Preparatory Separation

Trace analysis is particularly attractive for SFE-HPLC since quantitative transfer of all analytes extracted to the chromatographic system becomes possible. At present, on-line SFE-HPLC appears to be feasible for qualitative analysis only quantitation is difficult due to possible pump and detector precision problems. Sample size restrictions also appear to be another significant barrier to using on-line SFE-HPLC for quantitative analysis of real samples. On-line SFE-HPLC has therefore not proven to be a very popular hyphenated sample preparatory/separation technique. Although online SFE-HPLC has not been quantitatively feasible, SFE is quite useful for quantitative determination of those analytes that must be analysed by off-line HPLC, and should not be ruled out when considering sample preparatory techniques. In most cases, all of the disadvantages mentioned with the on-line technique (Table 7.15) are eliminated. On- and off-line SFE-HPLC were reviewed [24,128]. 

Rose (41) reported an apparatus based on zone convection electro-focusing. Its purpose was preparatory separation or treatment prior to column electrofocusing. 

BioMEMS Microfluidics Nanofluidics Preparatory separation Sample pre-fractionation... 

Sample pre-fractionation Preparatory separation Microfluidic devices Microsystems... 

Preparatory separation should be able to process large sample volume. While small sample consumption is beneficial for some applications (such as single-cell analysis), most proteomic samples (blood, for example) are available in the volume larger than 1 xL. Most microfluidic separation systems are based on miniaturized capillary electrophoresis, which is essentially an analytic (not preparatory) technique. Therefore, the overall sample throughput and the detection sensitivity in such separation are limited. 

Any preparatory separation device should be designed with the downstream sensing in mind. Many capillary electrophoresis separations utilize polymeric siev-... 

One distinguishes preparatory distillations that are designed to separate the fractions for subsequent analysis from non-preparatory analytical distillations that are performed to characterize the feed itself. For example, the distillation curve that gives the recovered volume or weight as a function of the distillation temperature characterizes the volatility of the sample. 

Ferric ion was immobilized on a Chelating Sepharose Fast Flow column preparatory to the separation of seven enkephalin-related phosphopep-tides.17 Non-phosphorylated peptides flowed through the column, and the bound fraction contained the product. The capacity of the column was found to be 23 pmol/mL by frontal elution analysis. Cupric ion was immobilized on Chelating Superose for the isolation of bovine serum albumin.18 Cupric ion was immobilized on a Pharmacia HiTrap column for the separation of Protein C from prothrombin, a separation that was used to model the subsequent apparently successful separation of Factor IX from prothrombin Factor IX activity of the eluate was, however, not checked.19 Imidazole was used as the displacement agent to recover p-galactosidase from unclarified homogenates injected onto a nickel-loaded IMAC column.20 Pretreatment with nucleases and cleaning in place between injections were required procedures. A sixfold purification factor was observed. 

A natural extension of column chromatography is high-pressure liquid chromatography, which combines separation, detection, and quantitation (and isolation in the case of preparatory work). Perhaps the single... 

The author has found the following GLC procedure to be suitable to determine the purity of sodium valproate and valproic acid. Preparatory to chromatography, the sodium valproate was acidified with a strong aqueous hydrochloric acid solution, and the valproic acid which is practically insoluble in water was separated. The separated free acid was then analyzed. 

If interference is a major problem the sample must be partially purified before analysis. This breaks the analysis into preparatory and quantitative stages. In order to reduce the technical difficulties resulting from such two-stage methods much work has gone into the development of analytical techniques such as gas and liquid chromatography in which separation and quantitation are effected sequentially. 

On the other hand, nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful tools for the structure elucidation of organic compounds. However, to solve the molecnlar strnctnre of a novel substance by NMR spectroscopy alone is often time-consnming (when compared to MS). Besides, the identification of components in a complex mixture usually requires the separation and/or isolation of the components of interest prior to NMR analysis. Therefore mnltiple preparatory chromatographic... 

Reaction of N-Acetv1-4-ani1nobutvra1dehvde Diethvi Acetal. 3. with 2.4-Pentand1o1. One g of 1 and 0.51 g of 2,4-pentandlol (eplmerlc mix) were heated In 1 g of HoO with p-toluenesulfonic acid (10 mg at 50 C for 1 h, then an additional 10 mg and heat at 70 C for 2.5 h). An aliquot was neutralized with KOH/EtOH, extracted with H2O and CH2CI2 (2X each), back extracted with brine and concentrated. 6LPC analysis showed two major product peaks (8.34 and 8.71 min). These were separated by preparatory SLPC to give the eplmerlc cyclic 2,4-pentandlol acetals 11 NHR (CDCI3) 6 5.83 (br S, 0.9, NH), 4.53 (t, 1,... 

In connection with the aforementioned study on polymerization mechanism of MMA77,78), Miyamoto et al. developed a preparatory method of separating blends of isotactic and syndiotactic PMMA82 The principle was based on a competitive adsorption of these different stereoisomeric polymers from a nonpolar solution (chloroform) onto an adsorbent surface (silica gel). The procedure was quite simple, as described below A given polymer blend was dissolved in chloroform, in which no stereocomplex formation usually occurs, and silica gel was then dispersed in this solution for adsorptive equilibration with the polymer species. The isotactic species could be isolated as the adsorbed component. In practice, its purity was ca. 80—90%, which depended on the added amount of silica gel. By repeating the same procedure, the purity could be enhanced. 

The dynamite ingredients are mixed with a solution of collodion cotton in nitroglycerine prepared separately or in a mixture of nitroglycerine with nitroglycol. The drying and milling of the ingredients are preparatory operations. 

Prior to use as authentic standards, the desired Cu2+ and Zn2+ pheophytins will have to be purified from other impurities stemming from the synthesis. This can be accomplished by simple preparatory or semipreparatory phase chromatography using the method described (see Alternate Protocol). If only a small amount of sample is required, collection of a few fractions from a separation using a standard analytical column may suffice. 

Gonzalez de Llano et al. (47) separated amino acids from low-molecular-weight peptides by means of size-exclusion chromatography on Sephadex G-10, with water as the solvent, as a preparatory step before RP-HPLC analysis of peptides from blue cheeses soluble in 5% PTA (Fig. 1). This technique has also been used (51a) to eliminate the amino acids from the ethanol-... 

After removal of such tar or gum, the concentrate is further evaporated at a temperature below about 50°C to about one-fourth the volume, i.e., 70 gallons is concentrated to about 15 to 20 gallons. This concentrate is cooled to a temperature of about 0°C to 5°C and allowed to stand for an extended period, such as overnight, whereupon there is a separation of crude crystalline glaucarubin therefrom. The crude crystals thus formed are removed by filtration and the mother liquors again concentrated to about one-half volume and cooled to permit separation of a second batch of crude glaucarubin crystals. The two batches of crude glaucarubin crystals are combined and dried preparatory to further purification. 

Roasting furnaces are in a class of reactors used by the metallurgical industry in a preparatory step for the conversion of ores to metals. There are three widely used roasted furnaces multiple hearth, fluidized bed, and flash roasters. In the multiple hearth configuration hot gases pass over beds of ore concentrate. The flash roaster injects pulverized ore with air into a hot combustion chamber. The fluidized bed roaster operates as described in a separate heading. 

A suspension of 2.10 g. of the freshly prepared diazonium salt and 50 ml. of ethanol is stirred in a 200-ml. Erlenmeyer flask and cooled to 0°C. while a solution of 4.7 g. of fcww-chloro-hydrido-bis(triethylphosphine) platinum (II) in 25 ml. of ethanol is added over a period of 10 minutes. The mixture becomes yellow immediately and is stirred at 0°C. for 10 minutes. At this point, yellow crystals of the aryldiimide complex usually separate. The mixture is filtered, and the filtrate is cooled to —78°C. to give a second crop of the diimide complex. Occasionally crystallization does not occur immediately. In this situation, the mixture is cooled to — 78°C. directly, and the crystals which form are filtered and washed with ether. In either case the total yield is about 4.9-5.4 g. (72-78%). (The checkers reported an 87% yield with a melting point of 105-108°C. with decomposition.) The purity of this material is adequate for most preparatory purposes. Further purification may be accomplished by conversion to the arylazoplatinum compound (Sec. D) followed by reprotonation with concentrated aqueous fluoroboric acid, HBF4. 

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