Direct analysis method of^(14)C radioactivity concentration in urine samples

Objective:To establish a rapid analysis method for the activity concentration of carbon-14(14C)in urine,in order to estimate the internal dose of 14C exposure,and to protect the health of occupational population.Methods:Liquid scintillation counting(LSC)combined with the function of transformed spectral index of the external standard spectrum(tSIE)was used to measure the quenching level and counting rate,and the spiked urine samples with different shades of color were measured by LSC.After establishing the efficiency-quenching curve,the quenching correction and activity concentration analysis of the actual samples were carried out.Results:By LSC and the data fitting,the relationship between efficiency and quenching index could be represented using the equation y=0.0013x-0.0177(R^(2)=0.978).Three actual spiked samples were tested to verify this method,with recoveries of 97%,102%,and 89%,respectively.14C activity concentration of 4 actual urine samples were 0.12,0.11,0.10 and 0.08 Bq/mL,respectively,while the corresponding extended relative uncertainties were 0.0652,0.0929,0.0893 and 0.1043,respectively.Conclusion:The direct analysis method of 14C activity concentration in urine samples was established using LSC.The recovery of 14C activity concentration in urine samples showed that the proposed method had relatively high accuracy.By studying on the source of uncertainty,the uncertainty of the analysis results mainly came from the statistical error of LSC,and the uncertainty component of counting efficiency.

Photocatalytic reduction of Cr(Ⅵ)by WO_(3)@PVP with elevated conduction band level and improved charge carrier separation property

Photocatalytic reduction of heavy metal ions is a green and promising technology which requires electrons with enough negative energy levels as well as efficient separation property from photo-generated holes of photocatalysts.For WO_(3),the low conduction band edge and the severe photo-generated charge carrier recombination limited its application in photocatalytic reduction of pollutants.In this work,we prepared WO_(3)@PVP with PVP capped WO_(3) by a simple one-step hydrothermal method,which showed an elevated energy band structure and improved charge carrier separation property.XRD,SEM,TEM,XPS,DRS,and the photocurrent density test were carried out to study the properties of the composite.Results demonstrated monoclinic WO_(3) with a size of~100-250 nm capped by PVP was obtained,which possessed fewer lattice defects inside but more defects(W^(5+))on the surface.Moreover,the results of the photocatalytic experiment showed the kinetic constant of Cr(Ⅵ)reduction process on WO_(3)@PVP was 0.532 h^(-1),which was 3.1 times higher than that onWO_(3)(0.174 h^(-1)),demonstratingWO_(3)@PVP with good photocatalytic capability for Cr(Ⅵ)reduction.This can be attributed to the improved charge carrier separation performance,the improved adsorption capacity and the elevated conduction band edge of WO_(3)@PVP.More importantly,the energy band structure of WO_(3)@PVP was proved elevated with a value as high as 1.14 eV than that of WO_(3) nanoparticles,which enables WO_(3)@PVP a promising material in the photocatalytic reduction reaction of heavy metal ions from wastewater.