Liquid scintillation continuous

Hiraide et al. [68] used continuous flow coprecipitation-floatation for the radiochemical separation of cobalt from seawater. The 60cobalt activity was measured by liquid scintillation counting with greater than 90% yield and a detection limit of 5 fCi/1 seawater. 

Rackbeta 1216 and 1218 liquid scintillation counters (LKB Wallac, Turku, Finland). Counting was continued for 5 min or until 5000 counts. Statistical significance of the differences was tested using Mann-Whitney s U test. / <0.05 was considered to be a statistically significant difference. 

There are two ways to operate the stop-flow mode. The by-level mode, which is based upon the defined count zone(s), operates by signaling the instalment to continue running until a radioactive peak above a designated level is detected. The instrument will then stop and count the predefined fraction (in seconds), which is defined in the count zone. A second way to operate the stop-flow mode is the by-fraction mode. The instalment will stop and count every fraction (in seconds) within the predefined count zone, regardless of whether any radioactivity is detected or not. The fraction size in the stop-flow mode and the volume of liquid scintillant used for counting can be automatically calculated by the instalment or the parameters can be defined by the user. 

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). 

Fig. 4 Superfusion neurotransmitter release assay in synaptosomes. (a) Schematic drawing of a superfusion setup. Synaptosomes are preloaded with radioactive neurotransmitter and captured on fiberglass filters in superfusion chambers under continuous superfusion with gassed physiological salt solution (e.g., Krebs bicarbonate buffer) using a peristaltic pump. After a 10- to 15-minute wash, neurotransmitter release is triggered by rapid switching of superfusion lines to a stimulating buffer (e.g., high-potassium solution). Superfusate is collected on a fraction collector, and radioactivity is measured by liquid scintillation, (b) Typical trace recording of tritium-labeled norepinephrine fractional release in rat cortical synaptosomes stimulated by high potassium and a-latrotoxin in the presence or absence of external calcium.

These were attached to a fraction collector, whose timing mechanism was altered to allow continuous sampling of 28 separate diffusion cells with increased sample and timing capacity. Radiolabeled drugs were used and were measured in a liquid scintillation counter directly interfaced to a computer network. We describe the details of this system which enable us to conduct reproducible flow-through diffusion experiments, assay the samples, and analyze the data quickly and efficiently. 

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. 

PG release from the two delivery systems was monitored using an automated, in vitro diffusion cell system. The devices were clamped in vertical glass diffusion cells with the releasing surface of the system facing into the receptor chamber. The latter contained NaCl-Na citrate buffer and was continuously perfused at 10 ml/hr. Perfusate was collected hourly for up to 48 hours. The receptor phase of the diffusion cell was magnetically stirred and was kept at 37°C. Samples were analyzed by liquid scintillation counting. For each delivery system, 6 replicates were run and the data provided both cumulative PG released and PG release rate per unit time. 

After tritium electrolytic charging, tritium behavior in Mo-B alloys was measured by a liquid scintillation counter. Released characteristics of tritium in Mo-<0.02 ppm B and Mo-2.5 ppm B are shown in Fig. 3, analyzing continuously for three days from measurable start. Diffusible tritium was almost released nearly after two days. They became to a constant value after three days and non-diffiisible tritium of about 0.09 ppm was remained in specimens. 

Phosphatidylinositol turnover was assayed by incorporation of labeled inositol into phospholipids. A431 cells were preincubated in HEPES-buffered saline containing [ H]inositol at 37°C for 30 min. Then, test chemical and EGF were added, and the incubation was continued for 60 min. Subsequently, 10% trichloroacetic acid containing 0.01 M sodium pyrophosphate was added, and the acid-insoluble fraction was scraped off from the dish in H2O. The lipid was extracted from it by the addition of CHCI3 and CH3OH (1 1), and [3r]inositol-labeled lipids were counted by liquid scintillation spectrophotometry. 

Over the past several years Radiological Effluent Technical Specifications (RETS) have been implemented at nuclear power facilities in the United States. These RETS control the evaluation and release of radioactive material to the off-site environs. Radiological measurements of these releases are conducted using gamma spectroscopy, liquid scintillation, gross counting techniques and continuous on-line monitoring. 

The release point for the HCF ventilation system exhaust is the HCF exhaust stack. Gaseous effluent discharged in the ventilation system is continuously monitored. The monitor electronically records selected beta-gamma emitting radionuclides as well as noble gases. The system is calibrated and maintained by representatives of the SNL ES H Center and is discussed in Chapter 7. Liquid effluent from the LECS is sampled prior to release into the sanitary system. The samples are analyzed by gamma spectroscopy and liquid scintillation. No discharges to the sanitary system are allowed until analyses show that levels are within the established release limits.. ... 

The system presented here, allows continuous measurement of the radioactivity of C02 the gas is bubbled through a liquid scintillation cocktail enclosed in a special vial, which is placed directly in the detection chamber of a liquid scintillation counter. 

Radioactivity is measured by continuous gas flow liquid scintillation. To obtain specific activity the radioactivity is divided by the CO2 concentration measured with an infra-red cell results are recorded as the logarithm of specific activity versus time. 

MONITORING OF COLUMN EFFLUENTS FOR RADIOACTIVITY BY CONTINUOUS LIQUID SCINTILLATION COUNTING... 

The disposal of radioactive waste continues to be a problem. The additional complications created by the chemical toxicity of toluene, dioxane and other LSC solvents impose a problem of waste disposal which may soon place severe restrictions on research involving radioactive tracers, especially where radioactivity is measured by means of liquid scintillation counting. There is need for intelligent, decisive action on the part of regulatory agencies reflecting perspective, relevance and objectivity with regard to waste disposal. Such action must be taken soon. 

There will of course continue to be a place for radioisotope methodology, especially for dilution and activation analysis, and some of the radionuclides will continue to be measured to greatest advantage by liquid scintillation counting. 

More recently we have measured the turnover rate of lAA in tomato shoots after different incubation times, as part of a study of lAA biosynthesis in that tissue. lAA was supplied to the surface of the youngest leaf, 1 cm or longer, of excised shoots from twenty, 4-week-old tomato plants, as a 10 /xl drop (2 1 1, ethanol propan-2-ol H2O) containing 3711 Bq pH]IAA (1.11 GBq//xmol). Uptake was allowed for 2 h, surface radioactivity was then removed by several washes with 50% aqueous propan-2-ol followed with water, and the plants equilibrated for 1 h. After 0,4,10 or 20 h incubation in continuous light, lAA was extracted, purified, derivatised to form the pentafluorobenzyl ester [10] and the specific activity measured by liquid scintillation counting and GC-ecd. The purity and identity of selected samples was confirmed by combined GC-MS. 

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