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Over the past few years, laser-induced breakdown spectroscopy (LIBS) has earned a lot of attention in the field of online polymer identification. Unlike the well-established near-infrared spectroscopy (NIR), LIBS analysis is not limited by the sample thickness or color and therefore seems to be a promising candidate for this task. Nevertheless, the similar elemental composition of most polymers results in high similarity of their LIBS spectra, which makes their discrimination challenging. To address this problem, we developed a novel chemometric strategy based on a systematic optimization of two factors influencing the discrimination ability: the set of experimental conditions (laser energy, gate delay, and atmosphere) employed for the LIBS analysis and the set of spectral variables used as a basis for the polymer discrimination. In the process, a novel concept of spectral descriptors was used to extract chemically relevant information from the polymer spectra, cluster purity based on the k-nearest neighbors (k-NN) was established as a suitable tool for monitoring the extent of cluster overlaps and an in-house designed random forest (RDF) experiment combined with a cluster purity–governed forward selection algorithm was employed to identify spectral variables with the greatest relevance for polymer identification. Using this approach, it was possible to discriminate among 20 virgin polymer types, which is the highest number reported in the literature so far. Additionally, using the optimized experimental conditions and data evaluation, robust discrimination performance could be achieved even with polymer samples containing carbon black or other common additives, which hints at an applicability of the developed approach to real-life samples.Graphical abstract

Cubic Li7La3Zr2O12 (LLZO) garnets are among the most promising solid-state electrolytes for next-generation Li batteries. However, despite intensive research in recent years, little effort is spent on proper chemical analysis of the material. For reliable LLZO investigation, knowledge about the exact chemical composition, especially the Li content, is of uttermost importance. Herein, we present a method for the laterally resolved stoichiometry determination of Al stabilized LLZO (Li7−3xAlxLa3Zr2O12) using LA-ICP-OES. To ensure reliable signal quantification, matrix-matched standards are prepared and carefully characterized using sample digestion and liquid ICP-OES measurement. An internal standard-independent calibration strategy based on 100 m% normalization is applied, enabling the quantification of all cations within the material. By comparing the obtained high-precision LA-ICP-OES calibrations with analog LA-ICP-MS measurements, it is shown that ICP-OES is the superior choice for the analysis of Li. The developed method is applied to record quantitative distribution images of an Al stabilized LLZO pellet, revealing macroscopic stoichiometry variations within the sample. To verify the analysis, the average stoichiometry obtained by the LA measurements is compared with the bulk composition determined via liquid ICP-OES analysis after sample fusion. The obtained values show excellent agreement, confirming the accuracy of the developed method.

Laser ablation of solids in liquid (LASIL) coupled with ICP-OES detection was used as a new sampling technique for the analysis of ceramic thin films. The quantitative analysis of such thin films requires high sensitivity, due to a very low absolute analyte amount. For this purpose, the ablation cell, which is a key element for online coupling of the particle generation and detection system, was improved and the washout times could be reduced by a factor of 6 compared to previous publications. To demonstrate the capabilities of this online-LASIL technique, the elemental compositions of gadolinium doped cerium oxide (GDC) thin films were determined and energy dispersive X-ray microanalysis (SEM-EDX) was used as a reference technique. The film thickness of the investigated samples ranged from 220 nm to 14 nm. While SEM-EDX comes to its limits for films below 110 nm, online-LASIL-ICP-OES shows constant high accuracy and precision for all investigated films.

Recommendations are given concerning the terminology of concepts and methods used in spectroscopy in analytical chemistry, covering nuclear magnetic resonance spectroscopy, atomic spectroscopy, and vibrational spectroscopy. © 2021 IUPAC and De Gruyter. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. For more information, please visit: http://creativecommons.org/licenses/by-nc-nd/4.0/ 2021.

The defect chemistry and electronic trapping energies in undoped single crystalline SrTiO3 were examined by electrochemical impedance spectroscopy (EIS) at low (25-160°C) and intermediate (500-700°C) temperatures. At intermediate temperatures, the electronic and ionic conductivity as well as the chemical capacitance of SrTiO3 were determined as a function of T and p(O2) by employing a modified transmission line equivalent circuit to accurately describe the measured system. Defect modelling based on chemical capacitance measurements is established as a new method to determine the concentrations and the thermodynamic properties of ionic and electronic defects in SrTiO3. This method has potential for a wide application for mixed ionic and electronic conducting materials. Impedance spectroscopy at low temperatures was used to further quantify the electronic trapping energies of the main ionic defects of SrTiO3. Utilization of the chemical capacitance allows the establishment of a defect model based solely on electrochemical measurements, which correctly predicts the conductivity and the chemical capacitance, unveiling the concentrations of internal defects. This analysis yields a concentration of 6 ppm for acceptor-type titanium vacancies in the investigated SrTiO3 single crystals, which was experimentally confirmed by complementary Positron Annihilation Lifetime Spectroscopy measurements. The employed method is sensitive for electronically relevant defects in concentrations even below 1 ppm.

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. 2020 The Authors. Published by Elsevier B.V.

The growing importance of fluoropolymers in high-tech applications and green technologies results in the rising need for their characterization. In contrast to conventional methods used for this task, laser-induced breakdown spectroscopy (LIBS) provides the advantage of a spatially resolved analysis. Nevertheless, the high excitation energy of fluorine results in low sensitivity of the atomic F(I) lines, which limits the feasibility of its LIBS-based analysis. This work presents a novel approach for quantitative mapping of fluorine in fluoropolymer samples. It bases on monitoring of molecular emission bands (CuF or CaF) arising from fluorine containing molecules. These species were generated during later stages of the LIBS plasma by a recombination of fluorine atoms originating from fluoropolymer sample with a molecule-forming partner (Cu or Ca) stemming from a surface coating. This approach enables F detection limits in the parts per million (μg g

Distinguished procedures for routine assessment of metal contents in powdered environmental samples need to be simple, fast, reliable and accurate. Using ICP-based measurement techniques usually sample digestion is necessary prior to liquid analysis. In this work, a method is presented which allows accurate quantification of Cd, Co, Cr, Cu, Mn and Ni in fly ash samples by means of electro-thermal vaporization (ETV) in combination with ICP-OES detection. Thus, time demanding sample digestion could be circumvented. For analysis slurries of the powdered samples are prepared and measured without any further complex sample preparation. The method was validated by analysis of BCR 176R (fly ash), demonstrating that calibration with aqueous standard solutions allows accurate quantification. Derived detection limits ranged from 2 μg/g to 25 μg/g, providing sufficient sensitivity for analysis of metallic contaminants in fly ash. The method was successfully applied to the analysis of municipal waste incineration ash samples from Spittelau, Vienna's municipal waste combustion plant.

Advanced materials such as complex metal oxides are used in a wide range of applications and have further promising perspectives in the form of thin films. The exact chemical composition essentially influences the electronic properties of these materials which makes correct assessment of their composition necessary. However, due to high chemical resistance and in the case of thin films low absolute analyte amounts, this procedure is in most cases not straightforward and extremely time-demanding. Commonly applied techniques either lack in ease of use ( i.e. , solution-based analysis with preceding sample dissolution), or adequately accurate quantification ( i.e. , solid sampling techniques). An analysis approach which combines the beneficial aspects of solution-based analysis as well as direct solid sampling is Laser Ablation of a Sample in Liquid (LASIL). In this work, it is shown that the analysis of major as well as minor sample constituents is possible using a novel online-LASIL setup, allowing sample analysis without manual sample handling after placing it in an ablation chamber. Strontium titanate (STO) thin layers with different compositions were analyzed in the course of this study. Precision of the newly developed online-LASIL method is comparable to conventional wet chemical approaches. With only about 15–20 min required for the analysis per sample, time demand is significantly reduced compared to often necessary fusion procedures lasting multiple hours.

Nowadays, metal analysis in polymers is experiencing growing interest due to increased environmental regulations and the need for sustainable polymer recycling strategies. Quick and reliable analyses are required to fulfill the demands of today's industry. Due to the high chemical inertness of most polymers, traditional solution-based analysis is often not an option and solid-sampling techniques such as Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) or Laser Induced Breakdown Spectroscopy (LIBS) have to be employed as an alternative. These, however, are typically prone to matrix effects and for each polymer type a separate reference material with known concentration may be required – an approach which is obviously not suitable if the polymer type is not even known. To overcome these difficulties, a tandem LA-ICP-MS/LIBS procedure coupled with statistical analysis has been used in this study. LIBS is known to be especially prone to matrix effects – which has been used as a benefit here. Complete broadband LIBS spectra with a wealth of information have been used as signatures for the investigated polymer types (polyimide, polymethylmethacrylate and polyvinylpyrrolidone) to serve the purpose of reducing matrix effects. While LIBS allowed the detection of alkali metals and alkali earth metals even at lower concentrations, LA-ICP-MS was used simultaneously for the analysis of other trace metals in the μg g−1 regime. Na, Sr, Co, In, and Pt were used as exemplary analytes at concentrations ranging from as low as 0.1 μg g−1 up to 300 μg g−1. Using the combined dataset of all three polymer types (in total 23 samples), multivariate calibration models could be constructed for all elements of interest. Validation was performed using a set of 22 external samples showing relative average deviations from their actual elemental content of 4.4%, but not more than 9.6%.

Providing unique advantages, laser-based analytical techniques such as LIBS have gained more and more popularity for quantitative elemental analysis in the last few years. However, to obtain reliable quantitative results, matrix-matched standards are required. A particular material of interest for quantitative trace metal analysis is synthetic polymers, which is among the most widely used materials in our modern world. As the exact composition of a polymer under investigation (polymer type and applied additives) is often not known, the selection of an appropriate matrix-matched standard is difficult. In this work, we investigate and assess different approaches for quantifying potassium in unknown polymer types or polymers with an unknown composition where matrix-matched standards cannot be employed. This is of great interest in the semiconductor industry where monitoring of mobile ions in applied polymers is crucial, and the composition of the polymer is often not known due to confidentiality. We use the unique capabilities of LIBS, providing adequate sensitivity for potassium, and additionally delivering polymer-specific emission signals. Two different multivariate approaches (Random Decision Forest classification combined with conventional univariate calibration and a Partial Least Squares model) are developed and applied. Therefore, an in-house prepared library of standards of 8 different polymer types (Acrylic, PAN, PI, PMMA, PSU, PVA, PVC and PVP) is prepared. The errors obtained from the multivariate approaches are compared with conventional matrix-matched as well as non-matrix-matched quantification. With our developed approaches, for some samples quantitative determination of potassium in the low μg/g range in unknown polymer types is achieved with a relative error less than 20% which is comparable to conventional matrix-matched quantification. For all other samples, relative errors in the range of 30%–90% are obtained, which offers a precision adequate for many applications. E.g. in the food-packaging- or semiconductor-industry in many cases it is sufficient to determine if the contamination level of a sample with an unknown matrix is below or above a certain threshold. In this case, the developed approach poses a significant improvement compared to non-matrix-matched quantification which often leads to deviations up to a factor 10 or more from the nominal concentration.

Solid oxide fuel cells (SOFCs) are one of the key technologies on the way to environmentally friendly power generation. Current research activities aim to reduce their operational temperature to intermediate temperatures (400–600 °C) to make their application more feasible. In a recent approach, lanthanum strontium iron oxide (LSF) thin film electrodes, a mixed ionic electronic conducting (MIEC) material, was decorated with tiny amounts of platinum nanoparticles, which led to a significant improvement of the oxygen reduction kinetics. To understand this material combination a precise characterization is of major interest, especially the exact amount of platinum on the surface. As the studied model-type thin film electrode requires a platinum current collector buried beneath the LSF to improve in-plane electron conductivity, a method providing quantitative information as well as sufficient depth resolution is needed. In this work, we further improved the recently presented approach of online laser ablation of solids in liquids (LASIL), which enabled in combination with ICP-MS detection a spatially resolved analysis of the sample composition. Careful optimization of laser parameters and carrier solution led to a depth resolution of 30 nm, which allowed a clear separation of the Pt-signals from the surface decoration and the underlying current collector. The amount of platinum on the surface was determined using calibration with a matrix matched standard and validated by another method. Finally, the imaging capabilities of the proposed online-LASIL approach have been employed to assess the homogeneity of the Pt-decoration, indicating significant variations within the investigated area. Thus, further improvements in the electrochemical properties of the investigated LSF electrodes could be anticipated by fabrication of MIECs with a more homogeneous platinum decoration.

Microspectroscopic techniques are widely used to complement histological studies. Due to recent developments in the field of chemical imaging, combined chemical analysis has become attractive. This technique facilitates a deepened analysis compared to single techniques or side-by-side analysis. In this study, rat brains harvested one week after induction of photothrombotic stroke were investigated. Adjacent thin cuts from rats’ brains were imaged using Fourier transform infrared (FT-IR) microspectroscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The LA-ICP-MS data were normalized using an internal standard (a thin gold layer). The acquired hyperspectral data cubes were fused and subjected to multivariate analysis. Brain regions affected by stroke as well as unaffected gray and white matter were identified and classified using a model based on either partial least squares discriminant analysis (PLS-DA) or random decision forest (RDF) algorithms. The RDF algorithm demonstrated the best results for classification. Improved classification was observed in the case of fused data in comparison to individual data sets (either FT-IR or LA-ICP-MS). Variable importance analysis demonstrated that both molecular and elemental content contribute to the improved RDF classification. Univariate spectral analysis identified biochemical properties of the assigned tissue types. Classification of multisensor hyperspectral data sets using an RDF algorithm allows access to a novel and in-depth understanding of biochemical processes and solid chemical allocation of different brain regions. This work was supported by MEIBio doctoral project of TU Wien and by the funding from the Austrian FFG within project 84247. This work was co-funded by NPRP grant no. NPRP-5-381-3-101 from the Qatar National Research Fund (a member of The Qatar Foundation). Scopus

Modern chemical imaging techniques provide spatially resolved information on the molecular and elemental composition of samples with both high spatial and spectral resolution. Over the past few decades these techniques, in particular, Fourier transform infrared (FTIR) spectroscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) have been successfully applied in histopathological research. This work demonstrates that the multivariate analysis of combined FTIR and LA-ICP-MS microscopy hyperspectral images can bring additional knowledge to biomedical research. The concept of such analysis was demonstrated while investigating two different tumor samples subjected to anticancer therapy. Combined analysis has revealed a correlation between the lateral distribution of analytes and sample properties within the different techniques. Correlations between alterations in the average protein secondary structure and platinum distribution were found, as well as between changes in the cell nuclear morphology and a reduction of physiologically relevant trace elements. The results of combined analysis suggested different degrees of tumor viability. Univariate analysis and k-means clustering successfully discriminated dead tumor regions and supported the results of combined analysis.

Integration of transient signals is a commonly applied supervised approach to estimating isotope ratios from single-particle LA-ICP-MS measurements. Spectra collected on individual particles suffer from relatively weak signal strength and short duration, both of which present challenges to the integration method. Moreover, since numerous particles are measured in an analytical run, analyst supervision is required for every individual particle to estimate isotope ratios by the integration method (e.g. specification of time window containing background and specification of time window for integration of the signal for every particle spectrum). In this paper we present a simple, unsupervised, robust alternative for estimating isotope ratios from LA-ICP-MS spectra, which can be rapidly applied to a large number of particle measurements. The approach relies on point-by-point data reduction followed by application robust statistical estimation methods.

Advanced materials are nowadays used in various industrial and scientific contexts, due to their particular and sometimes unique properties. In many cases, those properties are closely linked to the composition of the materials. An integral part in the characterization of advanced materials is therefore to determine their precise elemental composition, as well as to detect possible contaminants. With this information, the production as well as the properties of the final products can be optimized. To obtain such information in a routinely way, ICP-OES or ICP-MS are versatile tools, since those techniques allow sensitive multi-element analysis in a variety of matrices (e.g., high-purity materials, semiconductors, electronic components, metals, alloys, ceramics, and polymers). However, if using ICP-based techniques in their regular configuration, conversion of the solid material into a liquid solution is necessary. For this purpose, procedures such as acid digestion, fusion or dry ashing have been reported. However, although being well established, the application of these approaches is related with some drawbacks. Besides the problem of jeopardizing information on spatial distribution of analytes, some further shortcomings are risk of sample contamination and/or analyte losses, as well as increased time demand for sample preparation (especially in case of materials with high chemical resistance). Analyzing the solid sample directly is therefore an attractive alternative to conventional liquid analysis. Solid-sampling techniques which are frequently applied in combination with ICP-OES or ICP-MS detection are electro-thermal-vaporization (ETV) and laser-ablation (LA). Besides offering the mentioned advantages in sample preparation, solid-sampling techniques often allow for improvements in sensitivity, since unnecessary sample dilution could be avoided. Furthermore, LA (with restrictions also ETV) offers the possibility of spatially resolved analysis and depth profile analysis, providing information about the distribution of major, minor and trace constituents within the sample. The aim of this review is to discuss new analytical developments in ETV and LA in combination with ICP techniques for the quantitative determination of bulk, trace and ultra-trace elements in the routine analysis of advanced materials.

Nowadays, for the production of oxidation protection coatings in ultrahigh temperature environments, alloys of Mo–Si–B are employed. The properties of the material, mainly the oxidation resistance, are strongly influenced by the Si to B ratio; thus reliable analytical methods are needed to assure exact determination of the material composition for the respective applications. For analysis of such coatings, laser ablation inductively coupled mass spectrometry (LA-ICP-MS) has been reported as a versatile method with no specific requirements on the nature of the sample. However, matrix effects represent the main limitation of laser-based solid sampling techniques and usually the use of matrix-matched standards for quantitative analysis is required. In this work, LA-ICP-MS analysis of samples with known composition and varying Mo, Si and B content was carried out. Between known analyte concentrations and derived LA-ICP-MS signal intensities no linear correlation could be found. In order to allow quantitative analysis independent of matrix effects, a multiple linear regression model was developed. Besides the three target analytes also the signals of possible argides ( 40 Ar 36 Ar and 98 Mo 40 Ar) as well as detected impurities of the Mo–Si–B coatings ( 108 Pd) were considered. Applicability of the model to unknown samples was confirmed using external validation. Relative deviations from the values determined using conventional liquid analysis after sample digestion between 5 and 10% for the main components Mo and Si were observed.

In this work, a novel calibration approach for minor and trace element quantification in LA-ICP-MS imaging of biological tissues is presented. Droplets of aqueous standard solutions are deposited onto pre-cut pieces of filter paper, allowed to dry, and sputtered with a thin gold layer for use as pseudo-internal standard. Analysis of the standards using LA-ICP-MS is performed using radial line-scans across the filters. In contrast to conventionally used preparation of matrix-matched tissue standards, the dried-droplet approach offers a variety of advantages: The standards are easy to prepare, no characterization of the standards using acid digestion is required, no handling of biological materials is necessary, and the concentration range, as well the number of investigated analytes is almost unlimited. The proposed quantification method has been verified using homogenized tissue standards with known analyte concentrations before being applied to a human malignant mesothelioma biopsy from a patient who had not received any chemotherapeutic treatment. Elemental distribution images were acquired at a lateral resolution of 40 μm per pixel, limits of detection ranging from 0.1 μg g(-1) (Mn, Ni, Cu, Zn) to 13.2 μg g(-1) (K) were reached.

In this work, an innovative approach for determining the surface stoichiometry of complex metal oxide (CMO) thin films is presented. The procedure is based on treatment of the sample surface with different etching solutions, followed by on-line analysis of the derived eluates using inductively coupled plasma – mass spectrometry (ICP-MS). Via consecutive treatment of the sample surface with water and diluted HCl, a differentiation between water soluble and acid soluble parts of near surface regions in thin films is enabled. The developed procedure was applied for the analysis of dense La0.6Sr0.4CoO3−δ (LSC) thin films indicating the presence of a water soluble Sr-rich phase with sub nm-thickness on top of the LSC films. The step-wise optimization of this technique is reported and the results are compared to measurements performed by low-energy ion scattering (LEIS). The detrimental effect of the water soluble Sr rich phase on the oxygen exchange activity of LSC thin film electrodes is verified by electrochemical impedance spectroscopy (EIS).

In this study a combination of Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and Laser Induced Breakdown Spectroscopy (LIBS) was used for laterally resolved elemental analysis of biological samples. In general LA-ICP-MS is an excellent technique for the analysis of many trace elements. However, bulk components such as H or O are not accessible using this technique. In addition to those elements, also some other elements that are difficult or impossible to investigate using LA-ICP-MS (i.e., F, N, Cl, etc.), could be detected by LIBS. In this work, the simultaneous use of LIBS and LA-ICP-MS (tandem LA/LIBS) for the analysis of biological samples is presented, opening the door for the possibility of complete analysis of the elemental composition of a human tumor sample. Results show good correlation with the histological stainings. The obtained distribution images provide a valuable basis for further medical interpretation.

In this work the use of two laser assisted direct solid sampling methods, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and laser induced breakdown spectroscopy (LIBS) for the determination of the stoichiometry of novel diboride based materials is reported. To overcome the need for certified reference materials or matrix matched standards, which were usually required for quantitative investigations with LA-ICP-MS or LIBS, in this work liquid standards are employed. For LA-ICP-MS the concept of self-aliquoting micro-grooves and for LIBS conventional dried droplets were used. As a model for application of the developed analytical procedures the ternary system W1-xTaxB2-z was used. Fabrication of W1-xTaxB2-z thin films with varying stoichiometry was performed via magnetron sputtering. Reference compositions were obtained by liquid digestion of the samples and subsequent ICP-OES measurement. Both laser-assisted methods enabled fast and spatially resolved measurements, although the LA-ICP-MS method generally yielded more accurate results. It was shown that the method can easily be adapted for the stoichiometry determination of systems with different elemental composition.

In this study a novel and reliable Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) measurement protocol for the elemental characterization of size-segregated particulate was developed. Special efforts were made to improve and optimize sample pre-treatment steps and LA operating conditions to avoid some critical drawbacks encountered during analysis and to make the particulate samples suitable for an accurate and reproducible LA-ICP-MS analysis, regardless of the mass loading on each filter. For example, a new approach for dust-fixation on the sample-carrier was developed using a glycerol coverage, which allowed to overcome problematic sample losses during the ablation process. Under the optimum conditions, dust samples, blank filters and standards for calibration were analyzed by multiple rastering of defined spot areas. Quantitative analysis was accomplished with dried micro-droplets of aqueous standard solutions. Derived method detection limits varied between 0.001 and 0.1 ng m−3 and allowed even for the smallest particle fraction quantitative measurements. The accuracy of LA-ICP-MS results was verified by comparison with conventional ICP-MS analysis of selected PM samples after sample mineralization. The proposed LA treatment procedure benefits from a simple and fast sample preparation, thus overcoming the laborious pre-treatment steps required for wet chemical digestion. Moreover, the better sensitivity of the LA-ICP-MS approach provided more complete information about the mass concentration and size-distribution of the investigated elements, thus allowing to deeper investigate the composition of the most dangerous PM fractions in terms of health concern.

Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) is an attractive alternative to traditional procedures for the analysis of environmental samples (i.e., conventional liquid measurement after sample digestion). However, for accurate quantification, certified reference materials (CRM) are necessary which match the composition of the sample and include all elements of interest at the required concentration levels. The limited availability of appropriate CRMs hampers therefore substantial application. In this work, an LA-ICP-MS procedure allowing for accurate determination of trace element contents in powdered environmental samples is presented. For LA-ICP-MS analysis, the samples are mixed with an internal standard (silver oxide) and a binder (sodium tetra borate) and subsequently pressed to pellets. Quantification is accomplished using a calibration function determined using CRMs with varying matrix composition and analyte content, pre-treated and measured in the same way as the samples. With this approach, matrix-induced ablation differences resulting from varying physical/chemical properties of the individual CRMs could be compensated. Furthermore, ICP-related matrix-effects could be minimized using collision/reaction cell technology. Applicability of the procedure has been demonstrated by assessment of Cd, Cu, Ni, and Zn in four different environmental CRMs (NIST SRM1648a (urban particulate matter), NIST SRM2709 (San Joaquin Soil), BCR144 (sewage sludge), and BCR723 (road dust)). Signal evaluation was performed by alternative use of three CRMs for calculation of the calibration function whereas the remaining fourth CRM acted as unknown sample, resulting in a good agreement between measured and certified values for all elements and reference materials.

For laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) imaging experiments – as well as other techniques used for elemental or molecular mapping – the accordance of the measured distribution with the actual distribution is of utmost importance to guarantee reliability of the obtained images. In most experiments reported in the past, the experimental conditions have been chosen so that washout effects and signal carry-over are minimized by scanning the sample surface very slowly. Therefore, measurement times become very long and decently resolved images will require acquisition times of several hours up to more than one day. To increase the application range of LA-ICP-MS for imaging it is important to decrease the measurement times, which is best accomplished by increasing the scanning rates. However, depending on the instrumentation, this can lead to blurring and compromised image quality. In this work, we present a metric to compare the measured elemental distribution with their actual distribution based on a sample with visually distinguishable features. This approach allows quantitative determination of the image quality and enables comparison of multiple measurement conditions. This information can be used for method optimization, to get a reasonable tradeoff between image quality and measurement time.

A combination of analyte pre-concentration using dispersed particle extraction (DPE) and dried-droplet laser ablation inductively coupled mass spectrometry (LA-ICP-MS) was developed with the aim to quantify Pt and Pd in urban particulate matter with an aerodynamic diameter ≤2.5 µm (PM2.5). The PM2.5 aerosol was collected on cellulose ester filters during a sampling period of three days, with sampling intervals of 4 h only. Each of the filters was chemically digested, and the resulting solution was pre-concentrated using DPE. Droplets taken from the pre-concentrated sample were deposited on polymeric disks and dried. These dry spots were then analyzed by means of LA-ICP-MS. This approach allowed ICP-MS analysis of solutions with high content of dissolved sorbent particles coming from the DPE procedure. Furthermore, spectral interferences arising from sample-inherent matrix elements as well as solvent-related interferences could be removed by the proposed approach. The method was validated by determining the Pt concentration in Bureau Communautaire de Référence certified reference material (BCR CRM) 723 road dust certified reference material and a good agreement with the certified value was obtained. The temporal variation of Pt during the three-day sampling period is discussed, with respect to automotive traffic. The daily average of Pt measured in the air corresponds to typical values observed in urban areas in Central Europe. Although the pre-concentration of palladium is feasible with dispersed particle extraction, the method detection limits achieved here did not allow to quantify this element in the CRM or in the PM2.5 samples. The source for these high method detection limits for palladium are blank values arising from the filter material as well as the digestion procedure of the PM2.5 samples. Instrumental sensitivity of the approach would, however, suggest that palladium quantification is possible, provided the abovementioned blank issues are controlled better.

Nebulising liquid samples and using the aerosol thus obtained for further analysis is the standard method in many current analytical techniques, also with inductively coupled plasma (ICP)-based devices. With such a set-up, quantification via external calibration is usually straightforward for samples with aqueous or close-to-aqueous matrix composition. However, there is a variety of more complex samples. Such samples can be found in medical, biological, technological and industrial contexts and can range from body fluids, like blood or urine, to fuel additives or fermentation broths. Specialized nebulizer systems or careful digestion and dilution are required to tackle such demanding sample matrices. One alternative approach is to convert the liquid into a dried solid and to use laser ablation for sample introduction. Up to now, this approach required the application of internal standards or matrix-adjusted calibration due to matrix effects. In this contribution, we show a way to circumvent these matrix effects while using simple external calibration for quantification. The principle of representative sampling that we propose uses radial line-scans across the dried residue. This compensates for centro-symmetric inhomogeneities typically observed in dried spots. The effectiveness of the proposed sampling strategy is exemplified via the determination of phosphorus in biochemical fermentation media. However, the universal viability of the presented measurement protocol is postulated. Detection limits using laser ablation-ICP-optical emission spectrometry were in the order of 40 mu g mL(-1) with a reproducibility of 10 % relative standard deviation (n = 4, concentration = 10 times the quantification limit). The reported sensitivity is fit-for-purpose in the biochemical context described here, but could be improved using ICP-mass spectrometry, if future analytical tasks would require it. Trueness of the proposed method was investigated by cross-validation with conventional liquid measurements, and by analyzing IAEA-153 reference material (Trace Elements in Milk Powder); a good agreement with the certified value for phosphorus was obtained

LA-ICP-MS has often been applied for the analysis of trace elemental distributions in biological tissues. However, the strong matrix dependence of LA-ICP-MS analyses and highly variable matrix conditions aggravate reliable qualitative distribution analyses and thus for obtaining quantitative information elaborate quantification strategies have to be applied. In this work printed patterns on paper with thin gold layers as pseudo-internal standard have been proposed as an alternative approach to the commonly used matrix-matched tissue standards. Besides a major reduction of the workload for standard preparation the presented method allows for compensation of instrumental drifts during measurement as well as a reduction of matrix related effects. The developed method has been verified using matrix-matched tissue standards (deviations from the actual metal content less than 5% with relative standard deviations of less than 7%) and applied to platinum imaging on human malignant pleural mesothelioma samples after administration of individuals with platinum containing cytostatic drugs.

Conventional approaches for the analysis of platinum group elements (PGEs) in plant material suffer from sample digestion which results in sample dilution and therefore requires high sample intakes to maintain the sensitivity. The presented solid-sampling method avoids sample digestion while improving sensitivity when compared to digestion-based inductively coupled plasma optical emission spectrometry (ICP-OES) methods and allows the analysis of sample masses of 5 mg or less. Detection limits of 0.38 μg g− 1, 0.14 μg g− 1 and 0.13 μg g− 1 were obtained for Pt, Pd and Rh, respectively using a sample intake of 5 mg. The reproducibility of the procedure ranged between 4.7% (Pd) relative standard deviation (RSD, n = 7) and 7.1% (Rh) RSD for 25 ng analytes. For quantification, aqueous standards were applied on paper filter strips and dried. Only the dried filters were introduced into the electrothermal vaporization unit. This approach successfully removed memory-effects observed during analysis of platinum which occurred only if liquid standards came into contact with the graphite material of the furnace. The presented method for overcoming the Pt-memory-effects may be of further interest for the analysis of other carbide-forming analytes as it does not require any technical modification of the graphite furnace (e.g., metal inlays, pyrolytic coating). Owing to lack of suitable certified reference materials, the proposed method was compared with conventional ICP-OES analysis of digested samples and a good agreement was obtained. As a result of the low sample consumption, it was possible to determine the spatial distribution of PGEs within a single plant. Significant differences in PGE concentrations were observed between the shoots (stem, leaves) and the roots. Pd was mainly found in the roots, whereas Pt and Rh were also found in higher concentrations in the shoots.

In this work a new procedure for element specific analysis of silicon in airborne particulate matter is presented. The method is based on a preliminary treatment of the aerosol samples with nitric acid and perchloric acid leading to a mineralization of the organic sampling substrate, dissolution of soluble material and a homogeneous suspension of the remaining non-soluble sample fraction. ETAAS measurement of the derived slurries was performed using a Zr-treated graphite tube which prevents the formation of stable silicon carbide during sample measurement. Losses of volatile silicon species during sample pyrolysis were overcome by using Co(II) as matrix modifier and a pyrolysis temperature of only 300 degrees C. Furthermore this low pyrolysis temperature prevents charring of organic material which enables accurate ETAAS analysis. The method including the developed pretreatment procedure was evaluated using the Standard reference material 2709 (San Joaquin Soil) from NIST (National Institute of Standards and Technology, Gaithersburg, MD, USA). Suitability for measurement of Si in airborne particulate matter with an aerodynamic diameteror = 10 microm (PM10) was demonstrated by the analysis of selected aerosol samples and comparison of derived results with the findings obtained for the same samples after microwave digestion and subsequent ETAAS measurement. Finally the developed procedure was applied for the analysis of silicon in PM10 collected at an urban site in Vienna (Austria). Matrix matched calibration has been used for quantification of derived absorption signals. With the use of 20 microL sample injection volume for ETAAS analysis an instrumental detection limit of 52.2 microg L(-1) was obtained, which translates to method detection limits of approximately 0.52 microg m(-3) when considering the volumes of air collected per investigated aerosol sample. The reproducibility of analysis given as the relative standard deviation was 4.4% (n=12). Derived concentrations for Si in PM10 varied between 0.8 and 7.2 microg m(-3) which is in good accordance with the literature findings.

A procedure was developed for the selective determination of Pd in environmental aquatic solutions. The method is based on a preliminary microwave-assisted UV-digestion for the degradation of dissolved organic material, and the subsequent determination of Pd using a recently presented enrichment procedure with ETAAS detection. Due to the simultaneous use of microwave and UV irradiation only extremely small quantities of hydrogen peroxide were necessary to yield a quantitative degradation of interfering organic ligands. Thus the on-line pre-concentration of Pd in the digested samples using the complexing agent N,N-diethyl-N′-benzoylthiourea was possible without any further sample pre-treatment. Using a sample volume of 1.57 ml for FI-ETAAS analysis a limit of detection of 15 ng l−1 was obtained for the combined procedure, with a relative standard deviation being not more than 4.9%. The method was applied to quantify the water-soluble fraction of Pd in urban road dust. Extractions with a rain sample of pH 5.9 revealed that an average of 2.2% (n = 8) of the total Pd present in urban road dust was water soluble.

A method for accurate on-line ultra-trace analysis of palladium by inductively coupled plasma mass spectrometry has been developed. After separation of interfering cations by cation exchange chromatography, palladium was selectively adsorbed on to a C18 micro-column on-line which had been reversibly loaded with the complexing agent N,N-diethyl-N′-benzoylthiourea (DEBT). The palladium complex formed was eluted with methanol and introduced into an ICP-SFMS via microconcentric nebulization with membrane desolvation. Quantification of palladium was carried out by isotope dilution analysis. The results obtained via the isotope ratios of 105Pd/108Pd and 106Pd/108Pd agreed within their measurement uncertainty. For solid samples (total intake 100 mg, final sample volume of 10 mL after closed vessel microwave digestion) the limit of detection was 0.24 ng g−1 palladium (2 mL of digested sample). The necessity of combining matrix separation and pre-concentration for elimination of spectral interferences was demonstrated using soil samples. The method was validated by analysis of the certified reference material BCR-723 (road dust).

Pt, Pd and Rh concentration levels related to particle size distribution were measured in Viennese aerosol. The urban aerosol was studied over a period of 1 month during summer 2002 in a heavy traffic area. A 6-stage cascade impactor collected classified particles with aerodynamic equivalent diameter (aed)

A flow injection procedure with ETAAS detection for the on-line matrix separation and preconcentration of palladium in environmental samples such as airborne particulate matter and road dust was developed. The selective enrichment of palladium was performed on a C18 micro column which has been reversibly loaded with the complexing agent N,N-diethyl-N′-benzoylthiourea. The formed palladium complex was eluted with ethanol and directly introduced into the graphite furnace. With the use of a 1.57 ml sample loop a limit of detection of 23 ng l−1 and a limit of quantification of 39 ng l−1 were obtained for the determination of palladium, with a relative standard deviation being not more than 3.9%. The method including the developed digestion procedure has been evaluated using the certified reference material BCR-723 (road dust). Finally the procedure was applied for the analysis of aerosol samples from the urban site Vienna.

LA-ICP-MS imaging experiments are of growing interest within the field of biosciences. Revealing the distributions of major components as well as trace elements in biological samples can help to understand fundamental biological processes. However, highly variable sample conditions and changing instrumental parameters during measurement time aggravate reliable quantification especially in biological tissues. Normally matrix matched standards used for calibration are scarcely available and the manufacturing process thereof is rather complicated. Thus most experiments reported in the literature only delivered qualitative information on the analyte distributions. The use of appropriate internal standards facilitates the preparation of calibrations even without the utilization of matrix-matched standards. In the presented work an approach for providing reliable quantitative bio-images is proposed using gold thin-layers as an internal standard and patterns printed with commercially available inkjet printers as standards. The method development is based on copper from blue ink as the element of interest. It could be shown that gold standardization compensates instrumental drifts, matrix related ablation differences and day-to-day signal changes. Not only was the quality of the obtained images improved by gold standardization; while the relative standard deviation of the measurements was around 15% before standardization it could be decreased to less than 5% by gold standardization. Also quantitative information could be obtained for samples with unknown analyte concentrations. Depending on the used beam diameter limits of detection in the range of some hundreds ng g(-1) were achieved. The presented method is a promising and easy-to-handle alternative to matrix matched standards for signal quantification.

In the last years a great deal of research has been focused on the determination of harmful trace metals such as Cd, Co, Cr, Cu, Ni or Pb in airborne particulate matter (APM). However, the commonly applied determination of total element concentrations in APM provides only an upper-end estimate of potential metal toxicity. For improved risk assessment it is important to determine bio-accessible concentrations instead of total metal contents. The present review gives an overview of analytical procedures reported for measurement of bio-accessible trace metal fractions in APM. The different approaches developed for extraction of soluble trace metals in APM are summarized. Furthermore the analytical techniques applied for accurate determination of dissolved trace metals in the presence of complex sample matrix are presented. Finally a compilation of published results for bio-accessible trace metals in APM is included.

A comprehensive bulk and surface investigation of high-quality In2O3(001) single crystals is reported. The transparent-yellow, cube-shaped single crystals were grown using the flux method. Inductively coupled plasma mass spectrometry (ICP-MS) reveals small residues of Pb, Mg, and Pt in the crystals. Four-point-probe measurements show a resistivity of 2.0 +/- 0.5 x 10(5) Omega cm, which translates into a carrier concentration of approximate to 10(12) cm(-3). The results from x-ray diffraction (XRD) measurements revise the lattice constant to 10.1150(5) angstrom from the previously accepted value of 10.117 angstrom. Scanning tunneling microscopy (STM) images of a reduced (sputtered/annealed) and oxidized (exposure to atomic oxygen at 300 degrees C) surface show a step height of 5 angstrom, which indicates a preference for one type of surface termination. The surfaces stay flat without any evidence for macroscopic faceting under any of these preparation conditions. A combination of low-energy ion scattering (LEIS) and atomically resolved STM indicates an indium-terminated surface with small islands of 2.5 angstrom height under reducing conditions, with a surface structure corresponding to a strongly distorted indium lattice. Scanning tunneling spectroscopy (STS) reveals a pronounced surface state at the Fermi level (E-F). Photoelectron spectroscopy (PES) shows additional, deep-lying band gap states, which can be removed by exposure of the surface to atomic oxygen. Oxidation also results in a shoulder at the O 1s core level at a higher binding energy, possibly indicative of a surface peroxide species. A downward band bending of 0.4 eV is observed for the reduced surface, while the band bending of the oxidized surface is of the order of 0.1 eV or less.

A novel continuous-flow system for the dynamic extraction of water soluble metal fractions in airborne particulate matter (APM) with subsequent inductively coupled plasma optical emission spectrometric (ICP-OES) analysis of derived extracts is presented. The fully automated extraction system with on-line multi-element detection offers enhanced sensitivity when compared to batch-wise counterparts; additionally it provides information about the extraction process. With the developed procedure detection limits in the order of 1.5 (Ba) to 8.0 (Ni) ng extractable mass per investigated sample could be achieved, which translates to method detection limits for soluble metal concentrations in APM ranging from 0.2 ng m(-3) (Ba) to 0.9 ng m(-3) (Fe). Reproducibility of analysis was determined by replicate measurement (n=6) of an APM sample with an aerodynamic diameter ≤10 μm (PM10), derived results varied between 3.5% (Mn) and 12.1% (Ni) relative standard deviation. Method validation was accomplished by comparison of extracted soluble and remaining non-soluble fractions with the total metal contents of the investigated PM10 samples, showing an excellent mass balance for all elements. Application of the developed procedure for the analysis of water soluble metal fractions in PM10 samples (n=16) from Linz (Austria) indicated a high variability of extractable fractions ranging from 11.7±7.2% (Fe) to 48.8±15.4% (Mn) of the total metal contents.

Abrasion of modern car catalytic converters has resulted in increased deposition of anthropogenic platinum group elements (PGEs; Pd, Pt, Rh) in roadside soils, but still little is known about their solubility, bioavailability and reaction with the soil solid phase. As the extremely low PGE concentrations along with matrix interactions represent a major analytical limitation for studying the fate of PGEs in soils, we propose an advanced flow-injection (FI) system for measuring Pd, Pt and Rh within the same analysis using inductively coupled plasma-optical emission spectrometry (ICP-OES). A combined set of alumina micro-columns along with optimised eluents was employed for concurrent separation of disturbing cations and analyte enrichment to minimise interferences and improve the limits of detection (LOD) by a factor of 5 to 10 compared to conventional measurements, with satisfactory relative standard deviations (RSD) of 2–7%. The method proved to be suitable for simultaneous measurements of PGEs in weak soil extracts of contaminated soil representing potentially bioavailable fractions and sorption envelopes, providing information about the interaction of PGEs with the soil solid phase. The method offers new opportunities to explore the fate of PGEs in soils and similar environmental samples.

The present study describes an ETV-ICP-OES procedure for determination of bio-accessible fractions of Ba, Co, Cu, Mn, Ni and Pb in airborne particulate matter. The method is based on the preliminary extraction of trace metals with synthetic gastric juice using a physiologically based extraction test and the subsequent measurement of gastric extracts with ETV-ICP-OES. Signal quantification was based on external calibration with aqueous standard solutions using In as internal standard. The limits of detection (LOD) calculated as three times the standard deviation (3σ) of the signal derived from filter blank samples ranged from 1.8 ng (Mn) to 12.2 ng (Cu) for analyzed aliquots of 40 μl sample extracts which translates to a method detection limit of 0.11 ng m−3 (Mn) to 0.75 ng m−3 (Cu). The reproducibility of analysis is given as the relative standard deviation varied from 1.9% (Cu) to 5.7% (Ni). Compared to conventional ICP-OES measurement of sample extracts, the developed ETV-ICP-OES procedure was found to offer enhanced sensitivity. The accuracy of the developed method was assessed by analysis of the same sample set with the conventional ICP-OES procedure using liquid sample introduction as well as by comparison of total metal contents and the cumulated sum of extractable metal contents and those remaining after sample extraction, showing good recoveries for all investigated elements. Finally the developed procedure was applied for determination of bio-accessible trace metal fractions in PM10 samples collected from Graz-Sud (Austria) indicating that mean bio-accessible metal fractions varied between 32 ± 14% (Ni) and 97 ± 36% (Pb).

In this work a flow injection procedure with FAAS detection for the on-line determination of water-soluble Zn in airborne particulate matter samples is presented. The method is based on a preliminary extraction of samples with water under dynamic conditions and the subsequent on-line FAAS measurement of the dissolved fraction of Zn. As compared to traditional batch-wise systems, the developed on-line extraction procedure offers enhanced sensitivity and sample throughput, reduced risk of sample contamination and the absence of metal redistribution or readsorption processes. With the use of two filter punches (diameter 9 mm) for analysis an instrumental detection limit of 2 ng Zn was obtained, which translates to a method detection limit of approximately 0.4 ng m−3 when considering the volumes of air collected per investigated aerosol sample. The reproducibility of analysis given as the relative standard deviation was 2.6% (n = 6). The procedure was applied for analysis of water-soluble Zn in aerosol samples from two urban sites in Austria. Accuracy of derived results was confirmed by analysis of the same sample set with a traditional batch-wise extraction approach as well as mass balance determination.

Speciation analysis has gained in importance during the last years. This can be attributed to the increasing awareness of the influence of speciation of trace metals on their ecotoxic potential. Therefore, analytical methods for trace metal quantification with the additional option to distinguish between different species have to be developed. The presented fractionation method employs a Flow-Injection system consisting of three cartridges packed with different Solid-Phase-Extraction sorbents, namely a reversed phase sorbent, an anion exchange material and a cation exchanger. By passing the sample sequentially through these cartridges, the corresponding complexes are retained and thereby separated into a neutral, an anionic and a cationic fraction. Afterwards they are eluted directly into the nebulizer unit of the detecting ICP-AES. The resulting transient signals of the elution profile are recorded and evaluated to acquire both, the total metal concentrations and the distributions into the three mentioned classes in one measurement. By aiming for a higher degree of automatization, the presented method minimizes potential sources of error. Due to the occurring pre-concentration, enhanced detection limits could be achieved for the investigated elements Mg, Al, Ca, Cr, Mn, Fe, Co, Cu, Zn, Cd and Pb, which were analyzed simultaneously. The accuracy of the method was verified using standard addition series and the applicability of the technique to molten snow samples was demonstrated.

In this work we present a fully automated Sr/matrix separation method, based on flow injection (FI) hyphenated to a multiple collector-inductively coupled plasma-mass spectrometer (MC-ICP-MS). Our method compares favourably to the common, manual, batch Sr/matrix separation procedure, with respect to labour and reagent investment. We validated the system analyzing NIST SRM 987 Sr isotope reference material and digests of Asparagus officinalis at Sr concentrations of approximately 30–40 ng g−1 total Sr using separation columns containing approximately 40 μL of Sr specific resin. 33 consecutive runs of the NIST SRM 987 Sr isotope reference material could be repeated with 0.03% (2 RSD), yielding an average 87Sr/86Sr isotope ratio of 0.71030 which is well within the certified range. 5 Hungarian and 5 Austrian samples were determined to have 87Sr/86Sr isotope ratios ranging from 0.70504–0.70746 and 0.70884–0.70923 respectively. 87Sr/86Sr isotope ratios of single elutions could be measured with typical precisions of 0.02–0.1% (2 RSD) depending on signal intensities. 6 successive measurements could be repeated with 0.006–0.04% (2 RSD). Results presented in this work are in agreement with results previously obtained via off-line Sr/matrix separation and subsequent measurement of 87Sr/86Sr isotope ratios by MC-ICP-MS. We were able to use a single 40 μL column for Sr/matrix separation of 66 samples.

A method for on-line pre-concentration of platinum with subsequent determination by electro-thermal atomic absorption spectrometry (ETAAS) has been developed. After a preliminary treatment of the sample solution with tin(II)-chloride the formed anionic Pt–Sn complexes were on-line adsorbed on a C18 micro column which has been reversibly loaded with the chelating agent N,N-diethyl-N′-benzoylthiourea. The formed platinum complex was eluted with ethanol and directly introduced into the graphite furnace. Using a sample volume of 1.57 mL the limit of detection was calculated to be 0.1 μg L−1. The reproducibility of the method given as the relative standard deviation was 5.5% at a concentration level of 0.5 μg L−1 Pt (n = 10). The accuracy of the developed method has been demonstrated by the analysis of the certified reference material BCR-723 (road dust). The new method has been applied to the analysis of platinum in aerosol samples collected in a highway-tunnel in Vienna, Austria.

The interplay of structure, composition and electrical conductivity was investigated for Fe-doped SrTiO3 thin films prepared by pulsed laser deposition. Structural information was obtained by reciprocal space mapping while solution-based inductively-coupled plasma optical emission spectroscopy and positron annihilation lifetime spectroscopy were employed to reveal the cation composition and the predominant point defects of the thin films, respectively. A severe cation non-stoichiometry with Sr vacancies was found in films deposited from stoichiometric targets. The across plane electrical conductivity of such epitaxial films was studied in the temperature range of 250–720 °C by impedance spectroscopy. This revealed a pseudo-intrinsic electronic conductivity despite the substantial Fe acceptor doping, i.e. conductivities being several orders of magnitude lower than expected. Variation of PLD deposition parameters causes some changes of the cation stoichiometry, but the films still have conductivities much lower than expected. Targets with significant Sr excess (in the range of several percent) were employed to improve the cation stoichiometry in the films. The use of 7% Sr-excess targets resulted in near-stoichiometric films with conductivities close to the stoichiometric bulk counterpart. The measurements show that a fine-tuning of the film stoichiometry is required in order to obtain acceptor doped SrTiO3 thin films with bulk-like properties. One can conclude that, although reciprocal space maps give a first hint whether or not cation non-stoichiometry is present, conductivity measurements are more appropriate for assessing SrTiO3 film quality in terms of cation stoichiometry.