Laser ablation, analytical method Applications

At present the real strength of LA lies in the measurement of distribution patterns of minor and trace elements in solid samples with high spatial resolution. Homogeneity testing is an application of LA-ICP-MS. There is an increasing demand for the development and validation of accurate and robust analytical technologies for the determination of the chemical characteristics of polymeric products in support of industrial needs, EC regulations (e.g. Directive on toy safety) or research. Needs are particularly acute for techniques able to determine trace element contents in solids with a minimum sample preparation. For this purpose, laser ablation-based methods, such as LA-ICP-AES/MS and laser-induced plasma atomic emission spectrometry (LIP-AES, LA-AES or LIBS) have already... 

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 ... 

There are a few drawbacks to this method. Using 4 or 5 TIMS measurements to produce a U-series date profile across a bone is time consuming, although a single reliable U-series date is surely worth hundreds where the accuracy is not known. In future, the application of Laser-Ablation ICP-MS to measuring profiles will significantly reduce the analytical effort required to obtain a date. 

Use of inductively coupled plasma-mass spectrometry (1CP-MS) coupled to a laser-ablation sample introduction system (LA-ICP-MS) as a minimally destructive method for chemical characterization of archaeological materials has gained favor during the past few years. Although still a relatively new analytical technique in archaeology, LA-ICP-MS has been demonstrated to be a productive avenue of research for chemical characterization of obsidian, chert, pottery, painted and glazed surfaces, and human bone and teeth. Archaeological applications of LA-ICP-MS and comparisons with other analytical methods are described. 

Online isotope dilution technique LA-ICP-MS is proposed as the method of choice for quantitative element mapping and imaging even if no reference materials are available (42). For online solution-based calibration with LA-ICP-MS, a microflow total consumption nebulizer DS-5 (CETAC Technologies, Omaha, NE, USA) was inserted into the laser ablation chamber (21). It is more convenient to use solution-based calibration because such calibration can be performed easily, quickly and in any concentration range for many elements. The application of the online isotope dilution technique in LA-ICP-MS using a microflow nebulizer inserted into the laser ablation chamber to biological standard reference materials (e.g., apple leaves) yielded accurate analyte concentrations (42). 

This chapter is only concerned with spectroscopic techniques applicable to polymer/additive analysis insofar as not reported under the specific headings of laser ablation (c/r. Chp. 3.2) or laser pyrolysis (c/r. Chp. 3.5). Laser spectroscopy, which is no substitution of conventional methods but a valuable addition of the analytical toolbox, has extensively been reviewed [1,98]. Chemical spectroscopy with lasers [9] and applications of laser spectroscopy were described in monographs [1,3,99]. 

Solvent-free separation using IMS-MS when combined with solvent-free sample preparation and appropriate ionization methods provides TSA that are independent of analyte solubility and is applicable to complex mixtures. A new ionization method, LSI, which operates at AP with laser ablation of samples prepared in a MALDI matrix, has been effectively interfaced with a SYNAPT G2 IMS-MS instrument. Early results show separation of protein mixtures and that protein ion structures from LSI and ESI are similar. Further, a new matrix allows LSI multiply charged ion formation to be extended to solvent-free matrix preparations. Thus TSA by LSI-IMS-MS is a new approach to tissue imaging at high spatial resolution on high-end mass spectrometers such as the SYNAPT G2 and Orbitrap instruments. LSI has... 

Preparation of calibrators in solution can be effected by simple mixing of the correct amounts of the constituents in an appropriate matrix. There is little problem with either homogeneity or speciation of the analytes in that instance. This consideration applies directly to conventional ways of operating AAS, ICPAES and ICPMS. It also applies to XRF methods that employ fused beads, where the test material is homogenized in a flux. (The end-product is, of course, a solid solution). Where solid calibrators are used, more problems are usually encountered. The most common of such are problems of creating a sufficiently homogeneous mixture of the analytes in a realistic matrix, and problems of speciation of the analyte. Fortunately, neither of these is a serious problem in routine XRF, although they may be in specialist applications of ICPAFS and ICPMS, such as laser ablation work. 

For laser ablation as a method of sample introduction for ICP-MS, sohd-state lasers are preferred, because for these systems an acceptable compromise between output laser parameters and system costs is obtained. Nevertheless, excimer lasers are also becoming more popular regardless of the high maintenance demands, since the outstanding beam profile characteristics and high-energy output they offer are attractive features for several analytical applications. In... 

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