Separation and chromatographic

Manufacture. HFS containing 42% fmctose is produced commercially by column isomerization of clarified and refined dextrose hydrolyzate using an immobilized glucose isomerase. Enriched symp containing 90% fmctose is prepared by chromatographic separation and blended with 42% HES... 

Elution development is by far the most common method of processing a chromatographic separation and is used in all types of chromatography. Elution development is best described as a series of absorption-extraction processes which are continuous from the time the sample is injected into the distribution system until the time the solutes exit from it. The elution process is depicted in Figure 1. 

More sensitive detection methods and more objective recording methods (e g the employment of scanners) are constantly been striven for m order to overcome this illusion It IS for this reason too that fluorescent methods have been introduced to an increasing extent on account of their higher detection sensitivity This allows an appreciable reduction in the amount of sample applied, so that possible interfering substances are also present m smaller quantibes This increases the quality of the chromatographic separation and the subsequent m situ analysis... 

Electrolysis with a mercury cathode or with controlled cathode potential. (g) Application of physical methods utilising selective absorption, chromatographic separations, and ion exchange separations. 

Aldol reaction of the a-trimethylsilylated enolate 9 with aldehydes provides nearly equal amounts of chromatographically separable ( )- and (Z)-isomers of iron-acyl complexes 11 via silyloxide elimination from the intermedate aldolate 10 (Table 3). This methodology has been the most commonly employed entry to the (Z)-isomer series. 

For off-bead analysis, coupling between chromatographic separation and mass spectrometric detection has proven especially powerful. The combination between high performance liquid chromatography (HPLC) and electrospray ionisation mass spectrometry has the advantage that purity of product mixtures can be coupled on-line with the product identification. 

The submitters mixed active anhydrous silica gel with water (12% v>/w) and stored it in a sealed container for at least 24 hours prior to use. A ratio of 60-80 g. of silica gel per gram of crude product was used for column chromatographic separations, and a column was chosen that would give a 10 1 height diameter ratio of adsorbent. Columns were wet-packed with distilled petroleum ether (b.p. 60-68c), and after the crude product had been applied a step-gradient was run rapidly through 2% vjv ether in petroleum ether, 5% ether, and 10% ether. The column was then eluted with 20% vjv ether in petroleum ether until the bromohydrin acetate was obtained. 

Ito30 determined Tedion through the difference between absorption at 250 and 277 nm after thin-layer chromatographic separation and elution with methanol. 

Factors may be classified as quantitative when they take particular values, e.g. concentration or temperature, or qualitative when their presence or absence is of interest. As mentioned previously, for an LC-MS experiment the factors could include the composition of the mobile phase employed, its pH and flow rate [3], the nature and concentration of any mobile-phase additive, e.g. buffer or ion-pair reagent, the make-up of the solution in which the sample is injected [4], the ionization technique, spray voltage for electrospray, nebulizer temperature for APCI, nebulizing gas pressure, mass spectrometer source temperature, cone voltage in the mass spectrometer source, and the nature and pressure of gas in the collision cell if MS-MS is employed. For quantification, the assessment of results is likely to be on the basis of the selectivity and sensitivity of the analysis, i.e. the chromatographic separation and the maximum production of molecular species or product ions if MS-MS is employed. 

The effect of the buffer on the efficiency of electrospray ionization was mentioned earlier in Section 4.7.1. This is a good example of the dramatic effect that this may have - good chromatographic separation and ionization efficiency with formic, acetic and propionic acids, and good separation, although with complete suppression of ionization, with trifluoroacetic acid (TFA), the additive used for the protein application described previously. Post-column addition of propionic acid to the mobile phase containing TFA has been shown to reduce, or even... 

In contrast, in HPLC assays the chromatographic separation and the integration of the resulting analyte peak normally are just as or even more error-prone than is the preparation of the solutions here it would be acceptable to simply reinject the same sample solution in order to obtain a quasi-independent measurement. Two independent weighings and duplicate injection for each solution is a commonly applied rule. 

Designation, Chromatographic Separation, and Analysis. The abbreviation DBpD is used for dibenzo-p-dioxin, and the positions of chlorine... 

In contrast to the well-established methods for identifying and quantifying naturally occurring chlorophylls, very few reports concern quantitative analysis of chlorophyllin copper complexes in color additives and in foodstuffs. Analytical methods proposed are based on spectral properties, elemental analysis, chromatographic separation, and molecular structure elucidation or a combination of these procedures. 

Hyvarinen, K. and Hynninen, P.H., Liquid chromatographic separation and mass spectrometric identification of chlorophyll b allomers, J. Ghromatogr. A, 837, 107, 1999. 

Tpnnesen, H.H. and Karlsen, J., Studies on curcumin and curcuminoids Vll. Chromatographic separation and quantitative analysis of curcumin and related compounds, Z. filr Lebensm. und Forsch. A, 182, 215, 1986. 

Recently a new method was developed for the complete liquid chromatographic separation and diode array detection of standard mixtures of the 14 most frequently used synthetic colorants. Protocols for RP-HPLC - " and IP-HPLC techniques have been extensively described and the techniques were compared with micellar electrokinetic capillary chromatography, - which has been shown to be suitable for the analysis of synthetic colorants. 

The main uses of TLC include (1) qualitative analysis (the identification of the presence or absence of a particular substance in the mixture), (2) quantitative analysis (precise and accurate determination of a particular substance in a sample mixture), and (3) preparative analysis (purification and isolation of a particular substance for subsequent use). All these analytical and preparative applications of TLC require the common procedures of sample apphcation, chromatographic separation, and... 

Chromatographic Separation and Extraction with Foamed Plastics and Rubbers, G. J. Moody and J. D. R. Thomas... 

Validation of the complete analytical procedure (induding solvent extraction, cleanup of the extracts, isolation of the analytes of interest, and chromatographic separation and detection) requires the use of CRMs with matrices similar to those... 

The most significant differences (i.e. independence) in the analytical methods are provided in the final chromatographic separation and detection step using GC/ MS and LC-FL. GC and reversed-phase LG provide significantly different separation mechanisms for PAHs and thus provide the independence required in the separation. The use of mass spectrometry (MS) for the GC detection and fluorescence spectroscopy for the LG detection provide further independence in the methods, e.g. MS can not differentiate among PAH isomers whereas fluorescence spectroscopy often can. For the GC/MS analyses the 5% phenyl methylpolysiloxane phase has been a commonly used phase for the separation of PAHs however, several important PAH isomers are not completely resolved on this phase, i.e. chrysene and triphenylene, benzo[b]fluoranthene and benzofjjfluoranthene, and diben-z[o,h]anthracene and dibenz[a,c]anthracene. To achieve separation of these isomers, GC/MS analyses were also performed using two other phases with different selectivity, a 50% phenyl methylpolysiloxane phase and a smectic liquid crystalline phase. 

Chabaux F, Ben Othman D, Birck J-L (1994) A new Ra-Ba chromatographic separation and its application to Ra mass-spectrometric measurements in volcanic rocks. ChemGeol 114 191-197 Cheng H, Edwards RL, Hoff J, Gallup CD, Richards DA, Asmerom Y (2000) The half hves of uranium-234 and thorium-230. ChemGeol 169 17-33... 

Chabaux F, Ben Othman D, Birck JL (1994) A new Ra-Ba chromatographic separation and its application to Ra mass-spectrometric measurement involcanics rocks. Chem Geol 114 191-197... 

Goudie, A. J., and Rieman, III, W., Chromatographic separation and determination of fruit acids, Anal. Chim. Acta, 26, 419, 1962. 

Chromatographic Separations and Implications. Fractionation of hydrilla-inhibiting extracts has perhaps produced the most interesting results concerning the basis for hydrilla inhibition. Two fractions were generated, and best results were obtained with an older, preparative-scale Zorbax column. The effect of both fractions on hydrilla was tested using Warburg apparatus the first fraction did not affect either plant respiration or photosynthesis. The... 

Hu S, Li PCH (2000) Micellar electrokinetic capillary chromatographic separation and fluorescent detection of amino acids derivatized with 4-fluoro-7-nitro-2,l,3-benzoxadiazole. J Chromatogr A 876 183-191... 

In the last decade modifications to the pyrolysis process have been developed to improve analytical efficiency and increase detectability. In the same way as in conventional GC, derivatization reagents may be used to improve the chromatographic separation and response of polar compounds. In order to reduce the time required for the analysis, the risk of contamination and of losing part of the sample, on-line derivatization methods should be preferred and those based on quaternary ammonium hydroxides are certainly the most widely used. 

Herrera MC and Luque de Castro MD. 2005. Ultrasound-assisted extraction of phenolic compounds from strawberries prior to liquid chromatographic separation and photodiode array ultraviolet detection. J Chromatogr A 1100(1) 1 —7. 

A reduced peak capacity in one domain may be counterbalanced by an increased peak capacity in another domain. If we know the average peak width of a chromatographic separation and the gradient duration, we can calculate the maximum number of peaks that can be separated. (Note peak capacity does not mean that this number of compounds in a sample will be separated they may still co-elute). That means we can operate between two limits (1) a peak capacity of zero representing a flow injection analysis and (2) a minimal required peak capacity that defines the peak capacity to separate all compounds in a given mixture. Unfortunately, especially in the early stages of drug... 

In our laboratories, a cycle time of 90 sec can be achieved with a dilution factor of 1 25 for a given sample concentration, allowing the purity and identity control of two and a half 384-well microtiter plates per day. The online dilution eliminated an external step in the workflow and reduced the risks of decomposition of samples in the solvent mixture (weakly acidic aqueous solvent) required for analysis. Mao et al.23 described an example in which parallel sample preparation reduced steps in the workflow. They described a 2-min cycle time for the analysis of nefazodone and its metabolites for pharmacokinetic studies. The cycle time included complete solid phase extraction of neat samples, chromatographic separation, and LC/MS/MS analysis. The method was fully validated and proved rugged for high-throughput analysis of more than 5000 human plasma samples. Many papers published about this topic describe different methods of sample preparation. Hyotylainen24 has written a recent review. 

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