Direct solid sampling system for electrothermal vaporization and its application to the determination of chlorine in nanopowder samples by inductively coupled plasma optical emission spectroscopy.

An electrothermal vaporization (ETV) system using a tungsten boat furnace (TBF) sample cuvette was designed for the direct determination of chlorine in metallic nanopowders and fine powder samples with detection by inductively coupled plasma optical emission spectroscopy (ICP-OES). A portion of a powder or particle sample was placed into a small tungsten sample cuvette and weighed accurately. A modifier solution of aqueous or alcoholic potassium hydroxide was added to it. Then, the cuvette was positioned on the TBF incorporated into the ETV apparatus. The analyte was vaporized and introduced into the ICP optical emission spectrometer with a carrier gas stream of argon and hydrogen. The metal samples were analyzed by using an external calibration curve prepared from aqueous standard solutions. Few chemical species including analyte and some chlorine-free species were introduced into the ICP, because the analyte has been separated from the matrix before introduction. Under such dry plasma conditions, the energy of plasma discharge was focused on the excitation of chlorine atoms, and as a result, lower detection limits were achieved. A detection limit of 170 ng g(-1) of chlorine in solid metal samples was established when 60 mg sample was used. The relative standard deviation for 16 replicate measurements obtained with 100 ng chlorine was 8.7%. Approximately 30 batches could be vaporized per hour. The analytical results for various nanopowders (iron (III) oxide, copper, silver, and gold) and metallic fine powder samples (silver and gold) are described.