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.

Determination of multiple drugs of abuse in human urine using dispersive liquid–liquid microextraction and capillary electrophoresis with PDA detection

A new method was developed for pre-concentration and determination of multiple drugs of abuse in human urine using dispersive liquid–liquid microextraction(DLLME)and capillary electrophoresis(CE)with photodiode array detection.The method was based on the formation of tiny droplets of an organic extractant in the prepared sample solution using water-immiscible organic solvent(chloroform)dissolved in water-miscible organic dispersive solvent(isopropyl alcohol).The organic phase,which extracted eight drugs of abuse from the prepared urine solution,was separated by centrifugation.The sedimented phase was transferred into a small volume CE auto-sampler vial with 10μL of 1%HCl methanol solution and evaporated to dryness.The residue was reconstituted in lidocaine hydrochloride(internal standard)aqueous solution and introduced by electrokinetic injection into CE.Under the optimum conditions,acceptable linear relationship was observed in the range of 3.0–500 ng/mL with the correlation coefficient(r)of 0.9982–0.9994 for spiked urine samples.The limit of detection(LOD)(S/N=3)was estimated to be 1.0 ng/mL.A recovery of 75.7%–90.6%was obtained for spiked samples.The mean relative error(MRE)was within±7.0%and the relative standard deviation(RSD)was less than 6.9%.The proposed DLLME-CE procedure offers an alternative analytical approach for the sensitive detection of drugs of abuse in real urine samples.