Analysis laser ablation

These comments apply to the running of a low resolution quadrupole ICP-MS, capable of both solution and laser ablation analysis, since this is the most widespread form of the instrument. High resolution MC ICP-MS is, as they say, a whole other ball game ... 

Fig. 3. Graph showing Cr, Al, V, Co, Zn, Ga, Ru, Rh, Os, and Ir profiles from a laser ablation analysis of chromite with counts per second vs time. Apart from a small Ru ( Os, lr)-bearing PGM inclusion (diameter 2 pm), the chromites do not contain IPGE. Chromite sample is from a podiform chromitite from TMO.

Giorgis D., Cosca M., and Li S. (2000) Distribution and significance of extraneous argon in UHP eclogite (Su-Lu terrain, China) insight from in situ " Ar/ Ar UV-laser ablation analysis. Earth Planet. Sci. Lett. 181, 605 -615. 

Figure 8. Oxygen three-isotope plots showing resnlts from UV laser ablation analysis of CV meteorite eomponents (a) Mineralogieally altered and unaltered portions of a CAI from the Allende meteorite. The unaltered points were used by Young and Russell (1998) to suggest that the primordial oxygen reservoir(s) for the early solar system define a line with a slope of 1.00 and an intercept of -1.0 (the Y R line), (b) CAIs and chondmles from the CV meteorites Allende, Grosnaja, and Leoville. O isotopic data for these...

Okuda T, Kato J, Mori J, Tenmoku M, Suda Y, Tanaka S, He KB, Ma YL, Yang F, Yu XC, Duan FK, Eei Y (2004) Daily concentrations of trace metals in aerosols in Beijing, China, determined by using inductively coupled plasma mass spectrometry equipped with laser ablation analysis, and source identification of aerosols. Sci Total Environ 330 145-158... 

An alternate approach is to use a fusion technique. The samples are dissolved in a molten flux such as LiBO, Na COj, or other appropriate salts. Spike additions of the analyte elements can be added to the molten sample and flux in varying concentrations. The fused melt is solidified by pouring the molten flux onto a flat surface (aluminum or stainless steel plate), where it cools, forming a uniform glassy specimen suitable for direct laser ablation analysis. Ablation of the fluxed material, after solidification, is used to establish calibration curves for quantitation or for standard addition analysis. 

Fundamentally, introduction of a gaseous sample is the easiest option for ICP/MS because all of the sample can be passed efficiently along the inlet tube and into the center of the flame. Unfortunately, gases are mainly confined to low-molecular-mass compounds, and many of the samples that need to be examined cannot be vaporized easily. Nevertheless, there are some key analyses that are carried out in this fashion the major one i.s the generation of volatile hydrides. Other methods for volatiles are discussed below. An important method of analysis uses lasers to vaporize nonvolatile samples such as bone or ceramics. With a laser, ablated (vaporized) sample material is swept into the plasma flame before it can condense out again. Similarly, electrically heated filaments or ovens are also used to volatilize solids, the vapor of which is then swept by argon makeup gas into the plasma torch. However, for convenience, the methods of introducing solid samples are discussed fully in Part C (Chapter 17). 

Laser desorption to produce ions for mass spectrometric analysis is discussed in Chapter 2. As heating devices, lasers are convenient when much energy is needed in a very small space. A typical laser power is 10 ° W/cm. When applied to a solid, the power of a typical laser beam — a few tens of micrometers in diameter — can lead to very strong localized heating that is sufficient to vaporize the solid (ablation). Some of the factors controlling heating with lasers and laser ablation are covered in Figure 17.2. 

Some solid materials are very intractable to analysis by standard methods and cannot be easily vaporized or dissolved in common solvents. Glass, bone, dried paint, and archaeological samples are common examples. These materials would now be examined by laser ablation, a technique that produces an aerosol of particulate matter. The laser can be used in its defocused mode for surface profiling or in its focused mode for depth profiling. Interestingly, lasers can be used to vaporize even thermally labile materials through use of the matrix-assisted laser desorption ionization (MALDI) method variant. 

For solids, there is now a very wide range of inlet and ionization opportunities, so most types of solids can be examined, either neat or in solution. However, the inlet/ionization methods are often not simply interchangeable, even if they use the same mass analyzer. Thus a direct-insertion probe will normally be used with El or Cl (and desorption chemical ionization, DCl) methods of ionization. An LC is used with ES or APCI for solutions, and nebulizers can be used with plasma torches for other solutions. MALDI or laser ablation are used for direct analysis of solids. 

Laser based mass spectrometric methods, such as laser ionization (LIMS) and laser ablation in combination with inductively coupled plasma mass spectrometry (LA-ICP-MS) are powerful analytical techniques for survey analysis of solid substances. To realize the analytical performances methods for the direct trace analysis of synthetic and natural crystals modification of a traditional analytical technique was necessary and suitable standard reference materials (SRM) were required. Recent developments allowed extending the range of analytical applications of LIMS and LA-ICP-MS will be presented and discussed. For example ... 

Approximately 70 different elements are routinely determined using ICP-OES. Detection limits are typically in the sub-part-per-billion (sub-ppb) to 0.1 part-per-million (ppm) range. ICP-OES is most commonly used for bulk analysis of liquid samples or solids dissolved in liquids. Special sample introduction techniques, such as spark discharge or laser ablation, allow the analysis of surfaces or thin films. Each element emits a characteristic spectrum in the ultraviolet and visible region. The light intensity at one of the characteristic wavelengths is proportional to the concentration of that element in the sample. 

Initial results prove the high potential of LA-based hyphenated techniques for depth profiling of coatings and multilayer samples. These techniques can be used as complementary methods to other surface-analysis techniques. Probably the most reasonable application of laser ablation for depth profiling would be the range from a few tens of nanometers to a few tens of microns, a range which is difficult to analyze by other techniques, e. g. SIMS, SNMS,TXRE, GD-OES-MS, etc. The lateral and depth resolution of LA can both be improved by use of femtosecond lasers. 

An indication of the range of such clusters which might possibly be synthesized is given by the observation that mass spectroscopic analysis of the products of laser-ablation of CoS... 

Laser Ablation ICP Optical Emission Spectrometry ICP Mass Spectrometry Transmission Electron Microscopy with Energy-Dispersive X-Ray Analysis... 

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