Laser ablation , advances

The high precision with which Mg isotope ratios can be measured using MC-ICPMS opens up new opportunities for using Mg as a tracer in both terrestrial and extraterrestrial materials. A key advance is the ability to resolve kinetic from equilibrium mass-dependent fractionation processes. From these new data it appears that Mg in waters is related to mantle and crustal reservoirs of Mg by kinetic fractionation while Mg in carbonates is related in turn to the waters by equilibrium processes. Resolution of different fractionation laws is only possible for measurements of Mg in solution at present laser ablation combined with MC-ICPMS (LA-MC-ICPMS) is not yet sufficiently precise to measure different fractionation laws. 

Inductively coupled plasma-mass spectrometry (ICP-MS) has seen increasing use in trace element studies of ceramics in the last two decades. While early work using weak acid extraction proved problematic (/), recent work by Kennet et al. using microwave digestion (2) and by Larson et al. using laser ablation (3) have yielded considerable advances in the application of this technique. 

Common methods for the fabrication of metallic nanoparticle arrays are electron beam lithography, photolithography, laser ablation, colloidal synthesis, electrodeposition and, in recent time, nanosphere lithography for which a monodisperse nanosphere template acts as deposition mask. A review on advances in preparation of nanomaterials with localized plasmon resonance is given in [15]. 

The past decade may be characterized by an intense research effort to improve the sensitivity and reliability of ion mobility-based instruments for detection of explosives and to expand the inventory of detectable explosive substances. In addition, improvements in sampling techniques have been proposed, standards for calibration of ion mobility spectrometry (IMS) instruments and for method verification have been developed, and novel instrumental techniques based on laser ablation or electrospray ionization have been advanced. This has occurred due to the rising need for rapid, efficient, and reliable detectors of explosives that are used in acts of terrorism worldwide, as stated in many occasions (see Rame 12.1). Some idea about the scale of this trend can be gained from a recent report Austin, TX, 15 Septanber, 2011—Sales of Explosives, Weapons, and Contraband (EWC) Detection equipment to the world s airport authorities, amassed a significant 834.9 million in 2010, according to a recent study published by IMS Research, a leading provider of market research in the homeland security industry. ... 

The first instrument for laser ablation/ionization was described by Sinha et al. (1984). This had most of the features of the present-day instruments unfortunately, the technology available at that time severely limited its development and utility. A major advance was made by McKeown et al. (1991) with the use of TOFMS, which enabled the recording of a complete mass spectrum for each particle. Further developments, notably by Prather s group, have culminated in the first conmiercially available ATOFMS instrument. A schematic diagram of an ATOFMS system is shown in Figure 28.33. 

It would be an advantage to be able to analyze the chemical composition of individual oil inclusions. FTIR spectroscopy enables this to be partly achieved, but to provide the molecular detail needed for source and maturity assessment, an MS method is required. Advances in laser micropyrolysis GC-MS design mean that this is beginning to become possible. TOF-SIMS already shows great promise for chemical mapping of organic compounds in fluid inclusions and, in conjunction with laser ablation, may offer the best way to obtain chemical compositions of individual oil inclusions in the future. However, these techniques are unlikely to replace the power of detailed GC-MS with off-line crushing and will probably evolve as complementary techniques. 

Cocherie, A., Robert, M. (2008) Laser ablation coupled with ICP-MS applied to U-Pb zircon geochronology a review of recent advances. Gondwana Research, 14,597-608. 

So far the pulsed lasers with a pulse duration of some nanoseconds have been most widely used for LA-Nd YAG (1064, 532, 354.7. 266 nm), ex-cimer lasers XeCI (308 nm), KrF (248 nm). For these lasers the mechanisms responsible for the material removal are thermal melting and evaporation or some kind of explosive evaporation. As a result, so called fractional evaporation could occur—the elements with different melting and boiling temperatures evaporate from a melt at different rates. Because of this composition of a laser plume does not match the bulk composition. This was a serious problem as inadequate probing of a sample could not be corrected for by any sensitive detection scheme. The optimal conditions for laser ablation and advanced methods of data processing were found to avoid the problem of fractionation for different classes of samples in the case of nanosecond pulses. 

Advances in Laser Ablation-Multi-Collector Inductively Coupled Plasma Mass Spectrometry... 

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