Performance of the transverse heated filter atomizer for the atomic absorption determination of mercury

The transverse-heated filter atomizer (THFA) was used for the determination of Hg in aqueous solutions and organic solvent (IBMK) after the extraction of Hg with dithizone. The THFA design was similar to one previously described. The injected sample was distributed over the graphite fibre in the ring cavity between the external pyrocoated tube and internal tube-filter made of porous graphite. When the samples were atomised the Hg vapours entered the analytical zone along the tube axis through the porous walls of the inner tube. The aqueous or organic solutions of Hg can be directly analysed in the THFA without the addition of matrix modifiers, using the pyrolysis temperatures 500 and 400 degreesC, respectively, and an atomization temperature of 1300 degreesC. The addition of 0.1 mug Pd to the organic sample made it possible to increase the pyrolysis temperature to 500 degreesC. In comparison with the transverse-heated graphite atomizer (THGA), where sample volumes of 50 mul and 20 mul for aqueous and organic solutions, respectively, are used, large sampling volumes of 100-140 mul can be used with the THFA without distortion of the calibration curve. High sampling and drying temperatures provide an analysis cycle of approximately 40 s (without sampling time) for large volumes. The characteristic mass obtained for the determination of Hg in the THFA was found to be 55 and 79 pg, with and without the 0.1 mug Pd modifier, respectively, compared to 228 pg for aqueous solutions in the presence of 20 mug Pd in the THGA. Several reference materials were analysed directly or after extraction of the Hg by dithizone in IBMK. The results showed good agreement with the certified values.