Research Group Inorganic Trace Analysis
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Laser Ablation (LA)

NWR 213 Laser Ablation system (New Wave Research)

Laser Ablation is a solid sampling technique which is characterized by low sample consumption. It features a lateral resolution in the lower µm-range and depth resolution depending upon the sample material.

The solid sample (a) is placed in a chamber (b) which can be moved in x/y/z direction to allow z-focus adjustment and rastering of the sample-surface. In order to remove air from the chamber, it is constantly purged with argon or helium (1). A pulsed UV-laser (213nm, Nd:YAG solid state laser) is directed on the sample's surface (2) which causes sample ablation. An aerosol plume is formed (c) which is transported to the ICP-MS or ICP-OES via a connecting tube (3). Owing to a specially constructed chamber, washout times are very short (1-3s, depending on the gas-flow) which allows for high sample throughput and imaging.

Schematic of the Laser Ablation system

[under construction]

Electro Thermal Vaporisation (ETV)

ETV 4000 solid sampling unit (Spectral Systems)

Electro Thermal Vaporisation allows direct analysis of solid samples without any digestion step. The samples are evaporated thermally and the vapours are introduced into the plasma of an ICP-OES or an ICP-MS instrument. The ETV process is comparable to the electro thermal process used in the ET-AAS system, organic matrix is easily removed by a matrix pyrolysis step at moderate temperatures, the analytes are swiftly evaporated at high temperaratures:

       Transient signals obtained from ETV-analysis (Platinum Group Elements, data recorded with iCAP 6000 ICP-OES Spectrometer)

The solid sample is placed in a graphite boat (a) which is transferred inside a graphite tube (b). This tube is heated by resistance heating (the current is applied through connection pieces (c) and (d)); thermal radiation emanating from the walls causes homogenous heating of the sample.

Schematic section of the graphite furnace

Argon is used as a carrier gas (1); it is mixed with small amounts of “Freon” which dissociates at high temperatures and produces highly reactive components which enhance the formation of volatile species and ensure the quantitative evaporation of the target analytes. The vaporized analyte leaves the hot graphite tube (b) and it is very likely that it will re-condense on colder spots in the system. Therefore, a cooling gas (2) is injected tangentially to the main carrier flow which ensures that the vapour cools down without touching any walls. By doing so, particles with a very small diameter are produced and transferred into the plasma (3); due to the very small size of these particles, sedimentation is avoided and the transport efficiency from the ETV system to the plasma torch increases.

The following types of samples have already been analyzed using this system:

  • plant material
  • airborne particulate matter
  • sewage sludge
  • fly ash
  • rubber tires
  • ...