A method for determination of 226Ra and 228Ra in environmental samples using the α-β coincidence liquid scintillation counting (LSC) has been developed. Radium were preconcentrated from environmental samples by copr...A method for determination of 226Ra and 228Ra in environmental samples using the α-β coincidence liquid scintillation counting (LSC) has been developed. Radium were preconcentrated from environmental samples by coprecipitation with BaSO4, then purified from others radionuclide interferences using the cation column exchange (Bio-Rad AG 50 W-X4 resin with 200-400 mesh size and H+ form) and operating in warm temperature which is between 70-80oC. Then, the Ba(Ra)SO4 precipitate was filtered through the Millipore filter paper, dried and weighed to calculate chemical yield. The activity concentration of radium isotopes in mixture of liquid scintillation cocktails were measured using LSC after being stored for over 21 days to allow the growth of the progeny nuclides. The method has been validated with a certi-fied reference material supplied by the International Atomic Energy Agency and reliable results were obtained. The radiochemical yields for radium were 59% - 90% and recovery was 97% and 80% for 226Ra and 228Ra, respectively. Sixteen seawater and fish flesh samples collected in Kapar coastal water have been analyzed with the developed method. The obtained radium activity concentrations in seawater were in the range of 02.08 ± 0.82 mBq/L to 3.69 ± 1.29 mBq/L for 226Ra and 6.01 ± 3.05 mBq/L to 17.07 ± 6.62 mBq/L for 228Ra. Meanwhile, the activity concentrations of 226Ra and 228Ra in fish flesh were in the range of 11.82 ± 5.23 – 16.53 ± 6.53 Bq/kg dry wt. and 43.52 ± 16.34 – 53.57 ± 19.86 Bq/kg dry wt., respectively.展开更多
Purpose Among the several methods to measure ^(222)Rn in water,the liquid scintillation counting(LSC)technique is one of the most sensitive and widely used when analysing non-saline waters by liquid extraction,providi...Purpose Among the several methods to measure ^(222)Rn in water,the liquid scintillation counting(LSC)technique is one of the most sensitive and widely used when analysing non-saline waters by liquid extraction,providing excellent accuracy,precision and low-level detection limits.When using the liquid scintillation counter Tri-Carb 3170 TR/SL(Perkin-Elmer)it is not possible to make an automatic determination of the alpha/beta discrimination parameter,being necessary to evaluate the pulse decay discriminator(PDD)value manually to the ^(222)Rn determination.In this work,we describe the steps to perform the calibration of that type of equipment.Methods The method consists in the preparation of standard samples from a ^(226)Ra certified standard solution and the adjustment of the PDD value by hand until the percentage of alpha events reaches a plateau of a near-constant fraction of total events.The process consists in taking several measures between PDD 80 and 200 with 15 min counting time each.Within the plateau,the alpha/beta ratio was used to determine the plateau final range as well as the optimum PDD value.After that,the calibration standards and blanks were measured and the region of interest(ROI)was established by finding the maximum value for the figure of merit(FOM)in the upper and lower limits.Results The optimal PDD value of 148 was established by the alpha/beta ratio,and after that,it was possible to measure ^(226)Ra standards to perform the calibration.An efficiency of(9.758±0.035)×1^(0-1) was obtained.In routine measurements,a detection limit of about 0.50 Bq L^(-1) is achieved for a 120 min counting time.To evaluate the uncertainty budget,the uncertainties of the net count rate,the efficiency,the sample amount and the decay correction factor were considered.Conclusions A method was developed for the calibration of LSC Tri-Carb 3170 TR/SL with the optimization of the PDD using a ^(226)Ra standard solution.The acquisition to obtain the plot of the variation of the events fraction in each window(alpha and beta)in function of PDD allowed to evaluate a plateau where the fraction of events was at a minimum.Afterwards,it was possible to measure the set of ^(226)Ra standards after the equilibrium with ^(222)Rn and determine the efficiency for ^(222)Rn with a detection limit of about 0.50 Bq L^(-1) in routine analyses.展开更多
微量法培养人外周新鲜全血和 PHA 刺激淋巴细胞转化,用~3H-TdR 参入 DNA 合成观测不同浓度亚硒酸钠对转化淋巴细胞增殖的影响。结果表明,低浓度亚硒酸钠(1.18×10-~7mol)促进细胞的增殖,细胞 DNA 合成比对照组平均增高43.5%,而高浓...微量法培养人外周新鲜全血和 PHA 刺激淋巴细胞转化,用~3H-TdR 参入 DNA 合成观测不同浓度亚硒酸钠对转化淋巴细胞增殖的影响。结果表明,低浓度亚硒酸钠(1.18×10-~7mol)促进细胞的增殖,细胞 DNA 合成比对照组平均增高43.5%,而高浓度亚硒酸钠(1.18×10-~5mol)抑制细胞的增殖,细胞 DNA 合成比对照组平均降低93.3%。本实验除表明不同浓度亚硒酸钠对细胞增殖的上述双相作用外,还用回归作图法求得此双相作用的临界亚硒酸钠浓度为1.0×10-~6mol。展开更多
文摘A method for determination of 226Ra and 228Ra in environmental samples using the α-β coincidence liquid scintillation counting (LSC) has been developed. Radium were preconcentrated from environmental samples by coprecipitation with BaSO4, then purified from others radionuclide interferences using the cation column exchange (Bio-Rad AG 50 W-X4 resin with 200-400 mesh size and H+ form) and operating in warm temperature which is between 70-80oC. Then, the Ba(Ra)SO4 precipitate was filtered through the Millipore filter paper, dried and weighed to calculate chemical yield. The activity concentration of radium isotopes in mixture of liquid scintillation cocktails were measured using LSC after being stored for over 21 days to allow the growth of the progeny nuclides. The method has been validated with a certi-fied reference material supplied by the International Atomic Energy Agency and reliable results were obtained. The radiochemical yields for radium were 59% - 90% and recovery was 97% and 80% for 226Ra and 228Ra, respectively. Sixteen seawater and fish flesh samples collected in Kapar coastal water have been analyzed with the developed method. The obtained radium activity concentrations in seawater were in the range of 02.08 ± 0.82 mBq/L to 3.69 ± 1.29 mBq/L for 226Ra and 6.01 ± 3.05 mBq/L to 17.07 ± 6.62 mBq/L for 228Ra. Meanwhile, the activity concentrations of 226Ra and 228Ra in fish flesh were in the range of 11.82 ± 5.23 – 16.53 ± 6.53 Bq/kg dry wt. and 43.52 ± 16.34 – 53.57 ± 19.86 Bq/kg dry wt., respectively.
基金the Fundacao para a Ciencia e Tecnologia(FCT)support through the UID/Multi/04349/2013 projectfunding provided by FCTIFCCN(b-on).
文摘Purpose Among the several methods to measure ^(222)Rn in water,the liquid scintillation counting(LSC)technique is one of the most sensitive and widely used when analysing non-saline waters by liquid extraction,providing excellent accuracy,precision and low-level detection limits.When using the liquid scintillation counter Tri-Carb 3170 TR/SL(Perkin-Elmer)it is not possible to make an automatic determination of the alpha/beta discrimination parameter,being necessary to evaluate the pulse decay discriminator(PDD)value manually to the ^(222)Rn determination.In this work,we describe the steps to perform the calibration of that type of equipment.Methods The method consists in the preparation of standard samples from a ^(226)Ra certified standard solution and the adjustment of the PDD value by hand until the percentage of alpha events reaches a plateau of a near-constant fraction of total events.The process consists in taking several measures between PDD 80 and 200 with 15 min counting time each.Within the plateau,the alpha/beta ratio was used to determine the plateau final range as well as the optimum PDD value.After that,the calibration standards and blanks were measured and the region of interest(ROI)was established by finding the maximum value for the figure of merit(FOM)in the upper and lower limits.Results The optimal PDD value of 148 was established by the alpha/beta ratio,and after that,it was possible to measure ^(226)Ra standards to perform the calibration.An efficiency of(9.758±0.035)×1^(0-1) was obtained.In routine measurements,a detection limit of about 0.50 Bq L^(-1) is achieved for a 120 min counting time.To evaluate the uncertainty budget,the uncertainties of the net count rate,the efficiency,the sample amount and the decay correction factor were considered.Conclusions A method was developed for the calibration of LSC Tri-Carb 3170 TR/SL with the optimization of the PDD using a ^(226)Ra standard solution.The acquisition to obtain the plot of the variation of the events fraction in each window(alpha and beta)in function of PDD allowed to evaluate a plateau where the fraction of events was at a minimum.Afterwards,it was possible to measure the set of ^(226)Ra standards after the equilibrium with ^(222)Rn and determine the efficiency for ^(222)Rn with a detection limit of about 0.50 Bq L^(-1) in routine analyses.
文摘微量法培养人外周新鲜全血和 PHA 刺激淋巴细胞转化,用~3H-TdR 参入 DNA 合成观测不同浓度亚硒酸钠对转化淋巴细胞增殖的影响。结果表明,低浓度亚硒酸钠(1.18×10-~7mol)促进细胞的增殖,细胞 DNA 合成比对照组平均增高43.5%,而高浓度亚硒酸钠(1.18×10-~5mol)抑制细胞的增殖,细胞 DNA 合成比对照组平均降低93.3%。本实验除表明不同浓度亚硒酸钠对细胞增殖的上述双相作用外,还用回归作图法求得此双相作用的临界亚硒酸钠浓度为1.0×10-~6mol。
