Elution chromatogram

Fig. 2.45. Gradient elution chromatogram of flavonoids investigated. Peak identification 1 = naringin 2 = hesperidin 3 = quercitrin 4 = myricetin 5 = naringenin 6 = hesperetin 7 = luteolin 8 = apigenin 9 = flavone 10 = acacetin. Reprinted with permission from M. A. Hawryt et al. [136].

A simple way to estimate the appropriate isocratic conditions from the result of a gradient elution chromatogram is provided by the theory of linear solvent strength (LSS) gradients of Snyder (for a review, see ref. [528] or [527]). By definition, an LSS gradient obeys the following relationship ... 

Figure 5.14 Gradient elution chromatogram of a mixture of phenolic solutes. The six numbered peaks refer to the sample. The remaining signals to the blank. Linear gradient 0 — 100% methanol in water. /0=125 s. Figure taken from ref. [536]. Reprinted with permission.

Figure 9.5. LSC gradient elution chromatogram. Column 50 cm x 5 mm i.d. Bio-Sil A. Flow 0.5 mL/min. Sample 10 mg in 50 p,L. Reprinted with permission from R. P. W. Scott and P. Kucera, Anal. Chem. 1973, 45, 749. Copyright 1973, American Chemical Society.

It should be noted that Eqs. (1.7) and (1.8) are valid only if the migration velocity of a sample zone is constant during the elution, which means that the plate number can be determined only from isocratic chromatograms obtained at a constant composition of the mobile phase, temperature and flow rate. Plate number values evaluated from a gradient-elution chromatogram are subject to gross errors and have no real meaning. 

Pf is the instantaneous concentration of the strong eluting component in the mobile phase at the outlet of the column at the time the band maximum elutes from the column, Ri. R2 are the retention volumes of sample compounds with adjacent peaks, N is the number of theoretical plates determined under isocratic conditions and T, is the hold-up volume of the column. It should be noted that the correct plate number value cannot be determined directly from a gradient-elution chromatogram using Eq. (1.7) or Eq. (1.8), which assume a constant value of the retention factor A and hence can be applied for isocratic elution only. 

In summary, the wide rectangular profile is characterized by two concentration shocks, at times and fR,2/ for the first and the second component, respectively, by a residual of the injection plateau, and by a concentration plateau at C having a length At2- These characteristics define the three zones of the elution chromatogram of a binary mixture (Figure 8.1) the pure first component zone, the mixed zone, and the pure second component zone. Analytical solutions are provided to calculate the individual band profiles for a binary mixture. Table 8.1. We now study the elution profile of a narrow injection pulse, when Eq. 8.36 is no longer verified. 

This equation is valid everywhere in the column, and particularly at the coliurm exit, hence it can be used to describe the elution chromatogram. A perturbation Aqs of the stationary phase concentration of the additive takes place everywhere a perturbation of the mobile phase concentration of a sample component takes place. These perturbations migrate along the column at the constant component velocity Uz,i = h/(1 -I- Eq. 7.3). When a sample component perturbation... 

Lim and Ching [20] published about the separation of enantiomers of Praziquantel in an 8-column SMB plant. They designed the SMB process on the basis of elution chromatograms by their own method. 

Figure 30.2 Gradient polymer elution chromatograms showing three-arm star polymers containing varying degrees of hydroxyl functionalization. X =...

The scientific description of the appearance of a peak in an elution chromatogram is not given by its retention time but by its retention factor k (formerly called capacity factor k ). 

Figure 3.23 Gradient elution chromatograms for the same eight components as in Figure 3.19, calculated for linear solvent programs...

Typical elution chromatograms which show the separation of mixtures of BHT-Santonox R, are shown in Figure 3.5. It is noted that the water-methanol effluent front elutes the bulk of the Santonox R. A large error would result if some of the first part of the aqueous methanol fraction were discarded. 

Figure 3.5 Elution chromatogram of butylated hydroxy toluene and Santonox Reproduced from Campbell and Wise, Journal of Chromatography [2]...

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