LIBS as a novel tool for the determination of the imidization degree of polyimides.

Due to their outstanding chemical and physical properties, polyimides are widely used in industrial applications. The degree of imidization of polyimides significantly influences their properties, making it an important factor in tailoring the material for specific applications. Imidization refers to the process of converting a precursor poly(amic acid) by removing water, and it is essential to analyze this process in detail to tune the final structure and properties of the material. Conventional techniques for this task include Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), or differential scanning calorimetry (DSC), but they lack the possibility of spatially and/or depth-resolved analysis or do not enable in-line monitoring capabilities. To overcome these limitations, we propose laser-induced breakdown spectroscopy (LIBS) as a powerful tool for the monitoring of the imidization reaction. To establish a measurement method, a total of 130 in-house prepared, self-synthesized samples were thermally cured to exhibit varying imidization degrees. IR spectroscopy served as a reference technique during method development, and a novel formula for calculating the degree of imidization, based on the C2 and H signal trends, was introduced. The calculated imidization degrees of model thin films based on LIBS were in good accordance with the IR reference method although minor differences between the two methods were expected due to varying information depth and the size of the sampled area. Additionally, the robustness of the procedure was demonstrated by depth profiling of a stacked model polymer, spiking with commercially available additives and, ultimately, by analyzing industry-relevant polymer samples.

Towards a circular economy - Repurposing side streams from the potato processing industry by Chlorella vulgaris.

Common wastewater treatment strategies in the food industry do not include efficient remediation strategies for nitrogen, phosphorous and organic carbon. Incorporating microalgae in water treatment plants is rising in popularity because of their high nutrient and trace element uptake driven by light. In this study, four different side streams from an Austrian potato processing company have been screened for their applicability of microalgal cultivation. The side streams were assessed for Chlorella vulgaris growth and their requirement of any additional pretreatment or media supplementation. One side stream specifically, called blanching water II, a stream generated by boiling the potatoes for ease of peeling, turned out very useful to cultivate Chlorella vulgaris and concomitantly remedy the wastewater. Compared to a state-of-the-art cultivation in BG11, cultivating Chlorella vulgaris in blanching water II led to a 45 % increase in specific growth rate of 1.29 day-1 and a 48% increase in biomass productivity to 294.6 mg/L/day, while all nitrogen and phosphate present in the side stream were metabolized. Overall, the results demonstrate that the water remediation process for blanching water II shows vast potential in regard to water purification and waste to value approaches.

Laser ablation-inductively coupled plasma-mass spectrometry analysis reveals differences in chemotherapeutic drug distribution in surgically resected pleural mesothelioma.

AIMS: Pleural mesothelioma (PM) is a highly aggressive thoracic tumour with poor prognosis. Although reduced tissue drug accumulation is one of the key features of platinum (Pt) resistance, little is known about Pt distribution in human PM. METHODS: We assessed Pt levels of blood samples and surgically resected specimens from 25 PM patients who had received neoadjuvant Pt-based chemotherapy (CHT). Pt levels and tissue distributions were measured by laser ablation-inductively coupled plasma-mass spectrometry and correlated with clinicopathological features. RESULTS: In surgically resected PM specimens, mean Pt levels of nontumourous (fibrotic) areas were significantly higher (vs tumourous regions, P = 0.0031). No major heterogeneity of Pt distribution was seen within the tumourous areas. Pt levels correlated neither with the microvessel area nor with apoptosis rate in the tumourous or nontumourous regions. A significant positive correlation was found between serum and both full tissue section and tumourous area mean Pt levels (r = 0.532, P = 0.006, 95% confidence interval [95% CI] 0.161-0.771 and r = 0.415, P = 0.039, 95% CI 0.011-0.702, respectively). Furthermore, a significant negative correlation was detected between serum Pt concentrations and elapsed time from the last cycle of CHT (r = -0.474, P = 0.017, 95% CI -0.738--0.084). Serum Pt levels correlated negatively with overall survival (OS) (P = 0.029). CONCLUSIONS: There are major differences in drug distribution between tumourous and nontumourous areas of PM specimens. Serum Pt levels significantly correlate with full section and tumourous area average Pt levels, elapsed time from the last CHT cycle, and OS. Further studies investigating clinicopathological factors that modulate tissue Pt concentration and distribution are warranted.

In situ electrochemical observation of anisotropic lattice contraction of La0.6Sr0.4FeO3-δ electrodes during pulsed laser deposition.

La0.6Sr0.4FeO3-δ (LSF) electrodes were grown on different electrolyte substrates by pulsed laser deposition (PLD) and their oxygen exchange reaction (OER) resistance was tracked in real-time by in situ PLD impedance spectroscopy (i-PLD) inside the PLD chamber. This enables measurements on pristine surfaces free from any contaminations and the direct observation of thickness dependent properties. As substrates, yttria-stabilized zirconia single crystals (YSZ) were used for polycrystalline LSF growth and La0.95Sr0.05Ga0.95Mg0.05O3-δ (LSGM) single crystals or YSZ single crystals with a 5 nm buffer-layer of Gd0.2Ce0.8O2-δ for epitaxial LSF film growth. While polycrystalline LSF electrodes show a constant OER resistance in a broad thickness range, epitaxially grown LSF electrodes exhibit a continuous and strong increase of the OER resistance with film thickness until ≈60 nm. In addition, the activation energy of the OER resistance increases by 0.23 eV compared to polycrystalline LSF. High resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) measurements reveal an increasing contraction of the out-of-plane lattice parameter in the epitaxial LSF electrodes over electrode thickness. Defect thermodynamic simulations suggest that the decrease of the LSF unit cell volume is accompanied by a lowering of the oxygen vacancy concentration, explaining both the resistive increase and the increased activation energy.

Quantitative Depth Profiling Using Online-Laser Ablation of Solid Samples in Liquid (LASIL) to Investigate the Oxidation Behavior of Transition Metal Borides.

The increased demand for sustainability requires, among others, the development of new materials with enhanced corrosion resistance. Transition metal diborides are exceptional candidates, as they exhibit fascinating mechanical and thermal properties. However, at elevated temperatures and oxidizing atmospheres, their use is limited due to the fact of their inadequate oxidation resistance. Recently, it was found that chromium diboride doped with silicon can overcome this limitation. Further improvement of this protective coating requires detailed knowledge regarding the composition of the forming oxide layer and the change in the composition of the remaining thin film. In this work, an analytical method for the quantitative measurement of depth profiles without using matrix-matched reference materials was developed. Using this approach, based on the recently introduced online-LASIL technique, it was possible to achieve a depth resolution of 240 nm. A further decrease in the ablation rate is possible but demands a more sensitive detection of silicon. Two chromium diboride samples with different Si contents suffering an oxidation treatment were used to demonstrate the capabilities of this technique. The concentration profiles resembled the pathway of the formed oxidation layers as monitored with transmission electron microscopy. The stoichiometry of the oxidation layers differed strongly between the samples, suggesting different processes were taking place. The validity of the LASIL results was cross-checked with several other analytical techniques.

Identification of 20 polymer types by means of laser-induced breakdown spectroscopy (LIBS) and chemometrics.

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.

A Combined Deep Eutectic Solvent-Ionic Liquid Process for the Extraction and Separation of Platinum Group Metals (Pt, Pd, Rh).

Recovery of platinum group metals from spent materials is becoming increasingly relevant due to the high value of these metals and their progressive depletion. In recent years, there is an increased interest in developing alternative and more environmentally benign processes for the recovery of platinum group metals, in line with the increased focus on a sustainable future. To this end, ionic liquids are increasingly investigated as promising candidates that can replace state-of-the-art approaches. Specifically, phosphonium-based ionic liquids have been extensively investigated for the extraction and separation of platinum group metals. In this paper, we present the extraction capacity of several phosphonium-based ionic liquids for platinum group metals from model deep eutectic solvent-based acidic solutions. The most promising candidates, P66614Cl and P66614B2EHP, which exhibited the ability to extract Pt, Pd, and Rh quantitively from a mixed model solution, were additionally evaluated for their capacity to recover these metals from a spent car catalyst previously leached into a choline-based deep eutectic solvent. Specifically, P66614Cl afforded extraction of the three target precious metals from the leachate, while their partial separation from the interfering Al was also achieved since a significant amount (approx. 80%) remained in the leachate.

Multivariate analysis and laser-induced breakdown spectroscopy (LIBS): a new approach for the spatially resolved classification of modern art materials.

The ever-increasing speed of exchange of ideas, information, and culture allows contemporary art to be in constant growth, especially concerning the choice of artistic materials. Their characterization is not only crucial for the study of artistic techniques but also for research into the stability of the material and, consequently, the best preservation practices. For this aim, an analytical method should have the advantages of not requiring sample preparation, performing superficial micro-analysis, and obtaining detailed spectral information. For this study, laser-induced breakdown spectroscopy (LIBS) was employed. It was used for the identification of modern paints composed of inorganic pigments and organic binders, such as acrylics, alkyds, and styrene-acrylics. Principal component analysis (PCA) was used to classify the different pure materials, above all, the polymeric binders. To distinguish the paint mixtures, whose LIBS spectral results were more complex due to the pigment/binder interaction, a statistical method recently employed in the cultural heritage field was chosen, namely, random decision forest (RDF). This methodology allows a reduction of the variance of the data, testing of different training data sets by cross-validation, an increase of the predictive power. Furthermore, for the first time, the distribution of different inorganic pigments and organic binder materials in an unknown sample was mapped and correctly classified using the developed RDF. This study represents the first approach for the classification of modern and contemporary materials using LIBS combined with two different multivariate analyses. Subsequent optimization of measurement parameters and data processing will be considered in order to extend its employment to other artistic materials and conservation treatments.

Application of micro-dried droplets for quantitative analysis of particulate inorganic samples with LA-ICP-MS demonstrated on surface-modified nanoparticle TiO2 catalyst materials.

A quick, flexible and reliable method was developed, based on laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), for accurate assessment of nanomaterial composition with sample amounts in the picogram to nanogram range. We demonstrate its capabilities for the analysis of surface-modified TiO2 nanoparticulate (NP) catalyst materials. For sampling, suspensions of NP were deposited on a substrate material, ablated with a pulsed laser and then analysed using quadrupole ICP-MS. The calibration and quantification approach is based on the use of so-called micro-dried droplets (µDD) as the standard material. To overcome some of the major drawbacks of conventional dried droplet approaches, self-aliquoting wells were used in this work. By mimicking the ablation conditions for the sample and standard, it was possible to create a pseudo-matrix-matched calibration, not only for this specific NP composition but also for a larger variety of samples. A commercially available reference material (AUROlite™, Strem Chemicals) was used to compare the method against established methods such as slurry analysis and microwave-assisted digestion in combination with subsequent liquid sample measurement. The results obtained with the proposed procedure (0.74%wt ± 0.13%wt) are in good agreement to a certified value (0.8%wt) and added an additional layer of information. Due to the significantly reduced sampling size in comparison with the investigated liquid measurement approaches, it was possible to obtain information about the homogeneity of the catalyst material. The results indicate that the AUROlite™ reference material has a heterogeneous loading which requires more than 300 pg of material to be used to cancel out. This was not observed for the custom materials discussed in this work. Graphical abstract.

Multisensor Imaging-From Sample Preparation to Integrated Multimodal Interpretation of LA-ICPMS and MALDI MS Imaging Data.

Laterally resolved chemical analysis (chemical imaging) has increasingly attracted attention in the Life Sciences during the past years. While some developments have provided improvements in lateral resolution and speed of analysis, there is a trend toward the combination of two or more analysis techniques, so-called multisensor imaging, for providing deeper information into the biochemical processes within one sample. In this work, a human malignant pleural mesothelioma sample from a patient treated with cisplatin as a cytostatic agent has been analyzed using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). While LA-ICPMS was able to provide quantitative information on the platinum distribution along with the distribution of other elemental analytes in the tissue sample, MALDI MS could reveal full information on lipid distributions, as both modes of polarity, negative and positive, were used for measurements. Tandem MS experiments verified the occurrence of distinct lipid classes. All imaging analyses were performed using a lateral resolution of 40 µm, providing information with excellent depth of details. By analyzing the very same tissue section, it was possible to perfectly correlate the obtained analyte distribution information in an evaluation approach comprising LA-ICPMS and MALDI MS data. Correlations between platinum, phosphorus, and lipid distributions were found by the use of advanced statistics. The present proof-of-principle study demonstrates the benefit of data combination for outcomes beyond one method imaging modality and highlights the value of advanced chemical imaging in the Life Sciences.

Real-time impedance monitoring of oxygen reduction during surface modification of thin film cathodes.

Improvement of solid oxide fuel cells strongly relies on the development of cathode materials with high catalytic activity for the oxygen reduction reaction. Excellent activity was found for perovskite-type oxides such as La1-xSrxCoO3-δ (LSC), but performance degradation, probably caused by surface composition changes, hinders exploitation of the full potential of LSC. This study reveals that the potentially very high activity of the LSC surface can be traced back to few very active sites. Already tiny amounts of SrO, for example, 4% of a monolayer, deposited on an LSC surface, lead to severe deactivation. Co, on the other hand, causes (re-)activation, suggesting that active sites are strongly related to Co being present at the surface. These insights could be gained by a novel method to measure changes of the electrochemical performance of thin film electrodes in situ, while modifying their surface: impedance spectroscopy measurements during deposition of well-defined fractions of monolayers of Sr-, Co- and La-oxides by single laser pulses in a pulsed laser deposition chamber.

On-line dynamic extraction system hyphenated to inductively coupled plasma optical emission spectrometry for automatic determination of oral bioaccessible trace metal fractions in airborne particulate matter.

For a realistic evaluation of the potential hazard emanating from airborne particulate matter (APM), the determination of the total inhaled metal amounts associated with APM is insufficient in risk assessment. Additional information about metal fractions that can be mobilized by the human body is necessary, because only those soluble (also called bioaccessible) fractions can be absorbed by the human body, and thus potentially cause adverse health effects. In the present study, a dynamic flow-through approach as a front end to inductively coupled plasma optical emission spectrometry (ICP-OES) exploiting advanced flow analysis is employed for on-line handling of multiple APM samples and determination of bioaccessible trace metals under worst case extraction scenarios. The method is based on on-line continuous extraction of filter samples with synthetic gastric fluid followed by on-line ICP-OES measurement of the dissolved fraction of trace metals. The assembly permits an automated successive measurement of three sample replicates in less than 19 min. The on-line extraction procedure offers increased sample throughput and reduced risk of sample contamination and overcomes metal re-adsorption processes compared to the traditional batch-wise counterparts. Furthermore, it provides deeper information on the kinetics of the leaching process. The developed procedure was applied to the determination of bioaccessible metal fractions (Al, Ba, Cu, Fe and Mn as model analytes) in PM10 samples from Palma de Mallorca (Spain) and Vienna (Austria). Graphical Abstract On-line gastric bioaccessibility of elements in airborne particulate matter.

A comparison of sample preparation strategies for biological tissues and subsequent trace element analysis using LA-ICP-MS.

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is one of the most commonly applied methods for lateral trace element distribution analysis in medical studies. Many improvements of the technique regarding quantification and achievable lateral resolution have been achieved in the last years. Nevertheless, sample preparation is also of major importance and the optimal sample preparation strategy still has not been defined. While conventional histology knows a number of sample pre-treatment strategies, little is known about the effect of these approaches on the lateral distributions of elements and/or their quantities in tissues. The technique of formalin fixation and paraffin embedding (FFPE) has emerged as the gold standard in tissue preparation. However, the potential use for elemental distribution studies is questionable due to a large number of sample preparation steps. In this work, LA-ICP-MS was used to examine the applicability of the FFPE sample preparation approach for elemental distribution studies. Qualitative elemental distributions as well as quantitative concentrations in cryo-cut tissues as well as FFPE samples were compared. Results showed that some metals (especially Na and K) are severely affected by the FFPE process, whereas others (e.g., Mn, Ni) are less influenced. Based on these results, a general recommendation can be given: FFPE samples are completely unsuitable for the analysis of alkaline metals. When analyzing transition metals, FFPE samples can give comparable results to snap-frozen tissues. Graphical abstract Sample preparation strategies for biological tissues are compared with regard to the elemental distributions and average trace element concentrations.

Direct imaging of elemental distributions in tissue sections by laser ablation mass spectrometry.

We present a strategy for imaging of elements in biological tissues using laser ablation (LA) mass spectrometry (MS), which was compared to laser ablation inductively coupled plasma (LA-ICP) MS. Both methods were adopted for quantitative imaging of elements in mouse kidney, as well as traumatic brain injury model tissue sections. MS imaging (MSI) employing LA provides quantitative data by comparing signal abundances of sodium from tissues to those obtained by imaging quantitation calibration standards of the target element applied to adjacent control tissue sections. LA-ICP MSI provided quantitative data for several essential elements in both brain and kidney tissue sections using a dried-droplet approach. Both methods were used to image a rat model of traumatic brain injury, revealing accumulations of sodium and calcium in the impact area and its peripheral regions. LA MSI is shown to be a viable option for quantitative imaging of specific elements in biological tissue sections.

Self-aliquoting micro-grooves in combination with laser ablation-ICP-mass spectrometry for the analysis of challenging liquids: quantification of lead in whole blood.

We present a technique for the fast screening of the lead concentration in whole blood samples using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The whole blood sample is deposited on a polymeric surface and wiped across a set of micro-grooves previously engraved into the surface. The engraving of the micro-grooves was accomplished with the same laser system used for LA-ICP-MS analysis. In each groove, a part of the liquid blood is trapped, and thus, the sample is divided into sub-aliquots. These aliquots dry quasi instantly and are then investigated by means of LA-ICP-MS. For quantification, external calibration against aqueous standard solutions was relied on, with iron as an internal standard to account for varying volumes of the sample aliquots. The (208)Pb/(57)Fe nuclide ratio used for quantification was obtained via a data treatment protocol so far only used in the context of isotope ratio determination involving transient signals. The method presented here was shown to provide reliable results for Recipe ClinChek® Whole Blood Control levels I-III (nos. 8840-8842), with a repeatability of typically 3 % relative standard deviation (n = 6, for Pb at 442 µg L(-1)). Spiked and non-spiked real whole blood was analysed as well, and the results were compared with those obtained via dilution and sectorfield ICP-MS. A good agreement between both methods was observed. The detection limit (3 s) for lead in whole blood was established to be 10 µg L(-1) for the laser ablation method presented here. Graphical Abstract Micro-grooves are filled with whole blood, dried, and analyzed by laser ablation ICP-mass spectrometry. Notice that the laser moves in perpendicular direction with regard to the micro-grooves.

Recent advances in quantitative LA-ICP-MS analysis: challenges and solutions in the life sciences and environmental chemistry.

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.

Determination of rare earth elements in saline matrices using dispersed particle extraction and inductively coupled plasma mass spectrometry.

RATIONALE: Rare earth elements play an important role in identifying and indexing the origin of historical and geological samples. In this work, a new approach for the characterization of rare earth elements (REEs) in aqueous sample solutions with high salinity is presented. METHODS: Prior to analysis by inductively coupled plasma mass spectrometry (ICP-MS) the target analytes were separated from interfering matrix constituents by the use of surface-functionalized nanoparticles. Compared with common matrix separation techniques, such as solid-phase extraction (SPE), the strength of the method lies in the combination of an advanced extraction procedure with internal standard correction. Thus, known limitations of SPE such as column clogging or incomplete analyte elution could be completely circumvented. Furthermore, time-consuming approaches for signal quantification such as matrix-matched calibration could be avoided since the applied internal standard allows the correction of matrix-induced deviations in sample extraction and ICP-MS analysis. RESULTS: With the developed procedure detection limits <1 ng L(-1) could be achieved for all the investigated elements, with satisfactory relative standard deviations (RSDs) of 3-26% for unspiked samples and <1-2% for spiked samples. Results derived from recovery experiments with spiked oil accumulation water samples confirmed the applicability of the proposed procedure for the determination of REEs in highly saline sample solutions. The procedure was successfully applied to the study of oil accumulation water samples from different oil fields in Lower Austria. CONCLUSIONS: A sample pretreatment procedure with subsequent ICP-MS analysis for the accurate determination of REEs in aqueous sample solutions with high salinity has been developed.

Application of gold thin-films for internal standardization in LA-ICP-MS imaging experiments.

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.

Radial line-scans as representative sampling strategy in dried-droplet laser ablation of liquid samples deposited on pre-cut filter paper disks.

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 µg 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.

Capabilities of simultaneous 193 nm - LIBS/LA-ICP-MS imaging for microplastics characterization.

Microplastics (MPs) are currently one of the major environmental challenges within our society. With the awareness of the impact of MPs on the environment increasing over the last years, the need for increased monitoring as well as comprehensive analysis to better understand the fate and impact of MPs has become more and more important. A major aspect of MP characterization is the assignment of the polymer type of individual particles. Here, per- and poly-fluoroalkyl substances (PFAS), originating from fluor-containing polymers, have gained a lot of attention due to the severe environmental impact. Additionally, quantitative analysis of the metal content is of great interest in the field, since MPs are prone to either leaching (in)organic additives into the environment or taking up and accumulating hazardous components (e.g., heavy metals). In this work we demonstrate the capabilities of a simultaneous LIBS/LA-ICP-MS setup for the analysis of MPs. In the first part, we demonstrate the potential of targeted LIBS analysis for the imaging of fluor-containing polymers. Using a laser spot size of 5 µm combined with highly sensitive ICCD detection enables analysis of particles in the low µm range. In the second part we combine the polymer-identification capabilities of LIBS with the high sensitivity of ICP-MS to perform matrix-matched quantification of the metal content of individual MPs. In this case we use a spot size of 50 µm facilitating polymer classification with a broadband spectrometer, resulting in detection limits of 0.72 µg/g for Pb and 9.5 µg/g for Sn simultaneously measured using ICP-MS.