Column chromatography experimental procedures

The experimental procedure Is approximately standard chromatography. First, we set the desired column temperature and adjust the detector and injector temperatures to values about 30°C higher. Next we adjust the inlet and outlet pressure and measure the flow rate. Then, we set the detector current and attenuation to give maximum sensitivity with an acceptable baseline (typically the current is 50 mA with an attenuation of 1). For injections, we draw 1/2 the desired air into the syringe followed by the sample followed by the remaining 1/2 of the desired air. We establish the desired amount of air by trial and error to obtain a proper peak size. 

Typical Experimental Procedure (Scale Up). Stoichiometric amounts (6.2 mL) of 0.1 M methanolic solutions of the three supporting Ugi components and ethyl glyoxalate (7.75 ml) were combined and stirred at reflux overnight. The solvent was evaporated in vacuo and crude Ugi product dried under high vacuum. A 10% solution of AcCl in MeOH (25 mL) or a 10% solution of TFA (trifluoroacetic acid) in dichloroethane (25 mL) was added to the crude material and stirred at room temperature overnight. The solvent was evaporated in vacuo. The crude material was preadsorbed onto flash silica and purified by flash column chromatography (EtOAc hexane, 1 4) to yield the desired product 57 (192 mg, 71%) as a white solid. 

A few years later, by using the same experimental procedures, the same scientists prepared cyclic polybutadienes170 (Scheme 82). THF was the polymerization solvent, which results in a 60% 1,2-content. From the g values was concluded that some of the cyclic polybutadienes (PBd) were contamined by their linear precursors. A high-resolution column set was used in order to separate the linear from the cyclic polymer. In this work the characterization analysis was the most comprehensive presented so far. Recently, these cyclic PSs were analyzed by high-pressure liquid chromatography under critical conditions, which is a method that can separate linear and cyclic macromolecules according to their archi-... 

Concentration pulse chromatography (also called elution on a plateau, step and pulse method, system peak method, or perturbation chromatography) is experimentally much simpler [100,103,104]. The same experimental procedure is used as for the determination of smgle-component isotherms. First, the column is equilibrated with a solution of the multicomponent mixture of interest in the mobile phase. When the eluent has reached the composition of the feed to the column, a small pulse of the pure mobile phase (vacancy) or of a solution having a composition different from that of the plateau concentration (see end of this section) is... 

The steady-state partial oxidation reaction experiments were carried out in a quartz fixed-bed, flow reactor with 10 mm I.D. and a length of 50 mm. The analytical system consisted of two parts. Gas Chromatography (GC) and High Performance Liquid Chromatography (HPLC). GC was used to analyze on-line the reaction products that were in the gas phase. The GC (HP-5890) was equipped with a Chromosorb PAW 23% SP-1700 column (30 ft. 1/8") for FID, a Hayesep D column (15 ft. 1/8") and a Molecular Sieve 5A column (10 ft. 1/8") connected serially to TCD. Reverse-phase HPLC with a Spherisorb 5 ODS-2 (1 ft. 1/4") column was used off-line to analyze the products that were solid or liquid at room temperature. The details of the experimental procedures have been described elsewhere [12,13]. 

The earlier discussion in the present chapter has detailed the theory that relates performance of an LC column to its various parameters. An appropriate conclusion to the theoretical discussions given above can be made in the form of the following summary of the essential improvements in equipment, materials and experimental procedures of liquid chromatography effected as a consequence of this better understanding, in recent times, of the underlying theory of chromatography. 

The latter procedure has so far been applied successfully (/) to a large number of silicas suitable for column chromatography (60-200 mesh). Attempts to extend these techniques to thin-layer silicas have not been successful. In the case of silicas with calcium sulfate binder, experimental values of 5,. and St appear quite variable and do not agree with values that can be inferred from surface area, pore diameter, and chromatographic activity data. This suggests that calcium sulfate in some way interferes with the silica-silane reaction. For thin-layer silicas without binder, erroneously low values of S jSf are obtained. This is believed to be due to... 

Typical Experimental Procedure To freshly prepared LiNH2 (prepared in situ by dissolving 12mg atoms of lithium metal) in hquid NH3 (30mL) at -33°C was added a solution of chloride (1) (2 mmol) in THF (2mL) for 3 minutes, after which solid NH4CI was added and ammonia was evaporated. The residue was partitioned between water and ether and the ether layer was dried and concentrated to obtain the residue, which was purified by silica-gel column chromatography to get pure 2 in 90% yield. 

The theoretical basis for the chromatographic analysis of adsorption phenomena in gas and/or liquid phase was given by Don DeVault (ref. 1) and Glueckauf (ref. 2, 3). The mathematical procedure developed by these authors enables one to determine the adsorption isotherm of a solute from its elution profiles in column chromatography. The experimental procedure required for this method is far less laborious than those for the conventional static methods of adsorption measurement, and many experimental works have appeared since (ref. 4, 5). Many of these works, however, dealt with adsorption from gaseous phases, and applications to liquid phases are scarce (ref. 6, 7). 

Experimental procedure In a dried glass tube, Pd(OAc)2 (4.5mg, 0.02 mmol, 5 mol %), bathocuproine (10.8 mg, 0.03 mmol, 7.5 mol %), NFSI (315.0 mg, 1.0 mmol, 2.5 equiv) were dissolved in 1,4-dioxane (1.0 ml), and then the respective styrene (0.4 mmol, 1.0 equiv) was added. After the reaction mixture was stirred at 40-50°C for lOh, the solvent was removed under reduced pressure. The crade product was purified by column chromatography on silica gel with a gradient eluant of petroleum ether and ethyl acetate to afford the aminofluorination product... 

One of the key experimental procedures is the systematic removal of rRNA from the mRNA fraction. Typically, mRNA has a long poly A tail that can be captured on a poly T chromatography column or batch resin. The rRNA and tRNAs pass through the column and, after a suitable washing protocol, the mRNA fraction is concentrated and stored for subsequent experimentation. The effectiveness of the purification of a typical mRNA purification scheme was followed by RNA chromatography by Hornby and coworkers [34]. ft was found that at least two rounds of enrichment are usually required in order to remove the bulk of the nonpoly A RNA. 

Design and execute an experimental procedure for separating benzyl alcohol (7) from methyl benzoate (8) by normal-phase column chromatography. 

Mixtures of basic dyes may be separated by column chromatography on polyamide powder, usiug water or ethanol-water (80 + 20) or (60 + 30) as solvents [71]. Separations are possible by PC on impregnated paper [6, 18] or acetyl-paper [70]. TLC separations are advantageously shorter than these PC procedures. Many authors have worked on the TLC of basic dyes. Experimental conditions for separations are summarised in the following Table 128. 

This product may again be analyzed by gas chromatography. Follow the procedure and experimental conditions outlined above.The 1-octene impurity should have been removed during the column chromatography step. The small percentage of 2-octanol byproduct, however, more than likely will still be detected. The actual percent composition of the mixture can be calculated by determination of the areas under the chromatographic peaks (see Technique 1). 

The various experimental procedures that have been developed for its determination in different biological materials could be conveniently divided into bloassay or biological methods, chemical methods, radioactive tracer determinations, enzymatic techniques, paper, column, thin layer, gas chromatography, high performance liquid chromatography (HPLC) and automated methods (ref. Table 2.4 for references to these techniques and their grouping). The methods for determination of ascorhigen have also been listed separately in Table 2.4. A. 

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