Excitation-emission Matrix Fluorescence Research Articles

Identification of lu’an Guapian at different picking periods by using excitation–emission matrix fluorescence spectroscopy coupled with chemometrics

Lu’an Guapian (LAGP) is a renowned green tea, with its price significantly higher when picked before the Qingming Festival compared to after, posing risks of confusion and counterfeiting. This study proposed using an excitation-emission matrix (EEM) fluorescence method combined with chemometrics for rapid identification of tea picked before and after Qingming Festival. Firstly, the differences among the EEM fingerprints of different tea samples were analyzed using the alternating trilinear decomposition (ATLD) algorithm. To determine the differences between LAGP before and after Qingming Festival, the total contents of ten main components in tea were detected, and their effects on the EEM fluorescence fingerprint of tea were analyzed using correlation heatmaps. Finally, two chemometric algorithms, partial least squares discriminant analysis (PLS-DA) and k-nearest neighbor (k-NN), were used to classify LAGP before and after Qingming Festival, achieving a classification accuracy of 100% for the training set, test set, and prediction set. To further explore the potential of this method, LAGP was further classified in detail according to four detailed picking periods, achieving an accuracy of over 83%. The same chemometric algorithm was used to classify the data based on the high-performance liquid chromatography (HPLC) method, yielding results comparable to those of the EEM-based method, though slightly inferior. Variable importance projection (VIP) analysis shows that catechin analogs are the main contributors to the classification of LAGP. The results demonstrated the EEM method’s significant potential in identifying the picking time of green tea.

Film-immobilized carbon nitride for the degradation of pharmaceuticals: A continuous flow photoreactor performance upheld by excitation-emission matrix fluorescence spectroscopy

The validation of immobilized photocatalysts is a fundamental matter regarding the scaling-up process in the photocatalytic degradation of aqueous pollutants in natural surface waters. This work presents the comprehensive evaluation of graphitic carbon nitride (g-C3N4, CN) immobilized onto a polymeric film (F) placed inside a continuous flow operation planar reactor for the removal of a mixture of pharmaceuticals (i.e., venlafaxine, citalopram, carbamazepine, tramadol, ketoprofen, and diclofenac, 3 μM each) under visible light. The resulting CN/F (8 mg of CN per cm2 of film and with significant preservation of optical and structural properties after more than 350 h of reuse) yielded the complete removal under total recirculation of all pharmaceuticals after 90 min under visible light, except for ketoprofen, probably ascribed to competition for photogenerated holes, as suggested by the proposed mechanism. Under dead-end continuous flow mode, the steady-state conversion averaged 67 % in deionized water, increasing up to 76 %, and 80 % in natural surface waters obtained from the Douro River and the effluent from a wastewater treatment plant (Northwestern Portugal), respectively, related to the promotion effect of carbonates anions and organic matter. The assessment of excitation-emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor (PARAFAC) analysis further demonstrated the removal (ca. 50 %) of the protein- and humic-like substances contained in the collected wastewater, thus evidencing the continuous flow mode performance of the immobilized photocatalyst for real environmental applications.

Detection of E. coli using bacteriophage T7 and analysis of excitation‑emission matrix fluorescence spectroscopy

Conventional detection methods require the isolation and enrichment of bacteria, followed by molecular, biochemical, or culture-based analysis. To address some of the limitations of conventional methods, this study develops a machine learning (ML) approach to analyze the excitation-emission matrix (EEM) fluorescence data generated based on bacteriophage T7 and E. coli interactions for in-situ detection of live bacteria in the presence of fresh produce homogenate. We trained classification models using various ML algorithms based on the 3-D EEM data generated with bacteria and their interactions with a T7 phage. These ML algorithms, including linear Support Vector Classifier and Random Forest, demonstrate high accuracy (>0.85) for detecting E. coli at 102 CFU/ml concentration within 6 hours. Additionally, these ML models can differentiate among different E. coli concentration levels. For example, the Gaussian Process model achieved an accuracy of 92% in detecting different concentration levels of live E. coli. Application of these ML methods to detect E. coli in spinach homogenate yielded an accuracy of 89% using the linear-SVC model. Furthermore, feature selection techniques were employed to reduce the dimensionality of the data, revealing that only six features were necessary for achieving classification accuracy (>0.85) of spinach homogenate samples containing 102 CFU/ml of E. coli. These findings highlight the potential of this novel bacterial detection methodologies, offering rapid, specific, and efficient solutions for applications in food safety and environmental monitoring.

Application of excitation-emission matrix fluorescence spectroscopy and chemometrics for quantitative analysis of emulsified oil concentration

Application of excitation-emission matrix fluorescence spectroscopy and chemometrics for quantitative analysis of emulsified oil concentration

Mitigating Membrane Fouling in Abattoir Wastewater Treatment: Integration of Pretreatment Step with Zwitterion Modified Graphene Oxide–Polyethersulfone Composite Membranes

Composite polyethersulfone (PES) membranes containing N-aminoethyl piperazine propane sulfonate (AEPPS)-modified graphene oxide (GO) were integrated with either of the two pretreatment processes (activated carbon (AC) adsorption or polyelectrolyte coagulation) to assess their effectiveness in mitigating membrane fouling during the treatment of abattoir wastewater. The AEPPS@GO-modified membranes, as compared to the pristine PES membranes, showed improved hydrophilicity, with water uptake increasing from 72 to 118%, surface porosity increasing from 2.34 to 27%, and pure water flux (PWF) increasing from 235 to 673 L.m−2h−1. The modified membranes presented improved antifouling properties, with the flux recovery ratio (FRR) increasing from 59.5 to 93.3%. This study compared the effectiveness of the two pretreatment processes, AC, coagulation, and the integrated system (coagulation/AC-UF membrane), in the removal of natural organic matter (NOM) and improvement of abattoir wastewater’s pH, electrical conductivity, TDS, and turbidity. The integrated systems produced improved water quality in terms of pH, EC, TDS, turbidity, and organic content. The fluorescence excitation–emission matrix (FEEM) analysis exhibited almost no fluorescence peak post-treatment following organic loading removal. The quality of the water met the South African non-potable water reuse standards. The sole membrane treatment systems exhibited good fouling resistance without the pretreatment systems; however, integrating these systems can offer extended longer filtration periods, thereby assisting in cost aspects of the abattoir wastewater treatment system.

Aqueous photochemical aging of water-soluble smoke particles from crop straws burning

Most aqueous oxidation studies focus on single model precursors, while the photochemical aging of actual water soluble organic matter (WSOM) in particles emitted from biomass burning remains poorly understood. In this study, gas chromatography-mass spectrometry (GC/MS) was first used to analyze the WSOM in smoke particles emitted from three crop straws burning. The results show that the dominant WSOM in three crop straws (CS) smoke are phenolic substances with small differences. Aqueous photochemical aging of WSOM in CS smoke was investigated under simulated sunlight exposure. High-resolution aerosol mass spectrometry (HR-AMS) analyzed aqueous secondary organic aerosol (aqSOA) and it was found that the oxidation degree of aqSOA increased with prolonged aging. No obvious increase in the abundance of N-containing organic ions was observed over the course of aqueous aging. As aqueous aging progresses, the pH of the solution gradually decreases, accompanied by the continuous generation of organic acids. Studies on dithiothreitol (DTT) activity indicate that the impact of aqueous photochemical aging on health is not significant.The solution after photoaging shows relatively lower light absorption ability than the initial solution. The aqueous photochemical aging also led to a gradual reduction of fluorescence at excitation/emission = 250–260 nm/350 nm (protein-like substances) for CS smoke WSOM, suggesting the significant degradation of chromophores. However, three-dimensional excitation-emission matrix (EEM) fluorescence combined with parallel factor analysis (PARAFAC) revealed that aqueous aged CS smoke WSOM contains compounds with high humification index, confirming that the fluorophore composition is altered by aqueous aging. The humic-like substance (HULIS) concentration increased for the first 3 h and then decreased, closely matching the pattern of a new fluorescence peak. Finally, GC/MS analysis of the products indicated that there was obvious decline in proportion of methoxyphenol. The results of this study are important for understanding the aqueous-phase oxidation reactions of CS smoke WSOM in the atmosphere and their light-absorption characteristics and health impacts.

Novel insights into fouling mechanisms in anaerobic acidification membrane bioreactor: The leading role of pH value

Anaerobic acidification membrane bioreactors (AAMBRs) have recently emerged as effective systems for recovering volatile fatty acids (VFAs) from municipal wastewater. However, membrane fouling remains a critical challenge, with its underlying mechanisms not yet fully understood. Given its importance in inhibiting methanogenic bacteria and stabilizing VFAs production, this study explores the direct and indirect effects of pH on membrane fouling mechanisms in AAMBRs. The results demonstrated that compared to pH 7, the fouling potential of anaerobic sludge was significantly higher at pH levels of 5 and 10 owing to a decrease of sludge floc size and an increase of soluble microbial products (SMP) especially proteins. Analytical techniques such as confocal laser scanning microscopy (CLSM), fourier transform infrared spectroscopy (FTIR), and fluorescence excitation-emission matrix (F-EEM) analyses revealed a substantial increase in organic foulants particularly proteins on the membrane surface at pH levels of 5 and 10. Circular dichroism (CD) spectroscopy further indicated a significant change in protein secondary structure, specifically an increase in α-helix content under extreme pH conditions. Furthermore, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory indicated that elevated protein concentrations enhance the adhesion of sludge and SMP to membrane surfaces. Insights from the Flory-Huggins theory demonstrated that variations in protein structure significantly contribute to increased filtration resistance within the gel layer. Both experimental data and theoretical models underscore the dual role of pH in optimizing VFAs production and managing membrane fouling, offering insights for enhancing AAMBR performance and mitigating fouling issues.

Interactions between dissolved organic matter with different molecular weights and nonylphenol in surface water bodies

Dissolved organic matter (DOM) has a complex composition, which can interact with various pollutants and affect the removal of pollutants. Therefore, a thorough understanding of the interaction between the encccvironmental hormone nonylphenol (NP) and DOM is crucial for environmental impact and development. In this study, the interaction was investigated by means of excitation emission matrix (EEM) fluorescence spectroscopy, UV–Vis spectroscopy, FT-IR spectroscopy, nuclear magnetic resonance (NMR) and complex model analysis. The interaction between different MW DOM and NP was verified by the spectral characterization data. According to the characterization analysis, the main components of DOM in water samples were proteinoid (C1, C2, C4) with MW < 1 k Da, and their binding capacity (log Ka value) and binding site number (n) showed the maximum values (3.37, 3.24, 3.26; 0.81, 1.22, 0.52). For the humus like substance (C3) with larger molecular weight, the log Ka value and the number of binding points n increased with increasing molecular weight, and the maximum values were 3.13 and 0.31, respectively. It can be seen that low molecular weight proteins have strong binding ability and binding sites with NP, and high molecular weight humus also have strong binding ability. Overall, the interaction between DOM and NP has molecular weight dependence and heterogeneity. The purpose of this study is to deeply understand the interaction characteristics of different MW DOM with NP, and to provide theoretical support and reference for the study of the removal effects of NP pollutants.

Ultraviolet/dielectric barrier discharge enhanced ultrafiltration for treating natural water: Performance, mechanism and iodinated disinfection by-product fate

This study employed ultraviolet (UV)/ dielectric barrier discharge (DBD) pre-treatment to mitigate ultrafiltration membrane fouling and enhance the purification efficiency of natural surface water. Moreover, as an emerging contaminant, the iodinated disinfection by-products’ fate and degradation performance were discussed. The investigation revealed that the generation of numerous active species (⋅OH, ⋅O2−, 1O2, etc) under high input voltage and low pH conditions were advantageous for augmenting membrane flux, with sodium sulfate electrolyte playing a role in promoting the formation of selective sulfate radicals. Fluorescence excitation-emission matrix spectroscopy indicated that the UV/DBD system at 5.5 kV can effectively degrade proteins and humic substances in surface water, leading to an enhancement in water quality. With the assistance of UV radiation, macromolecular organic matter underwent extensive decomposition into smaller molecules, thus creating an ideal environment for controlling membrane fouling in the UV/DBD system. Additionally, it was identified the intermediate products and degradation pathways during iopamidol degradation by UV/DBD. It also affirmed the minimal risk of disinfection by-product generation with this strategy. The study provides a viable and efficient pre-treatment approach for mitigating membrane fouling and purifying water.

Investigation of extracellular polymeric substances (EPS) from cyanobacteria/blue green algae and their interaction with heavy metal ions: Insights from excitation-emission matrix fluorescence spectroscopy

Investigation of extracellular polymeric substances (EPS) from cyanobacteria/blue green algae and their interaction with heavy metal ions: Insights from excitation-emission matrix fluorescence spectroscopy

A crude, cold-pressed oil from elderberry (Sambucus nigra L.) seeds: Comprehensive approach to properties and characterization using HPLC, DSC, and multispectroscopic methods

The physicochemical characterization of fresh, undiluted, cold-pressed oil from elderberry seeds (EO) is presented. The results showed EO's uniqueness for the 93 % presence of essential fatty acids, including linoleic n-6 (41 %), α-linolenic n-3 (38 %), and oleic n-9 (13 %) acids with favorable ratios for human nutrition, n-3/n-6 = 0.93. A γ-tocopherol is the dominant tocopherol (96 %), with a concentration of 20.62 mg/100 g, indicating low oil oxidative stability. DSC heating and cooling traces determined the thermal properties. These results also revealed the presence of metastable triacylglycerol (TAG) structures composed of polyunsaturated fatty acids. The presence of characteristic groups for fatty acids and TAGs in EO was confirmed by FTIR-ATR spectra. For the first time, Langmuir monolayer studies on EO revealed its low compressibility, indicating its low emulsifiability, and the presence of minor components of EO, including tocopherols, phenolic acids, polyphenols, flavonoids, and carotenoids, was determined using UV–Vis absorption and fluorescence excitation-emission matrix (EEM) along with the chemometric method.

Enhancing compost quality through biochar and oyster shell amendments in the co-composting of seaweed and sugar residue

Aquaculture and agricultural production generate substantial amounts of waste, including seaweed (which has plant-stimulating properties), oyster shells, and sugar residues. Through composting and appropriate management, these wastes have the potential to be converted into beneficial soil amendments. However, there is a lack of research exploring the potential of composting in promoting the conversion of seaweed into more stable humified forms, as well as in assessing whether composted seaweed retains its beneficial effects on plant growth. Additionally, studies on using oyster shells as additives to reduce waste pressure and comparing their effectiveness with biochar are relatively scarce. This study examines the impact of incorporating 5% corn stover biochar (T1), 10% biochar (T2), and 10% oyster shell powder (T3) on key physicochemical properties, product quality, and microbial community dynamics during the co-composting of seaweed and sugar residues. Results indicate that organic matter (OM) loss in T1 and T2 increased by 31.2% and 26.4%, respectively, compared to the control (CK). Moreover, Excitation-emission matrix (EEM) fluorescence spectroscopy revealed that humic substances in T1 and T2 surged by 434% and 423%, respectively, far exceeding the 289% increase in CK. The 10% biochar treatment also improved alginate degradation and seed germination index, due to the presence of biostimulants in seaweed and an increased abundance of Cobetia. Microbial analysis post-composting showed that T2 and T3 significantly enhanced the diversity and richness of bacterial communities. Notably, although oyster shell powder did not improve the humification degree of compost as significantly as biochar, it achieved effective weight reduction of waste (OM loss of 43.57%, far exceeding CK's 35.34%) without hindering the composting process. All four compost treatments retained the plant-stimulating effects of seaweed and facilitated alginate degradation. These results underscore the potential of biochar to enhance composting efficiency and utilize composting to process large quantities of oyster shell waste.

Potential of solar photodegradation of antibiotics in shallow ditches: Kinetics, the role of dissolved organic matter and prediction models

Shallow ditches, which generally receive livestock or domestic sewage, are widely distributed in rural and suburban areas, making them important sites for antibiotic exposure. Because of the easy penetration of solar irradiation, the photochemical reactions of antibiotics tend to be active in shallow ditches. This study investigated the photodegradation potential of 21 commonly used antibiotics belonging to five categories in a typical shallow ditch by conducting simulated solar irradiation experiments. The influence of dissolved organic matter (DOM) in ditch water on the photodegradation of antibiotics was analyzed, and a model based on DOM changes was established to predict the degradation behavior of antibiotics. The results indicated that the degradation rates of different varieties of antibiotics in ultrapure water and ditch water followed the trend of fluoroquinolones > tetracyclines > sulfonamides > macrolides > lincosamides. In ditch water, direct photodegradation and photooxidation mediated by 3DOM∗ played predominant roles in the antibiotic photodegradation, whereas the contributions of singlet oxygen (1O2) and hydroxyl radicals (·OH) varied significantly depending on the reactivity of the antibiotics. A simple and effective model was proposed for predicting the photodegradation process of antibiotics in ditch water based on the degree of DOM photobleaching determined by excitation-emission matrix fluorescence spectroscopy coupled with parallel factor analysis. The prediction model was simplified by considering the similarity in photochemical properties within the same category of antibiotics and was validated by field tests. This study fills a critical research gap by evaluating the photodegradation of antibiotics in shallow ditches, thereby providing valuable insights into their fate and transport in shallow ditch water.

Impacts of an intensive traditional mariculture model on offshore environments as evidenced by dissolved organic matter and bacterial communities

Mariculture is a key protein source and economic driver but traditional methods pollute coastal waters, hindering sustainable development. Current research on the ecological impacts of mariculture mainly focuses on specific pollutants and lacks an assessment of the biogeochemical impacts of mariculture discharge. This study examined Xiangshan Bay, a representative intensive mariculture area in China, to explore the impact of mariculture tailwater discharge on water quality, focusing on dissolved organic matter (DOM) and bacterial communities. Based on the fluorescence excitation-emission matrix combined with parallel factor analysis, a characteristic fluorescence component C4 was identified in mariculture tailwater (intensity of 40 ± 4 %, n = 8), while higher C4 components (47 ± 3 %, n = 15) were found throughout the bay. Humic-like components from riverine input (C1 + C2: 32 ± 3 %, n = 15) and protein-like components from domestic sewage (C5: 2 ± 1 %, n = 15) were significantly lower in the seawater samples, indicating the strong influence of mariculture tailwater on the entire DOM structure of the bay. The bacterial community structure showed a response consistent with DOM, as revealed by nonmetric multidimensional scaling analysis. This showed that bacterial communities in mariculture tailwater and bay water samples clustered together, independent of riverine input. The SourceTracker model indicated that mariculture tailwater (91 ± 5 %) predominantly contributed to the bacterial community, with minimal contributions from riverine input (< 5 %). Co-occurrence network analysis further showed that under long-term high-intensity mariculture discharge, the C4 component became the core DOM and was closely associated with the bacterial community. The results here demonstrate the profound impact of traditional mariculture on coastal water quality and show that riverine input is not the primary pollution source in this region, providing clear directions for coastal environmental restoration efforts.

Promoting effects of ferric ions on Microcystis aeruginosa growth and arsenate accumulation and reduction at different phosphorus environments

The effects of different dissolved organic phosphorus (DOP) associated with distinct iron conditions (iron deficient (dFe), ferric ions (Fe3+), and colloidal iron (CFe)) on algal growth and arsenate (As(V)) metabolism were systematically evaluated and compared in Microcystis aeruginosa. Two chemical forms of DOP (D-glucose-6-phosphate (GP) and phytic acid (PA)), as well as dissolved inorganic phosphorus (DIP), were employed as distinct phosphorus environments. The results revealed that As(V) metabolism of M. aeruginosa was more influenced by different phosphorus forms than by different iron conditions. Conversely, the release of microcystins in the media was found to be significantly more affected by the different phosphorus forms than by the iron conditions. Moreover, DOP was observed to promote arsenic (As) biotransformation, particularly the efflux of methylated As from a single algal cell, whereas DIP was found to primarily facilitate As(V) accumulation in algae. The total As metabolism amount per algal cell under PA was observed to be five times that observed under DIP and GP. The influence of iron conditions on the synthesis of algal metabolites was notable, as evidenced by the metabolites identified in algae of aliphatic (δ 1.28–1.68), humic acid-like and aromatic protein-like substances through 1H-NMR spectra and three-dimensional excitation-emission matrix fluorescence spectroscopy analysis. This impact was particularly notable at Fe3+ conditions, due to the role of Fe3+ as a micronutrient with highly bioavailable forms, which enhanced the synthesis of organic compounds in algae and promoted algal growth. Consequently, Fe3+ could inhibit As accumulation under DIP but promote it under DOP. The obtained results facilitate a more comprehensive understanding of the combined role of different phosphorus forms and iron conditions in algal bloom outbreaks and As(V) metabolism.

PARAFAC under non-negativity constraint is adapted to recover the underlying Beer-Lambert law of the excitation-emission fluorescence matrix measurements acquired from analyte-triggered semiconductor QDs photoluminescence modulation. When and why?

BackgroundAnalyte-triggered semiconductor quantum dots (QDs) modulation in the presence of non-consistently responsive fluorescent species represents a challenging analytical issue in concrete multi-way data handling. QDs with heterogeneous sizes and/or uneven distribution of functional moieties on their surfaces exhibit significant fluctuations in the fluorescent response components, known as chemical rank, across different excitation/emission modes. This phenomenon may lead to a substantial deviation from the proportionality prescribed by Beer-Lambert law. Nonetheless, even in the presence of such deviation, a multi-way model may be successfully selected after determining a proper chemical rank in a QDs system. ResultsWe show that in a valid PARAllel FACtor (PARAFAC) model under properly determined chemical rank, meaningfully resolved pure spectral profiles can be reached for each fluorescent responsive constituent in the original excitation-emission fluorescence matrix (EEFM) measurements. This was thoroughly illustrated by applying PARAFAC trilinear decomposition of a three-way data array of two distinct datasets acquired from semiconductor QDs sensing systems with low-rank trilinear assumption. The first dataset, presented here for the first time, comprises EEFM measurements of the ligand-driven quenching of thiomalic acid (TMA)-capped AgInS2 (AIS) QDs by vomitoxin. The second dataset, employed for illustrative purposes, comprises EEFM measurements of the quenching, via cation bridging, of glutathione (GSH)-capped CdTe QDs by Pb(II). The results of this study enabled the determination of vomitoxin at a ppb level in real samples of fish feeds, showcasing the efficacy of the PARAFAC model in resolving spectral signatures (loadings) and pure concentration profiles (scores). SignificancePARAFAC under a properly examined chemical rank can be easily adapted for retrieval the underlying Beer-Lambert law of the original EEFM measurements with a low-rank trilinear structure through the chemically meaningful information either when (i) no deviation of Beer-Lambert law was observed as deeply discussed in connection with the dataset acquired from vomitoxin-driven molecular sensing through TMA-capped AIS QDs, or when (ii) substantial deviations of the Beer-Lambert law are evident, as discussed in connection with the dataset collected from sensing ionic species through Pb(II) bridging of GSH-capped CdTe QDs.

Variability of Bile Baseline Excitation-emission Fluorescence of Two Tropical Freshwater Fish Species.

The quantification of pollutant metabolites in fish bile is an efficient approach to xenobiotic pollution monitoring in freshwaters since these measurements directly address exposure. Fluorescence excitation-emission matrix spectroscopy (EEMS) has demonstrated to be a highly specific and cost-effective technique for polycyclic aromatic hydrocarbon (PAH) and PAH-metabolite identification and quantification. EEMS ability to quantify these compounds strongly depends on the intensity and variability of the bile baseline fluorescence (BBF). We found large differences in BBF among Aequidens metae (AME) individuals and of these with Piaractus orinoquensis (PIO). Moreover, BBF was large enough that solvent dilutions of over 1:400 were needed to avoid inner filter effects. We used parallel factor analysis (PARAFAC) to model the intra- and inter-species BBF variability. PARAFAC successfully decomposed the EEMS set into three fluorophores present in all samples, although in concentrations spreading over ~ 3 orders of magnitude. One of the factors was identified as tryptophan. Tryptophan and Factor 2 were covariant and much more abundant in AME than in PIO, while Factor 3 was ~ 6 times more abundant in PIO than in AME. Also, tryptophan was ~ 10x more abundant in AME specimens immediately caught in rivers than in their laboratory-adapted peers. The PARAFAC decomposition effectiveness was confirmed by the positive proportionality of scores to dilution ratios. A large inner filter indicates that Factor 2 is as strong a light absorber as tryptophan. Our results stress the need to include bile matrix variable components for the detection and quantification of pollutant metabolites using PARAFAC.

Determination of DEET, Icaridin, and IR3535 in insect repellents using excitation-emission matrix (EEM) fluorescence spectroscopy and multiway calibration

Due to rising temperatures in recent years, there has been an increase in outbreaks of arboviral diseases like Dengue, chikungunya, Zika, and yellow fever, which are primarily transmitted by two Aedes mosquitos. The outbreak has sparked significant concern among the population and prompted countries to heighten their precautions, specially by increasing the use of insects repellents. Regarding the regulatory demands of these products, this study develops a novel analytical method for the determination of DEET, Icaridin, and IR3535 in insect repellents combining excitation-emission matrix (EEM) fluorescence spectroscopy with higher-order multivariate calibration techniques. For this purpose, a dataset comprising 21 samples containing the studied active ingredients was used to construct Parallel Factor Analysis (PARAFAC) and Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) models. As a result, DEET, Icaridin, and IR3535 were quantified with a RMSEP lower than 1.84% for PARAFAC and below 11.30% for MCR-ALS. The EJCR test confirmed the accuracy of the proposed methods, which agreed with the high-performance liquid chromatography reference method at a 95% confidence level. These findings suggest that developing multiway calibration models using EEM proves to be accurate and cost-effective for quality control in repellent-based products.

Authentication of Argentinean extra-virgin olive oils using three-way fluorescence and two-way near-infrared data fused with multi-block DD-SIMCA

A trending problem of Extra Virgin Olive Oil (EVOO) adulteration is investigated using two analytical platforms, involving: (1) Near Infrared (NIR) spectroscopy, resulting in a two-way data set, and (2) Fluorescence Excitation-Emission Matrix (EEFM) spectroscopy, producing three-way data. The related instruments were employed to study genuine and adulterated samples. Each data set was first separately analyzed using the Data Driven-Soft Independent Modeling of Class Analogies (DD-SIMCA) method, based on Principal Component Analysis (for the two-way NIR data) and PARallel FACtor analysis (for the three-way EEFM data). The data sets were then processed together using the multi-block fusion method, based on the concept of Cumulative Analytical Signal (CAS). A comparison of the data processing methods in terms of sensitivity, specificity and selectivity showed the following order of excellence: NIR < EEFM < NIR + EEFM. This finding confirms the effectiveness of multi-block data fusion, which cumulatively improves the model performance.

Characteristics of water dissolved organic matter in Zoige alpine wetlands, China

BackgroundDissolved organic matter (DOM) plays a significant role in the biogeochemical cycle of crucial elements in aquatic ecosystem. However, it is still not clear on the spectral characteristics of water DOM in different types of alpine wetlands, which have less anthropogenic influences and intensive ultraviolet radiation. Here, we collected 107 water samples from marsh, lake, and river wetlands in the Zoige plateau, China, and analyzed the chemical characteristics, compositions, and potential sources of chromophoric DOM by combining UV–vis spectroscopy and excitation–emission matrix fluorescence spectroscopy coupled with parallel factor analysis (EEMs-PARAFAC).ResultsUVC and UVA fulvic-like substances were the prevailing fluorescence components in water DOM, which accounted for 23.74–71.59% and 16.76–30.01% of the total fluorescence intensity, respectively. Compared with the lake and river wetlands, fluoresce intensities of UVC and UVA fulvic-like substances in DOM were higher in marsh wetland. Marsh wetlands possessed the highest SUVA254, E2/E3, E2/E4, and E4/E6 of DOM, suggesting higher humification degree, higher relative molecular nominal size, and higher aromaticity. And the E2/E4 ratios in most water samples were higher than 12, indicating water DOM was mainly derived from autochthonous sources in alpine wetlands.ConclusionsWetland types strongly affected the spectral characteristics of water DOM in Zoige plateau. These findings may be beneficial for sustainable management of alpine wetlands.Graphical