Evaluation of uncertainty in the determination of bis- ether in tea leaves by accelerated solvent extraction technique and gas chromatography

A method has been developed for the determination of bis-(2,3,3,3-tetrachloropropyl) ether in tea leaves by accelerated solvent extraction technique(ASE) and gas chromatography(GC).The samples were extracted by accelerated solvent extraction(ASE) using hexane-acetone(1∶1,V/V) as the extraction solvent,purified with celite-sulfuric acid(10 g∶0.4 mL) using hexane as an eluent.The correlation coefficient in the concentration range at 0.010-0.40 mg/L was 0.999 1,The average recoveries of bis-(2,3,3,3-tetrachloropropyl) ether in tea at 5-30 ng/g fortification level were 90.2%,with relative standard deviations(RSD) of 4.7%.The limit of detection(LOD) of the method was 0.005 mg/kg.Uncertainties originated from the measurement of bis-(2,3,3,3-tetrachloropropyl) ether in tea leaves by ASE-GC method were analysed and evaluated.When bis-(2,3,3,3-tetrachloropropyl) ether content in tea was 0.053 1 mg/kg,the relative uncertainty(UreI) was calculated to be 0.003 6 mg/kg from the experimental data when the designed incredible probability was 95% and factor(k) was 2.The results of uncertainty analyses showed that the recovery rate,repeatability of determination and preparation process of standard solution were the key issues of the testing quality control.