Separation and chromatographic analysis

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

Egorov, O. B., O Hara, M. J., Farmer, O. T., Ill, and Grate, J. W., Extraction chromatographic separations and analysis of actinides using sequential injection techniques with on-line inductively coupled plasma mass spectrometry (ICP MS) detection, Analyst, 126, 1594-1601, 2001. 

The light and medium dark lithotypes are widely separated in their oxidation product yields (Table 1). Chromatographic separation and analysis of their Neutrals, Acids 1 and Acids 2 fractions generally resulted in the widest variation in structural type and yield for the lithotype series. The results of these analyses are depicted in Tables 2 and 3 along with Figure 6A, B and C. 

Isherwood, F. A., and Cruickshank, D. H., Chromatographic separation and analysis of mixture of pyruvic, oxalacetic and a-ketoglutaric acids. Nature 173, 121 (1954). 

Among these methods, liquid chromatographic separation and analysis have become the major chromatographic method for HS. While among the liquid chromatographic methods, those based on... 

Romanik, G., Gilgenast, E., Przyjazny, A. and Kaminski, M. (2007) Techniques of preparing plant material for chromatographic separation and analysis. Journal of Biochemical and Biophysical Methods, 70(2), 253-261. 

Van de Casteele K, De Footer H, Van Sumere CF (1976) Gas chromatographic separation and analysis of trimethylsilyl dervatives of some naturally occurring nonvolative phenolic compounds and related substances. J Chromatogr 121 49-63... 

This section is concerned with the isolation of organic acids as a group prior to further chromatographic separation and determination, primarily gas chromatographic. Separation and analysis by liquid-column chromatography are described in Section 4.2. 

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... 

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. 

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. 

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. 

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... 

Table 6 summarizes the conditions of the other high performance liquid chromatographic methods, which are reported in the literature for the separation and analysis of miconazole in bulk, pharmaceutical formulation, and biological fluids [60, 83-91]. 

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. 

Elaboration of the method for the identification of colour compounds by RPLC MS should comprise four steps (1) spectral characterization of reference materials (standards) and subsequent optimization of detection parameters, as well as those of their chromatographic separation (2) analysis of natural dyestuffs used as colouring materials in historical objects (3) analysis of model samples (dyed fibres, paintings) prepared according to old recipes (4) application of the acquired knowledge to identification of colourants present in historical objects. 

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. 

An additional consideration for sample preparation is to ensure that the final sample solution is miscible with the HPLC eluent and will not alter or degrade the column.62 The total time needed for sample preparation may be longer than that required to conduct chromatographic separation and therefore becomes is the rate-determining step for the analysis.63 A survey cited by several authors indicated that on average chromatography separation accounts for about 15% of the total analysis time, sample preparation, about 60%, and data analysis and reporting, 25%.64 66... 

Other combinations are available. For example, liquid chromatographs connected to mass spectrometers (known as liquid chromatography-mass spectrometry [LC-MS]) are fairly common. Almost any combination of two instruments that can be thought of has been built. In addition, two of the same instruments can be connected so that the output from one is fed directly into the other for further separation and analysis. Examples include two mass spectrometers in an MS-MS arrangement and two different gas chromatography columns connected in a series, known as GC-GC. To keep up with these advances, one needs to have a working knowledge of the fundamental principles involved in the techniques and of the abbreviations used for the various instrumentation methods. 

Thus, more sophisticated methods including preconcentration, chromatographic separation and sensitive and accurate detection are required for the compound-specific analysis of the broad range of surfactants. The request for more specific methods is further increased when the investigations not only centre on the parent compound, but also aim at the qualitative and quantitative determination of degradation intermediates, often formed at low concentrations, during the wastewater treatment process. 

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