On-line microplasma decomposition of gaseous phase interference for solid sampling mercury analysis in aquatic food samples.

In this work, dielectric barrier discharge (DBD) was first utilized to eliminate gaseous phase interference from complicated solid sample. So, a novel solid sampling Hg analyzer was first designed using a coaxial DBD reactor to replace catalytic pyrolysis furnace for sensitive mercury determination in aquatic food samples. The Hg analyzer mainly comprised an electrothermal vaporizer (ETV), a DBD reactor to decompose gaseous interfering substances including volatile organic compounds (VOCs), a gold-coil Hg trap to eliminate matrix interference and an atomic fluorescence spectrometer (AFS) as detector. These units were connected by a manifold integrating air and Ar/H2 (v/v = 9 : 1), fulfilling on-line decomposition of up to 12 mg dried aquatic food powder at ambient temperature. The proposed method detection limit (LOD) was 0.5 μg/kg and the relative standard deviations (RSDs) were within 5% for Hg standards as well as within 10% for real samples, indicating adequate analytical sensitivity and precision. In addition, the on-line DBD reactor consumes only 40 W, which is obviously lower than that (>300 W) of the commercial Hg analyzers; including the sample pre-treatment, the overall analysis could be completed within 5 min. This method is easier, greener and safer for Hg analysis in real samples obviating chemical reagents. The new DBD apparatus can facilitate the miniaturization and portability with low power consumption and instrumental size revealing its promising potential in direct Hg analysis instrumentation development.