Tracer liquid chromatograph

High Performance Liquid Chromatography. Tissue extracts were analyzed with a Varian model 5020 liquid chromatograph equipped with a Rheo-dyne model 7120 loop injector valve, a Tracer 970 variable wavelength detector set at 257 nm, an automated Hewlett-Packard 3385A printer-plotter system for determining retention times and peak areas, and a Waters /x Bondapak column (3.9 mm i.d. X 300 mm) for carbohydrate analysis. The buffer was eluted isocratically at 1 mL/min with a 1 4 (v/v) mixture of 0.01 M monobasic sodium phosphate (pH 4.46) and methanol. The minimum amount detectable was 10 ng. 

A liquid chromatograph, using water as the eluent, has a column length of 2.0 m. The column is packed with a porous synthetic medium which has a bulk density of 2.0 g/cm and a porosity of 0.25. You inject a water sample containing an ideal tracer salt and observe that a peak comes out in 133 sec. The peak has a width (as measured to encompass 68% of the mass) of 3.4 sec. However, when you inject a water sample containing acetate, the peak comes out in 8.0 min. 

Several tracers have been used in experiments describing axial mixing in fluidized beds of porous particles, e.g. acetone [37,57], Tryptophane [47], NaCl [49,56], radioactive tracers [58] and dextrane blue [59], It should be noted at this point, that measurement of RTD is not only important for determining possible domination of the chromatographic result by liquid mixing, Bo may as well be taken as a measure for the existence of a stable classified fluidized bed which is ready for sample application. Measurement of RTD in this case will provide a rational basis for the decision to start a large scale protein purification using a fluidized bed or to take measures for improvement of bed stability before application of valuable material. 

To summarize this section, a prerequisite for chromatographic NMR based on solid phases is a fast exchange kinetics among slow and fast diffusion environments of the tracer molecule. This is another analogy with liquid chromatography, where strongly bound molecules are a nuisance to the separation performance, as they tend to remain trapped behind. 

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). 

Investigations may be carried out on the tracer level, where solutions are handled in ordinary-sized laboratory equipment, but where the substance studied is present in extremely low concentrations. Concentrations of the radioactive species of the order of 10 m or much less are not unusual in tracer work with radioactive nuclides. A much larger amount of a suitably chosen non-radioactive host or carrier is subjected to chemical manipulation, and the behavior of the radioactive species (as monitored by its radioactivity) is determined relative to the carrier. Thus the solubility of an actinide compound can be judged by whether the radioactive ion is carried by a precipitate formed by the non-radioactive carrier. Interpretation of such studies is made difficult by the formation of radiocolloids, and by adsorption on glass surfaces or precipitates. Tracer studies provide information on the oxidation states of ions and complex-ion formation, and are used in the development of liquid-liquid solvent extraction and chromatographic separation procedures. Tracer techniques are not applicable to solid-state and spectroscopic studies. Despite the difficulties inherent in tracer experiments, these methods continue to be used with the heaviest actinide and transactinide elements, where only a few to a few score atoms may be available [11]. 

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