Ultra-trace Levels Research Articles

Method validation and geochemical modelling of chromium speciation in natural waters

The study focuses on validating reference methods such as ICP-OES and ICP-MS for detecting ultra-trace levels of chromium in groundwater, where concentrations are typically very low. Additionally, it verifies a hyphenated technique, IC-ICP-MS, for determining naturally occurring Cr(VI) in tested waters. The validation process involved various chromium analysis variants, including isotopes 52Cr and 53Cr in ICP-MS and IC-ICP-MS techniques, along with specific emission lines in the ICP-OES technique. Statistical data processing revealed that the achieved limits of quantification for Cr in different techniques ranged from 0.053 µg/L to 1.3 µg/L, with the associated measurement uncertainty estimated between 14% and 19% (at a coverage factor k = 2, 95%). For speciation analysis, it was possible to quantitatively determine Cr(VI) at concentrations as low as 0.12 µg/L, with the measurement uncertainty ranging between 10% and 14%. The Kruskal-Wallis test indicated that for the 14 water samples analysed, there was no statistically significant difference in the results obtained using different analytical techniques (p > 0.05). The geochemical modelling approach applied enhances the understanding of chromium speciation in water samples, verifying the accuracy of speciation analysis and identifying specific ion forms in which Cr(III) and Cr(VI) occur. In the analysed water samples, the concentration of Cr(VI) ranges between 0.13 and 35 µg/L, with the primary form identified as the oxoanion CrO42−. Importantly, statistical tests demonstrated no statistically significant differences between the total chromium concentration in water and the concentration of Cr(VI), indicating that the entire concentration of total chromium corresponds to Cr(VI) speciation.

Combination of spraying based liquid phase microextraction and liquid chromatography–tandem mass spectrometry for the determination of colchicine at ultra–trace levels in artificial urine and serum samples

Colchicine is a primary choice for the treatment of acute gouty arthritis, but this pharmaceutical active substance has serious side effects. For this reason, a sensitive and accurate analytical method is required to quantify colchicine at trace levels in order to evaluate the side effects deeply. In this study, liquid chromatography–atmospheric pressure ionization–tandem mass spectrometry (LC-API-MS/MS) was firstly combined with spraying based fine droplet formation liquid phase microextraction (SFDF-LPME) to determine colchicine in artificial serum and urine samples at ultra–trace levels. The SFDF-LPME-LC-API-MS/MS parameters were elaborately optimized to reach low detection limits. Dynamic range, limit of detection (LOD) and limit of quantitation (LOD) of the SFDF-LPME-LC/MS/MS were recorded as 5.34 – 173.69 ng/kg, 1.67 ng/kg and 5.57 ng/kg, respectively. The detection power of LC-API-MS/MS system was enhanced by 106-fold when the LOD values of LC-API-MS/MS and SFDF-LPME-LC-API-MS/MS methods were compared to each other. After the evaluation of system analytical performance, recovery experiments were conducted with the spiked artificial serum and urine samples. Percent recovery results for the spiked artificial serum and urine samples were figured out to be 99.1 % – 108.6 % and 89.4 % – 114.8 % via external standard calibration method, respectively. Additionally, matrix–matching calibration strategy was applied to calculate the recovery results, which were recorded as 94.6 % – 101.3 % and 79.0 % – 106.8 %, for the spiked artificial serum and urine samples, respectively. The obtained acceptable recovery results via the applied two calibration strategies proved the applicability and accuracy of developed method for the determination of colchicine at ultra–trace levels.

Study on the Determination of Perfluorocarboxylic Acids (PFCAs) in House Dust Samples by Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS) Method

Perfluorocarboxylic acids (PFCAs) are an important group of per- and polyfluoroalkyl substances (PFAS), which have been intensively produced and used due to their outstanding features such as high resistance and water and oil repellency. However, these are also typical organic pollutants with several adverse effects on environmental and human health. Studies on the analytical methods for PFAS in general, and PFCAs in particular, in the environments are necessary to characterize their potential emission sources and related health risks. In this study, analytical procedure for simultaneous determination of 12 PFCAs (C5–C18) in house dust samples was developed with 3 main steps: i) Dust samples were extracted by ultrasonication with methanol; ii) Dust extracts were cleaned up by dispersive solid phase extraction with graphitized carbon sorbent; and iii) Concentrations of PFCAs were determined by liquid chromatography tandem mass spectrometry (LC-MS/MS) method. The method was validated for recovery (72-95%), repeatability (RSD < 15%), and detection limits (0.10-1.0 ng/g). The proposed analytical method can be applied in pollution monitoring and assessment of PFCAs in settled dusts with several advantages like high accuracy, good detection ability at trace and ultratrace levels (i.e., ng/g or lower) with rapid, simple sample preparation procedure.

Novel optical optode for selective detection and removal of ultra-trace level of mercury ions in different environmental real samples

Owing to the high cost and unavailability of different analytical techniques, there is an urgent need to develop new techniques not only for detecting but also removing mercury ions in real samples. Thus, an optical chemical sensor based on the anchoring of phenanthraquinone monophenylthiosemicarbazone in a plasticized cellulose triacetate membrane was fabricated and applied to the recognition and removal of mercury ions from aqueous solutions. The synthesized optode was characterized by FT-IR, SEM, AFM, and thermal analysis. Several parameters, including the pH, temperature, contact time, washing solvent, and washing time, were optimized. Under optimal conditions, a promising optode film platform was utilized for sensing mercury ions, and the concentrations were calculated based on colorimetric analysis (Histogram, RGB) of digital images, visualization, and spectrophotometry. Also, an optical optode was used for complete adsorption of mercury ions from aqueous solutions. In addition, the regeneration of the synthesized optode was evaluated using 0.1 mol L− 1 nitric acid, which effectively removed all adsorbed mercury ions. The obtained data indicated good linearity in the sensing and adsorption of Hg2+ over a concentration range of 0.005–5000 µgL− 1 with a low limit of detection (LOD = 0.066 µgL− 1) and limit of quantification (LOQ, 0.22 µgL− 1). Furthermore, it showed good distinctions in the presence of coexisting ions, high stability (five months), good applicability, and reproducibility (RSD = 1.31%), making it a promising sensor for Hg2+ detection. On the other hand, the kinetic studies revealed that the pseudo-second-order was the best model for describing the adsorption behavior of mercury ions on the optode surface. Also, the thermodynamic parameters indicate spontaneous (ΔG0 < 0) and endothermic (ΔH0 < 0) reactions. Also, the maximum adsorption capacity was found to be 73.2 mg g− 1. Thus, the optodes were successfully applied for the detection and/or removal of Hg2+ in different real samples, including cucumber, fish, soil, and water samples, with excellent recoveries of 98.1–99.5%.

Determination of Anti-Diabetic Drugs in Health Supplements by Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS) Method

The mixing of unpermitted drugs with health supplements to increase effectiveness can cause negative effects to consumers, requiring quality testing of these products. In this study, an analytical method for simultaneously determination of 5 anti-diabetic drugs (ADDs) (i.e., metformin, phenformin, buformin, glibenclamide, and gliclazide) in health supplement samples was developed with a combination of ultrasonic extraction, dispersive solid-phase extraction (d-SPE), and liquid chromatography tandem mass spectrometry (LC-MS/MS). Hard capsule, soft capsule, and liquid samples were extracted with methanol twice, followed by activated carbon addition for extract clean-up and LC-MS/MS quantification. The analytical method was validated through various factors such as: specificity, limit of detection, limit of quantification, linearity, repeatability, and recovery. The method had high precision (mean recovery from 88% to 99%, relative standard deviation lower than 10%) and low detection limit of 0.1 mg/kg, meeting the requirements of detection of these substances at trace to ultra-trace levels in complex sample matrices. The validated method was then applied to analyze concentrations of 5 ADDs in 30 health supplement samples. Metformin was detected at a concentration of 2.20 mg/kg in one hard capsule sample, while the remaining samples did not contain ADDs at detectable levels.

An Efficient Fluorescent Chemosensing Probe for Total Determination and Speciation of Ultra-Trace Levels of Mercury (II) Species in Water.

The current study reports a novel fluorescent chemosensor based on the tagging agent 4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein (Rose Bengal, RB) for detection of trace levels of Hg2+in environmental water. The established probe has been based upon liquid-liquid extraction (LLE) of the developed ternary complex ion associate {[Hg (bpy)2]2+.[RB]2-} of Hg2+ -2,2- bipyridyl complex [Hg (bpy)2]2+ and RB at pH 9.0 onto chloroform and measuring the resulting fluorescence enhancement signal intensity at λex/em = 570/ (580-600) nm. The limits of detection (LOD) and quantification (LOQ) of for Hg2+ was calculated to be 6.06 and 20 nM with a linear dynamic range (LDR) of 0.02-20µM, respectively. The stability constant, stoichiometry, chemical equilibria, and the thermodynamic parameters (ΔH, ΔS, and ΔG) of the developed ion associate were evaluated and assigned. Student's t and F tests at 95% confidence were fruitfully used for validation of the proposed methodology for Hg2+ detection in water samples with the aid of inductively coupled plasma-optical emission spectrometry (ICP-OES). The established strategy was successfully applied for detection of trace levels of Hg2+ in water samples with acceptable results. The proposed probe was satisfactorily applied for total determination and speciation of Hg in various water samples. Integrating the functional chelating agent onto associate formation to improve the selectivity and sensing properties of the LLE combining sensing probe towards target analyte in water represent the main interest.

Ultratrace CO/SF6 Detection System Based on Differential Fourier Transform Infrared Spectroscopy Combined with the Weighted Sine Spectral Reconstruction Convolutional Neural Network (WSSR-CNN) Model.

Carbon monoxide (CO), as an indicator gas for fault diagnosis of gas-insulated switchgear, has the strongest absorption coefficient in the mid-infrared region, making Fourier transform infrared (FTIR) spectroscopy an ideal method for its concentration detection. However, there is extremely abundant absorption of SF6 in this region, resulting in a great challenge for CO/SF6 detection. To address this challenge, we report a high sensitivity online detection system for ultratrace levels of CO, which combines differential Fourier transform infrared (DFTIR) spectroscopy with a weighted sine spectral reconstruction convolutional neural network (WSSR-CNN). The differential technique is first introduced into FTIR for baseline correction of CO absorption signals. The novel WSSR method achieves feature extraction and denoising of weak spectral signals in strong interference by discretizing interfering signals and enhancing target signals. On this basis, the detection of CO concentration is realized using the CNN model. Finally, WSSR-CNN is compared with four other methods. Results showed that WSSR-CNN outperforms all four models with evaluation index R2 reaching 0.99982 and 0.99999 in the range of low concentration (0.096-0.986 ppm) and high concentration (1.984-52.193 ppm) and mean absolute percentage error of 0.97% and 0.22%, respectively. The lowest detection limit of the system at 1σ is 13 ppb, which is the best result reported so far for detecting CO/SF6 concentration based on FTIR.

Aptamer-Triggered Nucleic Acid Amplification Strategy for the Electrochemiluminescence Detection of Perfluorooctanoic Acid.

Per- and polyfluoroalkyl substances (PFASs) are a class of persistent micropollutants. Due to their chemical stability and bioaccumulation, concentrations of PFASs in environmental media, even at ultratrace levels, pose significant environmental and health risks. However, currently reported detection methods lack an effective signal amplification strategy, and the detection sensitivity is limited, which can not meet the requirements of ultratrace detection. Herein, a groundbreaking aptamer-recognition-driven nucleic acid strategy was developed to significantly amplify the detection signal of perfluorooctanoic acid (PFOA). Furthermore, step pulse (SP) was used instead of cyclic voltammetry (CV) as an electrochemical excitation method to modulate the low electrochemiluminescence (ECL) triggering potential of poly [9,9-bis (3'-(N, N-dimethylamino) propyl) -2,7-fluorene]-alt-2,7-(9,9-dioctylfluorene)] (PFN) nanoparticles (NPs) so that a strong signal of +0.80 V was emitted without any exogenous coreactants. PFN NPs coupled rolling circle amplification-assisted PAM-free CRISPR/Cas12a system to construct an ultrasensitive ECL aptasensor for PFOA detection and the limit of detection was as low as 1.97 × 10-15 M. This ECL system integrated the advantages of no exogenous coreactants, low trigger potential, and nucleic acid amplification strategy and provided an ultrasensitive method for monitoring trace PFOA in the real water sample.

Fabrication of Au-decorated V2O5 based sensor for ultra trace level detection of ammonia in an environment resembling human exhaled breath

Ammonia stands out as a significant breath biomarker for kidney-related diseases. Here we present the fabrication of a gold (Au) decorated V2O5 based sensor designed for detecting ammonia at parts per billion (ppb) level. The V2O5 particles were synthesized by thermal decomposition of ammonium metavanadate (NH4VO3) instead of using tedious and expansive synthesis routes. The product of the thermal decomposition of NH4VO3 was characterized utilizing various analytical techniques. Then this product (V2O5) was used for gas sensing study as original and when decorated with gold. The V2O5 based sensor, decorated with gold (Au) for a duration of 10 s, exhibits favorable characteristics including a linear response range spanning 50–5000 ppb, heightened sensitivity, stability, and remarkable resistance to humidity within the range of 50–90 % relative humidity (RH). Remarkably, the sensor demonstrates insensitivity towards higher concentrations of possible interfering liquid vapors. The sensor exhibits response and recovery times of 36 s and 300 s, respectively, in the presence of 1000 ppb ammonia and has the potential for accurately detecting and quantifying ammonia in an environment resembling human exhaled breath. The sensing device based on this material will be a valuable tool for clinical applications.

Green synthesis of self-oriented flower-like Ag@Ag2O nanostructures functionalized with L-Tryptophan for colorimetric simultaneous determination of ultra-trace level of thiamin and riboflavin

The study focuses on the green synthesis of Ag@Ag2O nanostructures using Padina algae extract and functionalizing them with L-tryptophan to enhance their properties as a colorimetric sensor for simultaneous detection of ultra-trace levels of thiamin and riboflavin. The nanostructures are characterized using techniques like XRD, FESEM, FTIR, TEM, AFM, and DLS to understand their morphology, structure, and interactions with target molecules. FESEM analysis revealed the hierarchical flower-like Ag@Ag2O nanostructures. The TEM image shows the formation of core-shell nanostructures. Also, DLS analysis and surface zeta potential spectra illustrated the aggregated nature of fabricated nanocomposites in the presence of vitamins. The study is the first to report simultaneous determination of thiamin and riboflavin using a colorimetric sensor based on Ag@Ag2O-L-Try nanocomposites using partial leas square (PLS). The dynamic range of thiamin and riboflavin was achieved in 0.1 mol L−1 acetate buffer pH 4 and the ratio Ag@Ag2O: L-try 1:1. The Ag@Ag2O-L-Try sensor exhibited two linear ranges of 0.1- 1.0 and 3-350 µMol L− 1 for riboflavin and a linear range 3.0–60 µMol L− 1 for thiamin. Also, low detection limit of 1.92 µMol L− 1 and 0.048 µMol L− 1 was obtained for riboflavin and thiamin, respectively. The results indicated that the success of the method depends on the selective and sensitive colorimetric assay of the sensor along with the simultaneous determination by the PLS algorithm. Hence, the proposed technique can be used for the accurate and precise determination of vitamins in different pharmaceutical syrup and tablet samples.

Potential-resolved real-time ultrasensitive sensing of bisphenol compounds based on ionic liquid coupled Zr-MOF@GO nanosensor

Bisphenol compounds, including BPA and BPS, are significant pollutants found in the environment, food, and daily necessities. They pose various adverse effects, including estrogenic, immunotoxic, metabolic, and reproductive toxicity, which severely threaten human health and ecological safety. Achieving simultaneous rapid detection of BPA and BPS is still very challenging due to their similar structures and co-existence in actual samples at ultratrace level. This study addresses the problem of developing an effective method for the rapid detection of BPA and BPS simultaneously. A new electrochemical nanosensor based on ionic liquid (IL) coupled Zr-MOF@GO was developed for ultrasensitive real-time detection of BPA and BPS. The Zr-MOF@GO/IL nanocomposite features a custom-built structure with an ordered framework, abundant pores, and highly coupled interfaces. The experimental findings demonstrate that the introduction of IL enhances the conductivity and dispersibility of the nanocomposite, improves the absorption capability for target bisphenols, and significantly improves the detection limit and linear range of the Zr-MOF@GO based electrochemical sensor. The sensor demonstrated wide linear ranges with detection limits of 5.5 nmol/L for BPA and 7.1 nmol/L for BPS (S/N = 3), respectively. Comparative studies revealed that the detection limits of the Zr-MOF@GO/IL-based sensor improved by an order of magnitude compared to the Zr-MOF@GO-based sensor. Additionally, the sensor exhibited superior analytical performance regarding reproducibility, stability, and selectivity. This study investigated the capability and synergy of IL coupled high-valent stable transition metal ZrIV-based MOFs in electrochemical sensing for the first time. This development sets a new benchmark in non-enzymatic electrochemical sensing, establishing the Zr-MOF@GO/IL-based sensor as a promising platform for the individual or simultaneous rapid detection of bisphenols in actual samples.

Principles and Applications of ZnO Nanomaterials in Optical Biosensors and ZnO Nanomaterial-Enhanced Biodetection.

Significant research accomplishments have been made so far for the development and application of ZnO nanomaterials in enhanced optical biodetection. The unparalleled optical properties of ZnO nanomaterials and their reduced dimensionality have been successfully exploited to push the limits of conventional optical biosensors and optical biodetection platforms for a wide range of bioanalytes. ZnO nanomaterial-enabled advancements in optical biosensors have been demonstrated to improve key sensor performance characteristics such as the limit of detection and dynamic range. In addition, all nanomaterial forms of ZnO, ranging from 0-dimensional (0D) and 1D to 2D nanostructures, have been proven to be useful, ensuring their versatile fabrication into functional biosensors. The employment of ZnO as an essential biosensing element has been assessed not only for ensembles but also for individual nanomaterials, which is advantageous for the realization of high miniaturization and minimal invasiveness in biosensors and biodevices. Moreover, the nanomaterials' incorporations into biosensors have been shown to be useful and functional for a variety of optical detection modes, such as absorption, colorimetry, fluorescence, near-band-edge emission, deep-level emission, chemiluminescence, surface evanescent wave, whispering gallery mode, lossy-mode resonance, surface plasmon resonance, and surface-enhanced Raman scattering. The detection capabilities of these ZnO nanomaterial-based optical biosensors demonstrated so far are highly encouraging and, in some cases, permit quantitative analyses of ultra-trace level bioanalytes that cannot be measured by other means. Hence, steady research endeavors are expected in this burgeoning field, whose scientific and technological impacts will grow immensely in the future. This review provides a timely and much needed review of the research efforts made in the field of ZnO nanomaterial-based optical biosensors in a comprehensive and systematic manner. The topical discussions in this review are organized by the different modes of optical detection listed above and further grouped by the dimensionality of the ZnO nanostructures used in biosensors. Following an overview of a given optical detection mode, the unique properties of ZnO nanomaterials critical to enhanced biodetection are presented in detail. Subsequently, specific biosensing applications of ZnO nanomaterials are discussed for ~40 different bioanalytes, and the important roles that the ZnO nanomaterials play in bioanalyte detection are also identified.

A novel molecularly imprinted composite–based electrochemical sensor constructed from o-phenylenediamine and gold nanoparticle–embedded multiwalled carbon nanotube for ultra trace level detection of triclosan

A novel molecularly imprinted composite–based electrochemical sensor constructed from o-phenylenediamine and gold nanoparticle–embedded multiwalled carbon nanotube for ultra trace level detection of triclosan

Large scale screening and quantification of micropollutants in fish from the coastal waters of Cochin, India: Analytical method development and health risk assessment

Urban estuarine and coastal water receive several micropollutants through industrial and agricultural influxes. The bioaccumulation of these micropollutants in fish and their entry into the coastal population's food chain raises significant food safety concerns. Hence, a comprehensive analytical method was developed for ultra-trace level quantification of 345 micropollutants in fish. The optimized sample preparation method could extract compounds suitable for both GC–MS/MS and LC-MS/MS analysis simultaneously. The target list of contaminants included 278 agricultural pesticides and also 102 endocrine disruptors covering polyaromatic hydrocarbons, polychlorinated biphenyls, organochlorines, and endocrine-disrupting pesticides. The GC–MS/MS with large volume injection (LVI) technique, and LC-MS/MS operating in MRM mode, achieved an LOQ of <2.00 ng/g for most of the analytes. The extraction strategy involved tri-phase partitioning between water, acidified acetonitrile, and hexane, followed by salting out. Dispersive solid phase cleanup (dSPE) with C18, Z-Sep+, CaCl2, and MgSO4 was able to reduce the matrix influence, and the method achieved satisfactory recovery in the range of 70.0–120.0 % for all the target analytes. The repeatability and reproducibility relative standard deviation values of the measured analytes were <20.0 %, and the Horwitz ratio values were well below 2. The method was used to accurately measure the target micropollutants in fish from the Cochin estuary, the highly urbanized portion of the Vembanad Lake, and an important Ramsar site. At least one or more of the 41 different micropollutants were identified and quantified in about 90.7 % of the 108 samples analyzed. The importance of large-scale screening and trace-level quantification methods in environmental monitoring and risk assessment is underscored by the results. The risk assessment showed a moderate risk of exposure to the nearby coastal population through the food chain.

Direct Determination of Metallic Contamination on and in Wafers Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry

A new analytical technique was developed for determination of metallic impurities in wafers using LA-GED-MSAG-ICP-MS. Up to 300 mm wafer can be analyzed directly without using a small, enclosed chamber. Particles generated by a femto-second laser ablation were aspirated together with a particle free clean air by an ejector and introduced to the ICP-MS (Inductively Coupled Plasma Mass Spectrometry) via GED (Gas Exchange Device). The air was exchanged by Ar gas and the particles came out from GED in Ar gas stream. For quantitation of LA-ICP-MS, MSAG (Metal Standard Aerosol Generation) was used. MSAG could introduce nearly a 100% of aqueous multi-element standard solution to the plasma of ICP-MS, which allowed precise quantitation using the method of standard addition while ablating wafer samples. This paper describes how the new analytical technique works for ultra-trace level of metallic impurities in wafers.

Efficient Solid-Phase Extraction of Neonicotinoid Insecticides from Environmental Water and Drink Samples Using a Postmodified Metal-Organic Framework.

Neonicotinoid insecticides (NNIs) are extensively utilized globally because of their efficient and broad-spectrum properties. However, their residues are also extensively distributed in the environment. Herein, MIL-101-SO3Na with abundant -NH- and sulfonate groups was synthesized via chloromethylation and nucleophilic substitution postmodification strategies and used to extract NNIs via solid-phase extraction. MIL-101-SO3Na was enhanced by introducing C-H···N hydrogen bonds to strengthen interaction forces and -SO3Na groups to adjust surface charge and enhance electrostatic attraction. This modification and the substantial specific surface area (998 m2·g-1) of the metal-organic framework markedly enhanced the enrichment efficiency of MIL-101. The proposed method based on MIL-101-SO3Na exhibited a minimal detection threshold (0.04-0.87 ng·L-1), an extensive linear spectrum (1-2000 ng·L-1), and notable accuracy (a variation of 3.02-11.8%) in water and drink samples. NNI concentrations between 0.25 and 24.2 ng·L-1 in fruit juice and tea samples were accurately identified using the proposed method, demonstrating its feasibility in practical applications. The postmodification of MIL-101-SO3Na is an exceptional and promising approach for the sensitive detection of ultratrace NNI levels in complex matrices.

Advancing Lung Cancer Diagnosis through NH2-MON-SPME-GC-MS/MS: Enhanced Sensitivity in Aldehyde Biomarker Detection from Exhaled Breath.

The sensitive detection of trace biomarkers in exhaled breath for lung cancer diagnosis represents a critical area of research in life analytical chemistry, with profound implications for early disease detection, therapeutic intervention, and prognosis monitoring. Despite its potential, the analytical process faces significant challenges due to the ultratrace levels of disease biomarkers present and the complex, high-humidity composition of exhaled breath. This study introduces a highly sensitive method for detecting aldehyde biomarkers in exhaled breath by integrating the use of amino-functionalized microporous organic networks (NH2-MON) as a solid-phase microextraction (SPME) fiber coating with gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) analysis. The method innovatively combines sample collection and extraction, achieving a dual-step enrichment process that significantly enhances both the enrichment efficiency and reproducibility of biomarker detection while effectively mitigating the interference caused by water vapor in exhaled breath. The NH2-MON, utilized as an SPME fiber coating, demonstrates exceptional enrichment capacity for five key aldehyde biomarkers, facilitating the development of a highly sensitive detection approach for these biomarkers in exhaled breath. Compared to previously reported methods, the proposed technique exhibits significantly lower limits of quantification, ranging from 0.77 to 11.89 pg mL-1, and achieves substantially higher enrichment factors, ranging from 9156- to 35723-fold. The practicality and feasibility of the method were validated through the analysis of exhaled breath samples from lung cancer patients, underscoring its potential application in the early diagnosis and monitoring of lung cancer.

Plasmonic Ag Nanoparticles on SiC for Use as SERS Substrate and in Integrated Optical Sensors for Bio-Chemical Applications

Development of optical chemical sensors for the detection of specific toxic chemicals at ultratrace levels and analysis of complex mixtures is crucial for new green and safe technologies [1, 2]. Metallic structures confined at the nanoscale acquire interesting properties such as strongly localizing E fields on their surfaces through Plasmonic Resonance under stimuli of light at certain wavelengths. This nanostructures are called plasmonic structures [3–5]. This effect is exploited to amplify the optical signal obtained by the molecules of interest, located near plasmonic structures [3, 6]. Purpose of the work is the development of innovative, easy to manufacture and cheap optical active layer consisting of Plasmonic Ag Nanoparticles on a Wide Band Gap semiconductor material such as Silicon Carbide to be used as substrate for Surface Enhanced Raman Scattering or for the fabrication of integrated optical sensor for remote chemical and biological applications. In this contest, the phenomenon of Ag thin film thermal dewetting on SiC substrate was implemented to develop a simple nanoparticles synthetic approach. Scanning Electron Microscopy confirmed the formation of Ag nanoparticles by thermal annealing of thin silver film. 4-MBA was used as probe molecule for SERS phenomenon investigation. The formation of a covalent bond between the silver nanostructures, acting as plasmonic "hot spots", and the species of interest enable its detection at very low concentrations, in the range of 10-5 M or less, in both Raman and UV-Vis configurations.

Nanospray Laser-Induced Plasma Ionization Mass Spectrometry for Sensitive and High-Coverage Analysis of Broad Polarity Organic Pollutants.

Accurate, sensitive, and high-coverage analysis of various organic pollutants in complex samples and single cells is significant in investigating their environmental behaviors and toxic effects. Here we proposed a nanospray laser-induced plasma ionization mass spectrometry (nLIPI-MS) method for sensitive and high-coverage analysis of broad polarity organic pollutants under ambient and open-air conditions. The nLIPI-MS method combines nanospray with laser-induced plasma ionization, enabling direct analysis without sophisticated sample pretreatment. For the analysis of nonpolar and very weakly polar organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and alkyl-PAHs, the nLIPI-MS method showed desirable analytical performance, with limits of detection of as low as the μg/L level. For moderately polar organic pollutants such as p-phenylenediamine quinones (PPD-Qs), nLIPI-MS displayed significant enhanced sensitivity by 1 to 2 orders of magnitude in comparison to nanoelectrospray ionization (nESI)-MS. For more polar organic pollutants such as per- and polyfluoroalkyl substances (PFASs), nLIPI-MS also showed good analytical performance, with a sensitivity improvement of 1.3- to 2.7-fold over that of nESI-MS. The sensitivity of nLIPI-MS for the analysis of PPD-Qs and PFASs reached as low as the ng/L level, enabling the analysis of ultratrace levels of these pollutants in complex samples and even single cells. Our experimental results demonstrated that nLIPI-MS was an extensive ambient MS method, showing desirable analytical performance for the analysis of organic pollutants with broad polarity ranges.

Depth dimension in seepage detection: Insights for exploration and geological gas storage surveillance

The search for surface hydrocarbon seeps has historically served as a fundamental tool in the early stages of oil and gas exploration. However, as easily detectable surface hydrocarbon seeps become increasingly scarce, advancement in analytical capabilities have shifted the focus towards detecting ultra-trace levels of hydrocarbons, commonly referred to as microseepages. While it is critical to understand the distribution of hydrocarbon microseepage for assessing petroleum systems and optimizing exploration efforts, the role of sampling depth in the detection of microseepage remains poorly understood. In this study, we investigated the influence of sampling depth on microseepage detection, using passive soil-gas sampling techniques at depths ranging from 0.5 to 10 m at sites with hydrocarbon-bearing reservoirs and dry wells. Organic geochemical analysis, including thermal desorption-gas chromatography-mass spectrometry (GC-MS), was employed to identify and quantify hydrocarbon and nonhydrocarbon compounds.The study result demonstrates that sampling at the Minimal Interference Zone (MIZ) depths of 5 m or greater significantly mitigates the risk of interference signals, thereby enabling the identification and quantification of hydrocarbon microseepages at trace and ultra-trace concentrations. At these depths, the attenuation of non-hydrocarbon compounds was observed, making the hydrocarbon signal markedly more distinguishable. Geochemical characterization of the samples revealed spatial and vertical heterogeneity in the distribution of hydrocarbon compounds, indicative of variations in the microseepage mechanisms potentially influenced by factors such as sedimentary basin settings and secondary alterations associated with the vadose zone. By utilizing passive soil-gas sampling techniques coupled with GC-MS, this study emphasizes the importance of sampling depth to improve the detection of reliable microseepage signal while reducing interference and background noise. The proposed technique not only refines existing methodologies for petroleum system assessments but also paves the way for broader geological applications. Specifically, the approach offers critical insights for the development of high-resolution geochemical surveys adaptable for surface background profiling in CO2 sequestration projects to monitor for storage efficiency and seal integrity.