Liquid scintillation fluid

Combustion methods are applied with very low radioactivities. HjO, COj and S02 can be determined either directly in the gas phase [243] or after trapping in liquid scintillation fluids. The enumeration of commercially available apparatuses for this purpose is beyond the scope of this review (see Refs. 244-250). 

Minimize the waste s hazards. Waste minimization methods specific to chemical, radioactive, or biological waste can be applied to multihazardous waste to mitigate or eliminate one hazard, which wOl then allow it to be managed as a single-hazard waste. For example, the substitution of nonignitable liquid scintillation fluid (LSF) for toluene-based LSF reduces a chemical-radioactive waste to a radioactive waste. 

Use of nonignitable scintillation fluid (e.g., phenylxylylethane, linear alkylbenzenes, and diisopropylnaphthalene) instead of flammable scintillation fluid (e.g., toluene, xylene, and pseudocumene). Liquid scintillation fluid that is sold as being "biodegradable" or "sewer disposable" is more appropriately labeled as "nonignitable" because biodegradability in the sanitary sewer can vary considerably with the local treatment facility. 

Liquid scintillation fluids Unisolve 1 (Koch-Light Laboratories, Colnbrook, Bucks., England), Instagel and Packard Emulsifier Scintillator No.299 (Packard Instrument Co. Inc., 2200 Warrenville Rd., Downers Grove, 111 60515). 

We solved the problem of isotope measurement in the effluent for HPLC by mixing coliamn effluent with liquid scintillation fluid and passing it through a hollow flow cell (Bakay, 1975a Bakay, 1975b Bakay, 1977). The quantitation of UV compounds and radioactivity was carried out simultaneously and was completed in 120 minutes. 

To assess rates of dissociation of previonsly bonnd radiolabeled nncleo-tides, ARDl (300 pmol in 450 /xl) was first stripped of bound nucleotides for 30 min at 30°. Incubation was then continned in the same medinm plus 10 mM MgCl2 and 3 /xM [ S]GDP (2 X lO dpm) or [ H]GDP (1.5 x lO dpm) for 40 min at 30° to allow nucleotide binding (total volume 600 1). A 100-/xl sample was transferred to a nitrocellulose filter which was washed, dried, and dissolved in liquid scintillation fluid for radioassay (zero time bound nucleotide). The remaining 500 /xl were diluted with 500 /xl of stripping buffer containing 2 mM GDP/ S or GDP and incubated at 30° with sampling at appropriate times for quantification of remaining bonnd nucleotide (Vitale et al., 2001). 

In the author s laboratory, the elution of radiolabelled samples is measured by liquid scintillation counting. Aliquots of collected fractions are mixed wtih OptiPhase Safe (LKB) liquid scintillation fluid using a maximum of 1 vol. of sample to 10 vols of scintillant. 

The lipids may be trapped directly in a liquid scintillation fluid continuously (Popjdk et al., 1959 Dutton, 1963) or in fractions (Dutton, 1963), and then counted. 

These two methods produce different release profiles in vitro. Figure 5 demonstrates the release kinetics of BCNU from wafers loaded with 2.5% BCNU pressed from materials produced using these two methods. The wafers containing tritiated BCNU were placed into beakers containing 200-ml aliquots of 0.1 M phosphate buffer, pH 7.4, which were placed in a shaking water bath maintained at 37 C. The shaking rate was 20 cycles/min to avoid mechanical disruption of the wafers. The supernatant fluid was sampled periodically, and the BCNU released was determined by liquid scintillation spectrometry. The BCNU was completely released from the wafers prepared by the trituration method within the first 72 hr, whereas it took just about twice as long for the BCNU to be released from wafers... 

Add scintillation fluid and determine radioactivity by liquid scintillation spectroscopy. 

Radioisotope Procedures. Radioactive volatile acids separated by Wiseman-Irvin chromatography were collected in 1 ml of 0.5N KOH. The aqueous fraction containing the acid was transferred to a scintillation vial and evaporated to dryness in a vacuum oven at 20 psi and 50 °C. The residue was redissolved in 0.1 ml distilled H2O before adding 4 ml of absolute ethanol and 15 ml of scintillation fluid 2,5-diphenyloxazole (PPO) and 0.01% 1,4-bis[2-(5-phenyloxazolyl)]benzene (POPOP) in toluene. Samples were counted in a liquid scintillation counter (Nuclear Chicago Corp.). 

Quantitate the radioactivity, as a measure of RT activity in 1 pL of the culture supernatant, either by liquid scintillation counting (cut out the spots and place them directly into scintillation fluid), by phosphorimage analysis and quantitation of relative pixel units, or by autoradiography and laser densitometry. 

In vitro and in vivo release kinetics were compared using two different approaches. In the first approach (the recovery approach) polymer implants containing a radioactively labeled substrate—,4C-labeled bovine serum albumin, /3-[14C]-lactoglobulin, or [3H]-inulin—were implanted subcutaneously into rates (in vivo) or released in phosphate-buffered saline, pH 7.4, at 37°C (in vitro). At various time points, the polymer implants were removed from the rats or the saline. They were then lyophilized to remove residual water and dissolved in xylene. When the polymer dissolved, the unreleased macromolecules precipitated to the bottom of the vial. Water was then added to dissolve the macromolecules scintillation fluid was next added, resulting in a homogeneous translucent emulsion which was counted via liquid scintillation. 

Assay. The standard assay mixture for determination of the activator consists of 1 nmol ganglioside Gmi, [ H]-labeled in the terminal galactose moiety ( 100,000 cpm), 5 mU p-galactosidase and up to 25 p,l of the suitably diluted activator sample, in a total volume of 50 jil of 50 mM citrate buffer, pH 4.5. The assays are incubated for 1 h at 37°C and then transferred to an ice-bath, and 1 ml of an ice-cold 1 mM galactose solution is added. The mixtures are loaded onto small (0.5—1 ml) columns of DEAE-cellulose (in Pasteur pipettes) that have been washed with distilled water. Liberated [ HJgalactose is washed out with 2 x 1 ml of 1 mM aqueous galactose solution, the combined effluents are collected in scintillation vials, and, after addition of 10 ml of scintillation fluid, their radioactivity is measured in a liquid scintillation counter. Blanks run with water instead of activator solution are subtracted. 

Thin layer chromatography. Chromatography on Brinkman silica gel plates was conducted with the solvent systems given in the appropriate tables. After development of the chromatogram, the position of C was determined by scraping the silica gel in 2 cm sections into scintillation vials. Scintillation fluid was added and the C was determined in a liquid scintillation spectrometer. 

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