Radioactive zones

Figure 2. Thin-layer radiochromatogram of urine (100 il) from rats injected with labeled PbTx-3. TLC plates were developed in two sequential solvent systems chloroform ethyl acetate ethanol (50 25 25 80 10 10). Radioactive zones were scraped and counted in a liquid scintillation counter. Native PbTx-3 runs at 13 cm.

In Chapter 7, approaches for visualization of zones in chromatograms are discussed, including use of nondestructive and destructive dyeing reagents, fluorescence quenching on layers with a fluorescent indicator, and densitometry. In Chapter 8, additional detection methods, such as those used for biologically active and radioactive zones, as well as the recovery of separated, detected zones by scraping and elution techniques are covered. 

A phosphor screen can be used like an autoradiography film to detect radioactive zones on PLC plates. The available screens are sensitive to x-rays and beta and gamma emissions from isotopes such as H, bij 32p 33p -pjjg screen captures... 

Besides increasing the sensitivity of detection methods, labeled molecules may be used to establish the identity of an unknown spot. If, after addition of a known, labeled substance to an unknown mixture of unlabeled substances, chromatography results in a spot in which the radioactive zone coincides in every detail with an unknown spot, also... 

Figure 2.3 Hormonal stimulation of arachidonic acid (AA) metabolism by medullary thick ascending loop of Henle cells prelabelled with [ " C]AA (0.4 /i Ci per 3 x 10 cells for 90 min at 2>7 Q). Following incubation with AVP (O/ 4 x 10 ° to 4 x 10 molL ), SCT (A, 10 ° to 2 X 10" mol/L) and bradykinin ( , 10" molL" ), the AA metabolites were separated by thin-layer chromatography. Radioactive zones corresponding to Pj and P were cut and counted using a liquid scintillation counter. The percentage increase in the formation of Pi and P2 above the unstimulated control value was plotted. The means + SEM for four experiments are shown...

After a pulse-label of one hour with [ C] glucose, and a further hour of chasing in the absence of label, a single radioactive zone was detected on the... 

Radioactive zones can be detected on thin layers by film autoradiography, digital autoradiography with a multiwire proportional chamber, use of charged-coupled devices, or bioimaging/phosphor imaging techniques. These methods differ in terms of factors such as simplicity, speed, sensitivity, resolution, linear range, and accuracy and precision of quantification, and the method of choice depends on the available instrumentation, the type of experiment, and the information needed. 

For LSC, radioactive zones are scraped from a glass-backed layer or cut from a layer with flexible backing (plastic or aluminum) and transferred into a vial, mixed with a scintillation solution (commercial cocktails are available), and indirectly quantified based on measurement of the light energy produced in a scintillator counter with a photomultiplier tube (PMT). As an alternative, scraped or cut zones can be eluted with solvent into a vial to isolate the radiolabeled sample and then counted. The number of counts for each zone can be plotted as a histogram profile of the radioactivity in the chromatogram along the lane of a TLC plate. 

TLRC can be used for animal, human, and plant metabolism analysis radiochemical purity and stability assessment toxicology and biochemical studies and separation, detection, and quantification of separated radioactive zones of all compound classes. Traditional film autoradiography and LSC continue to be widely used, but phosphor imaging and layer scanners are being increasingly applied. The instruments for these methods are highly automated and... 

Cl-Araoh idon io acid (AA) conversion by rabbit vasculature (see text for methods), The radioactive zones were detected by auto radiogra phy Hatched bars indicate the location of standard compounds and the Rf values are in parenthesis ... 

Notes 2- In order to Insure ready Identification of the components (except Po) whose concentrations are very low (or carrier-free) a simultaneous calibration run with an Inactive mixture of the same components may be made on an unused portion of the same paper. An alternative method Is to spot each component separately using KI as a strealc reagent. In the calibration run, concentrations are high enough to permit detection with streak reagents. The radioactive zones will be In the same relative positions as the Inert zones. 

The problems encountered in the USA over the Below Regulatory Concern policy were mentioned earlier. For similar reasons a policy of zoning in the French nuclear industry is being proposed, in which some areas are declared as containing radioactive materials and others are defined as being free from radioactive materials. The disposal of materials and structures within the radioactive zones will be managed without release from the zones, with the intention of avoiding the need for exemption and clearance. However, even with this approach it will be necessary to define what is "radioactive" and what is not. 

Methods for the quantitative evaluation of thin-layer chromatograms can be divided into two categories. In the first, solutes are assayed directly on the layer, either by visual comparison, area measurement, or densitometry. In the second, solutes are eluted from the sorbent before being examined further. Quantification of radioactive zones is not considered here but is discussed in Chapter 13. 

Prior to working with radioactive materials, the scientist should attend a pertinent training course or consult a standard source of information on radioisotope methodology to become familiar with the precautions used in the safe handling of radiochemicals in the laboratory (e.g., DuPont, 1988a Shapiro, 1972 Stewart, 1981). As much as possible, experiments should be carried out, and plates with radioactive zones stored, in a fume hood. 

TLC coupled with spectrometry and other analytical methods, video documentation, and computer imaging (Chapter 9) quantification by video densitometry (Chapter 10) validation of quantitative results (Chapter 11) and in situ instrumental measurement of radioactive zones (Chapter 13). The fomth edition continues to provide extensive coverage of sample preparation in Chapter 3. We believe that this coverage is unique and differs from that found in other available treatises on TLC. Because of the primary importance of commercial precoated plates, detailed instructions for preparing layers were removed (Chapter 3), and description of documentation by contact printing has been eliminated (Chapter 9). 

For liquid scintillation counting or scintillation autoradiography, the areas of sorbent containing radioactive zones are scraped into vials and mixed with scintillation fluid. The light emitted because of interaction of radioactive nuclei with the fluid is measured with a photographic film or scintillation counter. 

These are two different social and cultural positions, but the same interest is to avoid individual responsibility for the eventual health consequences of professional exposure and to see that his records are kept for institutional treatments, that is, to be sure they remain a collective project of civilization which specifices his presence in the radioactive zone considering that it was necessary to be there if you wanted to order people around and if you wanted to show them how to work properly. For him, to work was not only to actively participate in the production process it was -above all - to respect the rules as they alone can guarantee safety. He indicated that, the particular nature of the nuclear industry in comparison to metallurgy lies in the safety rules. The culture of the nuclear industry is a safety culture. It is necessary that the employees acquire this safety culture. ... 

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