Scintillation vials, disposal

Disposable electrodeposition cells are constructed from 20 ml polyethylene liquid scintillation vials with the bottoms cut off. The cap is replaced with a black plastic cap with a 1.6-cm hole in the top. A polished stainless steel disk is inserted into the cap with the polished side toward the inside of the vial and the cap is tightly screwed into place. The splatter guard is made from plastic test tube cap that is slightly larger than the scintillation vial and has a hole bored into it approximately 0.6 cm from the edge to allow the platinum wire anode to pass through. 

Cells are labeled in tissue culture (the use of multiwell plates is convenient for this type of experiments at least triplicates per each point of the experiment are prepared) by adding the desired amount of radioactivity, for the required length of time 0.5-1.0 /u.Ci/ml for long-term (24—40 h) labeling, 2.0-5.0 /rCi/ml for short (0.5-2 h) pulse labeling. At the end of the labeling time, the radioactive medium is removed, and the cell monolayers rinsed three times with ice-cold PBS. Both the medium and the washes have to be disposed of according to biosafety rules. Cell monolayers are then incubated at 4°C with ice-cold 10% TCA, for 15-30 min, to remove radioactivity present in the cells, not incorporated into DNA. Next, they are rinsed once with ice-cold 5% TCA, and finally they are solubilized with 0.5 M NaOH for several hours. The solubilized material is then transferred into scintillation vials, neutralized by the addition of HCl, diluted with at least 10 volumes of the scintillation cocktail. 

Electrodes and Instrumentation. Electrodes were mechanically polished with one micron diamond paste (Buehler) until satisfactory background voltammograms were obtained. A disposable, 20 ml scintillation vial served as a convenient, one-compartment electrochemical cell. 

Fig. 32 (179). Chemiluminescence assay of bovine erythrocuprein and different Cu2+-amino acid complexes at pJi 7.8. None Cu(Lys)2 50 nM Cu(His)a, 100 nM Cu-Tyr, 145 nM bovine erythrocuprein, 8 nM. The assay components were pipetted in a disposable scintillation vial at room temperature. The total volume was 2.22 ml. The assay mixture was composed of HEPES buffer, 50 mM xanthine, 0.33 mM catalase, 800 i.U. luminol, 1 mM The reaction was started with 0.08 units xanthine oxidase (definition as given by J. Cooper, P. A. Srere, M. Tabachnick and E. Rocker, Arch. Biochem. Biophys. 74 (1958) 306). The first reading was taken after 10 sec. During the counting the coincidence of the Packard scintillation counter was turned on. The background was 4 1 cpm...

If a cork-borer type sampler is available, push the tube through the material all the way, so that all layers of material are sampled. Some samplers are intended to be disposable. These should be capped and sent to the laboratory. If a non-disposable cork borer is used, empty the contents into a scintillation vial and send to the laboratory. 

Scintillation measurements are usually carried out using 20 ml standard vials, or 6 ml mini-vials equipped with screw caps. Disposable vials are available in polypropylene, polyester or polycarbonate. Glass vials, which must be of low potassium content because the naturally occurring 40K isotope is a /S emitter, can be re-used. Care should be taken that tbey do not get scratched. Cerenkov counting is usually carried out in 1 ml, 500 pi or 250 pi Eppendorf vials, placed either in special adaptors or in 20 ml standard vials. For accurate and reliable measurements, the positioning of the vials must all be the same, to ensure that the counting geometry with respect to the photomultiplier tube is identical. 

A liquid scintillation instrument does not only produce counts, but also radioactive waste. If we consider that an average instrument counts 20.000 samples per year using 200 liters of liquid scintillator, it produces more than this as waste. If the instrument uses 10 ml scintillator with 1 ml active sample and processes 20.000 experiments per year, it creates 220 liters of liquid and about 1.500 liters of solid waste from disposable plastic vials. Now the radioactive waste is usually destroyed by combustion, while earlier a considerable part of such aqueous - organic waste was poured into the regular sewage system. 

Today the handling of waste is covered in varying extent by governmental regulations in all countries, and is causing considerable waste treatment bills. The costs of disposal of the solid and liquid radioactive waste vary, but in many countries the disposal costs are close to the costs of scintillators. Also controversially today the disposable type of vial represents the majority of costs in the waste treatment. 

---