Scintillation cocktail

Liquid scintillation counting is by far the most common method of detection and quantitation of -emission (12). This technique involves the conversion of the emitted P-radiation into light by a solution of a mixture of fluorescent materials or fluors, called the Hquid scintillation cocktail. The sensitive detection of this light is affected by a pair of matched photomultiplier tubes (see Photodetectors) in the dark chamber. This signal is amplified, measured, and recorded by the Hquid scintillation counter. Efficiencies of detection are typically 25—60% for tritium >90% for and P and... 

Add scintillation cocktail or other detection amplifying reagent Z510 Master Laboratory Station... 

Figure 5.5 Scintillants. A range of organic scintiilants is available with different solubility and emission characteristics, Scintillant cocktails or mixtures contain a primary scin-tillant such as PPO and often contain a secondary scintillant which absorbs the radiation produced by the primary scintillant and re-emits it at a longer wavelength, e.g, POPOP,...

FIGURE 7.11 Schematic for radiochemical detection of analytes labeled with beta-particle emitters. Radio-labeled analytes in the column effluent are mixed with scintillation cocktail to produce light, which is detected and measured by the paired photomultiplier tubes and relayed to a data acquisition system. 

Filter the samples on Whatman GF/C glass fiber filters, wetted with Soln. E, in a holder manifold and wash twice with 2 ml of ice-cold Soln. D. Transfer the filters into scintillation vials, add scintillation cocktail, and count for radioactivity. 

The scintillation cocktail chosen depends on the radioisotope and the type and amount of solvent containing the labeled compound. High-energy (3 emitting isotopes, such as 32-phophorus, are detectable by several methods such as liquid scintillation (Cerenkov... 

A lot of ready-to-use scintillation cocktails are available. Besides counting efficiency, chemical, biologic, and environmental hazards should be reflected when choosing a cocktail. Since vials and their contents are radioactive waste, number and volume of vials should be as small as possible. 

To illustrate the composition of liquid scintillation cocktails (LSC), some formulations follow. 

Figure 17.3—Counting system, a) Device used to measure the activity of a low-energy radioisotope using the method of two coincident detectors. A single ft emission can produce hundreds of photons. It is thus possible to measure photons in opposite directions using two photomultiplier tubes (PMT). Counting only occurs if both PMTs produce a signal that is not offset by more than a few nanoseconds b) device involving a PMT in a counting well used to measure luminescence produced by a sample that has been mixed with a scintillation cocktail (in aqueous or non-aqueous media).

Pseudocumene is used as a component in liquid scintillation cocktails for clinical analyses. Pseudocumene and durene are oxidized to trimel-litic anhydride and pyromellitic dianhydride, respectively. Mesitylene is a key building block for important antioxidants and agricultural chemicals. Prehnitene, isodurene, pentamethylbenzene, and hexamethylbenzene... 

Stop-Flow Mode The LC-ARC StopFlow controller performs two major functions. First, the controller maintains the back pressure during stop-flow data acquisition. This function is crucial for maintaining the shape and resolution of a peak. The second function is to deliver a liquid scintillation cocktail necessary for peak detection by the radiochemical detector. 

In subsequent work, it was shown that a renewable separation-column approach could be used to capture and purify "Tc on a TEVA-Resin column set up between a pair of 2-position valves, as shown in Figure 9.6.83 After loading the sample and washing away interferences, the separation material was released from the column and delivered downstream to a collection vial. Scintillation cocktail was added to the vial off-line and the "Tc was determined radiometrically. In this approach, there is no need to elute the "Tc with strong acid, and a fresh suspension of separation material is delivered to the column body for each sample. 

Effluent from each CFSTR was collected periodically in 7-mL scintillation vials filled with 5 mL of Beckman Ready Safe scintillation cocktail. The mass of effluent captured (approximately 0.5 mL) was quantified gravimetrically. The radioactivity of the samples was measured with a Packard Tri-Carb 1900CA liquid-scintillation analyzer, and the corresponding TCE concentrations were calculated with a standard curve relating concentration to counts per minute. The sampling periods lasted between 7 and 10 d. 

Transfer 0.5 ml of the combined extract to a fresh scintillation vial, evaporate the solvent, resuspend the residue in 0.25 ml methanol or ethanol, add scintillation cocktail, and count using a 3H, 14C dual-label program. 

A third way to avoid pigment interference is to use a biological oxidizer. This specialized apparatus burns samples (dried onto pieces of filter paper) and collects the 3H and 14C directly into separate scintillation cocktails as water and CO2, respectively. 

On-line detection can be classified as either homogeneous or heterogeneous. In the homogeneous system, the effluent is mixed with a liquid scintillation cocktail before passing through a flow cell that is positioned in a scintillation counter. In the heterogeneous system, the effluent passes through a flow cell packed with a solid scintillator. 

The reaction was stopped by adding 25 pi EDTA and 25 pi TCA (trichloroacetic acid). The reaction mixture was then spotted on ionic paper (DEAE paper). The paper was washed three times with TCA and then with ethyl alcohol. The filter paper was air dried and put into a scintillation vial with a scintillation cocktail. Radioactivity was measured by a liquid scintillation counter (Blue Star). As a counting control, a blank silver composition was run through the complete procedure without viral load, to check any potential interference in the scintillation counter method. 

---