Ultima Gold Research Articles

Electrokinetic removal of radionuclides contained in scintillation liquids absorbed in soil type Phaeozem

Control samples of scintillation liquids – Phaeozem soil mixtures were prepared with different scintillation liquids as the support electrolyte, Install Gel® XF, (Ultima Gold AB™ and Ultima Gold XR™), to construct the polarization curves, and to select the cell potential with the highest mass transfer to remove 24Na (15 h) and 99mTc (6 h) as radiotracers from polluted Phaeozem soil. During the electrokinetic treatment (EKT), the removal of radionuclides contained in scintillation liquids absorbed in Phaeozem soil, liquid phase was characterized by Gas Chromatography coupled with a Flame Ionization Detector (GC-FID) and Fourier Transform Infrared Spectrometry (FTIR), solids by FTIR, before and after the application of cell potential. In this sense, the support electrolyte was selected based on the highest current generated (1 mA), as in the case of scintillation liquid 50% Ultima Gold XR™ + 50% Water (1:1), which was used for 6 h in the presence of a mesh and a titanium rod, as anode and cathode, respectively. Finally, the removal percentage accumulated in the liquid phase after the EKT of Phaeozem soil polluted by 99mTc was 61% close to the anode after 4 h. It was also 61% for 24Na close to cathode after 2 h, and after 4 h it was 71.8%.

Determination of 107Pd in radwaste using Ni ®Resin

A simple separation method for determination of 107Pd employing Ni ®Resin was established. Suitable conditions for Pd separation were tested. Palladium was adsorbed on Ni ®Resin from 0.5 mol L−1 HCl and eluted with 8 mol L−1 HNO3 with recoveries higher than 70 % determined by atomic absorption spectrometry. The method was applied for analysis of evaporator concentrate and radioactive sludge samples from nuclear power plants in Slovak Republic. In all analyzed samples were activity concentrations of 107Pd below minimum detectable activity. 107Pd was measured on liquid scintillation counter (TRICARB 2900/TR) using Ultima Gold AB scintillation cocktail.

Micellar phase boundaries under the influence of ethyl alcohol

The Compton spectrum quenching technique is used to monitor the effect of ethyl alcohol (EtOH) additions on phase boundaries in two systems. In toluenic solutions of the nonionic surfactant, Triton X-100, EtOH shifts the boundary separating the first clear phase from the first turbid phase to higher water:surfactant ratios. In a commonly used scintillant, Ultima Gold AB, the critical micelle concentration is not shifted. The molecular interactions behind the observations and implications for liquid scintillation counting are discussed.

Liquid scintillation counting methodology for (99)Tc analysis: a remedy for radiopharmaceutical waste.

This paper presents a new approach for liquid scintillation counting (LSC) analysis of single-radionuclide samples containing appreciable organic or inorganic quench. This work offers better analytical results than existing LSC methods for technetium-99 ((99g)Tc) analysis with significant savings in analysis cost and time. The method was developed to quantify (99g)Tc in environmental liquid and urine samples using LSC. Method efficiency was measured in the presence of 1.9 to 11 900 ppm total dissolved solids. The resultant quench curve proved to be effective for quantifying spiked (99g)Tc activity in deionized water, tap water, groundwater, seawater, and urine samples. Counting efficiency was found to be 91.66% for Ultima Gold LLT (ULG-LLT) and Ultima Gold (ULG). Relative error in spiked (99g)Tc samples was ±3.98% in ULG and ULG-LLT cocktails. Minimum detectable activity was determined to be 25.3 and 22.7 mBq for ULG-LLT and ULG cocktails, respectively. A preconcentration factor of 1000 was achieved at 100 °C for 100% chemical recovery.

The effect of sample stability on the determination of radioactivity for various radionuclides by liquid scintillation counting

For measuring a sample stored for a long period of time using liquid scintillation counting (LSC), it is necessary to study the long-term stability of the sample. The effect of sample stability on the determination of radioactivity for 241Am, 90Sr/90Y, 137Cs, 147Pm, 237Np/233Pa, and 3H by LSC has been investigated. The variation of quench level over time can be an indication of sample stability. If the variation in a sample is little, the effect of sample stability on the determination of the above radionuclides can be neglected. Otherwise, the sample stability will have impact not only on the counting efficiency (especially for low energy β emitters), but also on the results of α/β discrimination. For studying the stability of a sample, special attention should be paid to the radionuclides with chemical form apt to be adsorbed, because the quench level of a sample cannot be reflected by the quench index SQP(E) alone when significant physical quench exists. Shaking a sample stored for a long period of time and checking the LSC spectra can give the information on physical quench in the sample. In the range of this study, OptiPhase Hisafe 3 has much better quench resistance than Ultima Gold AB.

Validation of a method for measuring 226Ra in drinking waters by LSC

A simple method for measuring 226Ra in drinking waters has been validated and validation parameters are provided. It is based on the measurement by LSC of 222Rn, at equilibrium with 226Ra, which is absorbed into a water immiscible scintillation cocktail (Ultima Gold F) inside the counting vial. The validated application field ranges between the detection limit (2·10−3Bq/kg) to 150Bq/kg. The method has proven to be reliable, effective and suitable for wide-range measuring campaigns. A summary of results obtained in recent years is also given.

Radionuclide, scintillation cocktail and chemical/color quench influence on discriminator setting in gross alpha/beta measurements by LSC

Gross alpha/beta measurements in drinking waters enable radiochemical composition analysis in environmental studies providing efficient screening method that can indicate whether water contains elevated levels of any radionuclide. Routine gross alpha/beta activity monitoring in drinking waters has been carried out for a few years in laboratory for low-level radioactivity measurements in Novi Sad according to ASTM method, performing measurements on liquid scintillation counter Quantulus 1220 which can simultaneously generate alpha/beta spectra of samples by Pulse Shape Analysis (PSA circuit). In this paper, PSA discriminator impact was investigated to ensure obtaining of accurate and reliable alpha/beta activities. One novelty of presented work is PSA parameter setup with two combinations of radionuclides (241Am, 226Ra and 90Sr/90Y) with varying activity concentrations. Performed experiments also make contribution to investigations on the manner in which chemical and color quench affect optimal PSA parameter setting and further on, their altogether influence on gross alpha/beta activity measurements. Nitromethane, 15.8 M nitric acid and water, as well as yellow and yellow-orange dye, were used as quenching agents in order to test PSA/interference factor behavior in the presence of quenchers with different quenching strengths. Variation of PSA setting in quenched samples with two different commercially available cocktails (Ultima Gold LLT and OptiPhase HiSafe 3) was also tested. Lastly, application i.e. assessment of obtained PSA-SQP(E) correlation on the obtained results of activity concentrations of few artesian well water samples and colored spiked samples, based on the measured SQP(E) value of samples, has been demonstrated.

Electrokinetic Removal of Na-24 and Tc-99m Scintillation Liquid Content Absorbed in Soil Type Phaeozem

The application of radioisotopes in medicine and research generates radioactive waste. A large part of these wastes are composed by scintillation liquid (mixtures of solvents -toluene, xylene-, fluorescent materials and surfactants) contaminated with radioisotopes such as H-3 (12.3 y), C-14 (5730 y), U-238 (4.468x109 y), Th-232 (1.41x1010 y), Tl-204(3.7 y) or Na-22 (2.6 y), etc.. In the 80's, these wastes were absorbed on soil to covert it to a less hazardous form during interim storage. However this treatment was only a temporary solidification strategy and these wastes have to re-treated and conditioned. Therefore, the objective of this work is to assess the electrokinetic removal of Na-24 and Tc-99m contained in liquid scintillation absorbed on soil types Phaeozem.To define the experimental conditions of the electrokinetic treatment for the radioactive wastes previously described, control samples of liquid scintillation-soil mixtures were prepared with different scintillation liquid (INSTALL GEL ® XF, ULTIMA GOLD ABTM and Ultima Gold XR™) as support electrolyte and constructed the polarization curves, to select the potential with the highest mass transfer. Liquid phase was characterized by Gas Chromatography and Infrared (IR) Spectrometry, solids by IR and electrodes by Scanning Electronic Microscopy (SEM), before and after the application of potential. From polarization curves, the experimental conditions following were chosen in the sodium and technetium removal: working electrodes, meshes and rod of titanium, anode and cathode, Ultima Gold scintillation liquid XRTM:Water (1:1), step current 1 mA for 6 h. Subsequently radioactive control samples were prepared with soil-scintillation liquid Ultima Gold XRTM:Water (1:1), labeled with Na-24 or Tc-99m to determine the removal efficiency of these radioisotopes. Na-24 was chosen, instead of Na-22, by its short half-life (15.03 h) to facilitate handling of samples and reduce the radiation hazards involved in using Na-22 (2.6 y). In the case of Tc-99m, it is not adsorbed in the medium analyzed, and was used as a standard. The Na-24 and Tc-99m were quantified on a Gamma Spectrometer constituted by a Germanium Hyperpure detector connected to a multichannel card, in 140.5 keV and 1368.6 keV for Tc-99m and Na-24 respectively, at a fixed geometry., The liquid and solid phases were analyzed, as well as the electrodes, by the same analytical techniques mentioned previously, once both radiotracers decayed.From six supports electrolytes studied, three have not a diffusion current stable and three show a diffusion current plateau in 0.4 mA, 0.6 mA and 1 mA. It was chosen the support electrolyte with the higher current passage (1mA): scintillation liquid Ultima Gold XRTM:Water (1:1). According to IR analysis, soils not present any deterioration and in the liquid phase the amount of water increases, as the applied potential increases. The liquid phase chromatograms indicate that some compounds were modified in 5-7 V. The kinetic study of Tc-99m shows that 15% of Tc-99m is removed each hour near the anode, this value increasing to 20% in 4 hours. In the case of Na-24, a treatment for 4 h produces a diminution around 7% of the functional group -C=N- in the liquid phase, which corresponds to 2,5-Diphenyl-Oxazole and 2-Amino-5-choropyrimidine.

Nitromethane and other quenching agents used to determine the tritium activity concentration by liquid scintillation spectroscopy

The quenching properties of nitromethane, nitric acid, acetone and saturated solutions of chloroform, carbon tetrachloride, dichloro-methane, and a blend of carbon tetrachloride and chloroform mixed with an Ultima Gold uLLT liquid scintillation cocktail were investigated by using a Quantulus 1220 as well as TRICARB 2800TR liquid scintillation counters. With respect to all investigated quenching agents, nitromethane showed higher quenching action and solubility as well as a remarkable time stability. The implications of this finding for further routine tritium determinations are presented and discussed.

Experimental study of the influence of the counter and scintillator on the universal curves in the cross-efficiency method in LSC

The cross-efficiency method in LSC is one of the approaches proposed for the extension of the Système International de Référence (SIR) to radionuclides emitting no gamma radiation. This method is based on a so-called “universal cross-efficiency curve”, establishing a relationship between the detection efficiency of the radionuclide to be measured and the detection efficiency of a suitable tracer. This paper reports a study at LNHB on the influence of the scintillator and of the LS counter on the cross-efficiency curves. This was done by measuring the cross-efficiency curves obtained for 63Ni and 55Fe vs. 3H, using three different commercial LS counters (Guardian 1414, Tricarb 3170 and Quantulus 1220), three different liquid scintillator cocktails (Ultima Gold, Hionic Fluor and PicoFluor 15 from Perkin Elmer®), and for chemical and colour-quenched sources. This study shows that these cross-efficiency curves are dependent on the scintillator, on the counter used and on the nature of the quenching phenomenon, and thus cannot definitively be considered as “universal”.

Fructose–Maltodextrin Ratio Governs Exogenous and Other CHO Oxidation and Performance

Fructose coingested with glucose in carbohydrate (CHO) drinks increases exogenous-CHO oxidation, gut comfort, and physical performance. This study aimed to determine the effect of different fructose-maltodextrin-glucose ratios on CHO oxidation and fluid absorption while controlling for osmolality and caloricity. In a crossover design, 12 male cyclists rode 2 h at 57% peak power then performed 10 sprints while ingesting artificially sweetened water or three equiosmotic 11.25% CHO-salt drinks at 200 mL·15 min, comprising weighed fructose and maltodextrin-glucose in ratios of 0.5:1 (0.5 ratio), 0.8:1 (0.8 ratio), and 1.25:1 (1.25 ratio). Fluid absorption was traced with D2O, whereas C-fructose and C-maltodextrin-glucose permitted fructose and glucose oxidation rate evaluation. The mean exogenous-fructose and exogenous-glucose oxidation rates were 0.27, 0.39, and 0.46 g·min and 0.65, 0.71, and 0.58 g·min in 0.5, 0.8, and 1.25 ratio drinks, representing mean oxidation efficiencies of 54%, 59%, and 55% and 65%, 85%, and 86% for fructose and glucose, respectively. With the 0.8 ratio drink, total exogenous-CHO oxidation rate was 18% (90% confidence interval, ±5%) and 5.2% (±4.6%) higher relative to 0.5 and 1.25 ratios, respectively, whereas respective differences in total exogenous-CHO oxidation efficiency were 17% (±5%) and 5.3% (±4.8%), associated with 8.6% and 7.8% (±4.2%) higher fructose oxidation efficiency. The effects of CHO ratio on water absorption were inconclusive. Mean sprint power with the 0.8 ratio drink was moderately higher than that with the 0.5 ratio (2.9%; 99% confidence interval, ±2.8%) and 1.25 ratio (3.1%; ±2.7%) drinks, with total- and endogenous-CHO oxidation rate, abdominal cramps, and drink sweetness qualifying as explanatory mechanisms. Enhanced high-intensity endurance performance with a 0.8 ratio fructose-maltodextrin-glucose drink is characterized by higher exogenous-CHO oxidation efficiency and reduced endogenous-CHO oxidation. The gut-hepatic or other physiological site responsible requires further research.

An alternative method of OBT measurement for the limited quantity of environmental samples using a combustion bomb

The measurement of organically bound tritium (OBT) in environmental samples is much more difficult than the measurement of tritiated water (HTO). This study describes an alternative method for OBT determination in plant materials in which tritium-free polyethylene beads are added to the plant sample prior to combustion in a combustion bomb. It is not always possible to collect large enough amounts of some plants (e.g. algae, plankton, grass) within a specific area or specific period. Excellent water recovery is achieved when dry plant materials are combusted with polyethylene beads. When Ultima Gold AB is used as the scintillation cocktail, it is possible to measure the combustion water directly without distillation. Correction factors were derived for the plants used in the study to account for the dilution of the combustion water due to addition of the polyethylene beads. The alternative method has a number of advantages, including an increased yield of combustion water for liquid scintillation counting, less color quenching, reduced sample size and decreased analysis time. Finally, accuracy tests comparing results of the conventional method with those of the alternative method were carried out using environmental samples.

Impact of Al and Fe on the development of phenanthrene catabolism in soil

Heavy metals often occur as co-contaminants with polycyclic aromatic hydrocarbons (PAHs) and reportedly have adverse effects on biodegradation. In this study, the development of 14C-phenanthrene mineralisation in soil co-contaminated with aged or freshly added Al or Fe amendment was assessed. 14C-phenanthrene mineralisation was assessed using respirometry; respirometers incorporated a Teflon-lined screw-capped CO2 trap containing 1-M NaOH within a glass scintillation vial. The production of 14CO2 was assessed by the addition of Ultima Gold liquid scintillation fluid to the CO2 traps and subsequent liquid scintillation counting. Enumeration of phenanthrene-degrading bacteria was achieved by counting the colony forming unit count using the spread plate method. This investigation considered the effects of Al and Fe (50, 100, 250 and 500 mg/kg) on 14C-phenanthrene biodegradation in soil over 63-day contact time. Fresh Al amendments at lower concentrations (50 and 100 mg/kg) stimulated phenanthrene catabolism (p <0.05) at t = 21 and 42 days which may reflect an ‘Arndt–Schulz’ effect, but phenanthrene catabolism was significantly reduced (p <0.05) in 500 mg/kg aged Al this could be due to Al toxicity to phenanthrene degraders. Phenanthrene mineralisation was stimulated in the highest Fe concentration (500 mg/kg) in aged and fresh Fe amendments at t = 21 days. This could be because Fe is an essential requirement for microbial growth. The impact of Al or Fe on the catabolism of 14C-phenanthrene was dependent on incubation time and Al was more toxic than Fe to soil PAH catabolic activity. This could be because Al is a non-essential microbial requirement. Bioremediation of soils co-contaminated with PAH and heavy metal is a complex problem; therefore, studies on the impact of metals on PAHs biodegradation highlight the risks and biodegradation potential in contaminated soil.

Simultaneous determination of gross alpha, gross beta and 226Ra in natural water by liquid scintillation counting

The determination of gross alpha, gross beta and 226Ra activity in natural waters is useful in a wide range of environmental studies. Furthermore, gross alpha and gross beta parameters are included in international legislation on the quality of drinking water [Council Directive 98/83/EC].1 In this work, a low-background liquid scintillation counter (Wallac, Quantulus 1220) was used to simultaneously determine gross alpha, gross beta and 226Ra activity in natural water samples. Sample preparation involved evaporation to remove 222Rn and its short-lived decay daughters. The evaporation process concentrated the sample ten-fold. Afterwards, a sample aliquot of 8 mL was mixed with 12 mL of Ultima Gold AB scintillation cocktail in low-diffusion vials.In this study, a theoretical mathematical model based on secular equilibrium conditions between 226Ra and its short-lived decay daughters is presented. The proposed model makes it possible to determine 226Ra activity from two measurements. These measurements also allow determining gross alpha and gross beta simultaneously. To validate the proposed model, spiked samples with different activity levels for each parameter were analysed. Additionally, to evaluate the model's applicability in natural water, eight natural water samples from different parts of Spain were analysed. The eight natural water samples were also characterised by alpha spectrometry for the naturally occurring isotopes of uranium (234U, 235U and 238U), radium (224Ra and 226Ra), 210Po and 232Th. The results for gross alpha and 226Ra activity were compared with alpha spectrometry characterization, and an acceptable concordance was obtained.

Neutron-gamma discrimination with UGAB scintillator using zero-crossing method

The new-type scintillator, Ultima Gold Alpha-Beta (UGAB), was studied for its neutron-gamma discrimination capability. The figure-of-merit and peak-to-valley values for the neutron-gamma discrimination spectra of UGAB scintillator when exposed to (241)Am-Be neutron source were presented. The results show that this new-type scintillator can efficiently be used in neutron-gamma discrimination experiments.

The long-term stability on basic performances of a diisopropylnaphthalene-based liquid scintillation cocktail

The long-term stability of a cocktail is very important for liquid scintillation counting. The expiry date of a cocktail labeled on the container is usually one to three years later than the manufacture date, which is fairly short for the convenience of purchase, storage and use. Three batches of a diisopropylnaphthalene-based aqueous-miscible cocktail, Ultima Gold AB, with a span of 18 years of storage, have been compared on their basic performances, i.e. background count rate, counting efficiency, quench resistance, and α/β discrimination. We found that the 18-year storage has less impact on the basic performances than batch-to-batch variability in cocktail compositions, which means Ultima Gold AB has very good long-term stability. Therefore, in practice Ultima Gold AB can be used even beyond its expiry date, if it is properly stored for less than 18 years. This result will bring much convenience to plan the purchase, storage and use of the cocktail. In addition, the influence of statistical fluctuations on the quench parameter SQP(E) has been studied.

Activity standardisation of 45Ca and 204Tl using the new TDCR system at CMI

A new triple-to-double coincidence ratio (TDCR) system has been established at CMI as an additional technique for primary activity standardisation. Details of the detectors and the electronics are given. Construction of the optical chamber was validated using measurement of a 3H standard—the efficiency achieved with Ultima Gold was 58%. Several methods of efficiency variation (coloured bands painted on vial, positioning and photomultipliers defocussing) are compared. Activity concentrations of 204Tl and 45Ca were determined with the TDCR method and with the efficiency tracer technique. Advantages of the TDCR method compared to the efficiency tracing method and agreement between results are shown.

Application of TDCR-Geant4 modeling to standardization of 63Ni

As an alternative to the classical TDCR model applied to liquid scintillation (LS) counting, a stochastic approach based on the Geant4 toolkit is presented for the simulation of light emission inside the dedicated three-photomultiplier detection system. To this end, the Geant4 modeling includes a comprehensive description of optical properties associated with each material constituting the optical chamber. The objective is to simulate the propagation of optical photons from their creation in the LS cocktail to the production of photoelectrons in the photomultipliers. First validated for the case of radionuclide standardization based on Cerenkov emission, the scintillation process has been added to a TDCR-Geant4 modeling using the Birks expression in order to account for the light-emission nonlinearity owing to ionization quenching. The scintillation yield of the commercial Ultima Gold LS cocktail has been determined from double-coincidence detection efficiencies obtained for 60Co and 54Mn with the 4π(LS)β−γ coincidence method. In this paper, the stochastic TDCR modeling is applied for the case of the standardization of 63Ni (pure β−-emitter; Emax=66.98keV) and the activity concentration is compared with the result given by the classical model.

Molecular Identification of β-Citrylglutamate Hydrolase as Glutamate Carboxypeptidase 3

β-Citrylglutamate (BCG), a compound present in adult testis and in the CNS during the pre- and perinatal periods is synthesized by an intracellular enzyme encoded by the RIMKLB gene and hydrolyzed by an as yet unidentified ectoenzyme. To identify β-citrylglutamate hydrolase, this enzyme was partially purified from mouse testis and characterized. Interestingly, in the presence of Ca(2+), the purified enzyme specifically hydrolyzed β-citrylglutamate and did not act on N-acetyl-aspartylglutamate (NAAG). However, both compounds were hydrolyzed in the presence of Mn(2+). This behavior and the fact that the enzyme was glycosylated and membrane-bound suggested that β-citrylglutamate hydrolase belonged to the same family of protein as glutamate carboxypeptidase 2 (GCP2), the enzyme that catalyzes the hydrolysis of N-acetyl-aspartylglutamate. The mouse tissue distribution of β-citrylglutamate hydrolase was strikingly similar to that of the glutamate carboxypeptidase 3 (GCP3) mRNA, but not that of the GCP2 mRNA. Furthermore, similarly to β-citrylglutamate hydrolase purified from testis, recombinant GCP3 specifically hydrolyzed β-citrylglutamate in the presence of Ca(2+), and acted on both N-acetyl-aspartylglutamate and β-citrylglutamate in the presence of Mn(2+), whereas recombinant GCP2 only hydrolyzed N-acetyl-aspartylglutamate and this, in a metal-independent manner. A comparison of the structures of the catalytic sites of GCP2 and GCP3, as well as mutagenesis experiments revealed that a single amino acid substitution (Asn-519 in GCP2, Ser-509 in GCP3) is largely responsible for GCP3 being able to hydrolyze β-citrylglutamate. Based on the crystal structure of GCP3 and kinetic analysis, we propose that GCP3 forms a labile catalytic Zn-Ca cluster that is critical for its β-citrylglutamate hydrolase activity.

A Novel Non-SET Domain Multi-subunit Methyltransferase Required for Sequential Nucleosomal Histone H3 Methylation by the Mixed Lineage Leukemia Protein-1 (MLL1) Core Complex

Gene expression within the context of eukaryotic chromatin is regulated by enzymes that catalyze histone lysine methylation. Histone lysine methyltransferases that have been identified to date possess the evolutionarily conserved SET or Dot1-like domains. We previously reported the identification of a new multi-subunit histone H3 lysine 4 methyltransferase lacking homology to the SET or Dot1 family of histone lysine methyltransferases. This enzymatic activity requires a complex that includes WRAD (WDR5, RbBP5, Ash2L, and DPY-30), a complex that is part of the MLL1 (mixed lineage leukemia protein-1) core complex but that also exists independently of MLL1 in the cell. Here, we report that the minimal complex required for WRAD enzymatic activity includes WDR5, RbBP5, and Ash2L and that DPY-30, although not required for enzymatic activity, increases the histone substrate specificity of the WRAD complex. We also show that WRAD requires zinc for catalytic activity, displays Michaelis-Menten kinetics, and is inhibited by S-adenosyl-homocysteine. In addition, we demonstrate that WRAD preferentially methylates lysine 4 of histone H3 within the context of the H3/H4 tetramer but does not methylate nucleosomal histone H3 on its own. In contrast, we find that MLL1 and WRAD are required for nucleosomal histone H3 methylation, and we provide evidence suggesting that each plays distinct structural and catalytic roles in the recognition and methylation of a nucleosome substrate. Our results indicate that WRAD is a new H3K4 methyltransferase with functions that include regulating the substrate and product specificities of the MLL1 core complex.