Glow discharge laser ablation

Nondestructive radiation techniques can be used, whereby the sample is probed as it is being produced or delivered. However, the sample material is not always the appropriate shape or size, and therefore has to be cut, melted, pressed or milled. These handling procedures introduce similar problems to those mentioned before, including that of sample homogeneity. This problem arises from the fact that, in practice, only small portions of the material can be irradiated. Typical nondestructive analytical techniques are XRF, NAA and PIXE microdestructive methods are arc and spark source techniques, glow discharge and various laser ablation/desorption-based methods. On the other hand, direct solid sampling techniques are also not without problems. Most suffer from matrix effects. There are several methods in use to correct for or overcome matrix effects ... 

Hi) Methods based on mass spectrometry Spark-source mass spectrometry Glow-discharge mass spectrometry Inductively coupled-plasma mass spectrometry Electro-thermal vaporization-lCP-MS Thermal-ionization mass spectrometry Accelerator mass spectrometry Secondary-ion mass spectrometry Secondary neutral mass spectrometry Laser mass spectrometry Resonance-ionization mass spectrometry Sputter-initiated resonance-ionization spectroscopy Laser-ablation resonance-ionization spectroscopy... 

Many other types of atomization devices have been used in atomic spectroscopy. Gas discharges operated at reduced pressure have been investigated as sources of atomic emission and as ion sources for mass spectrometry. The glow discharge is generated between two planar electrodes in a cylindrical glass tube filled with gas to a pressure of a few torr. High-powered lasers have been employed to ablate samples and to cause laser-induced breakdown. In the latter technique, dielectric breakdown of a gas occurs at the laser focal point. 

Generally, AES systems are calibrated with multi-element standard samples. In the case of sparks, arcs, glow discharges, and laser ablation, solid samples are required, which are rarely available in large enough numbers to provide a satisfactory calibration. Hence, in solid sample analysis secondary standards are usually prepared. 

Inductively coupled plasma mass spectrometry (ICP-MS), laser ablation ICP-MS (LA ICP-MS), thermal ionization mass spectrometry (TIMS), secondary ion mass spectrometry (SIMS), glow discharge mass spectrometry (GDMS), resonance ionization mass spectrometry (RIMS), and accelerator mass spectrometry (AMS) have been used successfully to measure uranimn concentrations and isotope ratios in a wide range of sample matrices. The specific details of the methods are described fully in the relevant sections of this encyclopedia. There are specific advantages associated with each method, which depend on the sample of interest and the information required. 

The analysis of solids is time consuming and is prone to many sources of error. Analytical chemists have been trying for many years to analyze solid samples directly, without having to dissolve than. For some types of samples, this can be done by AAS. Solids can be analyzed using a glow discharge (GD) atomizer, by inserting small pieces or particles of sample directly into the flame or furnace or by the use of laser ablation. 

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