Use Of Liquid Scintillation Counting Research Articles

Expanded Applications of Liquid Scintillation Counting and Several Related Issues

Liquid scintillation counting (LSC) is widely used in the field of radiation measurements. Some main developments in the application of LSC in our laboratory have been introduced briefly in this paper. These developments include: the use of LSC alone to determine 152Eu and 241Am simultaneously instead of using the common γ spectrometry, and the use of LSC in combination with α or γ spectrometry in various cases. All these developments expand the applications of LSC, which can lead to significant increase in production of radioactive measurement work. In addition, we have discussions about several issues which are very important to LSC application, i.e. the quenching effect on α/β discrimination, the influences of anticoincidence shield on count rates for various kinds of radionuclides, the effect of statistical fluctuations in external standard spectrum on quench index parameter, and the long-term stability on basic performances of LSC cocktails.

In vitro screening of probiotic properties of Saccharomyces cerevisiae var. boulardii and food-borne Saccharomyces cerevisiae strains

The probiotic potential of 18 Saccharomyces cerevisiae strains used for production of foods or beverages or isolated from such, and eight strains of Saccharomyces cerevisiae var. boulardii, was investigated. All strains included were able to withstand pH 2.5 and 0.3% Oxgall. Adhesion to the nontumorigenic porcine jejunal epithelial cell line (IPEC-J2) was investigated by incorporation of 3H-methionine into the yeast cells and use of liquid scintillation counting. Only few of the food-borne S. cerevisiae strains exhibited noteworthy adhesiveness with the strongest levels of adhesion (13.6–16.8%) recorded for two isolates from blue veined cheeses. Merely 25% of the S. cerevisiae var. boulardii strains displayed good adhesive properties (16.2–28.0%). The expression of the proinflammatory cytokine IL-1α decreased strikingly in IPEC-J2 cells exposed to a Shiga-like toxin 2e producing Escherichia coli strain when the cells were pre- and coincubated with S. cerevisiae var. boulardii even though this yeast strain was low adhesive (5.4%), suggesting that adhesion is not a mandatory prerequisite for such a probiotic effect. A strain of S. cerevisiae isolated from West African sorghum beer exerted similar effects hence indicating that food-borne strains of S. cerevisiae may possess probiotic properties in spite of low adhesiveness.

The use of 96-well Scintiplates to facilitate definitive metabolism studies for drug candidates

Semi-quantitative analysis of the drug-related components in biological samples collected during definitive metabolism studies using radiolabelled drug candidates is commonly achieved by HPLC profiling, using either on-line radiochemical detection or off-line liquid scintillation counting (LSC) following collection of the HPLC eluent into vials. However, although the use of LSC with vials has high sensitivity, the approach is time-consuming, laborious and destructive, whilst on-line detection methods are inappropriate for samples with low-levels of radioactivity (commonly the case with plasma samples). The use of 96-well microtitre plates (Scintiplates) for fraction collection during HPLC profiling provides a sensitive, effective and efficient alternative method for the semi-quantitative analysis of radiolabelled components in biological samples. Furthermore, the approach is non-destructive, such that subsequent identification of the isolated components can be achieved. Although the Scintiplate methodology is not appropriate for the analysis of excreta samples, where quenching of the radiochemical signal by endogenous components was observed, the approach was demonstrated to be valid for the relative quantification of [ 14 C ]-labelled material in plasma samples for all species investigated. In addition, good sensitivity was observed, with a counting efficiency of 79% for [ 14 C ], such that a drug-related component accounting for 10–15 dpm is quantifiable. The utility of the methodology for profiling circulating metabolites was demonstrated by the analysis of a rat plasma sample following oral administration of [ 14 C ]-UK-349,862. The Scintiplate approach and subsequent mass spectrometric analysis resulted in the relative quantitation and specific characterisation of circulating metabolites accounting for 93% of the total plasma radioactivity.

Measurements of linear absorption coefficients of liquid scintillators using synchrotron radiation

The use of liquid scintillation counting as a fundamental radionuclide standardisation method requires a correct description of the physical phenomena induced by the interaction of the ionising radiation with the liquid scintillator. In particular the standardisation of radionuclides decaying by electron capture as 55Fe and other electron-capture nuclides, requires the knowledge of total linear absorption coefficients of the liquid scintillator used for absolute activity measurement. Total linear absorption coefficient measurements have been undertaken using synchrotron radiation. Linear absorption coefficients of two widely used commercial liquid scintillators were measured in the 5.5–23 keV energy range. Small discrepancies were noted between theoretical and measured values of the Ultima-Gold™ mass attenuation coefficients for low energy photons.

Determination of the Enantiomeric Purity of Commercial L-[U-14C] Valine: An Experiment Utilizing Reversed-Phase Thin-Layer Chromatography and Liquid Scintillation Counting

The enantiomeric purity of commercial L-[U-14C]valine was determined. The process involved sequential dilution with nonradioactive DL-valine, N-dansylation using dansyl chloride, and resolution using reversed-phase thin-layer chromatography in the presence of σ-cyclodextrin, a chiral mobile phase additive. Liquid scintillation counting of the bands corresponding to DNS-D- and L-valine gave the enantiomeric purity, as well as the percent radiochemical yield. Because the derivatization reaction proceeded without racemization, the results corresponded to the relative amounts of radioactive D- and L-valine in the commercial sample. The analyses were easily performed using less than 1 µ Ci of L-[U-14C]valine per pair of students. This laboratory experiment provides students with valuable experience in handling radioisotopes, illustrates the use of liquid scintillation counting as a sensitive detection method, reinforces important stereochemical relationships, and can be applied to the analysis of other rad...

Pharmacokinetics of tinzaparin (Logiparin®) - a low molecular weight heparin-after single and repeated intravenous administration in rats

After a single and repeated i.v. injections of 1 mg/kg 3H-radiolabelled tinzaparin once daily to rats for 7, 14, and 21 days, drug-related radioactivity in plasma, tissues, urine and faeces was measured by use of liquid scintillation counting. The decay in plasma could be described by a three-compartment model with half-lives of the two distributive phases and the terminal elimination phase of 15 min, 90 min, and 37 hrs, respectively. The peak plasma concentration did not change during repeated dosing, as opposed to the trough concentration which increased 3 fold. The decay in tissues was significantly different from that in plasma, and showed less fluctuations. Drug-related radioactivity accumulated gradually with repeated dosing, reaching accumulation ratios between 5 and 9, when based on trough concentrations. Slow elimination was observed from tissues, and significant amounts were still present 14 days after discontinuation of the repeated dosing. In the liver, the concentrations were almost constant during a dosing interval. After a single injection, 86% and 4% of the administered radioactive dose were excreted in urine and faeces over 7 days, respectively, the majority being recovered during the first 24 hrs, demonstrating that the major route of elimination was by renal excretion. The molecular mass distribution of radioactivity in urine was similar but not identical to the injected test substance. It was shifted slightly towards lower molecular mass and had no anti-factor Xa activity, suggesting that the heparin was either inactivated, presumably by desulphation, or that the antithrombin binding portion of the drug was cleared through a different route.

Use of liquid scintillation counting for fast determination of 89Sr and 90Sr in milk

This paper describes a method of reproducibly recovering strontium (Sr) in 90.4% yield from 2-litre samples of raw milk in an analysis time of 5–8 h. All species which may interfere with the measurement of 89Sr and 90Sr are effectively removed; decontamination factors for Ca, Y, Ba and Cs were found to be adequate, and the role of other possible interferences is discussed. The Sr isolate was dissolved in scintillation cocktail prior to counting of 89Sr and 90Sr in a single measurement with a low-level liquid scintillation spectrometer. Scintillation spectra and counting efficiencies for 89Sr, 90Sr and 90Y have been established. A simple spectral stripping technique may thus be applied to calculate activities from the spectra of real samples. Results of analyses of five 2-1 milk samples containing known activities of 89Sr and 90Sr were respectively 87.7 ± 3.5% and 90.4 ± 3.0% (± 1 S.D.) of the activities added. A correction factor for the Sr yield was not applied. The detection limit of 0.014 Bq for 90Sr samples free of 89Sr implies that the method is also useful for routine monitoring of 90Sr.

On the determination of phosphorus depth profile in phosphorus-doped silicon

The depth profile of phosphorus concentration in phosphorus-doped silicon was shown to be measureable with an accuracy of 1–3% by the use of liquid scintillation counting after neutron irradiation. Both the amount of Si and P are determined by neutron activation analysis followed by liquid scintillation counting for 1–5 hours after the end of irradiation and 5–10 days after irradiation, respectively. Concentrations as low as 10 ppm and thicknesses of 20 nm can be determined.

Transit time of epithelial cells in the small intestines of germfree mice and ex-germfree mice associated with indigenous microorganisms.

Germfree mice housed in isolators under controlled environmental and nutritional conditions were associated with an intestinal microflora. These associated animals and germfree mice drawn from the same population were tested for the rate at which the epithelial cells transited from the crypts of Lieberkuhn to the tips of the villi in their small intestines. The method for estimating the rate of transit of epithelial cells involved the use of liquid scintillation counting to determine the amount of radioactivity entering the cells while the animals were being injected with [3H]thymidine and statistical analysis of th data with a computer program developed for the purpose. As estimated by that method, the cells transited from the crypts to the villous tips in germfree mice in about 115 h and in the associated animals in about 53 h. In monoassociated mice, a strain of a Lactobacillus sp. had no effect on the transit time of the epithelial cells. A strain of Torulopsis pintolopesii stimulated uptake of 3[H]thymidine by the small bowel mucosae in mice monoassociated with the organisms for 5 weeks. In animals monoassociated with the yeast fo 3, 4, and 6 weeks, however, the radioactive compound was incorporated into the bowel mucosae to the same extent as the mucosae of germfree mice. Therefore, similarly to the Lactobacillus strain, T. pintolopesii has no obvious influence on the transit rate of small bowel epithelial cells.

Radiorespirometry and metabolism of cultured cells attached to petri dishes

A radiorespirometer was constructed for continuous quantitation of 14CO 2 released from specifically labeled substrates by intact cultured cells attached to plastic petri dishes. An airtight chamber is created by sealing the petri dish with a specially designed cover inside a thermostated holder. Rapid equilibration of released 14CO 2 with a 5% CO 2 95% air carrier gas is achieved by bubbling the carrier gas under the surface of the growth medium. Labeled CO 2 is removed from the carrier gas by trapping in an organic base and quantitated by liquid scintillation counting. Additions to or sampling of the growth medium may be performed during a run and the carrier gas may be modified to test the effects of anesthetics and different O 2 levels. The ability to continuously monitor 14CO 2 release can provide valuable information concerning the metabolic pathways of substrate oxidation which cannot be obtained from single 14CO 2 determinations. A capacity of 12 culture plates enormously increases the amount of data that can be collected in a given time. The use of liquid scintillation counting increases the sensitivity and resolution over the ion chamber and Geiger counter methods, and permits utilization of the procedure in a much wider range of laboratories. Data obtained for the oxidation of specifically 14C-labeled glucose and pyruvate by neonatal rat heart cells in culture, in both the presence and absence of oxygen, are provided as examples of the utility of the method.

What is the future of liquid scintillation counting in clinical chemistry and in clinical research?

The use of liquid scintillation counting in clinical laboratories and for biomedical research has increased greatly over the more than 25 years that commercial LS counters have been available. Vibrating reed electrometers and gas-filled ionization detectors for the measurement of tritium and carbon 14 respectively have been supplanted by LSC. Other commonly employed isotopes for which LSC is now the preferred method are: 32 P, 35 S, 45 Ca, 55 Fe, and the α-emitting actinides (McDowell and Weiss, 1976). Other isotopes counted by LSC have recently been listed by Gibson (1976), Bransome and O'Conner (1978), and Soini (1978).

The use of liquid scintillation counting in the studies of coal and coal-derived liquids

Coal and coal derived liquids were treated with radio labeled ( 14 C or 3 H) acetic acid, ethanol, methanol and water. Coal derived liquids were allowed to react with 1- 14 C-acetic anhydride in pyridine to form acetate derivatives of phenols, alcohols, primary and secondary amines. The samples were then oxidized and collected 14CO 2 or 3 H 2 O measured in a liquid scintillation counter. Good reproducibility and quantitative recovery of 14 CO 2 and 3 H 2 O were observed. The liquid scintillation counting method was very useful for quantitation of hydroxyl groups and primary and secondary amines in coal derived liquids. The amount of adsorption of acetic acid, ethanol, methanol, and water was also measured. They found it to be irreversibly adsorbed on coal. Other techniques, such as 1 H and 13 C nmr as well as titration of liberated acetic acid, are inefficient in quantitative determination of acid groups in coal. Only tracer methodology was able to determine adsorption of solvent on coal efficiently.

Apparent and actual 14C retention in the slower turnover bicarbonate pool in man when using liquid scintillation counting

The use of liquid scintillation counting to determine 14CO 2 expiration without correct calibration of the apparatus suggests that about 25% of the label is retained within the slower turnover bicarbonate pool. Calibration reduces this figure to 13% and is in agreement with the figure obtained using a calibrated ionisatin chamber. The discrepancy is due to reduction in the specific radioactivity in the vial, the mechanism involved being unknown, but it may be a characteristics of certain liquid scintillators under certain conditions.

Interfacial Adsorption of a Psychotomimetic Drug Using Liquid Scintillation

A study was conducted on the oil–water partitioning and interfacial adsorption of 3H-2-pyrrolidylmethyl N-methyl cyclopentylphenylglycolate (I), an anticholinergic psychotomimetic agent. A new technique for radiotracer adsorption was developed involving the use of liquid scintillation counting. Among the physical parameters examined were partition coefficient, permeation constant, stability constant, and rate constant of I in a two-phase system of water and a lipid, didodecyl phosphate (II). II greatly accelerated the rate of oil–water partitioning of I and exhibited interfacial adsorption with I. The presence of polyanions, such as hyaluronic acid in the aqueous phase, promotes the transfer of drug from the oil to water phase. Equations found applicable to permeation of ions across membranes have been used to describe drug transfer through an oil–water interface.

Zur Absolutmessung der Radioaktivität reinerβ-Strahler mit flüssigen Szintillatoren

The use of liquid scintillation counting for the absolute standardization of pure β-emitting radionuclides by means of the efficiency-tracing method is investigated. Special effects occuring by the use of liquid scintillators do not lead to important errors. Results of measurements of the nuclides35S and45Ca are given.

Use of liquid scintillation counting for the determination of distribution ratios of alpha emitters

Use of liquid scintillation counting for the determination of distribution ratios of alpha emitters

Benzene synthesis by low temperature catalysis for radiocarbon dating

A method is described for the ambient temperature synthesis of pure benzene from acetylene in 50–60 per cent yields that is suitable for low-level liquid scintillation counting. Application of this method to carbon dating essentially eliminates previous problems encountered in the use of liquid scintillation counting for this purpose. The method extends the sensitivity of the carbon dating method and yet requires only standard commercially available counting systems.

Practical aspects of internal-sample liquid scintillation counting

The appearance of commercially available equipment has made it practicable for chemists and biochemists to consider the use of liquid-scintillation counting for the assay of radioactive samples. The method offers excellent sensitivity for weak beta-emitting isotopes, including tritium. This is because of its 4π geometry for samples as large as several grams. The disadvantages of the technique are discussed in detail. The equipment is several times as expensive as most other counting apparatus. It is more complex to understand and to maintain. The method involves certain prerequisites of the sample material. These include adequate solubility in the rather limited group of alkyl benzene and polyther solvents that suffice as liquid-scintillation solvents, absence of color, and freedom from quenching action upon the scintillation phenomenon. Toluene remains the solvent of choice, but its usefulness has been broadened through the use of 2-ethylhexanoic acid and a quarternary ammonium base which form toluene-soluble salts with many cations and anions. The applicability of liquid-scintillation counting to any counting problems should be evaluated specifically. In general, however, some of the applications in which it appears to be the method of choice include nearly all tritium counting, assaying C 14 and S 35 samples of low specific activity, any type of counting where speed and ease of sample preparation are necessary, and the counting of volatile compounds.