In this work, we developed and optimized a method for the analysis of PAHs and nitro-PAHs in atmospheric particulate matter (PM) samples by using thermal desorption gas chromatography coupled with ...electron ionization single quadrupole mass spectrometry (TD-GC-(EI)-MS). The method uses thermal desorption from a PM on a filter sample as means of sample introduction to a column and obviates the need for complex extraction procedures, which are time-consuming and require environmentally unfriendly solvents. Moreover, the possibility of systematic errors is minimized and a significantly smaller amount of sample is required compared to traditional techniques requiring a pre-extraction step (approx. 10-times). Thirteen PAHs and three nitro-PAHs were used during method development. Although Tenax cartridges are typically used to capture volatile pollutants from the air, we found that glass-wool liner is the most suitable trap for the examined analytes after desorption from a quartz filter. Among the various instrument parameters which were tested and optimized, TD desorption flow and hold time, and temperature of the cooled injection system (CIS) proved to be most critical. We also found out that the matrix effect is especially pronounced in the case of high PM loadings, which should be kept in mind when planning the analysis. After the optimization, standard reference materials (ERM-CZ100 and NIST 1648a) were used for partial method validation and finally, real PM10 and PM2.5 samples from two Slovenian cities were successfully analyzed.
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•Simultaneous PAH and nitro-PAH determination in ambient PM without extraction.•Thermal desorption gas chromatography with electron ionization mass spectrometry.•Nitro-PAHs are successfully analyzed with TD-GC-(EI)-MS for the first time.•Much smaller amount of sample is needed compared to traditional methods.•Green method is suited for a better time resolution and SOA formation studies.
In the future, low-temperature proton exchange membrane fuel cells (PEMFC), together with batteries, are expected to compete and eventually replace conventional combustion engines in the automotive ...industry. Currently, the most promising strategy towards cost-effective and highly-active oxygen reduction reaction (ORR) electrocatalysts seems to be alloying of Pt with less expensive and less noble 3d transition metals (Cu, Co and Ni, …). A crucial issue to be resolved in the near future is, however, to bridge the gap between the remarkable activities measured on the laboratory scale with thin film rotating disk electrode (TF-RDE) and the industrial membrane electrode assembly (MEA). In the case of Pt-Cu alloy, one of the major reasons for this difficulty is inadequate removal of unstable Cu or in other words, improper ‘activation’. Inadequately removed Cu can act as an impurity by poisoning the Pt surface via the well-known underpotential deposition (UPD) interaction, resulting in the inhibition of ORR performance. Due to highly favourable experimental conditions, in-situ electrochemical activation (in-situ EA) in TF-RDE setup masks many of the issues one experiences when trying to do the same ex-situ. Thus, matching the ORR performance obtained after in-situ EA with ex-situ CA in the case of Pt-Cu system has not been properly addressed so far. Based on a deeper understanding of in-situ EA of our in-house designed Pt-Cu/C electrocatalyst we here demonstrate development of carbon monoxide (CO) assisted ex-situ CA method. By using this gram scale ex-situ CA method, we for the first time show that a Pt-Cu system can achieve very high ORR performances in TF-RDE setup without any need for the use of in-situ EA.
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•Lithium chloride is an emergent varroa control substance in beekeeping.•Lithium has an impact on both human well-being and honeybee health.•There is risk of lithium entering human food chain ...inadvertently.•Lithium accumulates in honeybee products such as pollen and honey.•Lithium accumulates in honeybee brood and increases mortality in adults.
Varroa destructor, the primary honeybee pathogen, is kept in check by various chemical compounds which may enter the human diet through honeybee products. Lithium is an emerging varroa control substance, and we investigated its accumulation in honey, bee bread, brood and adults along with the mortality of bees. Increased lithium concentrations were detected in workers, fed individually once per os with 10 µL of 25 mM LiCl in sucrose solution (6.50–40.10 mg/kg) or had the same solution available ad libitum (39.25–266.00 mg/kg). A three-day treatment of honeybee colonies with 25 mM LiCl in 1L/day sucrose solution increased lithium concentrations in five-day-old larvae, honey, and bee bread: up to 45.0, 1.2, and 47.0 mg/kg, respectively. Lithium concentrations peaked three days post-treatment in both larvae and honey and increased worker mortality was observed. The control colonies exhibited lithium concentrations below the limit of quantification (0.5 mg/kg). Prudence in lithium use is advised.
Nitroaromatic compounds (NACs) as important constituents of atmospheric humic-like substances (HULIS) and brown carbon (BrC) affect the Earth's climate and pose a serious environmental hazard. We ...investigated seasonal size-segregated NACs in aerosol samples from the urban background environment in Ljubljana, Slovenia. Total concentrations of twenty NACs in PM15.6 were on average from 0.51 ng m−3 (summer) to 109 ng m−3 (winter), and contributed the most to submicron aerosols (more than 74%). Besides 4-nitrocatechol (4NC) as the prevailing species, methylnitrocatechols (MNCs) and nitrophenols (NPs), we reported on some very rarely mentioned, but also on five novel NACs (i.e., 3H4NBA: 3-hydroxy-4-nitrobenzoic acid, 3MeO4NP: 3-methoxy-4-nitrophenol, 4Et5NC: 4-ethyl-5-nitrocatechol, 3Et5NC: 3-ethyl-5-nitrocatechol and 3MeO5NC: 3-methoxy-5-nitrocatechol). Concentrations of 3MeO5NC, 4Et5NC and 3Et5NC were enhanced during cold seasons, contributing up to 11% to total NAC in winter. In cold season, NAC size distributions were characterized with the peaks in the broader size range of 0.305–1.01 μm (accumulation mode), with 4NC and alkyl-nitrocatechols (∑(M/Et)NC) as the most abundant, followed by 4-nitrosyringol, nitrophenols and nitroguaiacols. In spring, a pronounced peak of ∑(M/Et)NC was observed in the accumulation mode (0.305–0.56 μm) as well as in the coarse one. A strong correlation of all NACs with ∑(M/Et)NC and levoglucosan indicates that primary emissions of wood burning were the most important source of NACs, but their secondary formation (e.g., aqueous-phase at higher ambient RH) in cold season could also be a significant one. In warmer season, NACs may be mostly derived from traffic-related aromatic VOCs. The contribution of NACs to the light absorption of the aqueous extracts was up to 10-times higher (contribution to Abs365 up to 31%) than their mass contributions to WSOC (up to 3%) of corresponding size-segregated aerosols, confirming that most of the identified NACs are strong BrC chromophores.
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•Extensive study on seasonal size-segregated nitroaromatics (NACs) in ambient aerosol.•Besides NACs usually reported, five novel NACs unambiguously quantified.•Seasonal variability of NACs with the highest contribution to submicron fraction.•Wood burning and traffic were the most important sources.•NACs contribution to WSOC light absorption up to 10-times higher than to WSOC mass.
This study explores quantitative bioimaging as enabled by laser ablation-inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOFMS), designing standardization methods based on robotic ...micro-droplet dispensing. The potential of producing controlled and highly precise pL-volume droplets was exploited to establish on-tissue isotope dilution and standard addition. Both strategies eliminate matrix effects and offer high metrological order traceable to SI units. The absolute quantity was obtained for μm-sized regions of interest in tissue samples, as defined by the extension of the deposited pL-volume droplet. While the gold standard isotope dilution (ID) was restricted to the accurate quantification of a single element, i.d. platinum in different tissue samples (mouse liver, spleen and tumor tissue), multiplexed matrix-matched calibration was obtained by on-tissue standard addition by depositing a dilution series of certified multi-element standards. Here, the working range was determined by the heterogeneity of the tissue samples and the background levels of elements intrinsically present and/or artificially introduced during sample preparation. Both methods, ID and standard addition served as reference methods for validation of external calibration using gelatin-based micro-droplet standards. Given full ablation, these external standards revealed a high dynamic range together with an excellent repeatability. Where applicable, the cross-validation revealed consistent quantitative results for the three quantification approaches. The comparable sensitivity obtained for standard addition and external standardization, respectively expressed as slope of the calibration function, provided proof that gelatin-based micro-droplets could serve as matrix-matched calibrations. Therefore, gelatin micro-droplets offer a valid tool for multiplexed matrix-mimicking standardization at high-throughput.
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•Gelatin micro-droplet standards provide multiplexed matrix-mimicking standardization at high-throughput for LA-ICPMS imaging.•The deposition of highly precise micro-droplets enables on-tissue isotope dilution and standard addition strategies.•Accurate and traceable quantification in tissue samples was enabled by isotope dilution and standard addition.
Water electrolysis is a very promising technology for sustainable hydrogen generation using renewable electrical energy. The excellent performance and dynamic behavior for storing electrical energy ...in hydrogen allow polymer electrolyte membrane (PEM) electrolysis to cover the gap between the intermittent renewable power production and the grid demand at different time horizons and scales. This work is addressed to the development and characterization of high performance nanostructured Ir-Ru-oxide electro-catalyst achieving for the rate determining oxygen evolution reaction a current density of 3Acm−2 at about 1.8V (> 80% enthalpy efficiency) with a low catalyst loading (0.34mgcm−2). The stability characteristics were studied in practical PEM electrolysis cells operating at 80°C, using several durability tests of 1000h each to evaluate the reliability of this electro-catalyst for real-life operation. Further insights on the degradation mechanism were acquired by subjecting the catalyst to potential steps in a specially designed electrochemical flow cell under corrosive liquid electrolyte with on-line monitoring of the dissolved ions. Structural, morphology, composition and surface analysis of the anode electro-catalyst after operation in the electrolysis cell, complemented by in-situ electrochemical diagnostics, provided important insights into the degradation mechanisms. Catalyst operation at high turnover frequency (TOF) was observed to cause a progressive change of Lewis acidity characteristics with time for both Ir and Ru cations thus influencing their ability to promote water oxidation.
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•Ir-Ru oxide catalysts (loading < 0.35mgcm−2) achieve 3Acm−2 with efficiency > 80%.•Degradation during 1000h tests increases mainly with operating turn over frequency.•Modification of Lewis acidity for Ir and Ru sites is responsible for performance loss.•Dissolution of Ir-Ru active species occurs according to their occurrence on the surface.
•Multi-element compositions of 272 Slovenian wines were determined.•Differences observed between wine growing regions.•Application of counter-propagation neural networks allowed discrimination.•Good ...results for a comparatively small wine-growing region.
Inductively coupled plasma mass spectrometry and optical emission were used to determine the multi-element composition of 272 bottled Slovenian wines. To achieve geographical classification of the wines by their elemental composition, principal component analysis (PCA) and counter-propagation artificial neural networks (CPANN) have been used. From 49 elements measured, 19 were used to build the final classification models. CPANN was used for the final predictions because of its superior results. The best model gave 82% correct predictions for external set of the white wine samples. Taking into account the small size of whole Slovenian wine growing regions, we consider the classification results were very good. For the red wines, which were mostly represented from one region, even-sub region classification was possible with great precision. From the level maps of the CPANN model, some of the most important elements for classification were identified.
Particulate matter (PM) is the major environmental pollutant. Its elemental composition is routinely monitored. Inductively coupled plasma mass spectroscopy (ICPMS) is commonly applied after a PM ...sample has been digested by an acid during a microwave treatment. In this case, sample preparation procedure is laborious, sometimes incomplete and produces toxic waste. In this paper we show that direct sample introduction to ICPMS by laser ablation (LA-ICPMS) is of huge advantage. Minimal quantity of a sample is required for the analysis (<1 cm2) and no chemical waste is produced. The study focused on the most universal and widely used quartz fibre filter samples and we show that LA-ICPMS can be successfully applied for the determination of the elemental composition of such samples. Some effort is, however, still needed to develop an autosampler for the LA-ICPMS system and to provide commercial matrix-matched standards for this application to be implemented in environment laboratories worldwide.
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•A new method for the direct analysis of PM on quartz fibre filters is presented.•No pre-treatment step is required and no waste chemicals are produced.•By LA-ICPMS, more than 20 elements can be measured at a time with low LODs.•Based on the homogeneity assessment less than 1 cm2 of filter sample is required.•LA-ICPMS proved itself at least as accurate as the current standard method.
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