Chromatographic response parameters

Equation 4.32 expresses the difference between the retention parameters Ai p of two solutes as a chromatographic response function ... 

NIR methods can be validated by the conventional protocols described in ICH and other regulatory guidelines as they are currently written however, some modifications have to be made to account for differences between spectrophotometric and chromatographic experimental parameters. For example, spiked recovery experiments are not relevant because NIR responses are sensitive to the production process. The criteria suggested for validating a NIR transmission method include ... 

It has also proven advantageous to use a combination of individual responses in order to optimize as many parameters as possible (39-43). The two performance goals for a separation of bisphenols by MEKC were good resolution among five peaks and short total analysis time (42). Thus, a chromatographic response function (CRF) was employed that was a product of two types of desirability functions, as used by Divjak et al. (30-33, 44). Resolution (R) between two adjacent peaks in an electropherogram was calculated using... 

The most important parameters related to chromatographic response (retention time, peak width, resolution), well known by GC users, are also fundamental in the characterization of GCxGC peaks. However, some of them take in GCxGC a new meaning for instance, resolution or peak capacity must be considered in a different way. Other characteristics, such as orthogonality or structured chromatograms, are specific of GCxGC. 

Since both GCxGC and GC are based in the same chromatographic processes, GCxGC will benefit from previous work on basic aspects of GC, but also more GC research will be required as a basis for the optimisation of GCxGC-based methods. Comparison of different strategies for optimisation and generalization of their results will require consideration of (1) the possible effect of the modulation process in the response parameters, which is disregarded in most approaches but appears to be of the utmost importance in others, and (2) the dependence of results in the particular composition of the test sample used for optimisation. 

The parameters 5, 5f and 5 are the parameters characterising the contribution of axial dispersion, film resistance and pore diffusion resistance towards the spread of the chromatographic response. They are given by ... 

Method of Moments The first step in the analysis of chromatographic systems is often a characterization of the column response to sm l pulse injections of a solute under trace conditions in the Henry s law limit. For such conditions, the statistical moments of the response peak are used to characterize the chromatographic behavior. Such an approach is generally preferable to other descriptions of peak properties which are specific to Gaussian behavior, since the statisfical moments are directly correlated to eqmlibrium and dispersion parameters. Useful references are Schneider and Smith [AJChP J., 14, 762 (1968)], Suzuki and Smith [Chem. Eng. ScL, 26, 221 (1971)], and Carbonell et al. [Chem. Eng. Sci., 9, 115 (1975) 16, 221 (1978)]. 

Electrolysis of mobile phase constituents will cause a continuous detector response (background current) resulting in a chromatographic baseline level that differs from the electrical detector zero-response level. The difference, baseline- offset, is an important analysis parameter, because baseline fluctuations (noise, drift) due to fluctuations in electrolysis conditions (potential, mobile phase flow rate, temperature) are proportional to baseline offset. See Figure 2-5 for an example of the influence of flow pulsation at different baseline offset... 

Reliable flame photometric detector quantification of organosulphur compounds requires careful optimization of the gas chromatograph parameters. Although the relative response of the flame photometric detector to various sulphur compounds remains somewhat controversial [7], analysis of organosulphur compounds by flame photometric detector is now relatively straightforward. 

The same chromatographic parameters were used in determining the molar response of the individual PCB isomers except, that the area responses were determined with a flame ionization detector. The flow rates of the hydrogen and air combustion gases were 30 and 300 mL/min, respectively. Response factors needed to... 

Although the mechanism of SEC separation is controlled by linear molecular size as well as other parameters, the separation pattern is very reproducible. Considering all the molecular parameters responsible for the size exclusion chromatographic separation pattern and the known separation patterns of a number of compounds, it is possible to predict the retention volume of a compound of known strucure. Based on the same principle the retention volume gives information on the structure of the molecule. 

The possibi Lity of mixed solution and adsorption phenomena contributing to chromatographic retention must be considered. Several factors are responsible for retention in GC, including bulk liquid partition, liquid interfacial adsorption, and solid support adsorption. One or all of these factors may play a major role depending upon the experimental parameters chosen (e.g., temperature, percent liquid phase, nature of "inert" support, solute. 

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