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At least 37 records · Page 2Linked to original sources
PubMed1990

[Solid scintillator "Ready Cap" for measurement with a liquid scintillation counter--spectra and counting efficiencies for 15 different radionuclides].

"Ready Cap", a small plastic container coated with solid scintillator has recently been introduced (Beckman Instruments, Inc.). Pulse height spectra and counting efficiencies obtained with a liquid scintillator and Ready Cap using a liquid scintillator counter were compared for 15 different radionuclides. For radionuclides emitting low-energy beta-rays or characteristic X-rays, the spectra for Ready Cap shifted toward the higher energy side compared with the spectra for the liquid scintillator. This tendency was reversed for the nuclides emitting higher-energy beta-radiations (36Cl and 32P). Generally, counting efficiencies both in Ready Cap and in liquid scintillator increased with increase in the energy of beta- or X-rays. For some nuclides, Ready Cap gave higher counting efficiencies and for others it gave lower values than in the liquid scintillator. However, the differences were not large within each nuclide. The use of Ready Cap is recommended for measurements of radionuclides when liquid scintillation cocktails have no means of waste disposal under the present Japanese radioisotope regulation.

Evaluation Studies as Topic↗
PubMed1975

How much light from rectangular scintillation counters?

Theoretical calculations have been made of the efficiency and uniformity of light collection at one end of a large rectangular liquid scintillation counter (80x20x18 cm). Three different arrangements were considered; (1) a system in which all surfaces of the counter other than the collecting surface were transparent to permit total internal reflection, (2) a similar system with a mirror placed close to the end opposite the collecting surface and (3) a system in which external reflectors were placed close to surfaces other than the collecting surface. In all cases, the effects of attenuation of light in the counter medium, inefficient total internal reflection and the reflectivities of external reflectors were considered and illustrated for selected values of these parameters. In an experimental counter of the same dimensions, the amplitude of the spectrum of a collimated 42-K source was used to measure the relative efficiencies of light collection for various reflector arrangements. In general the experimental values agreed with theory and the non-uniformity of response was within the predicted range. It is estimated that about 30% of scintillation light can be collected at one end of such a counter, with a non-uniformity not greater than 10%, if magnesium oxide is used as the external reflector at all other surfaces.

Light↗
PubMed1976

Simple modification of a liquid scintillation counter to decrease cost of and time for radioimmunoassay.

A simple, inexpensive modification in the elevator mechanism of a liquid scintillation counter allows for radioimmunoassay tubes (12 X 75 mm) containing the antibody-bound radioligand to be counted directly, thereby obviating the need for counting vials and considerably decreasing the amount of fluor used. Furthermore, because assay and counting are all done in the same tube, the modification shortens assay time and increases precision by avoiding what is often the most time consuming and inaccurate step, the transfer of antibody-bound radioligand to a counting vial. We find that use of this modification results in about a 75% decrease in the overall cost for materials and a substantial decrease in assay time.

Costs and Cost Analysis↗
PubMed1979

[Evaluation of the reproducibility in radioactivity measurements with liquid scintillation counters--intercomparison among several presently available counters of different models (author's transl)].

Experimental studies were carried out to evaluate the reproducibility in 3H measurements with presently available liquid scintillation counters. A set of 3H samples which have activities ranging from 10(4) to 10(7) dpm were prepared and measured repeatedly in every possible different order with six counters of different models. The results demonstrate that the measured counting rates of the samples are subjected to much greater variations than expected from counting statistics. The poor reproducibility was found to be attributed to rate dependent photomultiplier gain variations. The variations in counting rate as large as 10 per cent was observed in a particular counter. It is also found that rate dependent photomultiplier gain variations can cause the external channel ratio to shift, giving rise to error as large as 9% in the efficiency determination.

Evaluation Studies as Topic↗
PubMed1982

[Simultaneous measurement of 32P and a 33P double-labelled sample by liquid scintillation counter and its application to phosphorus compounds isolated by paper chromatography].

Simultaneous determination of 32P and 33P radioactivities was carried out with the liquid scintillation counter (Aloca LSC 670). For the quenching correction, the channel ratio method was used, and the proper gain and window level were set to get the maximum performance number or Klein-Eisler value. Using this method the radioactivities of the 32P and 33P double labelled compounds which were separated with paper chromatography were determined. New index, RSA (relative specific activity, i.e. 32P/33P) was proved to be effective as well as specific activity for the studies of the transport and metabolism of phosphorus compounds in the plant roots.

Chromatography, Paper↗
PubMed1998

Determination of the specific activity of sheep plasma amino acids using high-performance liquid chromatography: comparison study between liquid scintillation counter and on-line flow-through detector.

A method was developed for the determination of the specific activities of leucine and phenylalanine in plasma using a flow-through scintillation counter coupled with high-performance liquid chromatography components. Results were compared with those obtained from liquid scintillation counting. Differences in the specific activities of leucine and phenylalanine between the two methods were not statistically significant. We concluded that flow-through radioactivity detection can be used for quantitative amino acid assays. However, the minimum activity that can be detected may be prohibitively low in certain applications.

Animals↗
PubMed1983

The effect of sample composition and vial type on Cerenkov counting in a liquid scintillation counter.

The effect of sample vial type and sample composition on the Cerenkov count rate detected from 32P and 36Cl was studied using a liquid scintillation counter. When counting was done in the noncoincident mode, glass vials allowed higher counting efficiency than plastic vials. In the coincident mode light scattering caused by polyethylene and polyproplyene vials allowed higher counting efficiency than glass vials. Highest coincident counting efficiency was from plastic minivials in a glass carrier vial. Increased solute concentration in samples caused increased counting efficiency due to changes in the refractive index of the solution. This can cause significant counting efficiency changes with no sample channel ratio change in density gradient fractions. The use of wavelength shifters is shown to be inappropriate when the sample pH varies, as this can change the fluorescent properties of the shifters and thereby the observed count rate.

Chlorine↗
PubMed2004

Liquid chromatography-accurate radioisotope counting and microplate scintillation counter technologies in drug metabolism studies.

The present study involves an analysis of the performance of liquid chromatography (LC)-accurate radioisotope counting (ARC) and microplate scintillation counter (TopCount) technologies in drug metabolism studies. For the purpose of evaluating these systems, biological samples resulting from the metabolism of a radiolabeled [14C] compound, known as compound B, are analyzed using LC-ARC and TopCount under similar high-performance LC conditions. Counting efficiency is 83% for LC-ARC, 77% for TopCount, and linearity is R2 of 0.9998 versus 0.9984, respectively. The limit of detection for LC-ARC is 12 disintegrations per minute (dpm) with 1-min/fraction counting, yet for TopCount it is 8.7 dpm with 5-min/fraction counting. Under optimal conditions for each, the total run time of LC-ARC is approximately half that of TopCount. These results indicate that there is no significant difference between these two systems in terms of efficiency, linearity, and limit of detection. However, the LC-ARC system does not involve any manual operations, yet TopCount requires manual sample transfer and data import. This study shows that impressive progress has been made in the technology of radioisotope counting in drug metabolism using LC-ARC. This system enhances the resolution of radiochromatograms and is able to measure volatile metabolites that TopCount cannot detect at all. The ability to acquire mass spectra online is also a major advancement. The overall results suggest that the combination of LC-ARC with radioactivity detection and mass spectrometry has great potential as a powerful tool for radioisotope measurement in metabolite identification studies during drug discovery and development.

Chromatography, Liquid↗
PubMed1985

Data transfer from Beckman LS 5800 liquid scintillation counters to IBM personal computers.

This communication describes a short routine in BASICA for the IBM-PC, written to collect data from a Beckman liquid scintillation counter. In the form presented here the routine converts incoming bytes into separate lines and saves these lines in a file. There are many possible applications for further use of the data in these files. A few suggestions are given as to the format in which data can be stored and how to process these data automatically after all samples have been counted. The only hardware needed is an asynchronous communications adapter for the IBM-PC and an RS232 cable.

Electronic Data Processing↗
PubMed1996

A comparison of four aqueous-miscible liquid scintillation cocktails with an alpha/beta discriminating Wallac 1415 liquid scintillation counter.

This work was directed towards an assessment of alpha/beta separation, alpha detection efficiency, energy resolution, quench sensitivity, and background count rate for four commercially available liquid scintillation cocktails using a Wallac 1415 liquid scintillation counter. The four cocktails were Wallac Oy OptiPhase HiSafe 3 and HiSafe 2, and Packard Ultima Gold AB and Ultima Gold XR. Aqueous radioactive solutions were prepared in 0.1 N HCl and contained 241Am (5.49 MeV alpha) and 90Sr/90Y (0.46/2.28 MeV beta-). The radioactive solutions were loaded into the cocktails at a ratio of 1 mL of aqueous solution to 10 mL of cocktail in 20 mL high-density polyethylene (HDPE) liquid scintillation vials. The effect of three levels of chemical quench on the various properties of interest was assessed for each of the LS cocktails. Alpha/beta discrimination was quantified by the fraction of beta interactions that "spillover" into the alpha window and vice versa, at the working discriminator setting. The working discriminator setting was defined as the point where the spillover of beta interactions into the alpha window and alpha interactions into the beta window were equal. For the low-quench samples, Ultima Gold AB had the lowest spillover (0.25%) and Ultima Gold XR had the highest spillover (0.8%). For the high-quench samples, the spillover ranged from 4% (HiSafe 3) to 10.5% (Ultima Gold XR). The detection efficiency for 241Am was nearly 100% and decreased with increased quench because of loss from spillover. HiSafe 2 gave the best energy resolution, 500 keV (FWHM), for the low-quench sample. The lowest background count rate was achieved with Ultima Gold AB, 0.056 cpm in the 241Am window, for a low-quench blank.

Alpha Particles↗
PubMed1997

Batch analysis of the ATP content of bovine sperm, oocytes, and early embryos using a scintillation counter to measure the chemiluminescence produced by the luciferin-luciferase reaction.

This report describes an approach to using a commercial luciferin-luciferase kit and a scintillation counter for batch analysis of the ATP content of bovine sperm, oocytes and embryos. After ATP extraction, the luciferin-luciferase assay mixture was added to as many as 48 samples at one time, and the tubes counted once, and then again, in reverse order. The square-root of the geometric mean of the two counts for a tube was directly proportional to the ATP content. The measured ATP content was directly proportional to the number of sperm, oocytes, or blastocysts in a sample. The assay is sensitive enough to measure the ATP content of a single oocyte or blastocyst, or approximately 1000 sperm. The assay does not require the complicated and expensive automated sampling and mixing apparatus that is required for batch analysis using luminometer counting. This approach may significantly simplify the determination of the ATP content of large numbers of samples.

Adenosine Triphosphate↗
PubMed1983

Bioluminescence assay of calcium with a liquid scintillation counter.

The luminescence produced by Ca aequorin reaction in dilute solutions decays exponentially over a relatively prolonged period of time. The concentration of total Ca and of free Ca in Ca-EGTA buffers could be determined by measuring the decay of luminescence in a liquid scintillation counter. The method is also suitable for determining total Ca concentration in small tissue samples.

Aequorin↗
PubMed1964

CALCIUM ABSORPTION IN MAN: BASED ON LARGE VOLUME LIQUID SCINTILLATION COUNTER STUDIES.

A technique has been developed for the in vivo measurement of absorption of calcium in man after oral administration of 1 to 5 microcuries of calcium-47 and continuous counting of the radiation in the subject's arm with a large volume liquid scintillation counter. The maximum value for the arm counting technique is proportional to the absorption of tracer as measured by direct stool analysis. The rate of uptake by the arm is lower in subjects with either the malabsorption syndrome or hypoparathyroidism. The administration of vitamin D increases both the absorption rate and the maximum amount of calcium absorbed.

Absorption↗
PubMed2000

Use of a microplate scintillation counter as a radioactivity detector for miniaturized separation techniques in drug metabolism.

In miniaturized separation techniques, such as capillary electrophoresis (CE) or capillary liquid chromatography (LC), conventional on-line radioactivity detection of labeled compounds is restricted, because of insufficient sensitivity. It will be shown that a microplate scintillation counter for 96-well plates (TopCount) can be used as a sensitive and easy-to-handle radioactivity detector for capillary LC and CE. The attractive combination of capillary LC, eluent fractionation, and subsequent off-line counting is described. The new method is applied for rapid and sensitive separation and detection of 3H-labeled parent drug and its metabolites at levels between 25 and 700 cpm in rat urine. The advantages of capillary LC coupled to the TopCount, and combined with LC-MS data, can be of benefit in many analytical areas, including the characterization of metabolites at low concentration within complex biological fluids. With the same setup, the fractionation with subsequent off-line counting is equally applicable to CE. This is demonstrated with electrophoretically separated 14C-labeled impurities, nicely resolved from a negatively charged main compound, at low levels.

Animals↗
PubMed1988

Firefly luciferase luminescence assays using scintillation counters for quantitation in transfected mammalian cells.

The firefly enzyme luciferase catalyzes the luminescent reaction of luciferin with ATP and oxygen. The luciferase gene has recently been cloned and proposed as a reporter gene in procaryotic and eucaryotic cells. We present here a luciferase activity assay which relies on luminescence detection using a standard scintillation counter. This technique is simple, fast, inexpensive, and still very sensitive: as little as 0.02 pg (250,000 molecules) of enzyme is readily detected. The technique is optimized for the luciferase assay in mammalian cell lysates. Thus, the luciferase gene may become a very useful tool for gene regulation studies.

Animals↗