Direct determination of silicon in powdered aluminium oxide by use of slurry sampling with in situ fusion graphite-furnace atomic-absorption spectrometry.

A direct method for determination of silicon in powdered high-purity aluminium oxide samples, by slurry sampling with in situ fusion graphite-furnace atomic-absorption spectrometry (GF-AAS), has been established. A slurry sample was prepared by 10-min ultrasonication of a powdered sample in an aqueous solution containing both sodium carbonate and boric acid as a mixed flux. An appropriate portion of the slurry was introduced into a pyrolytic graphite furnace equipped with a platform. Silicon compounds to be determined and aluminium oxide were fused by the in situ fusion process with the flux in the furnace under optimized heating conditions, and the silicon absorbance was then measured directly. The calibration curve was prepared by use of a silicon standard solution containing the same concentration of the flux as the slurry sample. The accuracy of the proposed method was confirmed by analysis of certified reference materials. The proposed method gave statistically accurate values at the 95% confidence level. The detection limit was 3.3 microg g(-1) in solid samples, when 300 mg/20 mL slurry was prepared and a 10 microL portion of the slurry was measured. The precision of the determination (RSD for more than four separate determinations) was 14% and 2%, respectively, for levels of 10 and 100 microg g(-1) silicon in aluminium oxide.

Preconcentration by coprecipitation of arsenic and tin in natural waters with a Ni-pyrrolidine dithiocarbamate complex and their direct determination by solid-sampling atomic-absorption spectrometry.

A method for the determination of trace amounts of arsenic and tin in natural waters is described. Trace amounts of arsenic and tin were preconcentrated by coprecipitation with a Ni-ammonium pyrrolidine dithiocarbamate (APDC) complex. The coprecipitates obtained were directly analyzed by graphite-furnace atomic-absorption spectrometry (GFAAS) using the Ni-APDC complex solid-sampling technique. The coprecipitation conditions used for the trace amounts of arsenic and tin in natural water were investigated in detail. It was found that arsenic and tin at sub-ng mL(-1) levels were both coprecipitated quantitatively by Ni(PDC)2 in the pH range 2-3. The concentration factors by coprecipitation reached approximately 40,000 when 2 mg nickel was added as a carrier element to 500 mL of the water sample. The proposed method has been applied to the determination of trace amounts of arsenic and tin in river water and seawater reference materials, and the detection limits for arsenic and tin, which were calculated from three times of the standard deviation of the procedural blanks, are 0.02 ng mL(-1) and 0.04 ng mL(-1), respectively, for 500-mL volumes of water sample.