OTKA research grant T038017 (2002-2005)

Title:

Development of laser ablation and electrothermal sample introduction methods for atomic spectrometry of element distributions

Leader of grant: Tibor Kántor, D.Sci.

The laser-ablation (LA) sample introduction is characterized by the illumination of a small surface area of solid samples (10-100 micrometer in diam.) by a laser beam of ns-ps duration, which results in the formation of a high temperature vapor-aerosol mixture (laser ablation: LA). Cooling this mixture yields a solid aerosol of high dispersion which can be transported in a relatively long distance (1-2 m) into atomic spectroscopy sources without an extensive loss. In our pioneering work (1976), the aerosol was transported into analytical flames for atomic absorption detection, which made possible the development of direct, solid sampling analytical methods. The next step of development, on an international level, was the coupling of laser ablation to an inductively coupled plasma (ICP), which made possible the atomic emission spectrometry (AES) on a multi-element base, i.e., the simultaneous determination of a high number of elements. Coupling the laser ablation to ICP-mass-spectrometers (ICP-MS) resulted in a significant increase of the detection power (typically in the range of pg mass). The elaboration of application procedures for LA-ICP-MS, under the condition of advanced instrumental background, is currently an actual task in several laboratories. On of the important application of geological interest is the determination of element distributions of rare earth elements in minerals, in comparison with X-ray microprobe results. A further application field of our interest is the investigation of the distribution of doped elements in optical crystals.

The electrothermal vaporization (ETV) sample introduction method, has a similar principle of coupling to atomic spectroscopic measurement systems as outlined above for the LA method. The difference appears in that ETV method makes possible the direct analysis of solutions, suspensions (slurries) and powder samples, i.e., it is suited to the investigation of other type of materials, as compared to LA methods. The dosed amount of samples are typically 10-50 microliter solutions, or 0.1-10 mg powders, which can be either organic or inorganic materials. In the most widely used ETV units, the sample dosing is made into a horizontal graphite tube (graphite furnace: GF) which can be heated up to 2700 ^oC in argon atmosphere, with a heating rate up to 1000-2000 ^oC/s. One of the important tasks of present interest is the analysis of airborne aerosol particles which can be deposited electrostatically in the GF-ETV unit for a direct analysis. A further advantage of this method is related to the requirement of small sample amount which makes possible the analysis of element distributions in catalysts, sediments and biological substances.

Budapest, 30 September, 2002

Dr. Kántor Tibor, egyetemi tanár

Eötvös Loránd Tudományegyetem, Általános és Szervetlen Kémiai Tanszék

Pázmány Péter sétány 1/A. 1518 Budapest-112 Pf. 32. Tel.: 36 -1-209-0555/1242 mellék

Fax: 36-1-209-0602. E-mail: kantor@para.chem.elte.hu