Liquid-scintillation vials

Continuous automatic sampling is carried out from these cells into ordinary liquid scintillation vials by an ISCO brand (Lincoln, N.E.) Retriever III fraction collector whose timing mechanism has been altered so that nine timepoints can be sampled in intervals of up to 99.0 hours for 14 diffusion cells. 

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. 

The developed method generally follows the recommendations of the method RP515 from the U.S. D.O.E. A known volume of sample (500 mL) is acidified to 2 M HNO3. Sr tracer in O.IM HCl - ImM Sr(N03)2 is added to the sample to determine strontium recovery (activity between 10 and 20 Bq). Samples are filtered. Disk rinsing with 2 M HNO3 and dionized water eliminates possible interfering radioisotopes. Sr is then eluted with 6 mL of 0.025 M sodium EDTA (pH=l 1). 5 mL of the 6 mL of eluate are transferred in a liquid scintillation vial. These are counted at Sr/ Y equilibrium (about 3 weeks) after scintillation cocktail adding. 

To this end Ting and Helman (1972b) describe a mini liquid scintillation vial which allows the use of only 1 to 4 ml of scintillator rather than the 15-ml volvime used in the standard vial. Small vials of this type are now commercially available from a number of manufacturers. 

If the activity of the precipitate is to be measured the supernatant is discarded and the "last" drop is blotted from the lip of the tube. If, on the other hand, the supernatant is to be counted by liquid scintillation counting it must be transferred to a counting vial. Femandez-Pol (1975) suggests a modified liquid scintillation vial to allow transfer of the "last" drop by touching the lip of the tube to a small protuberance in the vial. 

The main difficulty in designing a satisfactory radiochemical assay for use in pharmacological assay is the separation of substrate and product. Once this can be achieved with simplicity, reliability, and speed, the whole assay procedure possesses a specificity and sensitivity unequalled by other methods. A laboratory with the necessary counting equipment and computing facilities to handle a large number of liquid scintillation vials has, in fact, a substantial capability for enzyme estimations. There are a number of general procedures applicable to more than one enzyme. Since they have not been published in a collected form elsewhere, they are listed below. 

Separate solid and liquid wastes. Radioactive wastes must be separated into solids (absolutely no liquids are permitted) and liquids. Liquid wastes must be kept separate according to chemical reactivity. For example, do not mix wastes containing acids with liquids containing bases, and do not mix aqueous liquids with organic liquids. Keep flammable organic solvent radioactive wastes in safety cans. Animal carcasses and liquid scintillation vials are also kept separate. 

E) turntable collecting tray whidi holds 24 liquid scintillation vials (F) start button (G) stop button. 

Uniformly labeled C-8-D with a specific activity of 2.99 juc/mg was administered orally to pregnant females at 2 /xg/kg/day from 6-15 days of gestation. Three females were sacrificed on alternate days during days 6-20 of pregnancy. Triplicate samples of fetus, placenta, blood, brain, abdominal fat, and sartorius muscle were procured from each female. The samples were dissolved in 1 ml of Soluene (Packard Instruments) to which 15 ml of Aquasol were added. Each sample vial was counted for 30 min in a Nuclear Chicago Mark I liquid scintillation counter. 

The activity of the polymers was determined in toluene solution with Koch-Light KL.356 xylene-based scintillator in 4 ml glass vials, at an efficiency of 24% for tritium and 75% for 14C by means of an IDL liquid scintillation counter type 6012. 

The contents of the scintillation vial are mixed thoroughly, and the radioactivity is measured in a Liquid Scintillation Counter for 10 minutes,... 

To extract the liberated fatty acids, 1.5 ml of 0.1 mM carbonate-bicarbonate buffer, pH 10.5 is added and the mixture is shaken for 10 s. Centrifugation for 45 min at 1500 xgin a swing-out rotor will separate the water from the lower organic phase. In a scintillation vial, 2 ml of the upper water phase are mixed with 50 pi of glacial acetic acid containing 500 pg ferric acid before the scintillation liquid is added (16 ml of Ecoscint toluene (7 1 volume). Liquid scintillation counting is done for 5 min and the LPL activity is calculated from the difference in counts between the blank and the sample vials [40]. 

The lowest Y value obtainable using the above-mentioned liquid scintillation counting systems is limited by the volume of the vial used (25 ml.). For lower Y values, a larger volume is necessary (3, 7). To determine the optimum volume, a system was designed as shown in Figure 1. A Teflon tube with a 5-cm. internal diameter was used as the container and reflector. Two Teflon sheets (0.3-mm. thick) closed both ends of the tube by two O-rings and two aluminum devices pressed... 

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. 

Sampling and Measurements. The determination of dissolved actinide concentration was started a week after the preparation of solutions and continued periodically for several months until the solubility equilibrium in each solution was attained. Some solutions, in which the solubilities of americium or plutonium were relatively high, were spectrophotometrically analyzed to ascertain the chemical state of dissolved species. For each sample, 0.2 to 1.0 mL of solution was filtered with a Millex-22 syringe filter (0.22 pm pore size) and the actinide concentration determined in a liquid scintillation counter. After filtration with a Millex-22, randomly chosen sample solutions were further filtered with various ultrafilters of different pore sizes in order to determine if different types of filtration would affect the measured concentration. The chemical stability of dissolved species was examined with respect to sorption on surfaces of experimental vials and of filters. The experiment was performed as follows the solution filtered by a Millex-22 was put into a polyethylene vial, stored one day, filtered with a new filter of the same pore size and put into another polyethylene vial. This procedure was repeated twice with two new polyethylene vials and the activities of filtrates were compared. The ultrafiltration was carried out by centrifugation with an appropriate filter holder. The results show that the dissolved species in solution after filtration with Millex-22 (0.22 ym) do not sorb on surfaces of experimental materials and that the actinide concentration is not appreciably changed with decreasing pore size of ultrafilters. The pore size of a filter is estimated from its given Dalton number on the basis of a hardsphere model used in the previous work (20). 

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. 

The concentration was further corrected for radiochemical purity according to the manufacturer s specifications because liquid scintillation counting measures the total sample activity and does not account for the presence of radiolabeled impurities. Stock solutions were stored at -15°C or -20° C in order to minimize sample loss due to hydrolysis. Injected sample solutions were prepared in 0.25 mL plastic vials by diluting stock solutions with buffer or deionized water and were also stored at -15° C or -20° C. 

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