Scintillation counting equipment

I A submerged cell-holding device Scintillation counting equipment (for p/y emissions)... 

Several companies producing scintillation counting equipment, e.g., Nuclear Chicago, Intertechnique, Packard, Picker Nuclear and Beckman, offer flow cell conversion kits. Unfortunately, these cells and also those described in the literature discussed in the review papers mentioned above, have cell volumes from 0.5 to 4 ml, which makes them unsuitable for use in combination with high-performance liquid chromatographic columns. 

Other methods suggested for counting these gamma isotopes in liquid scintillation counting equipment have a number of drawbacks, such as ... 

There are a number of techniques available to extract ATP from cells. Some use trichloroacetic acid (TCA), which also aids in stabilizing the molecule. TCA has a good extraction capacity, is relatively quick, has a reduced potential for human error, and does not discriminate between the different microbiological fractions of activated sludge. Luminescence produced in the luciferin-luciferase reaction can be measured using scintillation counting equipment or a range of luminometers currently on the market. 

The counting equipment used to establish quantitation is radioassay and radioimmunoassays may be either a gamma counter or a liquid scintillation counter depending upon the isotope being used. Most assays use as a label and require a... 

Analytical Methods. Liquid scintillation counting (LSC) was done using Packard Models 3375 and 3380 Liquid Scintillation Spectrometers equipped with automatic external standards. Solid samples were combusted in a Packard model 306 Sample Oxidizer prior to LSC analysis. 

As shown in Figure 3, our detectors came equipped with a cylindrical plastic cell about the size and shape of a scintillation counting vial into which a U-shaped tube had been drilled. When this cell has been packed with scintillation grade anthracene a flow cell quite satisfactory for aqueous systems is obtained. 

Since the fast centrifuge system SISAK is equipped with liquid scintillation counting LSC [12,58], it is in principle capable of investigating short-lived a-decaying nuclides of the transactinides, p/y pulses and a pulses are distinguished by pulse-shape discrimination PSD and pile-up pulses are rejected by a pile-up rejection system PUR. This analog electronics proved to result in insufficient background suppression. Thus, two new approaches... 

Cell harvesters were developed to capture multiple samples of cells on membrane filters, wash away unincorporated isotopes, and prepare samples for liquid scintillation counting on special equipment developed to process and count multiple samples. Despite miniaturization and improvements in efficiency of this technique, the disadvantages of multiple liquid handling steps and increasing costs for disposal of radioactive waste materials severely limit its usefulness. Although specific applications require measuring DNA synthesis as a marker for cell proliferation, much better choices are available for detecting viable cell number for HTS. 

Determination of Radioactivity. All samples were counted in a Nuclear Chicago Isocap 300 liquid scintillation counter equipped with a Teletype computerized for direct calculation of disintegrations per minute. Fifty microliters of blood were directly counted for radioactivity after solubilization (1 mL of 1 N NaOH). After incubation at room temperature for 15 min the sample was decolorized by adding 200 fxL of hydrogen peroxide and incubating at 80°C for 30 min. The processed samples were mixed with 100 fxL of 80% acetic acid and 15 mL of Insta-gel (Packard), and were counted. Approximately 60-100 mg of tissue were solubilized following the same method as for blood. From the collected urine an aliquot (2 mL) was counted directly with 15 mL Insta-gel. The feces were dried overnight at room temperature, and a 60-100-mg aliquot was combusted (12) and counted for radioactivity. 

Chemiluminescence (CL) was measured on all samples Immediately after plasma irradiation and before exposure to air or moisture and again after exposure to room air. CL in counts per min (CPM) was determined in a Packard 3255 liquid scintillation spectrometer equipped with low dark-noise photomultiplier tubes (RCA 4501/V4) and a Parkard 585 linear recorder. 

Automated sample-changing equipment has been available commercially for many years. In liquid scintillation counting (LSC) systems, several hundred vials may be placed in a train (see Section 8.5.2) for dark adaptation to allow decay of delayed... 

Planar radiochromatography was the first widely used technique for separation and detection of radiolabeled metabolites (Veltkamp, 1990). The technique is very sensitive, fast, and has relatively low equipment and operating costs, however, due to low separation resolution and poor precision in quantification, it has largely been replaced by HPLC-based radiochromatographic techniques in the pharmaceutical industry. Online radio flow detection (RED) and off-line liquid scintillation counting (ESC) have been routinely used for analysis of radiolabeled metabolites for the last 15 years (Veltkamp, 1990). 

As we have seen there are several ways and methods for sample preparation for radioactivity measurements by liquid scintillation counting. Depending on the isotope and on the physico-chemical properties of the labelled compounds, as well as on the available laboratory equipment it is necessary to select and adjust the most suitable sample preparation method for each analytical problem. Further methodological research will certainly provide more and better techniques. But still each user of liquid scintillation procedures has to innovate and optimize his specific sample preparation method. 

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