Liquid Scintillation Counting Method Research Articles

Determination of radiocarbon content in liquid fuel blends by accelerator mass spectrometry and liquid scintillation counting in the gliwice radiocarbon and mass spectrometry laboratory

Abstract The increase in biobased material usage requires the methods of verification to investigate the actual content of biocarbon in such materials, including liquid fuels. The determination of biocarbon in liquid samples using 14C required adaptation of existing sample preparation methods. In this study, both accelerator mass spectrometry (AMS) and liquid scintillation counting (LSC) methods were used to determine the content of 14C in six different liquid fuel blends produced from purely bio-based hydrotreated vegetable oil (HVO) and a 14C-free petrodiesel sample (ON/UF-BC). The results obtained for pure petrodiesel provide background values. The results indicate a good agreement between LSC and AMS, and a linear correlation between the 14C measurement results for blended samples and HVO content affirmed the reproducibility between the two methods. The repeatability of AMS results was tested on 10 aliquots of one of the blends, and the results were deemed reproducible.

Activity standard and calibrations for 227Th with ingrowing progeny

Thorium-227 was separated from its progeny and standardized for activity by the triple-to-double coincidence ratio (TDCR) method of liquid scintillation counting. Confirmatory liquid scintillation-based measurements were made using efficiency tracing with 3H and live-timed anticoincidence counting (LTAC). The separation time and the efficiency of the separation were confirmed by gamma-ray spectrometry. Calibrations for reentrant pressurized ionization chambers, including commercial radionuclide calibrators, and a well-type NaI(Tl) detector are discussed.

Mass Balance and Metabolic Pathways of Eliapixant, a P2X3 Receptor Antagonist, in Healthy Male Volunteers.

Overactive adenosine triphosphate signaling via P2X3 homotrimeric receptors is implicated in multiple conditions. To fully understand the metabolism and elimination pathways of eliapixant, a study was conducted to assess the pharmacokinetics, mass balance, and routes of excretion of a single oral dose of the selective P2X3 receptor antagonist eliapixant, in addition to an invitro characterization. In this single-center open-label non-randomized non-placebo-controlled phase I study, healthy male subjects (n=6) received a single dose of 50mg eliapixant blended with 3.7MBq [14C]eliapixant as a PEG 400-based oral solution. Total radioactivity and metabolites excreted in urine and feces, and pharmacokinetics of total radioactivity, eliapixant, and metabolites in plasma were assessed via liquid scintillation counting and high-performance liquid chromatography-based methods coupled to radiometric and mass spectrometric detection. Metabolite profiles of eliapixant in human invitro systems and metabolizing enzymes were also investigated. After administration as an oral solution, eliapixant was rapidly absorbed, reaching maximum plasma concentrations within 2h. Eliapixant was eliminated from plasma with a mean terminal half-life of 48.3h. Unchanged eliapixant was the predominant component in plasma (72.6% of total radioactivity area under the curve). The remaining percentage of drug-related components in plasma probably represented the sum of many metabolites, detected in trace amounts. Mean recovery of total radioactivity was 97.9% of the administered dose (94.3-99.4%) within 14 days, with 86.3% (84.8-88.1%) excreted via feces and 11.6% (9.5-13.1%) via urine. Excretion of parent drug was minimal in feces (0.7% of dose) and urine (≈0.5%). In feces, metabolites formed by oxidation represented > 90% of excreted total radioactivity. The metabolites detected in the invitro experiments were similar to those identified invivo. Complete recovery of administered eliapixant-related radioactivity was observed in healthy male subjects with predominant excretion via feces. Eliapixant was almost exclusively cleared by oxidative biotransformation (>90% of dose), with major involvement of cytochrome P450 3A4. Excretion of parent drug was of minor importance (~1% of dose). ClinicalTrials.gov: NCT04487431 (registered 27 July 2020)/EudraCT number: 2020-000519-54 (registered 3 February 2020), NCT02817100 (registered 26 June 2016), NCT03310645 (registered 16 October 2017).

ENVIRONMENTAL TRITIUM AND ITS MEASUREMENT CHALLENGES USING LIQUID SCINTILLATION COUNTING

Tritium, the radioactive isotope of hydrogen, is one of the most versatile radionuclides due to its role as a tracer of hydrogen and carbon structures. The liquid scintillation counting method is the preferred tritium measurement method especially in the case of numerous samples as radioactivity monitoring programs. The changes that appeared in the liquid scintillation spectrometers market and in the liquid scintillation cocktail formula demand adaptation of the laboratory routine procedure. Tritium level in the environmental water samples of 2022 is presented in the paper. The low level around 2 Bq/L imposes the necessity of tritium enrichment. Each of the above problems is extensively presented in this work together with some conclusions.

Calibration experiments for radon in drinking water measurements using portable-type electrostatic-collection radon monitors.

Portable-type electrostatic-collection radon monitors (RAD7) are often used for in-situ measurements of radon in water. In this study, we evaluated the calibration factors and their uncertainties for two RAD7 monitors based on comparative measurements with the liquid scintillation counting method. In the first experiment, we found that both RAD7 monitors had relatively large uncertainties due to leakage of radon gas that bubbled from the gaps between the lids of the desiccant container and the glass vial. Therefore, for the second experiment, these gaps were closed as much as possible using parafilm and clay, respectively. As a result, the relative uncertainties for both RAD7 monitors were significantly decreased. Furthermore, we collected spring water samples to confirm the reliability of radon concentrations. After closing the leakage point, the uncertainty of radon concentrations in spring water we measured using the typical protocol of the RAD7 were significantly lower, which improves the measurement.

A bilateral comparison between LNHB and PTB to determine the activity concentration of the same 125I solution

A bilateral comparison to determine the activity concentration of the same 125I solution was organized. As electron-capture radionuclide with a rather high atomic number, 125I must be regarded as difficult to measure. The situation is partly exacerbated by the fact that some established standardization methods, like photon-photon coincidence counting, can no longer be applied due to the unavailability of appropriate equipment and expertise.One aim of this work is to compare modern liquid scintillation counting methods for the standardization of 125I. Both participating metrology institutes have used their custom-built triple-to-double-coincidence ratio (TDCR) counters and the determined activity concentrations are in excellent agreement even though the ways to analyze the data and to compute counting efficiencies were widely independent. The results also agree with the outcome of 4π-γ counting that was carried out at LNHB.In both laboratories, the measurements were complemented by measurements with several secondary standardization methods which even allow to establish a link to the CCRI(II)–K2.I-125(2) comparison started in 2004. A good agreement between the TDCR results and the key comparison reference value of the 2004/2005 comparison was obtained.

Development of a secondary reference material for application in carbon-14 specific activity determination by thermal oxidation and liquid scintillation counting method

Abstract Carbon-14 (14C) is a pure beta-emitting radionuclide with a half-life of 5730 ± 30 y. Considering the long half-life and its biological importance, significant attention is given to monitoring 14C in the vicinity of nuclear facilities. The 14C measurement technique employed by the majority of environmental monitoring laboratories for impact assessments in the vicinity of nuclear facilities is based on the thermal oxidization of the samples and the determination of activity by liquid scintillation counting. One of the difficulties faced by these laboratories is the nonavailability of a suitable matrix-matching reference material which is truly representative of the type of sample being analyzed. In this study, an effort has been made to develop a reference material that is representative and has a similar thermal oxidation/combustion property as that of a typical terrestrial plant biota observed in the vicinity of the nuclear power plants of India for quality assurance programs. A prebomb era wood (~150 years old) was identified as a potential secondary reference material. The stable carbon ratio (d13C) of the sample was determined by isotopic ratio mass spectrometer (IRMS), and the mean value was −26.33 ± 0.47 ‰. The 14C specific activity of the sample was determined by accelerator mass spectrometry and a mean value of 221.6 ± 0.6 Bq kg−1 C was assigned as the reference value to the prebomb wood. In addition, measurements were performed by thermal oxidation in a tube furnace and by analysis of the 14C activity in a liquid scintillation counter.

Практичні аспекти застосування методу черенковського лічення з корекцією кольорового гасіння

Cerenkov counting is a convenient and effective method of counting high-energy beta radiation, which has long been used to measure a number of radionuclides, such as, in particular, 90Sr+90Y, in environmental objects. The traditional Cerenkov method requires the use of radiochemical sample preparation procedures, but these procedures may be simpler than those used, for example, for the liquid scintillation counting (LSC) method. We proposed the Cerencov method, which corrects color quench effect. The method is based on the correlation between the counting rates of the radiation of the sample and its external standard, which is observed for a wide range of color quenching of the samples. The use of such a Cerencov method allows measurement of high-energy -emitters, in particular, its use as an express method for the study of 90Sr+90Y in surface water. For a number of cases, the method makes it possible to avoid the use of long lasting and expensive sample preparation procedures. The results of the cross-testing of the samples obtained by the Cerencov method and direct measurement by the liquid scintillation counting method are in good agreement with each other.

Gross alpha and gross beta radioactivity levels in bottled mineral water samples in Morocco determined by liquid scintillation counting method

Gross alpha and gross beta radioactivity levels in bottled mineral water samples in Morocco determined by liquid scintillation counting method

Revisiting methods for the assessment of naturally-occurring radioactivity in drinking water

A comprehensive radioactivity characterisation of Castilla y León (Spain) groundwater intakes intended for human consumption is addressed between 2017 and 2021. This study responds to the radiological requirements stated in the European Council Directive 51/2013/EURATOM concerning drinking water for public health. Given that the gross α- and gross β-activity determination is used as a screening strategy for water radioactivity monitoring, the reliability of the thin-source deposit method (ISO 10704, 2019) has been improved to achieve representative values of the total activity coming from α- and β-particle emitters in the samples. More than 400 groundwater samples have been considered for this purpose, analysing their 238,235,234U, 228,226Ra, 210Pb, and 210Po activity concentrations, which are needed for the indicative dose assessment. These results, considered reference activity values, are compared with the gross α- and gross β-activities determined by the different procedure approaches. Ultimately, the results of the liquid scintillation counting method (ISO 11704, 2018) are also used to validate the optimised method.

Evaluation of radon concentration measurements in water using the radon degassing method

This study was the first to determine the effectiveness of radon concentration measurement in water using the degassing method as a screening method based on the liquid scintillation counter method. The degassing method used two radon monitors (AlphaGUARD and RAD7) and two monitor-attached degassing devices (AquaKIT and RAD H2O). These were effective screening methods based on the WHO guideline value of 100 Bq L−1. The screening values confirmed that a combination of the AlphaGUARD and AquaKIT was preferred. The results are useful for radon measurement for exposure control in drinking water and environmental in-situ field measurement.

Demonstration of low-level biogenic fuel content using quench curve and direct liquid scintillation counting (LSC) methods

An investigation into the direct method for liquid scintillation counting (LSC) quantification of biogenic fuel content in fuel blendstock is presented. This method development intentionally used a colored matrix (∼99 wt%), fossil diesel fraction, and low-level biogenic fractions (∼1 wt%) to determine the applicability of the LSC technique in colored blend mixtures. LSC procedures for quench correction, includingtheuse ofan instrument internal standard (QuantulusSQP values), color quench curves,andaninternal14C standardspike on samples containing low-level amounts of biogenic gasoline, jet, and diesel mixed with fossil fuel, were compared.Samples were analyzed on both Perkin-ElmerQuantulusand Tri-Carb instruments, and the 14C contents were compared with those determined by accelerator mass spectrometry (AMS). Results from the Tri-Carb instrument showed that percent differences of <10 % compared to AMS-reported values are achievable at 5-hour count times despite colored samples. A comparison between the impact of chemical and color quenching in the fuel samples showed that color quenching in highly colored samples reduces efficiency significantly more than chemical quenching, indicating that chemical quench curves are not appropriate for highly colored biofuel/fossil-fuel blended samples. Results indicate that both the direct method with internal spike quench correction and the use of a color-quench curve provide accurate results for 1 % biogenic fuel blends.Additionally, we have explored the use of Fourier transform infrared (FTIR) spectroscopy in measuring the biogenic content of the colored blended fuel samples. Preliminary results show the presence of biogenic carbon-derived fingerprints that are absent in fossil-derived sample. However, further work is needed to develop an FTIR-based quantitative method.

Simultaneous determination of gross alpha/beta activities in water by liquid scintillation counting and its applications in the environmental monitoring

Based on the standards of ISO11704-2018 and ASTM D7283-17, a method for simultaneous determination of gross alpha and gross beta activity concentrations in water by liquid scintillation counting (LSC) was established, which can be applied to various types of water samples in routine monitoring, such as drinking water, groundwater, geothermal water, seawater, and radioactive wastewater. The sample’s pH value and concentrated volume must be controlled to avoid quenching as much as possible. The validation tests show that the deviations of gross alpha and gross beta activities can satisfy quality control requirements in a wide range of activity ratios from 1:102 to 67:1. For the actual samples, the measurement results of the LSC method are in good agreement with those of the thick source method, in which the relative deviations of gross alpha and gross beta are both less than 15% for these two methods. Moreover, the LSC method performs better in detection limit and has a simpler pretreatment process than the thick source method.

SOIL AND ATMOSPHERIC AEROSOL CONTAMINATION AT THE TERRITORIES OF INFLUENCE OF FORMER URANIUM PRODUCTION FACILITIES “PRIDNIPROVSKY CHEMICAL PLANT”

Problems Statement and Purpose. The territory of the former Uranium production facility “Prydniprovsky Chemical Plant” (“PChP”) are located in Kamensky city, Dnipropetrovsk region, occupy the area of the upper and lower terraces of the Dnieper River (more than 300 hectares), where the remained legacy facilities and residues of the former uranium ore processing are located. After 1991 the production of Uranium concentrates ceased without remediated. Thus, up to 40 million tons of radioactive and chemical mineral residues of uranium production have accumulated within its industrial site and at the adjacent territories. Systemic monitoring studies began only in 2005. The studied environment characteristics were soils contamination, the tailings facilities where Uranium ore processing residues had accumulated, as well as atmospheric contamination by airborne aerosols. The purpose of this study stage is a comprehensive analysis of the spatial distribution of radionuclides of Uranium series at the legacy site territory and factors that can lead to a significant expansion of the contaminated area and scale of chronic environmental pollution under the influence of atmospheric transport and human exposure by inhalation. Data &amp; Methods. The field sampling and analytical methods (gamma, alpha spectrometry and liquid scintillation counting methods) for determination of radionuclides of U-Th decay series were in use for this study. Soils samples from the top layers (0–5 cm) and gamma-dose rate surveys performed. A two-week continues integrated sampling data on the radioactive aerosols ambient activity concentrations and radioactive atmospheric fallout from 7-th locations at the legacy site and adjacent areas used for the environment radioactivity site-specific analyses. For determination of radionuclides in the environment samples (aerosols, soils and in the raw ore mineral residues) the low background gamma-spectrometry method with HPGe detectors have been in use. The content of metals associated with aerosols measured on filters using atomic absorption spectrometry methods. The data analysis for longterm series of observations (2005–2017) carried out using statistical methods. The compliance environment contamination analyses for the legacy site were carried comparing averaged observed data with the established safety criteria and regional background observation data. Results. The main current sources of radiation emission to the environment at the legacy site are open dispersed residues of Uranium production accumulated at the tailings facilities and at the former U‑extraction infrastructure. The spatial analyses of the gamma dose rate at the U‑production legacy site and its soil chemical contamination showed that about 30% of its territory requires decontamination. It is shown that the effects of aerosol radioactive particles dispersion from the contaminated “hot spots” at the territory such as tailings and former U‑production infrastructure are local and do not extend significantly beyond the industrial site. The greatest effects of wind re-suspension and propagation observed during the period of earthworks during construction of the U‑tailings covers and residues management at the contaminated facilities. In worst cases during earthwork at the U‑tailings facilities specific activity concentrations of 238U, 226Ra associated with aerosols (dust) nearby the tailings facilities may exceed 100 times above background radioactivity concentrations level observed at the distance about 10 km from the legacy site in the Kamyanske city. However, the air contamination with radioactive dusts in the worst meteorological conditions (dry windy period observation) did not exceed safe level of air concentrations according national radiation safety standards of Ukraine. The content of metals associated with aerosol particles can also increase by 2–10 times, but also their transfer by wind at the site is local and does not have a significant impact on residential areas of the city. Significant inhalation risks may arise during the dismantling of production equipment and buildings of former uranium production. Therefore, during implementation of any engineering remediation works, it is advisable to provide dust suppression control and to remove all dispersed materials from the former Uranium extraction before dismantling of the contaminated buildings and U‑production equipment. The introduced methods of air sampling at the PChP legacy site and low background analytical methods for radionuclide determination in the laboratories allow to recommend them for site specific environment monitoring programs bringing the radioactive contamination PChP site in a safe state

Tritium radioactivity estimation in cement mortar by heat-extraction and liquid scintillation counting

Tritium extraction from radioactively contaminated cement mortar samples was performed using heating and liquid scintillation counting methods. Tritiated water molecules (HTO) can be present in contaminated water along with water molecules (H2O). Water is one of the primary constituents of cement mortar dough. Therefore, if tritium is present in cement mortar, the buildings and structures using this cement mortar would be contaminated by tritium. The radioactivity level of the materials in the environment exposed to tritium contamination should be determined for their disposal in accordance with the criteria of low-level radioactive waste disposal facility. For our experiments, the cement mortar samples were heated at different temperature conditions using a high-temperature combustion furnace, and the extracted tritium was collected into a 0.1 M nitric acid solution, which was then mixed with a liquid scintillator to be analyzed in a liquid scintillation counter (LSC). The tritium extraction rate from the cement mortar sample was calculated to be 90.91% and 98.54% corresponding to 9 h of heating at temperatures of 200 °C and 400 °C, respectively. The tritium extraction rate was close to 100% at 400 °C, although the bulk of cement mortar sample was contaminated by tritium.

Optimisation of CO2 absorption and liquid scintillation counting method for carbon-14 specific activity measurement in atmospheric air

A method for the determination of 14C activity in the ambient air was optimised with the development of a simple setup for the regeneration of CO2 from carbonate sample and saturating the absorber in <45 min for direct determination of activity by liquid scintillation counting (LSC). Atmospheric CO2 was trapped in NaOH solution and precipitated as BaCO3 by adding BaCl2. The carbonate sample was taken in a newly designed regeneration system, subjected to acid hydrolysis, and the absorber (CarboSorb-E) was saturated with the CO2 regenerated from carbonate sample. This allowed optimisation of CO2 absorption by the absorber (up to ~ 2.3941 g of CO2/10 mL with an average of 2.1688 g) and a minimum detectable activity value of 14 Bq kg−1C for a counting time of 300 min (8 Bq kg−1C for 1000 min) was achieved with Quantulus - 1220 LSC system. The necessity of (i) the measurement of the total volume of air sampled, (ii) the determination of trapping efficiency for CO2 in the NaOH, recovery of 14C in chemical processing of BaCO3, and subsequent regeneration and absorption processes, and (iii) independent determination of carbon content in the air for expressing the results in terms of 14C specific activity (Bq kg−1C), are avoided in this method. The method is capable of yielding accurate results, in a considerably shorter time when compared to previously reported methods, with a deviation of <2.2% from the target value (with a relative standard deviation of 1.1%, and a relative error of 0.53%) when ambient air samples from clean air region (region not affected by local anthropogenic sources of 14C) are analysed. Validation of the method was performed by (i) analysing BaCO3 sample derived from ambient air by accelerator mass spectrometry, and (ii) analysing the CO2 produced from the combustion of IAEA C3 reference material. Upon validation, the suitability of the method for determining small excess 14C specific activity in the vicinity of a nuclear power plant was demonstrated.

Determination of low-level biogenic gasoline, jet fuel, and diesel in blends using the direct liquid scintillation counting method for 14C content

The direct liquid scintillation counting (LSC) method was investigated for quantitative measurement of 14C in low-level biogenic gasoline, jet fuel, and diesel range hydrocarbons in fuel blendstock to determine the biogenic content. Carbon-14 (14C) is an ideal tracer for biogenic fuel products, due to the depletion of 14C in fossil-based fuel. Biogenic gasoline, jet fuel, and diesel range hydrocarbons prepared from distillation of hydrotreated pyrolysis oils were blended with toluene at 1–10 wt%. The blends were analyzed by the direct LSC method using both Perkin-Elmer Quantulus and TriCarb instruments, using an internal 14C standard as an indication of signal quench. This study shows that it is feasible to accurately determine the biogenic fraction of blended fuels containing 1 wt% biogenic fuel using the direct LSC method, suggesting that direct LSC could be an option for quality assurance testing of biomass-derived liquids at co-processing facilities. The Quantulus and TriCarb instruments were found to be comparable for low-level detection of 14C in blended samples, suggesting that some instrument flexibility may be available to potential users. Quenching effects were considered and several methods for quench correction were compared.

Application of synthetic benzoic acid technology in environmental radiocarbon monitoring

Environmental radiocarbon (14C) monitoring is gaining importance in China due to the recent rapid development of the nuclear industry. In this study, synthetic benzoic acid samples with the fingerprint of environmental 14C were generated by using the synthesis method, and the specific activity of 14C was determined using the liquid scintillation counting (LSC) method. The ultra-performance liquid chromatography (UPLC) analysis was performed in chemical properties test and results showed that the mean assay and yield of synthetic benzoic acid were 91.8% ± 2.4% and 84.5% ± 2.0%, respectively. Under adopted LSC counting conditions, the minimum detectable activity (MDA) of 64 Bq/kg C was achieved in our laboratory. The method's linearity was examined using a series of spiked samples, along with the 14C-free samples. The results showed a wide linear range up to 2000 Bq/kg C. Reproducible results were obtained from three batches of experiments with deviations in the intra-group and inter-group of 0.38%–3.06% and 1.24%–3.55%, respectively. Long-term evaluation of the system was found to be very stable (over 5 months storage) with the relative standard deviations of <1%. In addition, field applications in the vicinity of a nuclear power plant demonstrated that 14C data measured by our method was consistent with the accelerator mass spectrometry (AMS) method, suggesting the method's precision can meet the requirement of 14C monitoring near the nuclear facility. This is the first study to report the use of synthetic benzoic acid in environmental 14C monitoring, and it provides a new approach for improving the environmental 14C monitoring network.

Хронология неолитической керамики Байкало-Енисейской Сибири: основные идеи и новые данные

There are two main research areas in the Neolithic studies of the Baikal-Yenisei Siberia. One of them relates to research of mortuary traditions, another with a research of hunter-gatherer’s campsites. Ceramics is of the greatest importance for the cultural identification of campsites complexes. As a result of the Canadian-Russian project, for the Neolithic burials a clear chronological model based on AMS radiocarbon dates corrected for the freshwater reservoir effect (FRE) was created. There are several hypotheses for ceramic complexes that were proposed, but all of them predominantly were based on the radiocarbon dates obtained by the liquid scintillation counting method. This data cannot be admitted as reliable because of the limitation of this method, the big root-mean-square deviation, and the lack of data on stable carbon and nitrogen isotopes. Over the past few years, we have received in the Keck-CCAMS Group and Oxford Radiocarbon Accelerator Unit laboratories 35 new AMS-radiocarbon dates for the complexes with Neolithic ceramics. Samples taken for analyses were obtained from the 14 multilayered sites of the Angara region, Tunka valley, and Lake Baikal coast. They are represented by fragments of teeth, bones, and horns of the mammals (predominantly Cervidae and large ungulates) that accompanied pottery in cultural horizons. In five cases the carbonized organic residues (foodcrusts) from the inner surface of ceramic vessels were used as samples. In one more case, it was a strong humified soil cleaned from impurities. The technical assessment of the reliability of all dates was provided. The definitions obtained for faunal remains look the most correct. Dates obtained for foodcrust are likely significantly older, because of possible FRE influence. The geoarchaeological assessment of new dates and their correlation with the most reliable dates of previous years is provided. Based on the AMC-dating, the following chronometric frames for the Neolithic pottery of the Baikal-Yenisei Siberia are offered: Early Neolithic Net-impressed and the Khaita ceramics in the Angara region – 8539–6914 cal BP, on the Lake Baikal coast – 8160–6960 cal BP, in the Tunka valley – 7843–7681 cal BP; Ust-Belaya ceramics in the Northern Angara region – 7421–7014 cal BP (perhaps the real age is younger), in the Southern Angara region – 6730–6306 cal BP; Posolskaya ceramics on the Lake Baikal coast – 6750–6300 cal BP, in the Southern Angara region – 6730–6306 cal BP; Serovo and Dotted-comb ceramics on the Lake Baikal coast – 5841–4620 cal BP.

In vitro anti-inflammatory, anti-oxidant and in vivo anti-arthritic properties of stem bark extracts from Nauclea pobeguinii (Rubiaceae) in rats

Objective: To explore the immunomodulatory, anti-inflammatory, anti-oxidant and anti-arthritic activity of aqueous and methanolic extracts of Nauclea pobeguinii stem bark. Methods: For in vitro assays, the production of reactive oxygen species (chemiluminescence technique), the proliferation of T cells (liquid scintillation counter method), as well as the inhibition of cyclooxygenase, lipoxygenase, protein denaturation, and free radicals [DPPH, ABTS and nitric oxide (NO) inhibition methods] were evaluated. For in vivo assays, a polyarthritis model was induced by complete Freund’s adjuvant in rats. The aqueous and methanolic extracts of Nauclea pobeguinii stem bark were administered orally at 150 and 300 mg/kg. After 28 days of treatment, the total blood was taken to quantify the hematological parameters and the serum was used to evaluate the biochemical parameters (alanine aminotransferase, aspartate transaminase, phenylalnine ammonialyase, and proteins) and oxidative stress parameters (malondialdehyde, catalase, superoxide dismutase, glutathione and NO), and then the knee joint was removed for histological analysis. Results: The extracts of Nauclea pobeguinii significantly reduced the production of intra- and extracellular reactive oxygen species and decreased T cell proliferation. They had an inhibitory effect on cyclooxygenase, lipoxygenase, and protein denaturation, and both extracts had antioxidant capacity on DPPH, ABTS and NO. Both extracts alleviated joint inflammation and pain sensitivity after complete Freund’s adjuvant injection, reduced alanine aminotransferase, aspartate transaminase, alkaline phosphatase, NO and malondialdehyde levels, increased protein concentration, superoxide dismutase, catalase and glutathione activity, and restored the cytoarchitecture of the joint after complete Freund’s adjuvant injection. Conclusions: The aqueous and methanolic extracts of Nauclea pobeguinii have immunomodulatory, anti-inflammatory, anti-oxidant and anti-arthritic properties.