Target Analytes Research Articles

Quantification of florfenicol and its metabolites in fillets of Nile tilapia: Synthesis of metabolites and validation of an on-line solid-phase extraction-ultra high-performance liquid chromatography-tandem mass spectrometry method

This study concerns the synthesis of the florfenicol (FF) metabolites florfenicol amine (FFA), florfenicol alcohol (FFOH), and monochloroflorfenicol (FFCl), for their subsequent use as reference standards in On-line solid-phase extraction-ultra high-performance liquid chromatography-tandem mass spectrometry (SPE-UHPLC-MS/MS) analysis. The metabolites were characterized using 1H and 13C NMR, as well as HRMS, and their purities were confirmed by quantitative NMR to ensure analytical reliability. Validation of the developed analytical method showed that it presented acceptable performance, with linearity >0.99 for all the target analytes, accuracies within ±10 % of nominal concentrations, and intra- and inter-day precisions within 15 %. Application of this method to fillets from fish that had been treated with florfenicol (dose of 10 mg/kg bw daily) demonstrated its effectiveness in consistently detecting FF and its metabolites throughout the treatment. The results emphasized the utility of the method for enhancing pharmacokinetic and residue depletion research. The ability to precisely monitor the drug and its metabolites in treated fish provides important insights into florfenicol metabolism, laying the groundwork for further comprehensive profiling studies of metabolites in fish tissue.

Hierarchical magneto-colorimetric labels for immediate lateral flow immunoassay of chlorothalonil residues

Quantitative detection of pesticide residues in food and environmental samples using an improved lateral flow immunoassay (LFIA) is of considerable importance for real-time analysis. This paper proposes a highly sensitive LFIA platform based on a hierarchical magneto-colorimetric compact. This compact serves as both the target magnetic enrichment substrate and a photosensitive label. Initially, a large porous dendritic silica template is prepared and doped with superparamagnetic ferric oxide nanoparticles (Fe3O4 NPs) and colloidal gold nanoparticles (AuNPs) at high densities within its vertical channels. The sequential assembly of central–radial channels allow for the three-dimensional integration of these two components, enabling independent control of their discrete functions without mutual interference. Following alkyl organosilicon encapsulation and silica sealing, the composite spheres are then applied in LFIA to detect chlorothalonil residues. Fe3O4 NPs enhance the binding efficiency to target analytes, while AuNPs amplify the signal, leveraging their high loading densities and robust optical properties. The developed LFIA platform exhibited a detection limit of 0.34 ng/mL for chlorothalonil and a linear range of 0.0085–824 ng/mL. The recoveries varied between 85.1 % and 103.1 %, and the relative standard deviations were 1.25%–8.84 %. This LFIA approach demonstrates high sensitivity, specificity, reproducibility and flexible detection modes, making it highly suitable for the on-site monitoring of pesticide residues.

Surface Tailoring of MoS2 Nanosheets with Substituted Aromatic Diazonium Salts for Gas Sensing: A DFT Study.

Two-dimensional (2D) nanomaterials are useful for building gas sensors owing to their desirable electronic and optical properties. However, they usually suffer from selectivity, because they cannot discriminate between gas molecules. Functionalization with organic molecules can be used to tailor their surfaces to recognize a specific family of compounds. In this study, solid-state density functional theory (DFT) was used to elucidate the functionalization of MoS2 with substituted aromatic diazonium salts (R = -H, - CH3, -CO2H, -CHO, -OCH3, and -NO2). Results showed that chemical reaction with diazonium salts is favored to their physical adsorption (E ads = -0.04 to -0.38 eV vs E rxn = -1.47 to -2.20 eV), where organic cations have a preference to attach atop of sulfur atoms. Chemical functionalization induced a small variation in the bandgap energy not exceeding 0.04 eV; thus, the optical properties were well preserved. In the presence of ammonia, the substituted MoS 2 /2(a-f) responded to the target analyte through a change in the interaction energy, varying from -0.08 to -0.83 eV, where the best interaction energy was obtained for MoS 2 /2c, bearing the carboxylic acid group. In the presence of other gases such as CO2, SO2, and H2S, the interaction energy is lower (-0.14 to -0.35 eV), indicating good selectivity of the nanomaterials. Furthermore, the interaction increased in the presence of humidity, which was more realistic than that in the presence of neat NH3. This interaction was confirmed by computing the partial charges. Recovery times estimated from the interaction energies ranged from 0.31 s to several minutes, depending on the interacting molecules. Phenylcarboxyl-modified MoS2 nanosheets show great potential as candidates for the development of chemoresistive gas sensors that are specifically designed for detecting ammonia.

Functionalized N95 Face Mask with a Chemical-Free Paper-Based Collector for Exhaled Breath Analysis: SARS-CoV-2 Detection with a Printed Immunosensor as a Case Study.

Exhaled breath electrochemical sensing is a promising biomedical technology owing to its portability, painlessness, cost-effectiveness, and user-friendliness. Here, we present a novel approach for target analysis in exhaled breath by integrating a comfortable paper-based collector into an N95 face mask, providing a universal solution for analyzing several biomarkers. As a model analyte, we detected SARS-CoV-2 spike protein from the exhaled breath by sampling the target analyte into the collector, followed by its detection out of the N95 face mask using a magnetic bead-based electrochemical immunosensor. This approach was designed to avoid any contact between humans and the chemicals. To simulate human exhaled breath, untreated saliva samples were nebulized on the paper collector, revealing a detection limit of 1 ng/mL and a wide linear range of 3.7-10,000 ng/mL. Additionally, the developed immunosensor exhibited high selectivity toward the SARS-CoV-2 spike protein, compared to other airborne microorganisms, and the SARS-CoV-2 nucleocapsid protein. Accuracy assessments were conducted by analyzing the simulated breath samples spiked with varying concentrations of SARS-CoV-2 spike protein, resulting in satisfactory recovery values (ranging from 97 ± 4 to 118 ± 1%). Finally, the paper-based hybrid immunosensor was successfully applied for the detection of SARS-CoV-2 in real human exhaled breath samples. The position of the collector in the N95 mask was evaluated as well as the ability of this paper-based analytical tool to identify the positive patient.

Hydrogen-bonded organic frameworks as stationary phase for open-tubular capillary electrochromatography

BackgroundCapillary electrochromatography (CEC) stationary phases have always been the focus of attention. The selection of excellent stationary phases are the key to realize separate of different compounds. Hydrogen-bonded organic frameworks (HOFs) are porous materials connected by hydrogen bonds between molecules, which have the advantages of renewable, high specific surface area and mild synthesis conditions. At present, HOFs are used in gas adsorption and storage, catalysis and drug delivery. Because of its unique advantages, HOFs have a bright future as CEC stationary phases. ResultsUsing melamine (MA) and 1,3,6,8-tetra (4-carboxylphenyl)pyrene (H4TBAPy) as reaction monomers, a HOFs named MA/PFC-1 was synthesized by solvent evaporation at room temperature. The inner wall of the capillary column was coated with MA/PFC-1 by chemical bonding. Sulfonamides were used as the target analytes. The effects of pH, phosphate buffer solution concentration, organic additive content and applied voltage on sulfonamides separation were investigated. The MA/PFC-1-coated capillary column had good resolution (>1.5) and reproducibility. The intra-day, inter-day, column-to-column, and inter-batch precision of the retention times were 0.03%–0.09%, 0.04%–0.09%, 0.03%–0.14% and 0.06%–0.09%, respectively. The intra-day, inter-day, column-to-column, and inter-batch precision of the peak areas were 0.11%–0.25%, 0.13%–0.20%, 0.12%–0.15% and 0.08%–0.15%, respectively. The MA/PFC-1-coated capillary column was run 150 consecutive times, and the results showed no noticeable change, which proved that this method had good stability. SignificanceThis work applied HOFs to CEC. The results show the that MA/PFC-1-coated capillary column has good separation performance. The MA/PFC-1-coated capillary column has been successfully applied to the determination of sulfamethoxazole in tablets, which has practical application value. To open up the application of HOFs in CEC and provide a new idea for developing new CEC stationary phases.

Determination of calcium β‑hydroxy-β-methylbutyrate content in special medical formula food and sports nutrition food by solid-phase extraction and high performance liquid chromatography

Calcium β‑hydroxy-β-methylbutyrate (CaHMB) can promote muscle growth, prevent muscle atrophy, and enhance immunity, therefore, it is widely used as a nutritional supplement in special medical formula food and sports nutrition food. Many methods for the detection of CaHMB have been reported, but the pretreatment method for these reported literatures directly involves extraction using hydrochloric acid solution, without any purification steps. A method for accurately determining CaHMB in special medical formula food and sports nutrition food was established for the first time using solid-phase extraction (SPE) purification and high-performance liquid chromatography method (HPLC). The samples were extracted and precipitated protein using methanol-water solution, purified using SPE method and analyzed by HPLC on diode array detector (DAD) mode under external standard method. The method obtained excellent calibration linearity (r2>0.9993) and a satisfactory analysis of the targeted compound, which were evaluated with calibration standards over the range of 0.020–2.00 mg/mL. The limit of quantifications (LOQs), which defined as the lowest spiking level, were set at 0.4 g/100 g (special medical formula food) and 1.0 g/100 g (sports nutrition food). The average recoveries were within 92.9–104% for the analytes, and the relative standard deviations (RSDs) were below 3.93%, measured at low, medium, and high concentrations. Moreover, the positive sample analysis results indicated that CaHMB was detected on 10 real special medical formula food and sports nutrition food products, the contents of which were generally consistent with their labeled values, with measured values ranging from 97.1 % to 119 % of the labeled values. These results suggested that the developed highly sensitive and specific method is highly feasible for monitoring of the target analyte in special medical formula food and sports nutrition food.

A novel method for the simultaneous determination of drugs of abuse, ethyl glucuronide and synthetic opioids in human hair through a single digestion, purification and analysis in LC-MS/MS

Polydrug use is a serious health and social problem worldwide. Over the past several years, there has been an increasing tendency to combine narcotics, alcohol, sedatives, and/or stimulants. To the traditional drugs of abuse and alcohol, an increase of new abuse drugs such as synthetic opioids has been added. In the current study, the development and validation of an innovative and fast analytical procedure has been presented to determine drugs of abuse, ethyl glucuronide and synthetics opioids in 30 mg of human hair through a single digestion, purification and analysis in LC-MS/MS. A combine simple preparation of hair sample followed to a single chromatographic run of 10 min has been proposed. A full validation for 54 target analytes for the parameters of selectivity, linearity, limit of detection, limit of quantification, accuracy, precision, matrix effects, recovery, and dilution integrity was successful completed. The method was linear in different ranges with r values of at least 0.990; the value to the validated LLOQ values were in the range 0.1–100 pg/mg. The method offered satisfactory precisions (CV<15 % and accuracy ± 20 %). In conclusion, a significant reduction in the overall times of the analytical procedure and the reduction of consumables costs make this method extremely advantageous and undoubtedly useful in routine laboratory workflow analyses and open the way to the prospect of a further implementation which also includes other classes of xenobiotics.

Development of dispersive solid phase extraction method for the preconcentration of parathion ethyl as a simulant of nerve agent sarin from soil, plant and water samples prior to GC-MS determination.

In the presented study, an efficient and fast analytical method was developed for the determination of parathion ethyl as sarin simulant by gas chromatography-mass spectrometry (GC-MS). Dispersive solid phase extraction (DSPE) was performed to concentrate parathion ethyl from soil, plant and water samples. Reduced graphene oxide-iron (II, III) oxide (rGO-Fe3O4) nanocomposite was used as an adsorbent to collect the target analyte from the aqueous sample solutions. After the optimization of extraction/preconcentration parameters, optimum conditions for adsorbent amount, eluent type, mixing type/period, eluent volume and initial sample volume were determined as 15mg, acetonitrile, vortex/30s, 100 µL and 10mL, respectively. Under the optimum conditions, analytical performance of the developed DSPE-GC-MS method was evaluated in terms of limit of detection (LOD), limit of quantitation (LOQ) and dynamic range. Dynamic range, LOD and LOQ values were figured out to be 0.94-235.15µg/kg, 0.41µg/kg and 1.36µg/kg (mass based), respectively. Satisfactory percent recovery results (90.3-125% for soil, 93.5-108.7% for plant, 88.5-112.9% for tap water) were achieved for soil, plant and tap water samples which proved the accuracy and applicability of the developed method. It is predicted that the DSPE-GC-MS method can be accurately used for the detection of sarin in soil, plant and water samples taken from war territories.

Multicolorimetric Sensor Array Based on Silver Metallization of Gold Nanorods for Discriminating Dopaminergic Agents.

Dopaminergic agents are compounds that modulate dopamine-related activity in the brain and peripheral nerves within the pathways on both sides of the blood-brain barrier. Atypical levels of them can precipitate a multitude of neurological disorders, whose timely diagnosis signifies not only stopping the advancement of the illness but also surmounting it. A silver metallized gold nanorod (AuNRs) conditional sensor array, designed to detect dopaminergic agents for assessing nervous system disorders, yielded significant results in simultaneous detection and discrimination of Benserazide (Benz), Levodopa (L-DOPA), and Carbidopa (Carb). The array was composed of two different concentrations of silver ions as sensor elements (SEs), which generated unique signatures indicative of the presence of reductive target analytes, triggered by the incongruent formation of the Au@Ag core-shell, causing visual and fingerprint colorimetric patterns. Generating diverse responses is the key to the functionality of array-based sensing, which facilitated achieving spectral and color variation originating from the blue shift of AuNRs longitudinal localized surface plasmon resonance (LLSPR) in the extinction spectrum. Also, employing a smartphone camera enables clear visual discrimination across an extensive concentration span. Pattern recognition through linear discriminant analysis (LDA) underscored the robust discrimination accuracies of this sensor, along with quantification by means of partial least-squares regression (PLSR), affirming its potential for practical applications. Notably, the array demonstrated high sensitivity in detecting varied concentrations of target analytes, even in commercial drug samples. The sensor responses exhibited a linear correlation with the concentrations of Benz, L-DOPA, and Carb ranging from 1.59 to 100.0, 5.26 to 100.0, and 5.32 to 100.0 μmol L-1, respectively, and the minimum detectable concentrations for Benz, L-DOPA, and Carb were measured at 0.53, 1.75, and 1.77 μmol L-1, respectively. The implemented machine-learning-empowered array-based sensor represents advancements in dopaminergic agent tracing and naked eye detection.

Simultaneous determination of quaternary phosphonium compounds and phosphine oxides in environmental water and solid samples by ultrahigh performance liquid chromatography–tandem mass spectrometry

Quaternary phosphonium compounds (QPCs) and phosphine oxides (POs) are emerging contaminants that are attracting increasing attention. In the present study, a method for the quantification of QPCs and POs in multiple environmental media was developed using ultrahigh performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS). Analytes were extracted from water samples using solid phase extraction, and for the solid samples, ultrasonic extraction was employed. Compared with analytical methods established by previous studies, the approach developed in this study is more suitable for the quantitative analysis of compounds along with high sensitivity. The method quantification limit reached 0.12–2.55 ng⋅L–1 in water samples and 0.004–0.10 ng⋅g–1 in solid samples. The recoveries of target analytes spiked at low, medium and high concentrations in water and solid samples were in the range of 56.4–120 %, with relative standard deviations below 20 % (n = 6). Furthermore, the validated method succeeded in applying to analyse of eight QPCs and four POs in real environmental samples. At least five QPCs and two POs were detected in each environmental medium. This quantitative method would assist in further investigations on the occurrence, migration and the source of QPCs and POs.

Organic suspension droplet solid-phase dispersive liquid–liquid microextraction ultra-high performance liquid chromatography tandem mass spectrometry determination of antibiotic residues in water samples

A method was developed for the simultaneous detection of 38 antibiotic residues, which included 8 sulfonamides, 14 fluoroquinolones, 9 macrolides, and 7 anthelminthics, in drinking water, tap water, and environmental water. The method involved organic suspension droplet solid-phase dispersive liquid–liquid microextraction, followed by ultra-high performance liquid chromatography tandem mass spectrometry for the analysis of the water samples. Hypersil GOLD C18 chromatography column (100 × 2.1 mm, 1.9 μm) be used for separation of target analytes that were eluted by a gradient mobile phase composition of 0.2 % formic acid–water as mobile phase A and acetonitrile as mobile phase B at a flow rate of 0.2 mL min−1. Using 0.2 mL of octanoic acid as the extractant and 0.3 mL of acetonitrile as the dispersant. Under optimal conditions, the standard curve exhibits a good linear relationship within the range of 1–50 μg L−1. The spiked recovery rate of the method ranges from 63 % to 96 %, with a relative standard deviation of 0.6 % to 7.3 % (n = 6). The detection limit of the method is between 0.1 and 0.2 μg L−1. This method is characterized by its simplicity, speed, and high sensitivity, which sets the groundwork for investigating the exposure levels and environmental behavior of antibiotics.

Rapid UHPLC-MS/MS measurement of pregnanediol 3-glucuronide in spot urine samples for detecting ovulation.

Biochemical confirmation of ovulation typically involves measuring serum progesterone levels during the mid-luteal phase. Alternatively, this information could be obtained by monitoring urinary excretion of conjugated metabolites of ovarian steroids such as pregnanediol 3-glucuronide (PDG) using immunoassay techniques that have methodological limitations. The aim of the present study was to develop a mass spectrometry (MS)-based method for the rapid and accurate measurement of urinary PDG levels in spot urine samples. A "dilute and shoot" ultra-high-performance liquid cromatography tandem mass spectrometry (UHPLC-MS/MS) method was developed for measuring PDG urinary concentration with a 6-min analysis time. The method underwent validation in accordance with ISO 17025 documentation for quantitative methods, proving an efficient separation of PDG from other structurally similar glucuro-conjugated steroid metabolites and ensuring a sufficient sensitivity for detecting the target analyte at concentrations as low as 0.01 μg/mL. The validation protocol yielded satisfactory results in terms of accuracy, repeatability, intermediate precision, and combined uncertainty. Additionally, the stability of both the samples and calibration curves was also conducted. The application to real urine samples confirmed the method's capability to measure PDG levels throughout an entire menstrual cycle and detecting ovulation. The rapidity of the analytical platform would therefore enable high throughput analysis, which is advantageous for large cohort clinical studies.

Self-Assembled Plasmonic Structural Color Colorimetric Sensor for Smartphone-Based Point-Of-Care Ammonia Detection in Water.

Monitoring chemical levels is crucial for safeguarding both the environment and public health. Elevated levels of ammonia, for instance, can harm both humans and aquatic ecosystems, often indicating contamination from agriculture, industry, or sewage. Developing portable, high-resolution, and affordable methods for in situ monitoring of ammonia is thus imperative. Plasmonic sensors offer a promising solution, detecting ammonia by correlating changes in their optical response to the target analyte's concentration. While they are highly sensitive and can be fabricated in a variety of portable and user-friendly formats, some still require reagents or expensive optical equipment, which hinder their widespread adoption. Here, we present a self-assembled nanoplasmonic colorimetric sensor capable of directly detecting ammonia concentrations in aqueous matrices. The proposed sensor exploits the plasmonic resonance of the nanostructures to transduce changes in the chemical environment into alterations in color, offering a label-free method for real-time analysis. The sensor is fabricated using a self-assembling technique compatible with low-cost mass production based on aluminum and aluminum oxide, ensuring affordability and avoiding the use of other toxic chemicals. We developed a model to predict ammonia concentrations based on visible color change of the sensor, achieving a detection limit of 8.5 ppm. Furthermore, to address the need for on-site detection, we integrated smartphone technology for real-time color change analysis, eliminating the need for expensive, bulky optical instruments. Indeed, our approach offers a cost-effective, portable, and user-friendly solution for ammonia detection in water without the need for chemical reagents or spectrometers, making it ideal for field applications. Interestingly, this platform extends its applicability beyond ammonia detection, enabling the monitoring of various chemicals using a smartphone, without the need for any additional costly equipment.

Customized flexible platform - starting point for the development of wearable sensor for the direct electrochemical detection of kynurenic acid in biological samples

Kynurenic acid (KA) is an active metabolite of tryptophan with notable biological effects, such as antioxidant, neuroprotective, and anti-inflammatory properties. It often undergoes changes of the concentration in biological fluids in chronic diseases. Thus, detecting KA is of great importance for diagnosing inflammatory and neurodegenerative conditions, monitoring disease progression, and assessing responses to pharmacological treatment.This study aimed to design a tailored, flexible platform for sensitive and direct electrochemical detection of KA in biological fluids. Carbon-based electrodes were custom-printed in the lab using specialized inks and flexible substrates. The working electrodes were further functionalized with graphene oxide and subsequently electrochemically reduced to increase the sensitivity toward the analyte. An optimized differential pulse voltammetry protocol was developed for KA detection. The elaborated platform was firstly characterized and then evaluated regarding the analytical performances. It showed a good limit of detection (3 nM and demonstrated the capability to detect KA across a broad concentration range (0.01–500 μM). Finally, the elaborated flexible platform, was succesfully applied for KA determination in serum and saliva samples, in comparison with an optimized HPLC-UV method.The developed platform is the first example of in-lab printed flexible platform reported in literature so far for KA detection. It is also the first study reported in the literature of detection of KA in raw saliva collected from 10 subjects. The sensitivity towards the target analyte, coupled with the adaptability and portability, showcases the potential of this platform for thus illustrating great potential for further development of wearable sensors and biomedical applications.

Optical Fiber Probe with Integrated Micro-Optical Filter for Raman and Surface-Enhanced Raman Scattering Sensing.

Optical fiber Raman and surface-enhanced Raman scattering (SERS) probes hold great promise for in vivo biosensing and in situ monitoring of hostile environments. However, the silica Raman scattering background generated within the optical fiber increases in proportion to the length of the fiber, and it can swamp the signal from the target analyte. While filtering can be applied at the distal end of the fiber, the use of bulk optical elements has limited probe miniaturization to a diameter of 600 µm, which in turn limits the potential applications. To overcome this limitation, femtosecond laser micromachining was used to fabricate a prototype micro-optical filter, which was directly integrated on the tip of a 125 µm diameter double-clad fiber (DCF) probe. The outer surface of the microfilter was further modified with a nanostructured, SERS-active, plasmonic film that was used to demonstrate proof-of-concept performance with thiophenol as a test analyte. With further optimization of the associated spectroscopic system, this ultra-compact microprobe shows great promise for Raman and SERS optical fiber sensing.

Janus-structured colorimetric and fluorescent nanocomposites with highly luminescent retention to enhance point-of-care diagnosis

Lateral flow immunoassay (LFIA) with dual-readout signals offers significant advantages in point-of-care testing due to its adaptability to various analysis scenarios. However, colorimetric and fluorescent nanocomposites (cf-NCs) composed of plasmonic and luminescent components often suffer from low luminescent efficiency because of severe optical interference between the two functional components. Herein, we propose a simple self-assembly strategy for fabricating novel cf-NCs with a Janus structure (J-cf-NCs) using oleylamine ligand-coated gold nanoparticles (OA-AuNPs) and aggregation-induced emission luminogens (AIEgens) as building blocks. For comparison, two other cf-NCs with core–shell (CS-cf-NCs) and co-embedding (CE-cf-NCs) structures were synthesized to explore the effects of spatial intersection of OA-AuNPs and AIEgens on their optical properties. Our results demonstrate that J-cf-NCs exhibit the highest fluorescence retention (75 %), as the face-to-face spatial distribution of OA-AuNPs and AIEgens effectively prevents fluorescence resonance energy transfer and minimizes inner-filter effect-induced fluorescence quenching. When integrated with the LFIA platform, the developed J-cf-NC-LFIA demonstrated excellent detection performance for both qualitative and quantitative determination of various target analytes in sandwich and competitive formats. Specifically, the visual limit of detection (vLOD) for C-reactive protein using J-cf-NC-LFIA showed approximately an eight-fold improvement compared to the classical colloidal gold test strip, while the quantitative sensitivity was two orders of magnitude greater than that of colorimetric readout. Furthermore, the vLOD for aflatoxin M1 in milk samples was 0.5 ng⋅mL–1, with a quantitative sensitivity 38-fold higher than that of the colorimetric pattern. Overall, the proposed J-cf-NCs exhibit significant potential for enhancing the detection performance of LFIA platforms.

Highly sensitive ECL detection of miRNA based on self-generated coreactant and target-induced catalyzed hairpin assembly

BackgroundRecently, various techniques have been developed to accurately and sensitively detect tumor biomarkers for the early diagnosis and effective therapy of cancer. The electrochemiluminescence (ECL) method holding outstanding features including high sensitivity, ease of operation, and spatiotemporal controllability exhibited great potential for DNA/RNA detection, immunoassay, cancer cell detection, and environmental analysis. However, a glaring problem of ECL approaches is that the layer-by-layer modification on the electrode leads to poor stability and sensitivity of the sensors. Therefore, new simple and efficient methods for electrode modification which can effectively improve the ECL signal have attracted more and more research interests. ResultsBased on the dual amplification strategy of target-induced CHA and nanocomposite probes leading to self-generated co-reactant (H2O2), we proposed a highly sensitive miRNA-ECL detection system. The introduction of the target miRNA-21 triggers the CHA cycle amplification of DNA1 and biotin-modified DNA2, releasing the target miRNA-21 sequence for the target cycle reaction. After the reaction, the newly introduced DNA2 was combined with Au NPs modified with SA and Glucose oxidase (GOD). In the presence of oxygen, glucose was decomposed by GOD to produce H2O2, and then H2O2 was immediately catalyzed by the Hemin/G-quadruplex at the double-stranded end of the CHA product to produce a large amount of O2−•. As a co-reactant of luminol, the ECL signal was significantly enhanced, thereby achieving highly sensitive detection of miRNA-21 content and obtaining a low detection limit of 0.65 fM. The high specificity of the ECL biosensor was also proved by base mismatch. SignificanceCompared with other current detection methods, this sensor can achieve quantitative analysis of other target analytes by flexibly changing the probe DNA sequence, and provide a new feasible solution for the detection of tumor-associated markers. Benefiting from the improved sensitivity and selectivity, the proposed biosensing platform is expected to provide a new strategy for biomarkers analysis and outstanding prospect for further clinical application.

Ultrafast Gas Chromatography-Tandem Differential Mobility Spectrometry: Toward A New Generation of On-Site, Real-Time Trace-Explosives Detection.

In the defense and security sector, rapid detection of trace quantities of threat materials is paramount. Traditional instrumentation typically relies on standalone ion mobility techniques due to being inexpensive, portable, and highly sensitive. However, these techniques face limitations when handling complex samples, suffering from low resolving power (often less than 100) and ion-suppression effects, which can lead to false-positive and false-negative results. Here, we present a foundation to the solution through the hyphenation of the flow field thermal gradient gas chromatograph (FF-TG-GC) developed by HyperChrom with a tandem differential ion mobility spectrometer (DMS-DMS) developed in-house at New Mexico State University. The FF-TG-GC demonstrates the ability to separate a variety of nitroaromatic compounds of explosive significance in 20 s using a nitrogen carrier gas, highlighting the potential to offer selectivity advantages without substantially compromising high-throughput demands. These selectivity advantages are illustrated by the successful application of the FF-TG-GC-DMS-DMS to the detection and identification of single-nanogram loadings of 18 explosives and related substances in the presence of interfering materials, such as lactic acid, musk, and diesel. Furthermore, the system is capable of mitigating in-source ion-suppression effects by chromatographic separation of target analytes from background interference prior to ionization.

Identification of human metabolites of fast skeletal troponin activators Tirasemtiv and Reldesemtiv for doping control purposes.

The fast skeletal troponin activators (FSTAs) Reldesemtiv and Tirasemtiv were developed for patients suffering from neuro-degenerative diseases of the motor nervous system, e.g. amyotrophic lateral sclerosis (ALS). The drug candidates can increase the sensitivity of troponin C to calcium by selectively activating the troponin complex resulting in increased skeletal muscle contraction. Although the development of the drug candidates is currently discontinued because of missed end points in phase III clinical studies with patients with ALS, phase I clinical trials showed an increase in muscle contraction force in healthy humans. This effect could be abused by athletes to enhance performance in sports. As the substances are listed on the 2024 edition of the World Anti-Doping Agency's Prohibited List, the aim of this study was to identify and characterize metabolites of Reldesemtiv and Tirasemtiv to ensure their reliable identification in doping control analyses. The biotransformation of the drug candidates was studied in vitro using pooled human liver microsomes and 3D cultivated human hepatic cells of the cell line HepaRG, yielding a total of 11 metabolites of Reldesemtiv and eight of Tirasemtiv. In addition, a human elimination study was conducted to investigate the metabolism and elimination profile of Tirasemtiv and Reldesemtiv in vivo, suggesting the N-glucuronide of Tirasemtiv and hydroxylated 3-fluoro-2-(3-fluoro-1-methylcyclobutyl)pyridine as well as its glucuronide as suitable target analytes for routine doping controls. Applying a validating HPLC-MS/MS method, optimized to detect Reldesemtiv and Tirasemtiv in human urine, microdosing (50 μg) of each substance was traceable for 24-72 h.

Standardization via Post Column Infusion-A Novel and Convenient Quantification Approach for LC-MS/MS.

Mass spectrometry (MS) is a widely used analytical technique including medical diagnostics, forensic toxicology, food and water analysis. The gold standard for quantifying compounds involves using stable isotope-labeled internal standards (SIL-IS). However, when these standards are not commercially available, are prohibitively expensive, or are extremely difficult to synthesize, alternative external quantification techniques are employed. We hereby present a novel, convenient and cheap quantification approach-quantification via post column infusion (PCI). As a proof of concept, we demonstrated PCI quantification for the immunosuppressant tacrolimus in whole blood using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The validation results met the criteria according to the guideline on bioanalytical method validation of the European Medicine Agency (EMA), achieving imprecisions and inaccuracies with coefficient of variation and relative bias below 15%. Anonymized and leftover whole blood samples from immunosuppressed patients receiving tacrolimus were used for method comparison (PCI quantification vs. conventional internal standard (IS) quantification). Both methods showed strong agreement with a Pearson correlation coefficient of r = 0.9532. This novel PCI quantification technique (using the target analyte itself) expands the quantification options available in MS, providing reliable results, particularly when internal standards are unavailable or unaffordable. With the current paper, we aim to demonstrate that our innovative PCI technique has great potential to overcome practical issues in quantification and to provide guidance on how to incorporate PCI in existing or new LC-MS methods. Moreover, this study demonstrated a more convenient method for correcting matrix effects in comparison to alternative PCI techniques.