Analyte Concentration Research Articles

Refractive-index sensing based on terahertz cavity-modal confinement of Bragg metal grating structure

Abstract Integrated sensing platforms, which possess active layers of local electric-field oscillation in the terahertz (THz) frequency, can sensitively detect analytes via electromagnetic (EM) wave guidance, resonance, and spatial confinement in the system of THz time-domain spectroscopy. A Bragg grating structure of periodically perforated metal slits (PPMSs) is presented here as an active layer to generate the local electric-field oscillation of metal-cavity EM wave resonance that is coupled from 0.1–1 THz metal surface waves along the wavelength-scaled segments of metal slabs. The cavity modal confinement property, which is characterized from device transmittance or loss spectra, leads to the distribution of the metal-cavity wave resonance over a 35-pitch length and a 0.1–0.2 mm metal thickness of PPMSs. These distribution dimensions of metal-cavity wave resonance represent the longitudinal and transverse confinement performances, respectively. The PPMS-THz waves specified by 2D spatial confinement can realize the functional integration of a dielectric superstrate component and a sample adsorbing layer to adjust the dispersion responsivity and concentration of analytes, respectively. A refractive-index sensing application of glucose is presented by this integrated scheme for refractive-index sensing in a molecular density range of 0–24 μg/mm2, a resolution density of 1.6 μg/mm2, and a trace density of 2.61 μg/mm2. The PPMS-based THz integrated sensing platform facilitates the developments of specific test papers and relevant molecular surface modification to target molecules.

A recent overview of the application of emerging extraction medium-based sample preparation for the determination of aflatoxins and their precursors in food samples.

Food safety problem caused by aflatoxins (AFs) has become a major concern worldwide. However, due to the complexity of food matrices and the low concentration of analytes, the accurate and sensitive determination of AFs and their precursors in the biosynthetic pathway is extremely challenging, so the development of efficient sample preparation techniques has been urgently required. This paper reviews the recent advances in sample preparation based on some emerging extraction media for the determination of AFs and their precursors in different food samples, including ionic liquids (ILs) and IL-based composites, metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). These extraction media can be combined with different sample preparation techniques, such as dispersive liquid-liquid microextraction, solid-phase extraction, and magnetic/dispersive solid-phase extraction, mainly depending on their physicochemical properties. They exhibit efficient extraction and enrichment performance towards AFs and their precursors, which is attributed to their multiple-interaction mechanism and/or porous structure. This review also presents the current challenges and future prospects of these emerging extraction media for sample preparation of AFs and their precursors from food.

Steroid hormone concentrations in dried blood spots: A comparison between capillary and venous blood samples.

An important aspect of the shift towards dried blood spots (DBS) as a sample matrix for laboratory measurements, is the availability of robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods that can reliably quantify analyte concentrations in DBS. The development and validation of these LC-MS/MS methods, however, concerns an extensive process, for which large amounts of DBS samples are required. DBS are usually obtained from capillary blood samples, but they can also be prepared from venous (residual) blood samples, which are widely available in clinical laboratories. Therefore, we aimed to determine whether DBS prepared from (residual) venous blood samples, collected in EDTA blood tubes, can be used for future development and validation of LC-MS/MS methods to quantify steroid hormones in DBS. Capillary DBS and venous blood samples (EDTA tube and tube without additives) were collected from twenty healthy volunteers (12F/8M). From both venous blood samples, DBS were prepared volumetrically. Samples were analyzed using in-house developed LC-MS/MS methods for testosterone, androstenedione, 17-hydroxyprogesterone (17-OHP), cortisol, cortisone, corticosterone, and for dehydroepiandrosterone sulfate (DHEA-S). DBS made from venous blood collected in EDTA tubes compared with capillary blood showed a correlation coefficient of ≥ 0.89 for all steroid hormones except corticosterone (0.67). DBS made from venous blood collected in tubes without additives showed a strong correlation with both DBS made from venous blood collected in EDTA tubes (≥0.97 for all steroid hormones) and capillary DBS (>0.90) except corticosterone (0.64). DBS prepared from (residual) venous blood collected in EDTA blood tubes can be used for future development and validation of LC-MS/MS methods to quantify steroid hormones, except for corticosterone, in capillary DBS.

Comparative analysis of allowable total error specifications for coagulation factor assays utilizing China National External quality assessment scheme data and biological variation data.

It is necessary and challenging to establish reasonable and feasible total error specifications for coagulation factor assays for quality control and assessment. The aim of this study is to establish new total error specifications for coagulation factor assays by combining External Quality Assessment data with reliable biological variation data. Data from China National External Quality Assessment Scheme (28,408 results from 1,381 laboratories) were analyzed, stratifying External Quality Assessment data by reference intervals to establish concentration-dependent total error specifications. A "state-of-the-art" total error was defined at 80% best results of the participants. Then these specifications were compared with biological variation-derived total error to determine recommended total error specifications for different concentration levels. None of the measurands could meet biological variation-derived optimum total error. Eight parameters (FII, FVIII, FX at both high and low levels; FVII and FIX at high level) reached the desirable criteria. Only FXI at low level can't met the minimum criteria. The establishment of total error specifications for coagulation factor assays should be set separately according to different concentration levels and attainability of current testing technologies. Setting total error specifications should also consider clinical requirements and regulatory standards across different regions. Analyte concentration significantly influences laboratory performance, particularly for low-concentration coagulation factors. Total error specifications need updated periodically in the further. Tea, allowable total error; BV, biological variation; SOTA, state of the art; EQAS, External quality assessment schemes; ME, measurement error; RIs, reference intervals; BIVAC, Biological Variation Data Critical Appraisal Checklist; QIs, quality items; EFLM, European Federation of Clinical Chemistry and Laboratory Medicine; APS, analytical quality specifications; ISO, International Organization for Standardization; EQA, External quality assessment; PT, proficiency testing; RCPA, Royal College of Pathologists of Australasia; RfB, Reference Institute for Bioanalytics; ECAT, External Quality Control for Assays and Tests.

Comparing Equivalence‐Based Instruction to a PowerPoint Video Lecture to Teach Differential Reinforcement Descriptors to College Students

ABSTRACTDifferential reinforcement (DR) procedures involve systematically arranging the environment to increase the future frequency of socially important behaviors while minimizing or eliminating problem behaviors. The purpose of the present study was to compare the effects of computerized stimulus equivalence‐based instruction (EBI) to a pre‐recorded voiceover PowerPoint lecture to teach definitions and examples of differential reinforcement procedures to college students. The three classes comprised textual stimuli characterizing differential reinforcement of other (DRO), alternative (DRA), and incompatible (DRI) behavior. Each class contained three members: name, definition, and short vignette examples. To program for generalization, two vignette exemplars were used during training while a third exemplar was used to assess stimulus generalization. We used a between‐subjects group design to compare pretest and posttest performances of EBI and lecture participants across (a) computer match‐to‐sample (MTS), (b) card sorting, and (c) written tests (fill‐in and multiple‐choice), with the latter two used to determine the degree to which class‐consistent responding generalized from selection‐based responding to other response topographies (i.e., sorting and writing). Results demonstrated that EBI produced greater score increases than lecture for MTS and card sorting tests, but increases were comparable for the two groups for both fill‐in and multiple‐choice written tests. Another posttest at 1 week showed maintenance of performance gains. Implications for using EBI to teach behavior analytic content are discussed.

Simultaneous quantification of siRNA antisense and sense strands by hybrid liquid chromatography-mass spectrometry.

Most oligonucleotide bioanalytical assays currently only quantify the pharmacologically-active antisense strand, though there have been recent efforts to simultaneously quantify the sense strand using hybridization ELISA or solid phase extraction LC-MS. Hybrid LC-MS, which offers both high sensitivity and specificity unlike the currently used platforms, has not been applied to quantify both siRNA strands simultaneously. A hybrid LC-MS assay utilizing LNA capture probes was developed and applied to quantify both strands of a 21-mer lipid-conjugated siRNA (SIR-3) using tandem mass spectrometry (MS/MS). A similar approach using high-resolution mass spectrometry (HRMS) was also evaluated. The final LC-MS/MS method was capable of quantifying both strands of SIR-3 at concentrations between 0.600 and 1000 ng/mL in cynomolgus monkey tissue homogenates with acceptable accuracy and precision. The LC-HRMS assay demonstrated similar sensitivity and assay performance as the LC-MS/MS assay. Overall, this manuscript presents orthogonal methods to existing siRNA bioanalytical workflows that with high sensitivity and specificity can provide greater information about the concentration and biotransformation of an siRNA analyte.

Plasmonic Slippery Surface for Surface-Enhanced Raman Spectroscopy and Protein Adsorption Inhibition.

Slippery liquid-infused porous surfaces (SLIPSs) are a class of surface that offers low contact angle hysteresis and low tilt angle for water droplet shedding. This property also endows the surface with pinning-free evaporation, which in turn has been exploited for analyte concentration enrichment for Surface Enhanced Raman Spectroscopic applications and antibiofouling. Herein, we demonstrate a facile approach for creating SLIPS with low contact angle hysteresis and low tilt angle for water shedding by coating the equal-volume mixture of polydimethylsiloxane (PDMS) and silicone oil. By exploiting the in situ plasmonic particle reduction capability of the PDMS, the surface is converted to plasmonic SLIPS, which illustrates its potential as a sensitive analytical platform via surface-enhanced Raman spectroscopy. The Raman spectroscopic studies using crystal violet as a reference sample show a limit of detection of 76 pM. Further, we have demonstrated that the fabricated plasmonic substrate is found to be more efficient in inhibiting proteins (bovine serum albumin) on the surface compared to pristine PDMS surfaces. Our fabricated plasmonic surface can find applications in ultrasensitive molecular detection for applications related to analytical chemistry, diagnostics, environmental monitoring, and national security and more importantly can control the nonspecific adsorption of proteins.

One Step Visual Homogeneous Immunoassay of a Rheumatoid Arthritis Biomarker in Serum via Target-Regulated Steric Hindrance and Competitive Recognition.

Homogeneous analysis techniques offer several advantages as alternatives to heterogeneous immunoassays, such as simplicity and rapidity. In this study, a visual homogeneous immunoassay without a labeling process was developed based on target-induced steric hindrance to regulate competitive recognition mechanism. Specifically, as the analyte concentration varies, the change of microenvironment based on steric hindrance could affect the recognition of Cu2+ by signal probes. Herein, taking anticyclic citrullinated peptide antibody (anti-CCP) as an example, the method was verified. Cu2+ can bind to histidine (His), as well as signal probes. Cyclic citrullinated peptide containing His was served as the capture antigen, and the fluorescence of both CdTe quantum dots and calcein can be quenched by Cu2+. Then, this quenching effect can be regulated by the change of steric hindrance, so that anti-CCP analysis can be realized. The limit of detection of anti-CCP was as low as 0.002 and 0.01 U/mL in fluorescence mode and red, green, and blue (RGB) mode, respectively. Furthermore, clinical practicality was validated through 46 clinical samples, including rheumatoid arthritis patients (n = 28) and healthy donors (n = 18), with the assay demonstrating a sensitivity and specificity of 96.4% and 88.9%, respectively. Indeed, the results were consistent with those of clinical electrochemiluminescence immunoassays and digital radiography images. Overall, this method shows great potential for clinical application and offers a universal template for a label-free homogeneous immunoassay.

National scale assessment of the occurrence and risk of trace organic contaminants in Canadian Lake sediments.

In Canada studies on the presence of trace organic contaminants (TrOCs) such as pharmaceuticals, personal care products, pesticides and flame retardants in lakes have primarily focused on the water column at localized scales. To address this gap, the occurrence of 44 TrOCs, representative of various types of human activities, was investigated in surface sediments (0-2cm) from 193 lakes across Canada. A total of 28 targeted TrOCs were detected, with 99.5% of the samples containing at least one detection, and one lake exhibiting up to 12 detections. The most frequently detected contaminants (> 20% of samples) were the insect-repellent diethyltoluamide (DEET), the UV filter oxybenzone, the flame retardants tris(2-butoxyethyl) phosphate (TBEP), tris(2-chloroethyl) phosphate (TCEP), and triphenyl phosphate (TPP), the stimulant caffeine, and cotinine, a metabolite of the stimulant nicotine. Median reported concentrations of the targeted TrOCs ranged from 0.017pgg-1 to 359ngg-1, with a maximum value of 23,700ngg-1 observed for DEET in one lake. The geographic distribution of analyte concentrations varied by compound class: pharmaceuticals and consumer product additives were predominantly found in the more urbanized regions of Ontario and Quebec, whereas personal care products such as DEET and oxybenzone were more frequently detected in the western provinces of Canada. An environmental risk assessment based on an additive model conducted on three aquatic organisms (algae, cladocerans, and fish) revealed that 4% and 6% of the lakes posed a potentially high risk for cladocerans and algae, respectively. A geographical analysis indicated that lakes in the south of the eastern provinces of Canada presented the highest risks for all three species. These findings represent the first large-scale results detailing the extent of contamination caused by TrOCs on Canadian lake sediments. They establish reference levels that can guide future monitoring efforts and inform policy discussions aimed at protecting lake ecosystems.

Sorption Preconcentration of Heavy Metals on Graphene Oxide for Analysis of Waters by Electrothermal Vaporization ICP-OES

Background: Heavy metals (HMs) such as Cr, Hg, Pb, etc., are major threats to human health due to their toxic and carcinogenic properties. So, the determination of HMs concentrations in waters is an actual and important task. Methods: In this paper, the method includes a preliminary concentration of HMs and other analytes (Ag, Au, Ba, Be, Bi, Cr, Hg, In, Pb, Sn, and Zn) from water solutions on the graphene oxide and subsequent analysis of slurries of sorbent by electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP-OES) is developed for the first time. Results: The high efficiency of analytes sorption on graphene oxide made it possible to significantly increase the sensitivity of the analysis. The limits of detection of Ag, Au, Ba, Be, Bi, Cr, Hg, In, Pb, Sn, and Zn from 0.7 to 300 ng L-1 are achieved for ETV-ICP-OES analysis. The use of electrothermal vaporization for sample introduction allows the analysis of sorbent suspensions and avoids the desorption stage, reduces sample dilution, increases the preconcentration factor, and improves limits of detection (LODs) of analytes by 2-33 times compared to routine inductively coupled plasma optical emission spectrometry analysis (ICP-OES) with sorption preconcentration. Conclusion: For Ba, Be, Bi, Cr, In, Pb, Sn, and Zn ETV-ICP-OES provides LODs from 2 to 33 times lower compared to conventional ICP-OES analysis with sorption preconcentration due to higher preconcentration factor and transport efficiency of introducing of the analytes concentrates into the ICP. The developed method was applied to the analysis of real tap and mineral water samples. The results of analysis by ETV-ICP-OES with preconcentration of trace elements and ICP-OES were in good agreement. As a result of lower LODs of analytes, ETV-ICP-OES analysis provides the determination of concentrations of Ba, Bi, Sn, and Pb in tap and mineral water samples.

Luminescent Lanthanide Infinite Coordination Polymers for Ratiometric Sensing Applications.

Ratiometric lanthanide coordination polymers (Ln-CPs) are advanced materials that combine the unique optical properties of lanthanide ions (e.g., Eu3+, Tb3+, Ce3+) with the structural flexibility and tunability of coordination polymers. These materials are widely used in biological and chemical sensing, environmental monitoring, and medical diagnostics due to their narrow-band emission, long fluorescence lifetimes, and excellent resistance to photobleaching. This review focuses on the composition, sensing mechanisms, and applications of ratiometric Ln-CPs. The ratiometric fluorescence mechanism relies on two distinct emission bands, which provides a self-calibrating, reliable, and precise method for detection. The relative intensity ratio between these bands varies with the concentration of the target analyte, enabling real-time monitoring and minimizing environmental interference. This ratiometric approach is particularly suitable for detecting trace analytes and for use in complex environments where factors like background noise, temperature fluctuations, and light intensity variations may affect the results. Finally, we outline future research directions for improving the design and synthesis of ratiometric Ln-CPs, such as incorporating long-lifetime reference luminescent molecules, exploring near-infrared emission systems, and developing up-conversion or two-photon luminescent materials. Progress in these areas could significantly broaden the scope of ratiometric Ln-CP applications, especially in biosensing, environmental monitoring, and other advanced fields.

Ultrasensitive detection of six sepsis-associated proteins in neonatal saliva

Sepsis is a life-threatening condition that affects millions of newborns every year. Current diagnostic practices require painful, often repetitive, blood collections to isolate and culture the causative microorganism. Definitive return of results can take up to 5 days, exposing newborns to potentially unnecessary antibiotics. Developing a more rapid, non-invasive assessment of infectious status based upon host immune response provides an alternative diagnostic approach to infection screening. However, additional blood collection for multiplex quantification of inflammatory biomarkers in neonates remains prohibitive. Alternatively, saliva may serve as an informative biofluid, though detection of biologically relevant proteins in saliva remains challenging, with analyte concentrations 100 to 1000 times lower compared to blood. To address this challenge, we developed a panel of six ultra-sensitive single-molecule array (Simoa) assays for inflammatory biomarkers known to be associated with neonatal sepsis: serum amyloid A1 (SAA1), lipopolysaccharide-binding protein (LBP), chemokines CCL20, CXCL6, CXCL12; and the adipokine resistin. When these assays were tested on 40 neonatal salivary samples, we found that CXCL6 and CCL20 were significantly elevated in infected and septic neonates compared to those uninfected. The small volumes of fluid used (~10 μL saliva) and limited concentrations of these analytes in saliva (pg/mL) underscore the importance of ultra-sensitive measurements in the development of non-invasive diagnostics and reinforces the value of neonatal saliva as a viable sample matrix for monitoring infection. We hypothesize these assays could be useful in future diagnostic tests to discriminate between infected and uninfected neonates.

Integration of silver nanostructures in wireless sensor networks for enhanced biochemical sensing.

Integrating noble metal nanostructures, specifically silver nanoparticles, into sensor designs has proven to enhance sensor performance across key metrics, including response time, stability, and sensitivity. However, a critical gap remains in understanding the unique contributions of various synthesis parameters on these enhancements. This study addresses this gap by examining how factors such as temperature, growth time, and choice of capping agents influence nanostructure shape and size, optimizing sensor performance for diverse conditions. Using silver nitrate and sodium borohydride, silver seed particles were created, followed by controlled growth in a solution containing additional silver ions. The size and morphology of the resulting nanostructures were regulated to achieve optimal properties for biochemical sensing in wireless sensor networks. Results demonstrated that embedding these nanostructures in Polyvinyl Alcohol (PVA) matrices led to superior stability, maintaining 93% effectiveness over 30days compared to 70% in Polyethylene Glycol (PEG). Performance metrics revealed significant improvements: reduced response times (1.2ms vs. 1.5ms at zero analyte concentration) and faster responses at higher analyte levels (0.2ms). These outcomes confirm that higher synthesis temperatures and precise shape control contribute to larger, more stable nanostructures.The enhanced stability and responsiveness underscore the potential of noble metal nanostructures for scalable and durable sensor applications, offering a significant advancement over current methods.

Multiclass Steroid Profiling in Short-Finned Pilot Whale Blubber Using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

Wildlife scientists are quantifying steroid hormones in a growing number of tissues and employing novel methods that must undergo validation before application. This study tested the accuracy and precision of liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods for use on blubber samples from short-finned pilot whales (Globicephala macrorhynchus). We expanded upon a method for corticosteroid quantification by adding analytes and optimizing internal standard (IS) application. We optimized a method for the quantification of seven steroid hormones using LC-MS/MS with a C18 column. We assessed the accuracy and precision of this updated C18 method and an existing biphenyl method for use with pilot whale blubber by conducting a spike recovery experiment and calculating percent recovery and relative standard deviation (RSD) for each analyte. To explore the potential for running this method with fewer matched ISs, we compared the performance of multiple ISs for each analyte. All 11 adrenal and gonadal analytes showed good accuracy and precision in the spike recovery experiment, with recoveries between 82% and 110% and recovery RSDs below 10%. The C18 method detected all analytes at endogenous concentrations, except aldosterone. Although endogenous DHEA was detected, variability was high. IS comparisons showed 10 of 11 analytes could be calculated with comparable accuracy and precision using an IS substitute, but some substitutions significantly altered the analyte concentrations calculated. The C18 method was not sensitive enough for endogenous aldosterone detection. DHEA, which has not been previously quantified in blubber, was detected in all samples, but with high variability at lower concentrations. The methods in this study provide reliable detection and quantification of the other nine hormones tested and can be used for assessments of adrenal and gonadal steroid hormones from whales. Laboratories can reduce costs through IS substitution but should consider how these substitutions affect results.

Commutability assessment of new standard reference materials (SRMs) for determining serum total 25-hydroxyvitamin D using ligand binding and liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays.

Commutability is where the measurement response for a reference material (RM) is the same as for an individual patient sample with the same concentration of analyte measured using two or more measurement systems. Assessment of commutability is essential when the RM is used in a calibration hierarchy or to ensure that clinical measurements are comparable across different measurement procedures and at different times. The commutability of three new Standard Reference Materials® (SRMs) for determining serum total 25-hydroxyvitamin D [25(OH)D], defined as the sum of 25-hydroxyvitamin D2 [25(OH)D2] and 25-hydroxyvitamin D3 [25(OH)D3], was assessed through an interlaboratory study. The following SRMs were assessed: (1) SRM 2969 Vitamin D Metabolites in Frozen Human Serum (Total 25-Hydroxyvitamin D Low Level), (2) SRM 2970 Vitamin D Metabolites in Frozen Human Serum (25-Hydroxyvitamin D2 High Level), and (3) SRM 1949 Frozen Human Prenatal Serum. These SRMs represent three clinically relevant situations including (1) low levels of total 25(OH)D, (2) high level of 25(OH)D2, and (3) 25(OH)D levels in nonpregnant women and women during each of the three trimesters of pregnancy with changing concentrations of vitamin D-binding protein (VDBP). Twelve laboratories using 17 different ligand binding assays and eight laboratories using nine commercial and custom liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays provided results in this study. Commutability of the SRMs with patient samples was assessed using the Clinical and Laboratory Standards Institute (CLSI) approach based on 95% prediction intervals or a pre-set commutability criterion and the recently introduced International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) approach based on differences in bias for the clinical and reference material samples using a commutability criterion of 8.8%. All three SRMs were deemed as commutable with all LC-MS/MS assays using both CLSI and IFCC approaches. SRM 2969 and SRM 2970 were deemed noncommutable for three and seven different ligand binding assays, respectively, when using the IFCC approach. Except for two assays, one or more of the three pregnancy levels of SRM 1949 were deemed noncommutable or inconclusive using different ligand binding assays and the commutability criterion of 8.8%. Overall, a noncommutable assessment for ligand binding assays is determined for these SRMs primarily due to a lack of assay selectivity related to 25(OH)D2 or an increasing VDBP in pregnancy trimester materials rather than the quality of the SRMs. With results from 17 different ligand binding and nine LC-MS/MS assays, this study provides valuable knowledge for clinical laboratories to inform SRM selection when assessing 25(OH)D status in patient populations, particularly in subpopulations with low levels of 25(OH)D, high levels of 25(OH)D2, women only, or women who are pregnant.

Evaluating the Performance of Ethanol Electrochemical Nanobiosensor Through Machine for Predictive Analysis of Electric Current in Self‐Powered Biosensors

ABSTRACTIn this study, the focus is on ethanol nano biosensors based on alcohol oxidase (AOX) enzymatic reactions and the feasibility of generating electric current for biobatteries. The aim is to convert the latent energy in ethanol into electrical energy through the enzymatic oxidation process in the presence of an AOX enzyme. The release of electrons and the creation of a potential difference make the use of ethanol as a biofuel cell/self‐power biosensor in biologically sensitive systems feasible. To achieve this, glassy carbon electrodes were modified with gold nanoparticles to enhance conductivity, and the AOX enzyme was immobilized on the working electrode. The current generated through the enzymatic process was measured in various pH and analyte concentration conditions. Afterward, machine‐learning models, including multilayer perceptron (MLP), deep neural network, decision tree, and random forest, were employed to assess the impact of parameters on electric current generation, evaluate the error rate, and compare the results. The results indicated that the MLP model was the most suitable method for predicting the electric current produced under different pH, temperature, and ethanol concentration values. These findings can be utilized to identify optimal conditions and increase the current output for use as a reliable energy source in self‐powered biosensors. In conclusion, this study suggests a promising way to generate electricity by oxidizing ethanol with the AOX enzyme. The use of machine learning to analyze experimental data has provided insight into optimal conditions for maximizing electric current output for developing sustainable energy sources in biologically sensitive systems and biobattery technology.

Integrating Particle Motion Tracking into Thermal Gel Electrophoresis for Label-Free Sugar Sensing.

Bioanalytical sensors are adept at quantifying target analytes from complex sample matrices with high sensitivity, but their multiplexing capacity is limited. Conversely, analytical separations afford great multiplexing capacity but typically require analyte labeling to increase sensitivity. Here, we report the development of a separation-based sensor to sensitively quantify unlabeled polysaccharides using particle motion tracking within a microfluidic electrophoresis platform. Carboxymethyl dextran (20 kDa) was spiked into Pluronic thermal gel along with fluorescent nanoparticles (200 nm diameter) and loaded into single-channel microfluidic devices. Upon voltage application, the soluble sugar enriched into a concentrated band that induced motion of the insoluble particles as it passed. Bead displacement was tracked over time to produce electropherograms where peak areas were proportional to analyte concentrations. Key studies herein established the range of acceptable operating conditions (e.g., gel concentration, temperature) to characterize how the temperature-dependent rigidity of thermal gel influenced the analysis. Data processing strategies were then evaluated to identify conditions (e.g., exposure intervals, particle averaging, motion directionality) to maximize sensitivity. The quantitative response of the method was evaluated over a broad concentration range (0.5-5000 nM) where detection limits were found to be 520 pM for the 20 kDa sugar, providing a 106-fold superior mass LOD than a gold standard UV-vis absorbance method. Studies into the detection mechanism found that sensitivity was dependent on the molecular weight of the sugar as larger sugars produced greater responses. Collectively, these studies established best practices for integrating particle sensing into thermal gel separations for label-free polysaccharide quantitation.

Handling non-linearities and pre-processing in multivariate calibration of vibrational spectra

Backgroundseveral automatic pre-processing methods are available for coping with scattering effects in vibrational spectra (near and mid infrared, Raman) when linear multivariate models are applied for calibration. In contrast, almost no methods have been developed for data sets showing a non-linear relationship between instrumental signals and analyte concentrations or target properties. Resultsseveral data sets are studied, both simulated and experimental, showing different degrees of non-linearity: very low, intermediate, and high. For each of them, three multivariate models have been applied: classical partial least-squares (PLS), sequential pre-processing through orthogonalization (SO-PLS) and Kernel partial least-squares (K-PLS). The success of these models depends on the degree of non-linearity presented by each data set. The results are discussed in terms of the model structures. Significancethe need of developing new automatic pre-processing techniques for non-linear vibrational data sets is highlighted, in order to reach a similar status as the linear counterparts.

Changes in urinary concentrations of contemporary and emerging chemicals in commerce during the COVID-19 pandemic: Insights from the Environmental influences on Child Health Outcomes (ECHO) program.

Previous research indicates that the COVID-19 pandemic catalyzed alterations in behaviors that may impact exposures to environmental endocrine-disrupting chemicals. This includes changes in the use of chemicals found in consumer products, food packaging, and exposure to air pollutants. Within the Environmental influences on Child Health Outcomes (ECHO) program, a national consortium initiated to understand the effects of environmental exposures on child health and development, our objective was to assess whether urinary concentrations of a wide range of potential endocrine-disrupting chemicals varied before and during the pandemic. Drawing from three racially, ethnically, and socioeconomically diverse ECHO cohorts, we assessed key differences in urinary chemical concentrations related to environmental exposures through food packaging, use of disinfectants, personal care products and air pollutants using repeated urine samples in a subset of 47 participants, who contributed a urine sample prior to the pandemic (between October 2018 and February 2020) and a subsequent urine sample after the pandemic began (between March 2020 and April 2021). We measured urinary concentrations of analytes across several chemical groups, including polycyclic aromatic hydrocarbons (PAHs), phthalates/alternative plasticizers, synthetic phenols (parabens, bisphenols, triclosan, benzophenones), organophosphate esters (OPEs), insecticides and fungicides. Multivariable linear mixed models accounting for key covariates and clustering within cohort and across repeated samples were used to estimate the change in urinary analyte concentrations across time points. We observed decreases in urinary concentrations of some PAHs, bisphenols, benzophenones, and triclosan, and increases in specific OPEs. These biomarker data mirror some of the behavior changes reported in our prior work and support the observation that the pandemic-related behavior changes lead to alterations in chemical exposures that have been linked to adverse health outcomes.

Green chemistry: magnetic dispersive solid phase extraction for simultaneous enrichment and determination of V, Ni, Ti and Ga in water samples by HR-CS ETAAS.

This work presents a straightforward, highly sensitive, and cost-effective method for the simultaneous determination of V, Ti, Ni and Ga by high resolution-continuum source electrothermal atomic absorption spectrometer (HR-CS ETAAS) in aqueous environmental samples (tap and seawater samples). The system is based on retention of the analyte onto a novel magnetic nanomaterial (M@GO magnetic graphene oxide) functionalised with methylthiosalicilate (MTS). The formed complexes between the M@GO-MTS and the target analytes were broken, adding 1 mL of nitric acid (6%) and sonication for 5 min. The optimized method achieved detection limits of 0.71 μg L-1 for Ti, 0.20 μg L-1 for V, 0.04 μg L-1 for Ga, 0.66 μg L-1 for Ni. The accuracy of the proposed method was demonstrated by analysing two certified reference materials and by determining the analyte content in spiked environmental water samples. The results obtained using this method were in good agreement with the certified values of the standard reference materials, and the recoveries for the spiked tap water and seawater samples ranged from 94% to 120%.