...

The column should not be exposed to unnecessarily large volumes of solvent. Columns can be stored in a clean dry atmosphere, but they should be sealed by a flame or taped for very short periods of time. Some columns need to be stored in an atmosphere of nitrogen to avoid serious loss of selectivity. The manufacturer s instructions should be followed for column storage. 

The general procedure is as follows.64 The apparatus (Fig. 2.142) is set up for filtration using a porosity 3 cylindrical sinter. Table 2.14 gives guidelines for the choice of sinter size and amounts of silica, sample and solvent. Columns longer than 55 mm are neither practical nor necessary, since reduction in efficiency may be observed on large-scale set-ups. 

Reverse-Phase Chromatography—Separation mode on bonded phase columns in which the solvent/column polarities are the opposite of normal-phase separations. Polar compounds elute before nonpolar compounds, Nonpolar columns require polar solvents. 

Splitless injection involves keeping the injector split vent closed during the time the sample is deposited on the column, after which the vent is reopened and the inlet purged with carrier gas. In splitless injection, the inlet temperature is elevated with respect to the column temperature. The sample is focused at the head of the column with the aid of the solvent effect. The solvent effect is the vaporization of sample and solvent matrix in the injection port, followed by trapping of the analyte in the condensing solvent at the head of the column. This trapping of the analyte serves to refocus the sample bandwidth and is only achieved after proper selection of the solvent, column and injector temperatures. Splitless injection techniques have been reviewed in References 29 and 30. 

The naphthalene-rich bottoms from the solvent column then are fed to the naphthalene column where a naphthalene product (95% naphthalene) is produced. The naphthalene column is operated at near atmospheric pressure to avoid difficulties that are inherent to vacuum distillation of this... 

Organic Extraction GLC solvent column from water details Detector Comments LD Ref... 

Figure 3. Selectivity of modifier solvent (column 250 X 4.6 mm l.D. 10-pm Lichrosorb RP-8 other columns provide differing degrees of selectivity effects with...

Fig. 13. Results obtained with 4 mm samples in a 500 MHz gradient inverse triple resonance cryogenic NMR probe, (a) Non-spinning resolution of the -methanol multiplet for a 30 mm solvent column in a 4 mm tube, (b) Non-spinning resolution of the -methanol multiplet for a 22 mm solvent column in a 4 mm tube. As expected from Fig. 12, the resolution is lower with a solvent column of this short (the optimal solvent column for a 4 mm tube is 30 mm) is shown in Panel A. (c) Resolution of the -methanol multiplet for a 22 mm solvent column in a 4 mm tube with the sample spinning at 20 Hz. For very scarce samples when it is necessary to resort to the shortest possible solvent column height to facilitate the acquisition of high-quality 2D-NMR data, it may be beneficial to spin the sample during the acquisition of the proton reference spectra.

Classical separations by open column chromatography with different stationary phases (silica gel, reversed-phase C-18 or C-8, polyamide, cellulose) and elution with appropriate solvent mixtures are also useful for flavonoid fractionation and purification. Different column systems can be used. The classical open column chromatography uses relatively large particle sizes (0.2-6 mm), with limited resolution, and solvent filtration through the column proceeds by the pressure of the solvent column placed on top of the stationary phase. In other cases, smaller... 

The raw data in osmotic pressure experiments are pressures in terms of heights of solvent columns at various polymer concentrations. The pressure values are usually in centimeters of solvent (/ ) and the concentrations, c, may be in grams per cubic centimeter, per deciliter (100 cm ), or per liter, and so on. The most direct application of these numbers involves plotting hje) against c and extrapolating to (/r/c)o at zero concentration. The column height h is then converted to osmotic pressure n by... 

A typical two-solvent column chromatography setup is shown in Figure 1. Two solvents, A and B, can be withdrawn by a pump, with a valve to control... 

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