Tracer pulse chromatography

The next thing we note about chromatography is that it is equivalent to tracer injection into a PFTR. Whereas in Chapter 8 we used tracer injection to determine the residence time distribution in a reactor, here we have nearly plug flow (with the pulse spread somewhat by dispersion), but adsorption from the fluid phase onto the solid reduces the flow velocity and increases the residence time to be much longer than x. ... 

Mobile fluid interaction with the stationary phase in SFC was investigated with mass spectrometric tracer pulse chromatography (96). Using capillary supercritical fluid chromatography, the effect of methanol as an additive was studied on the partition behavior of n-pentane into 5 % phenylmethylsilicone stationary phase. The results showed that the mobile fluid uptake by the stationary phase decreased with increasing temperature and pressure. Thus suggests that stationary phase swelling, may occur in SFC. 

Analyte Competition on Polyimide Adsorbents Studied by Deuterated Tracer Pulse Chromatography... 

Deuterated tracer pulse chromatography (TPC) was used to characterize the retention behavior of Tenax-GC and four polyimide-based sorbent materials. Deuterated n-hexane, ethanol, 2-butanone, nltromethane, and benzene were used as compounds to probe ive types o chemical Interactions o the compounds with the polymers. Retention properties were Investigated with dry and humidified helium carriers both with and without the Incorporation of non-deuterated test compounds. Analyte competition was shown to occur on all of the sorbents. Humidity affected the retention of the probe compounds on the polyimides to a much greater extent than on Tenax-GC. The technique was shown to elucidate subtle differences In sorbent behavior. 

Figure 2. Schematic Description of Dynamic Tracer Pulse Chromatography. Arrows at t=0 and t2 indicate injections of deuterated "pulse" compounds. The additional arrow in B indicates the initiation of the organic front.

Two different implementations of these methods have been developed, the tracer pulse technique (or elution of an isotope on a plateau) and the concentration pulse technique (or elution on a plateau). They are very different in principle although they share much theoretical backgroimd. Only the second one has now any practical applications in liquid chromatography. 

Tracer-pulse chromatography has been used to measure gas-solid phase equilibria. It allows the accurate measurement of sorption isotherms even at elevated temperatures and with multicomponent systems (37). 

The effective diifusivity measurement of gases by tracer-pulse chromatography in porous solids has been extended to include zeolites [faujasites, mordenites, 3A and 5A molecular sieves (35)]. The measured diffusions in this case were a strong function of molecular size. 

Earlier treatments of the tracer-pulse chromatography technique can be found in Helfferich and Peterson (39, 40). 

Recently the radioactive tracer pulse chromatography was used by Barrere and Deans to investigate the absorption reaction of CO2 in liquid diethanolamine (4J). One of the significant contributions to the field of adsorption rate measurement by chromatographic techniques can be found in a recent paper by Padberg and Smith (4Ia). 

Arnell, R. and Fornstedt, T. (206) Validation of the tracer-pulse method for multicomponent liquid chromatography, a classical paradox revisited. Anal. 

G. Barnett, R. Hawks, and R. Resnick [/. Ethnopharmacol., 3, 353 (1981)] of the National Institute on Drug Abuse have studied cocaine pharmacokinetics in the human body. Cocaine was given to human subjects by intravenous administration. Gas chromatography-mass spectroscopy was used to determine the concentration of this drug in blood plasma samples. From the measurements reported below, determine whether the data are consistent with the response of a single CSTR to a pulse injection of tracer. Also determine the mean residence time of the material in the body. 

Hyun, S.H., and Danner, R.P., Adsorption equilibrium constants and intraparticle diffusivities in molecular sieves by tracer-pulse chromatography, AlChE J., 31(7), 1077-1085 (1985). 

There are various methods to determine D, including the pulsed NMR method, the tracer method, and chromatography. Readers are referred to a detailed description, including characteristics, of measurement, in Part 2, Chapter 2, Section 4, Transport and Permeability (Material Diffusion). The measurement of D is done in what follows here by pulsed NMR. 

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