Chemical Trace Research Articles

The 2020–2022 paroxysmal episodes of the South-East Crater (Mt. Etna): insights into high-frequency eruptive activity from petrological monitoring

Over the last 20 years, the South-East Crater (SEC) of Etna has produced high-intensity explosive activity including Strombolian explosions and lava fountains associated with lava effusion. In the 2020–2022 period, SEC volcanic activity was characterized by two paroxysmal sequences from 13 December 2020 to 1 Apr 2021 (SEQ1) and from 19 May to 23 October 2021 (SEQ2); another two paroxysms occurred on 10 and 21 February 2022. The 2020–2022 eruptive activity was monitored by the Istituto Nazionale di Geofisica e Vulcanologia-Osservatorio Etneo (INGV-OE) with instrumental networks, field surveys, and laboratory analyses. A detailed record of the chemical variations of glass was acquired in the framework of the syn-eruptive petrological monitoring; chemical (major and trace elements) and isotopic (Sr and Nd) compositions of bulk rocks completed the study. The findings of the petrological monitoring, coupled with volcanological parameters and literature data, allowed magma evolution to be tracked and the subsurface magmatic processes responsible for the observed compositional variations to be inferred. Changes in magma supply rates and mixing between an evolved magma stored in the shallow reservoir and a more primitive magma ascending from intermediate depths controlled magma evolution during the 2020–2022 paroxysmal activity. We discuss magmatic processes in the plumbing system before and during the eruption and the relationship between rate of magma supply and the eruptive dynamics. Finally, the 2020–2022 paroxysmal activity of SEC tested the INGV-OE procedures of petrological monitoring, in the framework of monitoring best practices.

TENG-driven single-droplet green electrochemical etching and deposition for chemical sensing applications

Selected area electrochemical etching (EE) and electrochemical deposition (ED) are widely used for fabricating microstructures and devices, but they require complex processes and expensive equipment and generate significant electrolyte waste. This study demonstrates a novel single-droplet electrochemical system using a triboelectric nanogenerator (TENG) for self-powered selected area EE and ED reactions. Utilizing TENG's pulsed power, Al nanostructures were created by EE, while nano-Ag and Cu2O nanocubes were synthesized by ED. The generated nanomaterials were applied to detect trace chemicals through the Surface-Enhanced Raman Scattering effect. The electrochemical reaction area can be controlled by droplet size, and patterns can be created using a needle movement platform. The size and density of nanostructures can be adjusted by the TENG's current, collision frequency, and electrolyte concentration. The deposition gradient from the center to the edge of the droplet is controlled by the distance between the needle and the substrate. COMSOL Multiphysics calculations show that a smaller D creates a larger electric field gradient. However, the varied deposition gradients were attributed to competition of electric field, diffusion effects, and capillary flow. This proposed green technology offers low cost, simplicity, no waste electrolyte, and self-powering capabilities, pioneering new research directions in EE and ED.

Revealing new pathways for the reaction of Criegee intermediate CH2OO with SO2

Criegee intermediates play an important role in the tropospheric oxidation models through their reactions with atmospheric trace chemicals. We develop a global full-dimensional potential energy surface for the CH2OO + SO2 system and reveal how the reaction happens step by step by quasi-classical trajectory simulations. A new pathway forming the main products (CH2O + SO3) and a new product channel (CO2 + H2 + SO2) are predicted in our simulations. The new pathway appears at collision energies greater than 10 kcal/mol whose behavior demonstrates a typical barrier-controlled reaction. This threshold is also consistent with the ab initio transition state barrier height. For the minor products, a loose complex OCH2O ∙ ∙ ∙ SO2 is formed first, and then in most cases it soon turns into HCOOH + SO2, in a few cases it decomposes into CO2 + H2 + SO2 which is a new product channel, and rarely it remains as ∙OCH2O ∙ + SO2.

Geochronology and geochemistry of the Banjiaoyuan tin deposit, southern Hunan Province and its geological implications

Situated in the central part of the Southern Hunan segment of the Nanling Metallogenic Belt, the Banjiaoyuan tin deposit represents a significant Indosinian quartz vein type tin deposit. Based on field geological surveys and petrographic observations, the mineralization in the area can be divided into three stages: (I) early greisen stage, (II) cassiterite-quartz vein stage, and (III) late barren quartz vein stage. The dating results show that the 40Ar-39Ar plateau age of muscovite in stage I is 215.51 ± 0.87 Ma, and the Rb-Sr isochronous age of quartz mineral in stage II is 214.2 ± 3.1 Ma (MSWD = 1.3), both of which are coincide with the cassiterite U-Pb lower intercept age (215.7 ± 1.3 Ma, MSWD = 1.2), confirming the existence of metallogenic events in this region during the late Indosinian. The δD and δ18O of quartz in stage II range from −66.2 to −80.2 ‰, and 3.71 to 6.17 ‰, respectively, indicating that the ore-forming fluid is mainly derived from a mixture of magmatic-hydrothermal fluids and a small amount of meteoric water. We applied LA-ICP-MS chemical mapping and trace elements analysis to cassiterites, found that they underwent a transition from oxidation to reduction during precipitation when the fluids tend to be more volatile-rich and highly fractionated. The formation of the Banjiaoyuan tin deposit is closely related to the late Indosinian magmatic activity in the Yangmingshan region. Besides, the deep and peripheral parts of the mining area also have the potential for large-scale vein-type and greisen-type W-Sn mineralization.

Coating effects of a strain sensor on durability and sensitivity using the fiber loop ringdown spectroscopy technique

A sensor region in a single-mode optical fiber loop was created and utilized in order to study the coating effect on sensor durability and system sensitivity by the Fiber Loop Ringdown Spectroscopy (FLRDS) technique. The sensor system was simply designed without any additional optical components. The bending loss theory in the single-mode fiber (SMF) was taken into account in data calculation. After stretching was performed on 10.0 cm long coated and noncoated sensorheads from the mid-points, the strain detection limits were determined as 5.3345 με and 6.7497 με with bare and coated sensorheads, respectively. The purpose of this study is to analyze the effect of N,N-Diethyl-p-phenylenediamine (NDPD) coating of the sensorhead on the sensor durability and sensitivity. The baseline stability of the system was obtained as 1.18% by considering a hundred consecutive data. Regarding to obtained results, the difference between calculated total optical losses of FLRDS systems with noncoated and NDPD coated sensorheads shows that coating sensorhead enhanced the sensor durability and the system sensitivity. An FLRDS system with high sensitivity, simple design and easy setup offers real-time measurement with continuous monitoring and provides advantages on durability by modification the sensorhead such as NDPD coating. Due to its attractive features such as low cost, simplicity, easy setup, high sensitivity, increased durability and continuous monitoring, an FLRDS system has a wide range of application areas in structural health monitoring, transportation, early detection, biomedical, chemical trace elements, rail and asphalt applications for continuous monitoring in a real-time merit.

The importance of the soluble and colloidal pools for trace metal cycling in deep-sea pore waters

Physical and chemical trace metal speciation are important for our understanding of metal cycling and potential toxicity to marine life. Trace metals can behave differently in diffusion processes or particle-solution interactions and have different bioavailabilities depending on their physical and chemical forms, which often depend on redox conditions. Here we investigated dissolved (< 0.2 µm) and soluble (< 0.02 µm) concentrations of Mn, Co, Ni, Fe, Cu, V, Mo, U, Cd, and As in oxic and suboxic deep-sea sediments of the central equatorial Pacific Ocean. Vanadium, Mo, U, As, and Cd showed no significant concentration differences between their dissolved and soluble forms, suggesting that they are present as inorganic ionic species or organic complexes in the truly dissolved or small colloidal fraction. In contrast, the colloidal fraction (> 0.02 µm < 0.2 µm) of Mn, Co, Ni, and Cu increased with depth in oxic pore waters and Fe had the largest but variable colloidal pool. Soluble Mn, Co, and Ni were released in the uppermost 2-4 cm in the sediment because of reductive dissolution. The increasing colloidal fraction with depth suggests a decrease in the concentration of small organic ligands with depth, that are abundant in the surface sediment pore waters, and instead an increasing importance of larger (> 0.02 µm) inorganic nanoparticles and colloids such as Mn and Fe (oxyhydr)oxides that control Mn, Fe, and Co cycling at depths > 10 cm. The distribution of Ni and Cu cannot be exclusively explained by inorganic nanoparticles and a shift from low to larger high molecular weight organic ligands might occur. These findings provide new insights into trace metal distributions in the dissolved phase, highlighting the diversity of metal complexes and the need to incorporate these in future calculations of benthic metal fluxes and ecotoxicity assessments, especially in oxic pore waters.

The effect of grain size on the distribution and fractionation of the major chemical trace and rare earth elements in shale, silt and sand rocks of the Muqdadia formation in north of Iraq

(17) samples were collected from Muqdadia formation from various areas in Erbil governorate and Aqra district north of Iraq, which were represented by the sections (A, B, D, R, W). (10) samples were used in analyzing the element using Plasma–Mass Spectrometry (ICP–MS) Analysis and the Inductive Couple Plasma–Mass Spectrometry (ICP–MS) Analysis for four granule sizes after these granules were separated from each sample. The elements included were Al, Fe, Mg, Ca, Na, K, Ti, P, Rb, Cs, Sr, Ba, Au, Mo, Pb, Cu, Zn, As, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Cr, Ni, Co, Mn, Sc, V, Zr, Hf, Ta, Nb, Th, U, Ga, La, Dy, Ho, Er, Tm, Yb, Lu, Y.The geochemical study revealed that there is no significant variation in the content of the main, trace and rare earth elements in the four sizes of shale, silt, fine sand and coarse sand. Also, it was found that the sizes of silt and fine sand contain the highest portion of the trace elements and the rare earth element.It was also, noticed that the patterns of the rare earth elements in the granule sizes are similar in general with some differences, as these differences were reflected in some changes in the portions of these elements.In general, it was observed that the total content of the rare earth elements in the various sizes is relatively small and this might be due to two main factors; the high decrease by calcite (calcium carbonate) and the free silica (quartz) and the other reason is that the mineral that contain REEs are mostly derived from rock sources (mafic or ultra-mafic), which contain these elements with low concentrations.Patterns of REE in the study samples and the four sizes are similar to the pattern of (PAAS) with slight differences like the presence of LREE and on a lower level in HREE and also the presence of negative anomaly Ce*/Ce in the size of shale, silt, fine sand and coarse sand.Although there are variations in the values of anomaly Eu* /Eu, the values are not far from the acceptable PAAS values and they are, generally, higher than PAAS due to the presence of the mafic and ultra-mafic component in the sediments of the current study. In all the sizes, except the shale size, it was found that ∑ REE varies and increases with the increase of the contents of Al2O3 and Fe2O3.As for the shale size, it was found that the relationship between REE∑, Mn and P2O5 is negative and this is because the shale were sedimented in river environments that don’t permit them to absorb sufficient amounts of REE as is the case with the shale that are sedimented in sea environments where there is a direct contact with the seawater that although contains slight concentrations of REE but they are effective when they are adsorbed on shale particularly when the average sedimentation of the shale is low. But in the current study, the shale is river sediments and the river contains insignificant concentrations of REE and the sediment in the river is faster compared to the sea environment and this case doesn’t permit the shale to adsorb large portions of REE.

Molecular Engineering and Confinement Effect Powered Ultrabright Nanoparticles for Improving Sensitivity of Lateral Flow Immunoassay.

The application of traditional lateral flow immunoassay (LFIA)-based gold nanoparticles (AuNPs) to measure traces of target chemicals is usually challenging. In this study, we developed an integrated strategy based on molecular engineering and the spatial confinement of nanoparticles (NPs) to obtain ultrahigh quantum yields (QYs) of aggregation-induced emission (AIE) fluorescence NPs and employed them for the highly sensitive detection of T-2 toxin on the LFIA platform. Tetraethyl-4,4',4″,4‴-(ethene-1,1,2,2-tetrayl)tetrabenzoate (TCPEME), an AIE luminogen, was designed using molecular engineering to lower the energy gap, achieving higher QYs (26.26%) than previous AIEgens (13.02%). Subsequently, TCPEME-doped fluorescence NPs (TFNPs) achieved ultrahigh QYs, up to 84.55%, which were generated from the strong restriction of the NP state, efficiently suppressing nonradiative relaxation channels verified by ultrafast electron dynamics. On the LFIA platform, the sensitivity of the designed TFNP-based LFIA (TFNP-LFIA) was 10.4-fold and 4.3-fold more sensitive than that of the AuNP-LFIA and TPENP-LFIA for detecting the T-2 toxin, respectively. In addition, TFNP-LFIA was used for detecting T-2 toxin in samples and showed satisfactory recoveries (79.5 to 122.0%) with CV (1.49 to 11.75%), which implied excellent application potential for TFNP-LFIA. Overall, dual improvement of the molecule in fluorescence performance originating from the molecular engineering and spatial confinement of NPs could be an efficient tool for promoting the development of high-performance reporters in LFIA.

Three‐dimensional plasmonic substrate as surface‐enhanced Raman spectroscopy (SERS) tool for the detection of trace chemicals

AbstractA three‐dimensional (3D) plasmonic substrate was developed using gold nanorods (GNRs) onto a tapered fiber surface using optical tweezing. To determine the efficacy of the substrate, Raman spectra of two toxic chemicals Rhodamine 6G (R6G) and Crystal Violet (CV) were studied. The “dip and dry” method was used to adsorb the chemicals along the tapered fiber length. The minimum concentration detected for CV and R6G was 10−12 M. We have reported the characteristics and unique features of the manufactured substrate.

Water quality of the southern Tibetan Plateau: hydrogeochemical assessment of the Yarlungzangbo River

The Yarlungzangbo River is the largest river system draining the northern slopes of the Himalayan ranges on the southern Tibetan Plateau and has a crucial role in the supply of water downstream. We investigated the chemical composition of the Yarlungzangbo River and its major tributaries (the Nianchu and Lhasa rivers). Water samples ( n = 165) were collected and analysed for major ions and trace elements. Multivariable analyses showed that the geology and climate are the major explanatory variables for the spatiotemporal variations of the water chemistry in this river system. The water chemistry is mainly controlled by carbonate weathering, with Ca 2+ and HCO 3 − as the dominant ions. Another potential ion source affecting the river water chemistry is the discharge from hot springs, which is rich in Na + , Cl − , SO 4 2− and Li, resulting in higher solute concentrations in the source region and upstream, with the total dissolved solids reaching 176.9 mg L −1 . The concentrations of most trace elements are generally low, although elevated concentrations of As (16.6 μ g L −1 ) and Sb (2.08 μ g L −1 ) are found in the headwaters and additions from untreated wastewater are evident. These concentrations exceed the national drinking water standard for China and the World Health Organization drinking water guideline, posing a risk to people living in both the local and surrounding areas. Supplementary material: The basic field records, water chemical compositions and trace elements of the Yarlungzangbo River and its main tributaries, and concentrations of chemicals of health significance as described by the international guideline (WHO) and the China national guideline (GB) for drinking water quality are available at https://doi.org/10.6084/m9.figshare.c.6850720

Plasmonic filter paper for preconcentration, separation and SERS detection harmful chemicals in chili product by fluid flow

We proposed a triple functional SERS substrate by immobilized Ag nanoparticles on the surface of filter paper. The high dense Ag nanoparticles were distributed on the SERS substrate via in-situ growth process. By optimizing the parameter in preparation process, the optimal filter paper SERS substrate was fabricated by using 30 mM of AgNO3 with 20 S growth time. Due to capillary-effect wicking of cellulose fiber, the paper SERS substrate provide simple, fast and pump-free function for transferring analyte onto sharp tip through development of fluid. The fluid flow also brings target concentrate effect within the tip area. Furthermore, the separation feasibility was obtained during the development process of fluid. The preconcentrated effects not only enhanced the SERS signal of analyte, but also improve the fluorescence visible effect. The filter paper SERS substrate was successfully used for separating, concentrating and detecting Sudan dye from chili product, the detection limit could achieve 10−6 M. This study developed a portable, cost-effective and eco-friendly SERS substrate for separating and detecting trace chemical in food.

Psychotropic substances in the air of Italian cities ten years later: The chemical trace of (ab)use behaviours

Psychotropic substances (PSs) affect the air of cities, tracing the consumption habits of people. Two extensive seasonal campaigns were performed in Italy (36 sites) between 2018 and 2019, aimed at characterizing PSs in airborne particulate matter (PM) at the same locations investigated in 2009, improving the knowledge of relationships linking PSs with source-related air contaminants, and possibly pointing out the changes of the (ab)use prevalence in the country. To reach a more comprehensive picture of the environmental pollution contour, other contaminants including n-alkanes, polycyclic aromatic hydrocarbons (PAHs) and phthalates were investigated together with PSs. The occurrence of both licit and illicit drugs was confirmed in the air at concentration levels ranging from a few pg/m3 (overall cocaine and cannabinoids in the summer outside of big cities) to some ng/m3 (illicit drugs during winter in the city centers and caffeine), and up to tens of ng/m3 (nicotine during the winter). The PS concentration trends observed in the cities were distinct from those of total n-alkanes, PAHs and PM. Meanwhile, the concentration values of illicit substances seemed linked to prevalence rates along Italy, though quantitative relationships haven't been assessed yet neither in neat values, nor as concentration ratios vs. nicotine and PM. Furthermore, the trends of illicit PSs looked coherent with the prevalence rates recorded in the Rome metropolitan area from 2009 to 2013 and in 2019.

Sensitive and high laser damage threshold substrates for surface-enhanced Raman scattering based on gold and silver nanoparticles.

Surface-enhanced Raman scattering (SERS) is a sensitive and fast technique for sensing applications such as chemical trace analysis. However, a successful, high-throughput practical implementation necessitates the availability of simple-to-use and economical SERS substrates. In this work, we present a robust, reproducible, flexible and yet cost-effective SERS substrate suited for the sensitive detection of analytes at near-infrared (NIR) excitation wavelengths. The fabrication is based on a simple dropcast deposition of silver or gold nanomaterials on an aluminium foil support, making the design suitable for mass production. The fabricated SERS substrates can withstand very high average Raman laser power of up to 400mW in the NIR wavelength range while maintaining a linear signal response of the analyte. This enables a combined high signal enhancement potential provided by (i) the field enhancement via the localized surface plasmon resonance introduced by the noble metal nanomaterials and (ii) additional enhancement proportional to an increase of the applicable Raman laser power without causing the thermal decomposition of the analyte. The application of the SERS substrates for the trace detection of melamine and rhodamine 6G is demonstrated, which shows limits of detection smaller than 0.1ppm and analytical enhancement factors on the order of 104 as compared to bare aluminium foil.

High-Temperature Co-Electrolysis and Degradation by Oxidized Trace Contaminants in Feed Gases

The transformation of our energy system will likely require the indirect electrification of the sectors heating, chemical industry and mobility by power-to-X processes, because not all processes can easily use electrical power directly. The high-temperature co-electrolysis using solid-oxide cells (SOCs) can produce syngas compositions desired by the downstream power-to-X process without the need of a reverse water-gas shift reactor and is therefore particularly well suited to produce synthesis gas as feedstock for various power-to-fuel and power-to-chemicals processes. Besides, a coupling of heat-producing downstream processes would increase system efficiency significantly.1 Besides the intrinsic degradation processes of the cells (e.g. nickel migration) and stacks (e.g. contact deterioration) any additional processes triggered by impurities in the feed gases are of relevance for any technical applications. Under certain circumstances, impurities can be introduced by Balance of Plant (BoP) components like the steam generators or preheaters that can release silicon species.2 Also, the feed gases themselves may contain harmful substances. This poisoning effect must be taken into account, because economically gases of lower qualities are preferred as purification steps increase the costs of the syngas. Depending on the exact source of carbon dioxide (CO2) the supplier uses, it contains different secondary components, of which sulfur species are of particular concern. In contrast to fuel-cell mode operation, in electrolysis mode operation hydrogen sulfide (H2S) is not the most likely candidate, but sulfur dioxide (SO2). The reasons for this is that CO2 may be obtained from combustion processes and that hydrogen sulfide is not stable in the atmosphere but has a short half-life time.Therefore, understanding the influence of SO2 contained in the supplied carbon dioxide on the performance of the co-electrolysis is of great importance. There is substantial knowledge about the impact of H2S in feed gases in fuel-cell mode, but the impact of sulfur dioxide in electrolysis mode is not as well investigated. Skafte et al. reported a severe effect in CO2 electrolysis with as low as 20 ppb H2S.3 In the context of this application, the relevant sulfur species present in the feed gases will be SO2. It should be noted, that the heterogenous reduction of SO2 with hydrogen or carbon monoxide is catalyzed by oxides with oxygen vacancies and mobility like CeO2 or YSZ and facilitated by the presence of transition metals.4 Intermediary steps and products beside H2S can include significant amounts of elemental S and COS and the formation of sulfided nickel seems likely. The formation of these products depends on the exact reaction conditions, e.g. temperature, H2/SO2 ratio, steam content, which makes the situation more complex as in fuel-cell mode with hydrogen as fuel. Jeanmonod et al. came to the conclusion, that even concentrations of SO2 as low as 0.5 ppm caused irreversible degradation in Ni/YSZ electrodes in co-electrolysis mode.5 This contribution will report about investigations performed on the degradation caused by sulfur dioxide and silicon species in sub-ppm concentrations in SOCs with Ni/YSZ and Ni/GDC fuel electrodes operated in co-electrolysis mode, using stacks in the Jülich F10 and F20 design. These targeted their impact, potential recovery, possible damage mechanisms and safe thresholds of sulfur dioxide in carbon dioxide. For this the authors performed long-term stationary operation, monitoring of poisoning experiments by electrochemical impedance spectrocopy and post-test analysis of cells, including SEM/EDX and chemical trace analyses. Acknowledgement The authors would like to thank their colleagues at Forschungszentrum Jülich GmbH for their great support and the Helmholtz Society as well as the the German Federal Ministry of Education and Research for financing these activities as part of the Kopernikus P2X-2 project (03SFK2Z0-2). References (1) Peters, R.; Wegener, N.; Samsun, R. C.; Schorn, F.; Riese, J.; Grünewald, M.; Stolten, D. A Techno-Economic Assessment of Fischer–Tropsch Fuels Based on Syngas from Co-Electrolysis. Processes 2022, 10 (4), 699. https://doi.org/10.3390/pr10040699.(2) Schäfer, D.; Queda, L.; Nischwitz, V.; Fang, Q.; Blum, L. Origin of Steam Contaminants and Degradation of Solid-Oxide Electrolysis Stacks. Processes 2022, 10 (3), 598. https://doi.org/10.3390/pr10030598.(3) Skafte, T. L.; Blennow, P.; Hjelm, J.; Graves, C. Carbon Deposition and Sulfur Poisoning during CO2 Electrolysis in Nickel-Based Solid Oxide Cell Electrodes. Journal of Power Sources 2018, 373, 54–60. https://doi.org/10.1016/j.jpowsour.2017.10.097.(4) Liu, W.; Sarofim, A. F.; Flytzani-Stephanopoulos, M. Reduction of Sulfur Dioxide by Carbon Monoxide to Elemental Sulfur over Composite Oxide Catalysts. Applied Catalysis B: Environmental 1994, 4 (2–3), 167–186. https://doi.org/10.1016/0926-3373(94)00019-0.(5) Jeanmonod, G.; Diethelm, S.; Van Herle, J. The Effect of SO 2 on the Ni-YSZ Electrode of a Solid Oxide Electrolyzer Cell Operated in Co-Electrolysis. J. Phys. Energy 2020, 2 (3), 034002. https://doi.org/10.1088/2515-7655/ab8b55.

Experimental and numerical evaluations of flexible filter paper substrates for sensitive and rapid identification of methyl parathion pesticide via Surface-enhanced Raman scattering (SERS)

The residue of methyl parathion (MP) pesticide on agricultural products causes some health-related problems; therefore, it is necessary to identify the amount of this pesticide on these products. Surface Enhanced Raman Spectroscopy (SERS) is a fast, reliable, as well as accurate technique for detecting trace pesticides, biological substances, and chemicals. For this purpose, filter paper substrates (FPS) coated with gold nanoparticles (AuNPs) were used as SERS-active sensors to detect MP. First, AuNPs were fabricated by a simple chemical reduction method. Then, UV–Vis, XRD, TEM, FE-SEM, and DLS were employed to characterize the prepared AuNPs. Afterward, the AuNPs were coated dropwise on FPS to prepare flexible SERS-active substrates (Flex-SERS-Subs) to detect molecular vibrations of MP. The limit of detection (LOD) of detecting MP was obtained to be 10−12 M. The Raman spectra and peak signals acquired via experiments were validated using the density functional theory (DFT) method. Moreover, the RSD was calculated to be 3.39% for ten repeated measurements. In addition, the enhancement factor was calculated by experimental and numerical methods to be 9.820 × 104 and 10.324 × 104, respectively. Therefore, the developed method showed promising outcomes for the related investigations and has the potential to lead the development of similarly fabricated sensors for the detection of trace pesticides.

Hadamard Transform Ion Mobility Spectrometry Based on Matrix Encoding Modulation.

Ion mobility spectrometry (IMS) has been widely used for the on-site detection of trace chemicals, but continue to suffer from a low duty cycle of ion injection. The Hadamard transform ion mobility spectrometry (HT-IMS) technique was employed to address the problem with increased signal-to-noise ratio (SNR). However, in this work, through simulation, a certain deviation between the mathematical principle of Hadamard transform and actual data collection process was found, which resulted in a distortion of the baseline in the spectrum. The reason behind this problem was analyzed and a novel IMS based on Sylvester-type Hadamard matrix encoding modulation (Sylvester-HT-IMS), together with a set of date collection and processing technique, was proposed. Sylvester-HT-IMS offered much improved quality of deconvoluted spectrum and overall performance in the simulation. In experimental verification, with reactant ions and product ions characterized, Sylvester-HT-IMS showed improved SNR and ion discrimination over both conventional signal-averaged IMS (SA-IMS) and HT-IMS, providing an alternative method for multiplexed IMS.

Influence of biosolids and sewage effluent application on sitagliptin soil sorption

Biosolids and sewage effluent application to agricultural fields is becoming a win-win practice as both an economical waste management strategy and a source of nutrients and organic matter for plant growth. However, these organic wastes contain a variety of trace chemicals of environmental concern such as pharmaceuticals and personal care products (PPCPs), which may pose a risk to agricultural fields and ecosystems. This work aims to investigate the sorption of sitagliptin on four agricultural soils, evaluate the effects of biosolids and sewage effluent application, and elucidate the main sorption mechanism of the pharmaceutical on soils. The sorption study revealed that the sorption capacities of sitagliptin on different soils were positively related to the contents of soil organic matter and negatively associated with soil pH values. The application of biosolids and sewage effluent decreased the sorption capacity of sitagliptin, which may be attributed to the loading of dissolved organic matter derived from organic wastes. The Freundlich isotherm model demonstrated that the addition of biosolids from 0 to 100 % (W/W) consistently decreased the sorption affinity (Kf) of sitagliptin from 1.69 × 102 to 3.82 × 101 mg(1-n) Ln kg−1. Sewage application at 0, 10, 50, and 100 % (V/V) also reduced the Kf values from 1.69 × 102 to 9.17 × 101 mg(1-n) Ln kg−1. Attenuated Total Reflection (ATR)-Infrared (IR) spectroscopy analyses suggested that electrostatic interactions between carbonyl and amino groups of sitagliptin and the negatively charged soil surface are the main sorption mechanisms. In a co-solute system, the sorption affinity of sitagliptin on the soil decreased with increasing metformin concentrations, suggesting that competitive sorption may reduce the sorption capacity of individual contaminants in soil systems containing multiple PPCPs.

Embeddable Soil Moisture Content Sensor Based on Open-End Microwave Coaxial Cable Resonator

In this paper, we propose and demonstrate a novel corrosion-resistant, embeddable open-end coaxial cable soil moisture sensor. This microwave resonator is constructed using two reflectors along the coaxial line. The first reflector is a metal post at the signal input end, short-circuiting the inner conductor to the outer conductor. The second reflector comprises a welded metal plate parallel to the open-end of the coaxial line, maintaining a fixed gap. A moisture-sensitive Polyvinyl Alcohol (PVA) film is inserted into this gap. The resonance frequency of the open-end coaxial cable resonator is highly dependent on the fringe capacitance, which varies with soil moisture levels. As such, tracking resonance frequency changes allows for correlation with soil moisture fluctuations. We provide a detailed discussion of the embeddable open-end microwave coaxial cable resonator (EOE-MCCR) mathematical model and a proof of concept for soil moisture measurement. The demonstration experiments investigate soil moisture content ranging from 4% to 24%. The prototype device exhibits a soil moisture measurement sensitivity of 0.76MHz/% for soil moisture between 4% and 10%, and 1.44MHz/% for soil moisture between 10% and 24%. The soil moisture sensor presented here is robust, easy to manufacture, chemically resistant, low-cost, and suitable for long-term applications and potential industrial uses. This innovative sensor is ideal for sensing applications in harsh environments, advancing the field of chemical trace sensing.

Surface-Enhanced Raman scattering (SERS) filter paper substrates decorated with silver nanoparticles for the detection of molecular vibrations of Acyclovir drug

Acyclovir (ACV) drug, a common antiviral agent, is frequently used as the primary clinical treatment method for treating hepatitis B, herpes simplex, and varicella zoster viruses due to its potent therapeutic effect. In patients with compromised immune systems, this medication can stop cytomegalovirus infections, and high doses of this drug are required; however, such prescription leads to kidney toxicity. Therefore, timely and accurate detection of ACV is crucial in many areas. Surface-Enhanced Raman Scattering (SERS) is a reliable, rapid, and precise approach for the identification of trace biomaterials and chemicals. Filter paper substrates decorated with silver nanoparticles (AgNPs) were applied as SERS biosensors to detect ACV and control its adverse effects. Initially, a chemical reduction procedure was utilized to produce AgNPs. Afterward, UV–Vis, FE-SEM, XRD, TEM, DLS, and AFM were employed to examine the properties of prepared AgNPs. In order to prepare SERS-active filter paper substrates (SERS-FPS) to detect Molecular vibrations of ACV, AgNPs prepared by immersion method were coated on filter paper substrates. Moreover, the UV–Vis DRS analysis was carried out to assess the stability of filter paper substrates and SERS-FPS. The AgNPs reacted with ACV after being coated on SERS-active plasmonic substrates and could sensitively detect ACV in small concentrations. It was discovered that the limit of detection of SERS plasmonic substrates was 10-12 M. Moreover, the mean RSD for ten repeated tests was calculated as 4.19%. The enhancement factor for detecting ACV using the developed biosensors was calculated to be 3.024 × 105 and 3.058 × 105 experimentally and via simulation, respectively. According to the Raman results, SERS-FPS for the detection of ACV, fabricated by the present methods, showed promising results for SERS-based investigations. Furthermore, these substrates showed significant disposablity, reproducibility, and chemical stability. Therefore, the fabricated substrates are capable to be employed as potential SERS biosensors to detect trace substances.

Effect of dust morphology on chemical transport and UV-Vis trace gas retrieval models

Effect of dust morphology on chemical transport and UV-Vis trace gas retrieval models