Radioactive tracers solution

Blank determinations were made by adding the same amount of radioactive tracer solutions, iron carrier-solution and purified 6N hydrochloric acid as used for the sea water samples to an empty acid-washed 10-liter polyethylene container. After washing the bottle for a few minutes, the acid solution was carried through the same procedure as described above. 

Isotope dilution begins with the addition of a known amount of calibrated radioactive tracer solution R[ to a sample of mass nii in solution. By measuring the mass recovered mi and the radionuclide amount at the end of the procedure, Ri, one calculates the initial mass. Designating Si and as the specific activity (i.e., the ratio of radionuclide amount to the mass of the same element, at the beginning and end, respectively) and OTri as the mass associated with the radionuclide tracer initially gives the following relationships ... 

The first two tests measure the fraction of radionuclide loss to walls, while the others only show relative retention in solution. A deficiency in these tests for samples with low radionuclide content is that the obtained count rate often is too low for precise determination of loss. A radioactive tracer solution can provide higher count rates but may not represent the conditions in the actual sample. 

The tracer solution is made from oil soluble bromobenzene with the radioactive isotope Br-82. The tracer solution is injected through a thin nozzle inserted into the pipeline through the valve previously connected to the injection instrumentation. The injection device provides a very sharp beginning and termination of the fraction of labelled oil. 

The most widely used experimental method for determining surface excess quantities at the liquid-vapor interface makes use of radioactive tracers. The solute to be studied is labeled with a radioisotope that emits weak beta radiation, such as H, C, or One places a detector close to the surface of the solution and measures the intensity of beta radiation. Since the penetration range of such beta emitters is small (a ut 30 mg/cm for C, with most of the adsorption occurring in the first two-tenths of the range), the measured radioactivity corresponds to the surface region plus only a thin layer of solution (about 0.06 mm for C and even less for H). 

Glaser and Lichtenstein (G3) measured the liquid residence-time distribution for cocurrent downward flow of gas and liquid in columns of -in., 2-in., and 1-ft diameter packed with porous or nonporous -pg-in. or -in. cylindrical packings. The fluid media were an aqueous calcium chloride solution and air in one series of experiments and kerosene and hydrogen in another. Pulses of radioactive tracer (carbon-12, phosphorous-32, or rubi-dium-86) were injected outside the column, and the effluent concentration measured by Geiger counter. Axial dispersion was characterized by variability (defined as the standard deviation of residence time divided by the average residence time), and corrections for end effects were included in the analysis. The experiments indicate no effect of bed diameter upon variability. For a packed bed of porous particles, variability was found to consist of three components (1) Variability due to bulk flow through the bed... 

On the basis of exchange of radioactive tracers between electrode and solution, estimates of the exchange current could be made5. 

Capsules were equilibrated with a tracer solution overnight. A capsule pellet (0.2-0.5 ml) was then placed in 5 ml test buffer (PBS or RPMI-1640 medium, Gib-co/BRL, New York, NY) on a shaker and a 0.2-ml aliquot was immediately sampled by a screen-protected pipette with further samples being taken over the next 700 s. The tracer quantity was assayed using the methods described below. A final sample was taken after the capsules has been in contact with the buffer for several hours (equilibrated tracer quantity) and the increment to the tracer concentration at each time was calculated. From the progress of tracer to equilibrium on a semilog plot a slope denoted as the zero -order rate flux constant was obtained and has been used as a measure of capsule permeability. [3H] -Glucose (580 daltons),insulin (6.2 kDa), and ovalbumin (45 kDa) have been used as tracers. Radioactivity was measured by means of a Packard 2000CA Liquid Scintillation Counter (Packard Instruments,... 

In the case of trace metals, adsorption is typically much faster than the time intervals for which it is practically possible to separate the cells. Therefore, in practice, values of kf and kr are most often estimated by assuming that water loss from the hydrated cation is rate-limiting (Eigen-Wilkins mechanism, see Section 4.3.1 above). In some cases, uptake transients can be observed at the start of a short-term uptake experiment or by using pulse-chase experiments for which a metal solution containing a radioactive tracer is replaced by a solution... 

Other techniques for the diffusion of gas through monolayers at the liquid interface have also been investigated (Blank, 1970). In these methods, the differential manometer system was used to measure the adsorption of gases such as C02 and 02 into aqueous solutions with and without the presence of monolayers. The Geiger-Mueller counter with a suitable sorbent and a radioactive tracer gas was used to measure the reduction of evolution of H2S and C02 from the surface solution when a monolayer was present. 

The decomposition of metal thiosulphates to the corresponding sulphide is well known and is generally assumed to occur by breaking of the S-S bond in thiosulphate. Thus, it has been shown, by a radioactive tracer method, that if thiosulphate is prepared by dissolving radioactive S in sulphite solution ... 

A ligroin solution of monooctyl- a-anilinobenzylphosphonate was used [67] to separate a mixture of Eu3+, Tb3+ and U6+. The course of the extraction was followed by using radioactive tracers, 152Eu and 160Tb.The separation factor (/ ) for Eu is in the range of 103 to 104. 

A radioactive tracer method was developed to quantitatively measure the adsorption of high molecular wt compds on the surfaces of powdered expls. Expts were conducted by allowing a pre-weighed amt of powdered expl to equilibrate with a fixed volume of radioactive adsorbate in an appropriate solvent. The expl must be either insoluble or of very low solubility in the solvent used. At equilibrium, an aliquot of supernatant soln is removed and its radioactivity is measured. The loss in radioactivity is a measure of the amt of adsorbate taken up by the expl. By varying the concn of adsorbate in the soln, an adsorption isotherm can be constructed relating amount adsorbed with solution concn... 

Several investigators have used radioactive tracer methods to determine diffusion rates. Bangham et al. (32) and Papahadjopoulos and Watkins (33) studied transport rates of radioactive Na+, K+, and Cl" from small particles or vesicles of lamellar liquid crystal to an aqueous solution in which the particles were dispersed. Liquid crystalline phases of several different phospholipids and phospholipid mixtures were used. Because of uncertainties regarding particle geometry and size distribution, diffusion coefficients could not be calculated. Information was obtained, however, showing that the transport rates of K+ and Cl" in a given liquid crystal could differ by as much as a factor of 100. Moreover, relative transport rates of K+ and Cl" were quite different for different phospholipids. The authors considered that ions had to diffuse across platelike micelles to reach the aqueous phase. 

Long, A. O., and J. E. Willard Reactions of Ions in Aqueous Solution with Glass. Studies with Radioactive Tracers. Ind. Eng. Chem. 44, 916 (1952). 

Adsorption of surfactants "Loss from solution" method, direct measurement using radioactive tracers, ellipsometry, nephelometry... 

The self-diffusion of the individual components is strongly affected by the formation of micelles in the solution. This applies to the surfactant, the counterion, the water, and to solubilized molecules. As illustrated in Fig. 2.11 for sodium dodecyl sulfate, surfactant and counterion diffusion are very weakly dependent on concentration below the CMC while a marked decrease in the micellar region is observed for the surfactant and a less marked one for the counterion37. Water diffusion shows a stronger concentration dependence below the CMC than above it. Self-diffusion studies using radioactive tracers have been performed to obtain information on CMC, on counterion binding, on hydration and on intermicellar interactions and shape changes. 

Two sets of experiments were conducted using six radioactive tracers simultaneously. Starting concentrations are given in Table III. Radionuclides were eluted from the cells with ground-water solutions using a peristaltic pump. Effluent was collected at 90-min intervals by means of a fraction collector connected to the cell with small-bore Teflon tubing. Concentrations of the various isotopes in the effluent were measured by gamma spectrometry. 

Ideally, metals, complexes and colloids of dimensions larger than the specified molecular weight cut-off (MWCO) are quantitatively retained while species smaller than the pore size pass with the solution across the filter membrane. Because of the excellent analytical precision achievable with radioactive tracers,... 

A tracer usually is a solution of a standardized radionuclide that is an isotope of the analyte radionuclide. With the identical chemical behavior of tracer and analyte, the yield of the tracer, determined radiometrically, represents the yield of the analyte. In this respect, the radioactive tracer has the same function as the stable carrier. Furthermore, for alpha particles of the usual 4-10 MeV energy in a thin source, the ratio of net count rate to activity is the same for the tracer and the analyte, so that the analyte activity is directly calculated from the activity of the tracer and ratio of the net count rates at the peaks of the analyte relative to the tracer, measured with an alpha-particle spectrometer. 

Standardization by Counting. For this method, a detector initially is calibrated for detection efficiency pertinent to the utilized tracer with a standard radionuclide in quantity and radioactivity form that is known and traceable to NIST. The tracer solution is then prepared for counting, counted, and labeled for radionuclide concentration on the basis of the net count rate and the detection efficiency. Its activity is calculated together with the counting error, adjusted for radioactive decay and dilution. All of these measurements should be performed in replicate to provide average values and their measurement uncertainty. 

Compare the activity reported for the tracer solution with the activity obtained with the proportional counter and the alpha-particle spectrometer based on their respective counting efficiency (s) values, adjusted for sample volume and radioactive decay. Discuss whether the differences in activity are significant and decide which values are more reliable and should be associated with the tracer solution for subsequent measurements of plutonium. 

In principle, chemical information on a system can only be obtained with methods that do not alter the species present in solution. However, in order to get this information, an external perturbation must be applied to the system and its response must be analyzed. In the case of radioactive tracer, where the radioactivity measurement is the only way to detect the element (but it does not allow the identification of the form of the species), two types of external perturbation can be applied (i) by contacting the system with a second phase and subsequently observing the distribution of the radionuclides between the two phases (static or dynamic partition) or (ii) by applying an electrical potential or a chemical gradient (transport methods). So far, transport methods have not yet been used in one-atom-at-a-time... 

The radioactive tracer used was obtained by iodine 125-labeling of the conjugate of APS-314d and histamine, according to Hunter and Greenwood s method (1962). Stored at -30 °C the iodinated tracer was stable for at least 3 months without any loss of performance. It was diluted extemporaneously in assay buffer to obtain a solution containing 80 000 cpm per ml. 

This phenomenon has been studied by different combined electrochemical techniques such as -> spectroelec-trochemistry, radioactive -> tracer method, -> electrochemical quartz crystal microbalance, conductivity etc. by varying the experimental parameters, e.g., film thickness, the composition and concentration of the electrolyte solutions, the wait-time at different waiting potentials, and temperature [iii-x]. Several interpretations have been developed beside the ESCR model. The linear dependence of the anodic peak potential on the logarithm of the time of cathodic electrolysis (wait-time) -when the polymer in its reduced state is an insulator -has been interpreted by using the concept of electric percolation [ix]. Other effects have also been taken into account such as incomplete reduction [vii], slow sorp-tion/desorption of ions and solvent molecules [iii-vi], variation of the equilibrium constants of -+polarons and - bipolarons [viii], dimerization [xi], heterogeneous effects [xii], etc. 

The uptake of cocaine to hair after preliminary exposure to various acidic and basic solutions is shown in Figure 10. Three sets of experiments were performed. In the first experiment, hair was exposed to base (0.1 M sodium carbonate, pH 12) for 3 h and then washed extensively with water rmtil the water was neutral. This was then followed by two phosphate buffer rinses at pH 5.3 for 10-min periods. The hair was then exposed to 5 pg/mL of cocaine, containing a radioactive tracer, in phosphate buffer at pH 5.3 for 1 h. After exposure the excess cocaine was removed with three water rinses of 10 min each and the hair was dried. Then the hair was decontaminated with ethanol and six phosphate washes, digested, and the cocaine concentration determined by scintillation counting as per previously described procedures. Approximately twice as much cocaine was incorporated into the hair pretreated by exposure to base as compared to hair not subjected to any pretreatment. In the second experiment, hair was pretreated with 0.1 M HCl, then treated as in the first experiment. In this case approximately one sixth as much cocaine was incorporated as the control. In the third experiment, hair was pretreated with 5% acetic add and treated as in the... 

Starting with a known cj outside a cell and determining the internal concentration both initially (i.e., for t = 0) and at some subsequent time , we can calculate P from Equation 1.12 if AIV is known. Even when AN is not known, the relative permeability coefficients for two substances can be determined from the time dependencies of the respective cj s. The previous derivation can be extended to the case in which cj is zero. In that case, PjAtIV equals ln[cj(0)/cj( )], an expression that can be used to describe the diffusion of a photosynthetic product out of a chloroplast or some substance from a cell into a large external solution initially devoid of that solute. Such studies can be facilitated by using radioactive tracers, which usually are initially present only in one region. 

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