Elution regimes

A concrete example comes from the experimental works with the radionuclides characterized by lx, much shorter than t c. A long continuous on-line experiment formally looks like the frontal chromatography of the products. However, when the decay events of such nuclides are registered immediately by the material of the column, the resulting internal chromatogram is the same as it would be in the elution regime. The random processing time tf equals the random individual lifetime of the nucleus. 

Fig. 4.8 Simulated zone profiles at various d A [22], All curves elution regime =...

Fig. 7 presents partial results of dynamic regime experiments for chromate adsorption and desorption by ODA-clinoptilolite. As shown by breakthrough curves, ODA-clinoptilolite column quantitatively removes chromate species from simulated waste water , apparently more efficiently by lower flow rate. Consequently to similar configuration of chromate and sulfate molecules, such loaded column was more efficient to regenerate with Na2S04 than NaCl solution, as elution curves at the Fig. 7 illustrate. 

The simultaneous determination of LAS and its potential biodegradation intermediates of low molecular weight (C < 8), as sulfonated and non-sulfonated, has been performed by RP-HPLC-UV using a gradient regime with the mobile phase at pH 2.2 [29]. Compound elution with the same number of carbon atoms in the carboxylic chain was as follows SPCs, hydrophenyl carboxylic acids and finally phenylcarboxylic acids. 

FIGURE 1.36 General scheme for the process of CPC and mobile phase flow regime for the descending mode of CPC (insert bottom left) used for the CPC separation of dichlorprop with [mono-ll-octadecylthio-h ls-10,ll-dihydroquinidinyl)]-l,4-phthalazine as chiral selector. Elution profiles for dichlorprop after injection of 366 mg racemate, amolar ratio r = 1 of loaded dichlorprop to total selector present in the rotor, and arotor speed of 1100 rpm. Stationary phase, 10 mM selector in methyl tert-butylether mobile phase, 100 mM sodium phosphate buffer (pH 8) flow rate 3 mLmin temperature, 25°C. (Reproduced from E. Gavioh et ah. Anal. Chem., 76 5837 (2004). With permission.)... 

Our approach to identifying eluting peaks in the absence of authentic standards has been to match the chromatographic profiles with the K+IDS mass spectral results since both techniques address similar molecular weight regimes. We also use standards for quantitative comparison when possible. In most cases this approach has been successful. When this approach does not suffice, we resort to time-consuming fraction collection followed by spectroscopic identification. 

We will discuss the quantitative characteristics of IC and TC, which are of importance when the techniques are used in studies of radiochemistry of the heaviest elements. Most interesting are the fast TC separations in open columns, which would yield reasonable resolution of mixtures and information on the adsorption-desorption energetics of the species involved. It is reasonable to start with what has been learned about isothermal chromatography and can be applied to thermochromatography. In the latter field, empirical works aimed at useful separations have prevailed. Here, we will pay interest primarily to the scarcer fundamental studies and theoretical developments which dealt with the characteristics of the resulting adsorption zones. Special conditions of the studies of TAE chemistry require attention to both the elution and frontal regimes of TC processing. 

Fig. 4.1 Ideal (dashed curve) and real thermochromatograms in frontal regime [3]. The 7 d marks the position of the ideal, r) (z)-like elution thermochromatogram.

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