High Relative Standard Deviation Research Articles

Distance-based analytical device integrated with carbon nanomaterials for sarcosine quantification in human samples.

Astraightforward distance-based paper analytical device (dPAD) was developedfor monitoring sarcosine levels in human samples for the rapid diagnosis and prognosis of prostate cancer and related symptoms. This assay eliminates the need for the expensive horseradish peroxidase (HRP) enzyme by utilizing carbon nanodots (CDs) as a peroxidase-like nanozyme. The proposed dPAD sensor consists of a sample zone pre-deposited with sarcosine oxidase (SOx) and CDs, and a detection zone containing 3,3',5,5'-tetramethylbenzidine (TMB). When a solution containing sarcosine is added to the sample zone, hydroxyl radicals (•OH) are produced through SOx oxidation and subsequent peroxidase catalysis by the CDs. The formed •OH radicals immediately flow to the detection zone via capillary force, where they oxidize TMB, resulting in a visible colour change from colourless to blue. Sarcosine quantification is effortlessly accomplished by measuring the distance of the blue colour in the detection zone. The developed dPAD offers a linear working range between 12.5 and 35.0nmol L-1 (R2 = 0.9959) and a detection limit (LOD) of 10.0nmol L-1. This covers the clinical range for urinary sarcosine determination, thereby suggesting no additional sample preparation or dilution is needed. The sensor shows high precision with the highest relative standard deviation (RSD) of 4.58% and demonstrates excellent selectivity with no observed interferences. Furthermore, recovery studies in human control urine samples ranged from 98.67 to 101.50%, with the highest RSD of 2.03%. Correspondingly, our dPAD method showed a great match with the performance of a commercial ELISA method for detecting sarcosine in human control serum. The sensor is more cost-effective, user-friendly, and accessible than previous methods. Overall, the proposed method represents a promising analytical tool for sarcosine quantification. The concept is also applicable for broader analytical applications in detecting other biomolecules.

Simultaneous estimation of nebivolol hydrochloride and amlodipine besylate in human plasma employing an innovative HPLC chromatographic method

Abstract Background This study developed and validated a simple, robust, and cost-effective RP-HPLC bioanalytical method for the determination of nebivolol hydrochloride (NBH) and amlodipine besylate (AMB) in human plasma. Briefly, NBH and AMB were extracted from plasma through protein precipitation using 5% formic acid and acetonitrile. Chromatographic separation was achieved using an Inertsil ODS-3 V column (150 mm × 4.6 mm, 5 μm) with a mobile phase composed of acetonitrile and buffer (40:60, v/v). The analysis was conducted using UV detection at 215 nm. Results The bioanalytical method demonstrated linearity for NBH (4.50–180.12 μg/mL) and AMB (3.50–140.06 μg/mL). It exhibited good selectivity and sensitivity, with LLOQ responses within ≤ 20% of the analyte signal. Accuracy and precision were within acceptable limits. The extraction recovery from human plasma showed a CV (%) of 1.15% for NBH and 1.35% for AMB, indicating consistent recovery rates. Stability studies on drug-spiked human plasma at LQC and HQC levels confirmed the stability of the drugs under various conditions. Conclusion The present bioanalytical method successfully quantified NBH and AMB simultaneously in plasma samples. It demonstrated suitability, supported by high recovery rates and low relative standard deviations. With its proven linearity, accuracy, and precision, this technique is well suited for drug identification in plasma samples.

The signal quality improvement of laser-induced breakdown spectroscopy due to the microwave plasma torch modulation

BackgroundLaser-induced breakdown spectroscopy (LIBS) is a versatile analytical technique for element determination in solids, liquids, and gases. However, LIBS suffers from low detection sensitivity and high relative standard deviation (RSD), restricting its large-scale applications. the process of a physical sampling can, in some cases, compromise the mechanical strength of the component under examination. It should be considered that too large laser energy is bound to cause damage to samples which cannot be tolerated in the process of safe production in the nuclear industry. It is necessary to find a method to obtain high elemental signal intensity in low energy laser. ResultsHere, we present a novel approach by integrating microwave plasma torch (MPT) with LIBS, referred to as MPT-LIBS, which effectively addresses the limitations associated with traditional LIBS. The MPT-LIBS technique is evaluated using Cu samples with a low laser pulse energy of 0.55 mJ. A remarkable enhancement factor of over 70 for Cu I 521.82 nm line is demonstrated, while that of Cu I 324.75 nm and 327.40 nm lines exceeding two orders of magnitude. Furthermore, the RSDs of all Cu spectral lines are reduced, especially for Cu I 521.82 nm, which is decreased from 11.48 % to 1.36 %. This indicates a significant improvement in signal stability. Characterization of the tested samples using con-focal microscopy reveals that the ablation area of MPT-LIBS is only 1.36 times of that of LIBS. The limit of detection of Cu I 324.75 nm line is reduced from 52.8 ppk to 319 ppm. Significance and noveltyThis study not only offers valuable guidance for improving signal stability and the limit of detection in LIBS, but also demonstrates minimal sample damage due to its low ablation amount. Consequently, the proposed methodology has the potential to significantly advance LIBS technology, expanding its applicability in industrial applications.

Fabrication of a highly sensitive conductive copolymer layer modified immunosensing tool for cytokeratin-19 fragment detection

Design of a new and highly selective impedimetric biosensor based on the immobilization of a fragment of cytokeratin subunit 19 (CYFRA 21-1)-specific antibodies onto a conductive copolymer layer (poly(epoxy-substituted thiophene)-co-poly(3,4-ethylenedioxythiophene), CCL)-coated indium tin oxide (ITO) for the determination of CYFRA 21-1 in serum samples was reported. CCL was applied as a working electrode-modifying reagent to prepare the surface of the working ITO electrode, and CYFRA 21-1-specific antibodies bound to epoxy ends present in the copolymer layer matrix. The impedimetric response of the immunosensor to CYFRA 21-1 was recorded, and the signaling mechanism of the suggested immunosensor was based on an increase in the charge transfer resistance in the presence of target CYFRA 21-1. The developed biosensor exhibited excellent selectivity for CYFRA 21-1, and it could detect CYFRA 21-1 in a linear dynamic range from 0.0125 to 35 pg/mL with a limit of quantification (LOQ) of 12.25 fg/mL. The designed biosensor showed good storage stability, high sensitivity, suitable repeatability and reproducibility, and acceptable long-term stability. The clinical analysis of the manufactured immunosensor was explored for the analysis of serum samples, and high recoveries and good relative standard deviations (RSDs) were obtained in the range of 97.01 and 103.17 %, respectively. This copolymer-based biosensor could be a feasible tool for clinical diagnosis in complex serum samples.

Highly sensitive and selective detection of amoxicillin using molecularly imprinted ratiometric fluorescent nanosensor based on quantum dots.

A dual-emission ratiometric fluorescence sensor (CDs@CdTe@MIP) with a self-calibration function was successfully constructed for AMO detection. In the CDs@CdTe@MIP system, non-imprinted polymer-coated CDs and molecule-imprinted polymer-coated CdTe quantum dots were used as the reference signal and response elements, respectively. The added AMO quenched the fluorescence of the CdTe quantum dots, whereas the fluorescence intensity of the CDs remained almost unchanged. The AMO concentration was monitored using the fluorescence intensity ratio (log(I647/I465)0/(I647/I465)) to reduce interference from the testing environment. The sensor with a low detection limit of 0.15μg/L enableddetection ofthe AMO concentration within 6min. The ratiometric fluorescence sensor was used to detect AMO in spiked pork samples; it exhibited a high recovery efficiency and relative standard deviation (RSD) of 97.94-103.70% and 3.77-4.37%, respectively. The proposed highly sensitive and selective platform opens avenues for sensitive, reliable, and rapid determination of pharmaceuticals in the environment and food safety monitoring using ratiometric sensors.

Simple distance-based thread analytical device integrated with ion imprinted polymer for Zn2+ quantification in human urine samples.

This article presents the development of a distance-based thread analytical device (dTAD) integrated with an ion-imprinted polymer (IIP) for quantitative monitoring of zinc ions (Zn2+) in human urine samples. The IIP was easily chemically modified onto the thread channel using dithizone (DTZ) as a ligand to bind to Zn2+ with methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as well as 2,2-azobisisobutyronitrile (AIBN) as cross-linking agents to enhance the selectivity for Zn2+ detection. The imprinted polymer was characterized using Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy and Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS). Under optimization, the linear detection range was from 1.0 to 20.0 mg L-1 (R2 = 0.9992) with a limit of detection (LOD) of 1.0 mg L-1. Other potentially interfering metal ions and molecules did not interfere with this approach, leading to high selectivity. Furthermore, our technique exhibits a remarkable recovery ranging from 100.48% to 103.16%, with the highest relative standard deviation (% RSD) of 5.44% for monitoring Zn2+ in human control urine samples, indicating high accuracy and precision. Similarly, there is no significant statistical difference between the results obtained using our method and standards on zinc supplement sample labels. The proposed method offers several advantages in detecting trace Zn2+ for point-of-care (POC) medical diagnostics and environmental sample analysis, such as ease of use, instrument-free readout, and cost efficiency. Overall, our developed dTAD-based IIP method holds potential for simple, affordable, and rapid detection of Zn2+ levels and can be applied to other metal ions' analysis.

Development and Validation of the HPLC Method for Simultaneous Quantification of Glucose and Xylose in Sugar Cane Bagasse Extract.

A validated rapid high-performance liquid chromatography (HPLC)-refractive index (RI) method was developed for the identification and quantification of glucose and xylose in hydrolyzed bagasse extract. The separation of compounds was achieved on Eurokat® H column (300 × 8mm, 10μm) at 75°C, using 0.01N sulfuric acid solution as mobile phase and 0.6mL/min as flow rate. The method was validated based on accuracy, precision, linearity, robustness, uncertainty, limit of detection (LOD) and limit of quantification (LOQ). Total chromatographic analysis time per sample was ~11min. Calibration plots were linear over the concentration ranges 11-100μg/100μL for glucose and xylose. The LOD was 0.8ppm and LOQ was 2.5ppm. The high recovery and low relative standard deviation confirm the suitability of the method for determination of glucose and xylose in bagasse extract. The proposed HPLC-RI method was accurate, fast and robust and required less run time due to less analytes retention times and allowed optimal energy consumption owing to lower column oven temperature.

Distance-based paper analytical devices integrated with molecular imprinted polymers for Escherichia coli quantification.

Thedevelopment of distance-based paper analytical devices (dPADs) integrated with molecularly imprinted polymers (MIPs) to monitor Escherichia coli (E. coli) levels in food samplesis presented. The fluidic workflow on the device is controlled using a designed hydrophilic bridge valve. Dopamine serves as a monomer for the formation of the E. coli-selective MIP layer on the dPADs. The detection principle relies on the inhibition of the E. coli toward copper (II) (Cu2+)-triggered oxidation of o-phenylenediamine (OPD) on the paper substrate. Quantitative detection is simply determined through visual observation of the residual yellow color of the OPD in the detection zone, which is proportional to E. coli concentration. The sensing exhibits a linear range from 25.0 to 1200.0CFUmL-1 (R2 = 0.9992) and a detection limit (LOD) of 25.0CFUmL-1 for E. coli detection. Additionally, the technique is highly selective with no interference even from the molecules that have shown to react with OPD to form oxidized OPD. The developed device demonstrates accuracy and precision for E. coli quantification in food samples with recovery percentages between 98.3 and 104.7% and the highest relative standard deviation (RSD) of 4.55%. T-test validation shows no significant difference in E. coli concentration measured between our method and a commercial assay. The proposed dPAD sensor has the potential for selective and affordable E. coli determination in food samples without requiring sample preparation. Furthermore, this strategy can be extended to monitor other molecules for which MIP can be developed and integrated into paper-microfluidic platform.

Green synthesis of azo-linked porous organic polymer for enrichment of nitroimidazoles from water, shrimp and Basa fish

Reliable monitoring of nitroimidazoles (NDZs) is of great significance to public health. Herein, an azo-linked porous organic polymer (Res-POPs) was prepared by green synthesis method using natural resveratrol as monomer for the first time. Using Res-POPs as sorbent, a facile method coupling solid-phase extraction with high performance liquid chromatography-diode array detection was developed for effective detecting NDZs. The method achieved good linearities (0.06 ∼ 100 ng mL−1 for water, 1.8 ∼ 200 ng g−1 for shrimp, and 1.5 ∼ 200 ng g−1 for Basa fish) with determination coefficients above 0.995, low detection limits (0.02 ∼ 0.05 ng mL−1, 0.60 ∼ 1.00 ng g−1 and 0.50 ∼ 0.90 ng g−1 for water, shrimp and Basa fish), high method recovery (85 %∼114 %) and relative standard deviations below 8.2 %. The results demonstrated the superiority and the promising potential of the established method for detection of NDZs compared with the reported method.

Glyphosate detection via a nanomaterial-enhanced electrochemical molecularly imprinted polymer sensor

Glyphosate (GLY) is a widely used herbicide with an important role in agriculture. It effectively controls weeds, enhancing agricultural yield and product quality. However, its use raises significant concerns such as potential risks to non-target ecosystems and human health. In response to these concerns, we develop an electrochemical sensor with a molecularly imprinted polymer (MIP) and gold nanoparticles for GLY detection. The sensor includes a screen-printed carbon electrode (SPCE) functionalized with gold nanoparticles and a self-assembled polyvinyl carboxylic acid chloride (PVC-COOH) layer. GLY compounds interact with carboxylic groups and are encapsulated by a polymer of methacrylic acid (MAA) cross-linked with ethylene glycol dimethacrylate (EGDMA). Electrochemical performance was assessed using differential pulse voltammetry (DPV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Morphological characterization was performed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM). The sensor exhibits impressive selectivity, detecting GLY within a range of 273–1200 pg/mL with minimal interference from other pesticides. It boasts a low detection limit of 0.8 pg/mL (signal-to-noise ratio S/N = 3) by DPV and 0.001 pg/mL by EIS. The sensor’s versatility extends to various sample types, including surface water, agricultural wastewater, soil, and cucumber, demonstrating high recovery rates (> 96.05%) and low relative standard deviation (RSD) (< 5.7%). The developed MIP sensor is proven to be a valuable tool for rapid and highly sensitive detection of GLY in diverse environmental and agri-food samples.

Distance-based paper analytical device for multiplexed quantification of cytokine biomarkers using carbon dots integrated with molecularly imprinted polymer.

This article introduces distance-based paper analytical devices (dPADs) integrated with molecularly imprinted polymers (MIPs) and carbon dots (CDs) for simultaneous quantification of cytokine biomarkers, namely C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) in human biological samples for diagnosis of cytokine syndrome. Using fluorescent CDs and MIP technology, the dPAD exhibits high selectivity and sensitivity. Detection is based on fluorescence quenching of CDs achieved through the interaction of the target analytes with the MIP layer on the paper substrate. Quantitative analysis is easily accomplished by measuring the distance length of quenched fluorescence with a traditional ruler and naked eye readout enabling rapid diagnosis of cytokine syndrome and the underlying infection. Our sensor demonstrated linear ranges of 2.50-24.0 pg mL-1 (R2 = 0.9974), 0.25-3.20 pg mL-1 (R2 = 0.9985), and 1.50-16.0 pg mL-1 (R2 = 0.9966) with detection limits (LODs) of 2.50, 0.25, and 1.50 pg mL-1 for CRP, TNF-α, and IL-6, respectively. This sensor also demonstrated remarkable selectivity compared to a sensor employing a non-imprinted polymer (NIP), and precision with the highest relative standard deviation (RSD) of 5.14%. The sensor is more accessible compared to prior methods relying on expensive reagents and instruments and complex fabrication methods. Furthermore, the assay provided notable accuracy for monitoring these biomarkers in various human samples with recovery percentages ranging between 99.22% and 103.58%. By integrating microfluidic systems, nanosensing, and MIPs technology, our developed dPADs hold significant potential as a cost-effective and user-friendly analytical method for point-of-care diagnostics (POC) of cytokine-related disorders. This concept can be further extended to developing diagnostic devices for other biomarkers.

A new strategy for the determination of dinobuton fungicide by square wave stripping voltammetry on the multi-walled carbon nanotube electrode

Dinobuton is a fungicide with a dinitrophenol group pesticide, and its electrochemical behavior was investigated by cyclic voltammetry (CV) and square wave stripping voltammetry (SWSV) on a multi-walled carbon nanotube paste electrode (MWCNTPE). First of all, optimum parameters such as pH, step potential, frequency, puls amplitude, deposition time and, deposition potential were specified by using SWSV on the MWCNTPE. In the negative potential scans, two cathodic peaks appeared at nearly −480 mV and –760 mV due to the nitro groups on the molecule and the second sharp one appeared at −760 mV (versus Ag/AgCl) was used for analytical purposes. The linear working range was found to be within 3.74–25.8 μM on the MWCNTPE by SWSV in pH 7.0 Britton Robinson (BR) buffer solution. The limit of detection (LOD) and limit of quantification (LOQ) values were found to be 0.73 μM and 2.43 μM, respectively. The interference study was conducted in the presence of some pesticides such as triasulfuron, azinphos-methyl, bromoxynil-octanoate, dialifos, fipronil, vinclozolin, iprodione, procymidone, and some selected metal ions withal. Furthermore, the proposed method was also applied to apple juice, tap water, and grape juice, and percent recoveries (%) were detected as 105.9 ± 4.3; 98.3 ± 0.9; 103.7 ± 2.5% with relative standard deviations of 4.0, 1.0, and 2.4%, respectively. On the other hand, percent relative errors were calculated as 5.90, 1.65, and 3.74%, respectively. High recoveries and low relative standard deviations indicate that the applicability of the proposed method in both matrix and real samples is satisfying.

A highly sensitive micelle-enhanced synchronous spectrofluorimetric determination of the recently approved co-formulated drugs, bilastine and montelukast in pharmaceuticals and human plasma at nanogram levels.

In this study, the simultaneous determination of bilastine and montelukast, two recently approved co-formulated antihistaminic medications, was accomplished using a quick, sensitive, environmentally friendly, and reasonably priced synchronous fluorescence spectroscopic approach for the first time. Enhancement of the method's sensitivity down to nanogram levels was achieved by the addition of sodium dodecyl sulfate (1.0% w/v) as a micellar system. According to the results, bilastine and montelukast's fluorescence was measured at 255.3 and 355.3nm, respectively, using Δλ of 40.0nm and distilled water as a green diluting solvent. With respect to the concentration ranges of bilastine (5.0-300.0ng/ml) and montelukast (50.0-1000.0ng/ml), the method showed excellent linearity (r ≥ 0.9998). The results showed that the suggested method is highly sensitive, with detection limits of 1.42 and 13.74 ng/ml for bilastine and montelukast, respectively. Within-run precisions (intra- and interday) per cent relative standard deviations (RSD) for both analytes were <0.59%. With high percentage recoveries and low percentage RSD values, the designed approach was successfully applied for the simultaneous estimation of the cited medications in their dosage form and human plasma samples. To evaluate the green profile of the suggested method, an analytical GREENNESS metric approach (AGREE) and green analytical procedure index (GAPI) metric tools were used. These two methods for evaluating greenness confirmed that the developed method met the highest number of green requirements, recommending its use as a green substitute for the routine analysis of the studied drugs. The proposed approach was validated according to ICHQ2 (R1) guidelines.

Green Alternatives in Pharmaceutical and Bioanalytical Analysis of TDM Required Drugs: Procainamide.

In drug analysis, using non-hazardous solvents instead of the ones harmful to humans and the environment is a green strategy to protect analysts and environmental health. Procainamide (PCA) is an antiarrhythmic drug requiring therapeutic drug monitoring (TDM) because of its narrow therapeutic window and serious side effects. The aim of this study is to develop validated green HPLC methods to be used in drug quality control and TDM analysis for PCA, thus indicating the further applicability in the analysis of TDM-required drugs, such as immunosuppressants, anti-cancer drugs, and psychiatric drugs. Human-friendly ethanol was selected as an organic solvent in the mobile phase. PCA was eluted from NUCLEODUR 100-5 C8 ec (5 μm, 150 x 4.6 mm) column by a mobile phase containing ethanol and 50 mM NaH2PO4 buffer (5:95, v/v). The mobile phase flow rate was 1.0 ml min-1, the column temperature was 35 °C, and the wavelength at the PDA detector was 278 nm. Retention time for PCA was 5.0 min and 7.7 min for paracetamol as an internal standard (IS). In the green HPLC method for pharmaceutical analysis, the highest relative standard deviation (RSD) and mean recovery values were 1.32% and 98.89%, respectively. In the analysis of plasma, the sample preparation step was only smooth protein precipitation by ethanol. Thus, the bioanalytical method was fully green having a limit of detection (LOD) of 0.3 μg ml-1 and a limit of quantification (LOQ) of 0.8 μg ml-1. The therapeutic plasma concentration for PCA was reported in the range of 4-12 μg ml-1. As a result, the green HPLC methods developed and validated in this study were selective, accurate, precise, reproducible, and trustable and have the quality for the application in pharmaceutical and TDM analysis of PCA, thus encouraging green HPLC analysis of other TDM required drugs.

Laser–induced breakdown spectroscopy combined with surface coating to enhance emission line intensity of metallic elements in metal sheet

Emission intensity plays an important role in laser–induced breakdown spectroscopy. A new sample preparation method is proposed to enhance the emission intensity for determining metallic elements. A layer of epoxy resin film is cured on the surface of a metal sheet sample, and a laser beam is used to ablate the film and form a circular hole through it. Results show that by using the proposed method, the emission intensity for Al, Cr, Cu, Fe and W increases by 66.7%–699.6%, and the relative standard deviation (RSD) decreases from 6.5%–25.5% to 0.2%–12.9%. This suggests that emission lines with high intensity and low RSD can be obtained using the proposed method. This convenient and low–cost method has the potential for improving the quantification and imaging performance of bulk samples.

A portable smartphone-assisted Tb-MOF-based agar-slice probe for the rapid and on-site fluorescence assay of malachite green in aquatic products

In this study, a new Tb-MOF fluorescence probe was developed for the detection of malachite green (MG) in real aquatic products. Fluorescence sensing experiments revealed that MG can effectively quench the green fluorescence of Tb-MOF suspensions, and the detection process exhibits the advantages of high sensitivity, a wide linear range (0–80 μM), a low detection limit (10.8 nM) and a rapid response time. Selective detection of MG is achieved primarily through fluorescence resonance energy transfer (FRET) and photoinduced electron transfer (PET) mechanisms. Furthermore, a smartphone-assisted Tb-MOF-based agar slice detection platform was constructed for the visual and quantitative detection of MG. Additionally, the on-site detection of MG in crucian and shrimp samples was accomplished with high recoveries (99.8 %-107.99 %) and low relative standard deviations (RSD < 2.2 %). This developed detection platform introduced a low-cost, portable and user-friendly approach for MG detection.

Near blowout instabilities and identification based on multivariate analysis with high-speed multi-species optical diagnostic techniques

Early prediction and depth analysis of lean blowouts are desirable for both aeroengine and stationary gas turbines. This study used a combination of high-speed multi-species optical diagnostic techniques and multivariate analysis methods to investigate near-blowout instabilities and identify combustion conditions. The flame root dynamic behavior and heat release pulsation characteristics were investigated using advanced modal decomposition methods. Results showed that a near-blowout flame exhibited a characteristic frequency (∼200 Hz) or “fingerprint” related to the temporal and spatial coupling characteristics of CH and OH radicals. Furthermore, flame image feature screening and multivariate fusion for combustion condition identification are reported for the first time. Significant differential features and effective fusion models were investigated and discussed. The identification accuracy of the multivariate fusion feature model compared with that of the geometric feature model improved by more than 24 %. Moreover, simplified fusion models of low-order moment and geometric features were constructed with relatively high identification accuracy (99 %) and low relative standard deviation value (14.1 %). These results demonstrate the significant potential of combining multi-species optical diagnostic techniques and multivariate analysis methods, thereby expanding their application to the field of combustion science.

Two-in-one sensing platform for the detection of exosomes based on molybdenum disulfide-based nanozymes

Compared with single-mode detection strategies, multi-mode sensing strategies have attracted more and more scientists’ attention due to their higher detection accuracy and credibility. Herein, a two-in-one sensing platform was designed for human breast cancer cell line (MCF-7)-derived exosomes detection by coupling the high catalytic activity of gold-platinum core-shell nanoparticles-decorated molybdenum disulfide nanozymes (MoS2-Au@Pt) with the specific recognition ability of aptamers (Apt). Probe DNA1 (P1) was assembled on the surface of MoS2-Au@Pt nanozymes to form MoS2-based signal amplified nanoprobes (MNP), which can efficiently catalyze 3, 3′, 5, 5′-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2) reaction strategy to produce distinct electrochemical and colorimetric responses. The added target exosomes triggered the dissociation of the “probe DNA2-Apt-MNP” sandwiched structure and the release of MNP from the electrode surface due to the preferential reaction of anti-CD63 aptamer and exosomes, leading to both electrochemical signal and solution color were reduced. According to this interesting sensing principle, the developed electrochemical/colorimetric dual-mode aptasensor showed excellent sensitivity and specificity for exosomes analysis with low detection limits of 9.3 particles mL−1 (electrochemical) and 4.2 × 103 particles mL−1 (colorimetric), respectively. Furthermore, this dual-mode aptasensor can determine exosomes in human serum with high recoveries (>93 %) and low relative standard deviation (RSD, <8 %), suggesting that the developed dual-mode detection strategy is a promising sensing method for accurate, sensitive and selective analysis of biomarkers in clinical samples.

Method validation and monitoring of emamectin benzoate in mature banana fruit with peel and pulp through Liquid chromatography-Mass spectrometry/ Mass spectrometry (LC-MS/MS)

Emamectin benzoate has been frequently used in the banana ecosystem to combat the damage of pseudostem weevil. Therefore, the present study was conducted to validate the method, to assess harvest time residues and monitor emamectin benzoate residues in mature banana peel and pulp samples through LC-MS/MS. The validated method was used to determine emamectin benzoate residue in market banana samples. The study used Waters Alliance LC and Acquity TQD with an electrospray ionization interface in the positive ion mode. An isocratic flow of 0.1% formic acid (HCOOH) in water and 0.1% HCOOH in acetonitrile (CH3CN) was utilised for separation. CH3CN was utilised to extract emamectin benzoate residue from the samples, and a dispersive solid-phase extraction technique was used for subsequent cleanup. Linearity tests were performed with standard solutions containing 0.01 to 0.1 g mL-1, with three replicates for each concentration. For mature banana peel &amp; pulp and mature banana pulp matrices, satisfactory recoveries of 79.85 to 95.09% and 89.20 to 100.94%, respectively and high precision relative standard deviations of 0.56 to 2.34% and 2.33 to 6.88%, respectively were obtained. For mature banana (peel and pulp, pulp alone) fruits, the lower detection and quantification limits were (0.003, 0.008), and (0.002, 0.007). The validated approach was utilised to analyse mature banana fruit samples obtained from emamectin benzoate treated fields and banana samples purchased from the local market. Results showed satisfactory validation of parameters like linearity, the limit of detection and quantification, and recovery for determining emamectin benzoate residues in banana fruit.

Camellia oleifera derived carbon dots modified TiO2 as sensor for the rapid detection of 4-nitrophenol in wastewater

This paper presents an innovative electrochemical sensor utilizing carbon dots modified with titanium dioxide (TiO2-CDs) for the rapid and accurate detection of 4-nitrophenol (4-NP) in wastewater. This sensor offers a cost-effective and efficient approach to on-site monitoring of 4-NP, a highly toxic and persistent environmental pollutant. The modification of the electrode material with TiO2-CDs significantly enhances the sensor's performance by improving sensitivity, selectivity, and stability. The synthesis of TiO2-CDs involves the integration of carbon dots derived from biomass with TiO2, resulting in a composite material with an enlarged surface area and enhanced photocatalytic properties. The unique hollow spherical structure of the TiO2-CDs further amplifies their photon absorption capacity. Electrochemical characterization validates the successful modification of the electrode surface and demonstrates the electrocatalytic activity of the TiO2-CDs modified electrode towards 4-NP. The sensor exhibits a linear correlation between the peak oxidation current and the concentration of 4-NP, enabling precise and reliable quantification. Notably, the sensor's detection range spans from 10 μM to 350 μM, with an impressively low detection limit of 0.12 μM. Real sample analysis of wastewater underscores the sensor's practical utility, revealing high recovery rates and minimal relative standard deviations. The development of this electrochemical sensor, based on TiO2-CDs, presents a promising solution for the swift and accurate detection of 4-NP in wastewater, offering potential advancements in pollution control, environmental monitoring, and wastewater treatment strategies.