Direct and simultaneous determination of arsenic, manganese, cobalt and nickel in urine with a multielement graphite furnace atomic absorption spectrometer

摘要

A simple method was developed for the direct and simultaneous determination of arsenic (As), manganese (Mn), cobalt (Co), and nickel (Ni) in urine by a multi-element graphite furnace atomic absorption spectrometer (Perkin–Elmer SIMAA 6000) equipped with the transversely heated graphite atomizer and longitudinal Zeeman-effect background correction. Pd was used as the chemical modifier along with either the internal furnace gas or a internal furnace gas containing hydrogen and a double stage pyrolysis process. A standard reference material (SRM) of Seronorm~(TM) Trace Elements in urine was used to confirm the accuracy of the method. The optimum conditions for the analysis of urine samples are pyrolysis at 1350 ℃ (using 5% H_2 v/v in Ar as the inter furnace gas during the first pyrolysis stage and pure Ar during the second pyrolysis stage) and atomization at 2100 ℃. The use of Ar and matrix-free standards resulted in concentrations for all the analytes within 85% (As) to 110% (Ni) of the certified values. The recovery for As was improved when mixture of 5% H_2 and 95% Ar (v/v) internal furnace gas was applied during the first step of a two-stage pyrolysis at 1350 ℃, and the found values of the analytes were within 91–110% of the certified value. The recoveries for real urine samples were in the range 88–95% for these four elements. The detection limits were 0.78 μg l~(-1) for As, 0.054 μg l~(-1) for Mn, 0.22 μg l~(-1) for Co, and 0.35 μg l~(-1) for Ni. The upper limits of the linear calibration curve are 60 μg l~(-1) (As); 12 μg l~(-1) (Mn); 12 μg l~(-1) (Co) and 25 μg l~(-1) (Ni), respectively. The relative standard deviations (R.S.D.s) for the analysis of SRM were 2% or less. The R.S.D.s of a real urine sample are 1.6% (As), 6.3% (Mn), 7.0% (Ni) and 8.0% (Co), respectively.