Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) is a widely accepted method for direct sampling of solid materials for trace elemental analysis. The number of reported applications is high and the application range is broad; besides geochemistry, LA-ICP-MS is mostly used in environmental chemistry and the life sciences. This review focuses on the application of LA-ICP-MS for quantification of trace elements in environmental, biological, and medical samples. The fundamental problems of LA-ICP-MS, such as sample-dependent ablation behavior and elemental fractionation, can be even more pronounced in environmental and life science applications as a result of the large variety of sample types and conditions. Besides variations in composition, the range of available sample states is highly diverse, including powders (e.g., soil samples, fly ash), hard tissues (e.g., bones, teeth), soft tissues (e.g., plants, tissue thin-cuts), or liquid samples (e.g., whole blood). Within this article, quantification approaches that have been proposed in the past are critically discussed and compared regarding the results obtained in the applications described. Although a large variety of sample types is discussed within this article, the quantification approaches used are similar for many analytical questions and have only been adapted to the specific questions. Nevertheless, none of them has proven to be a universally applicable method.

Pulsed laser deposited La_0.6Sr_0.4CoO_3−δ (LSC) thin film electrodes on yttria stabilized zirconia (YSZ) single crystals were investigated by impedance spectroscopy, time of flight secondary ion mass spectrometry (ToF-SIMS) and inductively coupled plasma optical emission spectrometry (ICP-OES). Effects caused by different film deposition temperatures, thermal annealing and chemical etching were studied. Correlations between changes in electrode polarization resistance of oxygen reduction and surface composition were found. At high deposition temperatures and after thermal annealing an inhomogeneous cation distribution was detected in the surface-near region, most manifest in a significant Sr enrichment at the surface. An activating effect of chemical etching of LSC is described, which can lower the polarization resistance by orders of magnitude. Chemistry behind this activation and thermal degradation was analyzed by ToF-SIMS and ICP-OES measurements of in-situ etched LSC films. The latter allow quantitative depth resolved compositional analysis with nominally sub nm resolution. High resolution scanning electron microscopy images illustrate the accompanying changes in surface morphology. All measurements suggest that stoichiometric LSC surfaces intrinsically exhibit very high activity towards oxygen reduction.

In the last few years, LIBS has become an established technique for the assessment of elemental concentrations in various sample types. However, for many applications knowledge about the overall elemental composition is not sufficient. In addition, detailed information about the elemental distribution within a heterogeneous sample is needed. LIBS has become of great interest in elemental imaging studies, since this technique allows to associate the obtained elemental composition information with the spatial coordinates of the investigated sample. The possibility of simultaneous multi-elemental analysis of major, minor, and trace constituents in almost all types of solid materials with no or negligible sample preparation combined with a high speed of analysis are benefits which make LIBS especially attractive when compared to other elemental imaging techniques. The first part of this review is aimed at providing information about the instrumental requirements necessary for successful LIBS imaging measurements and points out and discusses state-of-the-art LIBS instrumentation and upcoming developments. The second part is dedicated to data processing and evaluation of LIBS imaging data. This chapter is focused on different approaches of multivariate data evaluation and chemometrics which can be used e.g. for classification but also for the quantification of obtained LIBS imaging data. In the final part, current literature of different LIBS imaging applications ranging from bioimaging, geoscientific and cultural heritage studies to the field of materials science is summarized and reviewed.

Brown carbon is a ubiquitous and unidentified component of organic aerosol which has recently come into the forefront of atmospheric research. This component is strongly linked to the class of humic‐like substances (HULIS) in aerosol whose ultimate origin is still being debated. Using a simplified spectroscopic method the concentrations of brown carbon have been determined in aqueous extracts of fine aerosol collected during the CARBOSOL project. On the basis of the results of 2‐year measurements of several aerosol constituents at six European sites, possible sources of brown carbon are inferred. Biomass burning (possibly domestic wood burning) is shown to be a major source of brown carbon in winter. At elevated sites in spring, smoke from agricultural fires may be an additional source. Direct comparison of measured brown carbon concentrations with HULIS determined by an independent method reveals that the two quantities correlate well at low‐elevation sites throughout the year. At high‐elevation sites the correlation is still high for winter but becomes markedly lower in summer, implying different sources and/or atmospheric sinks of brown carbon and HULIS. The results shed some light on the relationships between atmospheric brown carbon and HULIS, two ill‐defined and overlapping components of organic aerosol.