Retention-time coordinates

DLC. (b, d, and f) Reduced retention-time coordinates x and y. Equations of lines defining spatial boundaries are reported. 

With regard to comprehensive LC data elaboration, the acquired data is commonly elaborated with dedicated software that constructs a matrix with rows corresponding to the duration of the second-dimension analysis and data columns covering all successive second-dimension chromatograms. The result is a bidimensional contour plot, where each component is represented as an ellipse-shaped peak, defined by double-axis retention time coordinates. When creating a 3D chromatogram, a third axis by means of relative intensity is added. The colour and dimension of each peak is related to the quantity of each compound present in the sample. Figure 4.9 illustrates an example of data elaboration in comprehensive LC. 

Multiway and particularly three-way analysis of data has become an important subject in chemometrics. This is the result of the development of hyphenated detection methods (such as in combined chromatography-spectrometry) and yields three-way data structures the ways of which are defined by samples, retention times and wavelengths. In multivariate process analysis, three-way data are obtained from various batches, quality measures and times of observation [55]. In image analysis, the three modes are formed by the horizontal and vertical coordinates of the pixels within a frame and the successive frames that have been recorded. In this rapidly developing field one already finds an extensive body of literature and only a brief outline can be given here. For a more comprehensive reading and a discussion of practical applications we refer to the reviews by Geladi [56], Smilde [57] and Henrion [58]. 

It should be noted that the equivalent continuously operated process of the batch reactive membrane process is the membrane reactor depicted in Fig. 4.26(b). Here, the spatial coordinate z replaces the time coordinate of the batch process. Feasibility analysis has the task of estimating the retentate composition which is attainable at infinite reactor length. 

The analysis of the chemical composition of the sample was conducted by coupled SEC-FTIR using the LC Transform. After separating the sample with respect to molecular size, the fractions were deposited on the germanium disc and FTIR spectra were recorded continuously along the sample track. In total, a set of about 80 spectra was obtained which was presented in a three-dimensional plot (Fig. 29). The projection of the 3D plot on the retention time-IR frequency coordinate system yielded a two-dimensional representation, where the intensities of the absorption peaks were given by a color code. Such a contour plot readily provides information on the chemical composition of each chromato-... 

The diameter scale can be obtained from retention coordinates (i.e., the retention time axis) by applying to... 

In the TC processing the average molecular speed and the flow rate vary with z because of changing temperature. The retention time and the coordinate for any temperature profile of the column are related by the equations ... 

The interaction by ji coordination of Ag(I) between silver ions and C=C double bonds or aromatic groups is the basic principle for many effective chromatographic separations. Silver trifluoroacetate and silver trifluoromethanesulfonate are very soluble in poly(methylphenylsiloxane), due to the presence of phenyl groups. Such stationary phases were studied for the GC separation of benzene-cyclohexene-cyclohexane mixtures. The salting-out effects and formation constants of the complex of Ag(I) with various olefinic and aromatic compounds were estimated based on retention time measurements271. 

Chromatographic resolution is defined as the distance between the concentration maxima of two elution zones, expressed in the units of the mean standard deviation of these zones. When considering a chromatographic record plotted in coordinates with the detector response as a function of the solute concentration in the column effluent on the ordinate, and the time elapsed from the start of the chromatographic run on the abscissa, the resolution (RS) of the peaks of compounds 1 and 2 having the retention times ri the standard deviations ct and a,2 can be described by the relation... 

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