Search Results (405)

The efficient detection of volatile organic compounds (VOCs) is critically important in the domains of environmental protection, healthcare, and industrial safety. The development of metal oxide semiconductor (MOS) heterojunction gas-sensing materials is considered one of the most effective strategies to enhance sensor performance. This review summarizes and discusses the types of heterojunctions and their working principles, enhancement strategies, preparation methodologies, and applications in acetone and ethanol detection. To address the constraints pertaining to low sensitivity, sluggish response/recovery times, and elevated operating temperatures that are inherent in VOC sensors, several improvement methods are proposed, including doping with metals like Ag and Pd, incorporating additives such as MXene and polyoxometalates, optimizing morphologies through a fine design, and self-doping via oxygen vacancies. Furthermore, this work provides insights into the challenges faced by MOSs heterojunction-based gas sensors and outlines future research directions in this field. This review will contribute to foundational theories to overcome existing bottlenecks in MOS heterojunction technology while promoting its large-scale application in disease screening or agricultural food quality assessments. Full article

Carbonyl compounds are important oxygenated volatile organic compounds (VOCs) that play significant roles in the formation of ozone (O₃) and atmospheric chemistry. This study presents comprehensive field observations of carbonyl compounds during an unusual wintertime ozone pollution event at a suburban site in Guangzhou, South China, from 19 to 28 December 2020. The aim was to investigate the characteristics and sources of carbonyls, as well as their contributions to O₃ formation. Formaldehyde, acetone, and acetaldehyde were the most abundant carbonyls detected, with average concentrations of 7.11 ± 1.80, 5.21 ± 1.13, and 3.00 ± 0.94 ppbv, respectively, on pollution days, significantly higher than those of 2.57 ± 1.12, 2.73 ± 0.88, and 1.10 ± 0.48 ppbv, respectively, on nonpollution days. The Frame for 0-D Atmospheric Modeling (F0AM) box model simulations revealed that local production accounted for 62–88% of observed O₃ concentrations during the pollution days. The calculated ozone formation potentials (OFPs) for various precursors (carbonyls and VOCs) indicated that carbonyl compounds contributed 32.87% of the total OFPs on nonpollution days and 36.71% on pollution days, respectively. Formaldehyde, acetaldehyde, and methylglyoxal were identified as the most reactive carbonyls, and formaldehyde ranked top in OFPs, and it alone contributed 15.92% of total OFPs on nonpollution days and 18.10% of total OFPs on pollution days, respectively. The calculation of relative incremental reactivity (RIR) indicates that ozone sensitivity was a VOC-limited regime, and carbonyls showed greater RIRs than other groups of VOCs. The model simulation showed that secondary formation has a significant impact on formaldehyde production, which is primarily controlled by alkenes and biogenic VOCs. The characteristic ratios and backward trajectory analysis also indicated the indispensable impacts of local primary sources (like industrial emissions and vehicle emissions) and regional sources (like biomass burning) through transportation. This study highlights the important roles of carbonyls, particularly formaldehyde, in forming ozone pollution in megacities like the Pearl River Delta region. Full article

Acetone detection is of significant importance in various industries, from cosmetics to pharmaceuticals, bioengineering, and paints. Sensor manufacturing involves the use of different semiconductor materials as well as different metals for doping and functionalization, allowing them to achieve advanced or unique properties in different sensor applications. In the healthcare field, these sensors play a crucial role in the non-invasive diagnosis of various diseases, offering a potential way to monitor metabolic conditions by analyzing respiration. This article presents the synthesis method, using chemical solutions and rapid thermal annealing technology, to obtain Al-functionalized and Ni-doped copper oxide (Al/CuO:Ni) nanostructured thin films for biosensors. The nanocrystalline thin films are subjected to a thorough characterization, with examination of the morphological properties by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analysis. The results reveal notable changes in the surface morphology and structure following different treatments, providing insight into the mechanism of function and selectivity of these nanostructures for gases and volatile compounds. The study highlights the high selectivity of developed Al/CuO:Ni nanostructures towards acetone vapors at different concentrations from 1 ppm to 1000 ppm. Gas sensitivity is evaluated over a range of operating temperatures, indicating optimum performance at 300 °C and 350 °C with the maximum sensor signal (S) response obtained being 45% and 50%, respectively, to 50 ppm gas concentration. This work shows the high potential of developed technology for obtaining Al/CuO:Ni nanostructured thin films as next-generation materials for improving the sensitivity and selectivity of acetone sensors for practical applications as breath detectors in biomedical diagnostics, in particular for diabetes monitoring. It also emphasizes the importance of these sensors in ensuring industrial safety by preventing adverse health and environmental effects of exposure to acetone. Full article

Background: kidney transplant recipients are exposed to multiple pathogenic pathways that may alter short and long-term allograft survival. Metabolomic profiling is useful for detecting potential biomarkers of kidney disease with a predictive capacity. This field is still under development in kidney transplantation and metabolome analysis is faced with analytical challenges. We performed a cross-sectional study including stable kidney transplant patients and aimed to search for relevant associations between baseline plasmatic and urinary metabolites and relevant outcomes over a follow-up period of 3 years. Methods: we performed a cross-sectional study including 72 stable kidney transplant patients with stored plasmatic and urinary samples at the baseline evaluation which were there analyzed by nuclear magnetic resonance in order to quantify and describe metabolites. We performed a 3-year follow-up and searched for relevant associations between renal failure outcomes and baseline metabolites. Between-group comparisons were made after classification by observed estimated glomerular filtration rate slope during the follow-up: positive slope and negative slope. Results: The mean estimated GFR (glomerular filtration rate) was higher at baseline in the patients who exhibited a negative slope during the follow-up (63.4 mL/min/1.73 m² vs. 55.8 mL/min/1.73 m², p = 0,019). After log transformation and division by urinary creatinine, urinary dimethylamine (3.63 vs. 3.16, p = 0.027), hippuric acid (7.33 vs. 6.29, p = 0.041), and acetone (1.88 vs. 1, p = 0.023) exhibited higher concentrations in patients with a negative GFR slope when compared to patients with a positive GFR slope. By computing a linear regression, a significant low-strength regression equation between the log 2 transformed plasmatic level of glycine and the estimated glomerular filtration rate was found (F (1,70) = 5.15, p = 0.026), with an R² of 0.069. Several metabolites were correlated positively with hand grip strength (plasmatic tyrosine with r = 0.336 and p = 0.005 and plasmatic leucine with r = 0.371 and p = 0.002). Other urinary metabolites were found to be correlated negatively with hand grip strength (dimethylamine with r = −0.250 and p = 0.04, citric acid with r = −0.296 and p = 0.014, formic acid with r = −0.349 and p = 0.004, and glycine with r = −0.306 and p = 0.01). Conclusions: some metabolites had different concentrations compared to kidney transplant patients with negative and positive slopes, and significant correlations were found between hand grip strength and urinary and plasmatic metabolites. Full article

Background: This proof-of-concept study aimed to assess the diagnostic potential of gas chromatography–mass spectrometry (GC-MS) in profiling volatile organic compounds (VOCs) from exhaled breath as a diagnostic tool for the chronic coronary syndrome (CCS). Methods: Exhaled air was collected from patients undergoing invasive coronary angiography (ICA), with all samples obtained prior to ICA. Post hoc, patients were divided into groups based on coronary lesion severity and indications for revascularization. VOCs in the breath samples were analyzed using GC-MS. Results: This study included 23 patients, of whom 11 did not require myocardial revascularization and 12 did. GC-MS analysis successfully classified 10 of the 11 patients without the need for revascularization (sensitivity of 91%), and 7 of the 12 patients required revascularization (specificity 58%). In subgroup analysis, GC-MS demonstrated 100% sensitivity in identifying patients with significant coronary lesions requiring intervention when the cohort was divided into three groups. A total of 36 VOCs, including acetone, ethanol, and phenol, were identified as distinguishing markers between patient groups. Conclusions: Patients with CCS exhibited a unique fingerprint of exhaled breath, which was detectable with GC-MS. These findings suggest that GC-MS analysis could be a reliable and non-invasive diagnostic tool for CCS. Further studies with larger cohorts are necessary to validate these results and explore the potential integration of VOC analysis into clinical practice. Full article

Short-chain fatty acids (SCFAs) in feces are inextricably linked to intestinal homeostasis and can be used as potential markers for metabolic diseases. In this study, an efficient and simple method was developed for the purification of SCFAs without the need for derivatization of the samples. The SCFAs (acetic, propionic, isobutyric, butyric, isovaleric, valeric, and hexanoic acid) were extracted from a small amount (50 mg) of fecal and intestinal samples using acetone combined with solid phase extraction column (Bond Elut Plexa) enrichment. Quantitative analysis was performed using gas chromatography with a flame ionization detector. The developed method has shown very good limits of detection (LOD, 0.11–0.36 μM) and limits of quantification (LOQ, 0.38–1.21 μM) with excellent linearity (R² ≥ 0.9998), good recovery (98.34–137.83%), and high reproducibility (RSD ≤ 1.30). The applicability of this method was also demonstrated by testing the fecal and cecum contents of different species from mammals (mice, pigs) to insects (honeybees). The technique is highly suitable for analyzing complex, small amounts of intestinal and fecal SCFAs. Full article

Our research focused on the integration of Flammulina velutipes soluble dietary fiber (Fv-SDF) into wheat flour during the production of dried noodles, delving into the impact of different addition ratios of Fv-SDF on both dough processing characteristics and the quality of the micro-fermented dried noodles. The viscometric and thermodynamic analyses revealed that Fv-SDF notably improved the thermal stability of the mix powder, reduced viscosity, and delayed starch aging. Additionally, Fv-SDF elevated the gelatinization temperature and enthalpy value of the blend. Farinograph Properties and dynamic rheology properties further indicated that Fv-SDF improved dough formation time, stability time, powder quality index, and viscoelasticity. Notably, at a 10% Fv-SDF addition, the noodles achieved the highest sensory score (92) and water absorption rate (148%), while maintaining a lower dry matter loss rate (5.2%) and optimal cooking time (142 s). Gas chromatography-ion mobility spectrometry (GC-IMS) analysis showed that 67 volatile substances were detected, and the contents of furfural, 1-hydroxy-2-acetone, propionic acid, and 3-methylbutyraldehyde were higher in the Fv-SDF 10% group. These 10% Fv-SDF micro-fermented noodles were not only nutritionally enhanced, but also had a unique flavor. This study provides a valuable theoretical basis for the industrial application of F. velutipes and the development of high-quality dried noodles rich in Fv-SDF. Full article

Argemone ochroleuca Sweet is an alien invasive weed dominating most cultivated lands, however, the phytochemicals present in this plant and the effects of these on the germination and growth of economically important crops such as maize are not well-documented. The objective of the study was to characterize the phytochemistry of the shoots and roots of A. ochroleuca and determine whether the extracts could inhibit the germination of maize seeds. The shoots and roots of A. ochroleuca were extracted in water, hexane, and acetone. Ten maize seeds were used in the germination bioassay. A phytochemical analysis was conducted using gas chromatography-mass spectrometry (GC-MS). The effects of the A. ochroleuca water, hexane, or acetone extracts on maize seed germination were concentration and plant-part dependent. The highest reduction was recorded from the water extract with 82%. Identified compounds with high percentages in A. ochroleuca were 9,12-octadecadienoic acid (Z,Z) and 9,12,15-octadecatrienoic acid, (Z,Z,Z)-. The present study indicated that A. ochroleuca extracts suppress the germination of maize seeds, likely due to the presence of both the identified and potentially unidentified phytochemicals that were not detected by the selected method. There is, however, a need to establish the relationship between the phytochemical compounds and the enzymes responsible for germination. Full article

Organophosphates are widely used in the livestock industry. In this study, we developed a method for detecting 27 organophosphate insecticides in animal-derived foods, including beef, pork, chicken, milk, and eggs, using liquid chromatography–tandem mass spectrometry. A modified QuEChERS method was optimized for sample pretreatment. A mixture of acetonitrile and acetone was used as the extraction solvent, and MgSO₄ and NaCl were used as salts. Among the five different dispersive solid-phase extraction systems, MgSO₄, primary secondary amines, and C18 were selected for purification because they had the highest recovery rates and least matrix effects. The matrix-dependent limit of quantitation was 0.0005–0.005 mg/kg, and the correlation coefficient of the matrix-matched calibration curve was >0.99, which was acceptable for quantifying residues below 0.01 mg/kg—the default maximum residue limit in a positive list system. The recovery efficiencies ranged from 71.9 to 110.5%, with standard deviations ranging from 0.2% to 12.5%, satisfying the SANTE guidelines. The established analytical method was used to monitor organophosphates in animal-derived foods obtained from a local market, and no pesticides were detected. With respect to industry standards, our proposed method is recommended for practical organophosphate detection in animal-derived foods. Full article

In the first part of this study, the electrochemical polymerization of two compounds, 3,5-dihydroxybenzoic acid and 2′,6′-dihydroxyacetophenone, was compared in dimethyl sulfoxide solvent on platinum and glassy carbon electrodes. The voltammograms obtained showed remarkable differences between the two monomers and between the two electrode materials. The acetophenone derivative formed electropolymer remnants at the electrodes, while in the case of the benzoic acid derivative, practically no passivation occurred, and the scanning electron microscopic results reinforced this. A few stackings adsorbed only after electropolymerization from a highly concentrated solution of dihydroxybenzoic acid. As a modifying layer on the platinum and glassy carbon electrodes, the prepared films from 2′,6′-dihydroxyacetophenone were tested for tributylamine in acetonitrile and in an aqueous solution of a redox-active compound, hydroquinone, during the stirring of the solution. More stable amperometric current signals could be reached with modified platinum than with glassy carbon, and the significant influence of the organic washing liquid after deposition was established via the study of noise level. In this respect, acetone was the best choice. The amperometric signals with the modified platinum obtained upon the addition of aliquots of the stock solution resulted in a 3.29 μM detection limit. Full article

An ultrasound-assisted dispersive liquid–liquid microextraction by solidifying floating organic droplets, coupled to a form of temperature-programmed gas chromatography flame ionization detection, has been developed for the extraction and determination of thymol and carvacrol. This method utilizes undecanol as the extraction solvent, offering advantages such as facilitating phase transfer through solidification and enhancing solvent-focusing efficiency. The optimal gas chromatography conditions include a sample injection volume of 0.2 µL, a split ratio of 1:10, and a flow rate of 0.7 mL min⁻¹. The extraction conditions entail an extraction solvent volume of 20 µL, a disperser solvent (acetone) volume of 500 µL, pH 7.0, 7.0% NaCl (3.5 M), a sample volume of 5.0 mL, an ultrasound duration of 10 min, and a centrifuge time of 7.5 min (800 rpm). These conditions enable the achievement of a high and reasonable linear range of 3.5 to 70. 0 μg mL⁻¹ for both thymol and carvacrol. The detection limits are found to be 0.95 and 0.89 μg mL⁻¹, respectively, for thymol and carvacrol. The obtained relative standard deviations, 2.7% for thymol and 2.6% for carvacrol, demonstrate acceptable precision for the purpose of quantitative analysis. Full article

In this study, a neural network was developed for the detection of acetone, ethanol, chloroform, and air pollutant NO₂ gases using an Interdigitated Electrode (IDE) sensor-based e-nose system. A bioimpedance spectroscopy (BIS)-based interface circuit was used to measure sensor responses in the e-nose system. The sensor was fed with a sinusoidal voltage at 10 MHz frequency and 0.707 V amplitude. Sensor responses were sampled at 100 Hz frequency and converted to digital data with 16-bit resolution. The highest change in impedance magnitude obtained in the e-nose system against chloroform gas was recorded as 24.86 Ω over a concentration range of 0–11,720 ppm. The highest gas detection sensitivity of the e-nose system was calculated as 0.7825 Ω/ppm against 6.7 ppm NO₂ gas. Before training with the neural network, data were filtered from noise using Kalman filtering. Principal Component Analysis (PCA) was applied to the improved signal data for dimensionality reduction, separating them from noise and outliers with low variance and non-informative characteristics. The neural network model created is multi-layered and employs the backpropagation algorithm. The Xavier initialization method was used for determining the initial weights of neurons. The neural network successfully classified NO₂ (6.7 ppm), acetone (1820 ppm), ethanol (1820 ppm), and chloroform (1465 ppm) gases with a test accuracy of 87.16%. The neural network achieved this test accuracy in a training time of 239.54 milliseconds. As sensor sensitivity increases, the detection capability of the neural network also improves. Full article

Microplastics (MPs), typically defined as plastic fragments smaller than 5 mm, are pervasive in terrestrial and marine ecosystems. There is a need for rapid, portable, low-cost detection systems to assess health and environmental risks. Fluorescent tagging with Nile Red (NR) has emerged as a popular detection method, but variations in fluorescent emissions based on NR solvent, plastic polymer, excitation wavelength, and additives complicate standardization. In this study, seven plastic samples stained with acetone-based NR were analyzed using a fluorescent spectrometer to identify optimal emission peaks across UV-Vis excitation wavelengths. These findings aid in selecting appropriate excitation wavelengths and optical filters for future detection systems. Additionally, a straightforward polymer identification scheme was validated against field-collected plastic samples, whose material composition was confirmed via Fourier Transform Infrared Spectroscopy. This work contributes towards developing accessible microplastic detection technologies by characterizing the fluorescent properties of NR-stained plastics and enhancing the capability for effective environmental monitoring. Future research will expand the dataset to include diverse plastics with varying additives and weathering, and incorporate computer-vision tools for automated data processing and polymer identification. Full article

Tidal wetlands, commonly known as salt marshes, are highly productive ecosystems in temperate regions worldwide. These environments constitute a unique flora composed primarily of salt-tolerant herbs, grasses, and shrubs. This study investigated the therapeutic properties of ten salt marsh plants collected mainly from Palk Bay and Mannar Gulf against Candida disease. This study examined the changes in natural plant products associated with their anti-Candida growth activity during two distinct seasonal changes—monsoon and summer. The potential of the salt marshes to inhibit the growth of five different Candida strains was assessed using four solvents. In phytochemical analysis, the extracts obtained from a Launaea sarmentosa exhibited the highest results compared to the other plant extracts. Fourier transform infrared spectroscopy revealed 12 peaks with alkane, aldehyde, amine, aromatic ester, phenol, secondary alcohol, and 1,2,3,4-tetrasubstituted. Gas-chromatography–mass spectrometry detected 30 compounds. Cyclotetracosane, lupeol, β-amyrin, and 12-oleanen-3-yl acetate showed the highest peak range. In particular, plant samples collected during the monsoon season were more effective in preventing Canda growth than the summer plant samples. In the monsoon season, the salt marsh plant extracted with ethyl acetate showed a high anti-Candida growth activity, while in the summer, the acetone extract exhibited a higher anti-Candida growth activity than the other solvents. The hexane extract of L. sarmentosa showed the highest inhibition zone against all Candidal strains. Furthermore, compounds, such as β-amyrin, lupeol, and oxirane, from the hexane extract of L. sarmentosa play a vital role in anti-Candida activity. This paper reports the potential of tidal marsh plant extracts for developing new antifungal agents for Candida infections. Full article

Sorghum, a cereal grain rich in nutrients, is a major source of phenolic compounds that can be altered by different processes, thereby modulating their phenolic content and antioxidant properties. Previous studies have characterised phenolic compounds from pigmented and non-pigmented varieties. However, the impact of processing via the cooking and fermentation of these varieties remains unknown. Wholegrain flour samples of Liberty (WhiteLi₁ and WhiteLi₂), Bazley (RedBa₁ and RedBa₂), Buster (RedBu₁ and RedBu₂), Shawaya black (BlackSb), and Shawaya short black 1 (BlackSs) were cooked, fermented, or both then extracted using acidified acetone. The polyphenol profiles were analysed using a UHPLC-Online ABTS and QTOF LC-MS system. The results demonstrated that combining the fermentation and cooking of the BlackSs and BlackSb varieties led to a significant increase (p < 0.05) in total phenolic content (TPC) and antioxidant activities, as determined through DPPH, FRAP, and ABTS assays. The 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity of WhiteLi₁, BlackSb, RedBu₂, and BlackSs increased by 46%, 32%, 25%, and 10%, respectively, post fermentation and cooking. Conversely, fermentation only or cooking generally resulted in lower phenolic content and antioxidant levels than when samples were fully processed compared to raw. Notably, most of the detected antioxidant peaks (53 phenolic compounds) were only detected in fermented and cooked black and red pericarp varieties. The phenolic compounds with the highest antioxidant activities in pigmented sorghum included 3-aminobenzoic acid, 4-acetylburtyic acid, malic acid, caffeic acid, and luteolin derivative. Furthermore, the growing location of Bellata, NSW, showed more detectable phenolic compounds following processing compared to Croppa Creek, NSW. This study demonstrates that sorghum processing releases previously inaccessible polyphenols, making them available for human consumption and potentially providing added health-promoting properties. Full article