Superior Detection Limit Research Articles

Quantitative Analysis of Drugs in a Mimetic Tissue Model Using Nano-DESI on a Triple Quadrupole Mass Spectrometer.

Mass spectrometry is a powerful analytical technique used at every stage of the pharmaceutical research process. A specialized branch of this method, mass spectrometry imaging (MSI), has emerged as an important tool for determining the spatial distribution of drugs in biological samples. Despite the importance of MSI, its quantitative capabilities are still limited due to the complexity of biological samples and the lack of separation prior to analysis. This makes the simultaneous quantification and visualization of analytes challenging. Several techniques have been developed to address this challenge and enable quantitative MSI. One such approach is the mimetic tissue model, which involves the incorporation of an analyte of interest into tissue homogenates at several concentrations. A calibration curve that accounts for signal suppression by the complex biological matrix is then created by measuring the signal of the analyte in the series of tissue homogenates. Herein, we use the mimetic tissue model on a triple quadrupole mass spectrometer (QqQ) in multiple reaction monitoring mode to demonstrate the quantitative abilities of nanospray desorption electrospray ionization (nano-DESI) and compare these results with those obtained using atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI). For the tested compounds, our findings indicate that nano-DESI achieves lower standard deviations than AP-MALDI, resulting in superior limits of detection for the studied analytes. Additionally, we discuss the limitations of the mimetic tissue model in the quantification of certain analytes and the challenges involved with the implementation of the model.

OptoAssay-Light-controlled dynamic bioassay using optogenetic switches.

Circumventing the limitations of current bioassays, we introduce a light-controlled assay, OptoAssay, toward wash- and pump-free point-of-care diagnostics. Extending the capabilities of standard bioassays with light-dependent and reversible interaction of optogenetic switches, OptoAssays enable a bidirectional movement of assay components, only by changing the wavelength of light. Demonstrating exceptional versatility, the OptoAssay showcases its efficacy on various substrates, delivering a dynamic bioassay format. The applicability of the OptoAssay is successfully demonstrated by the calibration of a competitive model assay, resulting in a superior limit of detection of 8 pg ml-1, which is beyond those of conventional ELISA tests. In the future, combined with smartphones, OptoAssays could obviate the need for external flow control systems such as pumps or valves and signal readout devices, enabling on-site analysis in resource-limited settings.

In Situ growth of high-crystallinity MOF@CTF core-shell hybrid heterostructures and their application in photoelectrochemical sensing of vancomycin

Vancomycin is a first-line drug for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant bacterial infections. It is of great significance to develop rapid detection methods for vancomycin in different matrices. In this work, a novel method for the in-situ preparation of MOF@CTF core-shell hybrid heterogeneous structures was proposed and applied to the photoelectrochemical detection of vancomycin. The insolubility of the imine precursor structure in homogeneous solvents and the Lewis acidic centers in the MOF structure induced the initial arrangement of CTF on the surface of PCN-224. By encapsulating a layer of highly crystalline CTF structure onto the initial morphology of PCN-224, a MOF@CTF heterogeneous structure was formed. Importantly, the introduction of anthracene-based electron-donating groups into the CTF structure and the formation of a donor-acceptor system with triazine rings enhanced the photoconversion efficiency of the heterogeneous structure by establishing a continuous separated built-in electric field within the core-shell structure. The successful in-situ synthesis of the core-shell hybrid heterogeneous structure was confirmed through microscopic morphology, PXRD, XPS, and FT-IR. Furthermore, investigations into the semiconductor properties of the heterogeneous structure, including semiconductor type, bandgap, and photo-voltage, were conducted. Results showed that the heterogeneous structure exhibited a doubled photocurrent density compared to the original PCN-224. Additionally, a molecularly imprinted photoelectrochemical sensor (MIPECS) for vancomycin was constructed. Under optimized conditions, the sensor demonstrated a superior concentration response range (0.1 nM - 1 μM) and detection limit (0.031 nM, 3σ/S, n = 11). Simultaneously, the potential applicability of the sensor in animal-derived foods, serum, and environmental water samples was evaluated, yielding satisfactory results.

High sensitivity ctDNA assays in genitourinary malignancies: current evidence and future directions.

In the recent decade, analysis of circulating tumor DNA (ctDNA) has improved cancer care by allowing for rapid detection of actionable molecular targets. A new generation of circulating DNA tests is now becoming available commercially. These tests are characterized by a superior limit of detection of 0.01% vaF or better, allowing for the detection of radiologically occult molecular residual disease (MRD). MRD tests have the potential to revolutionize neoadjuvant and adjuvant treatment. In addition, these tests can be used as tumor markers to assess disease response. We reviewed the current evidence for the use of high-sensitivity MRD assays with particular focus on the genitourinary tumors. Multiple studies have now been reported in urothelial, renal, and recently testicular carcinoma. We find that the sensitivity varies across tumor types in the adjuvant setting and may reach a high of 100% in urothelial cancer. Specificity in tumor-informed MRD appears to be preserved across tumor types (98%-100%). Several trials are now prospectively validating MRD testing in biomarker integral studies, mainly in urothelial carcinoma.

Loop-mediated isothermal amplification assay detects multiple alleles of blaOXA-51-like genes in Acinetobacter baumannii and other Gram-negative bacteria despite primer-template mismatches

The known intrinsic and polymorphic blaOXA-51-like genes of Acinetobacter baumannii were recently reported in other non-A. baumannii Gram-negative pathogens. Accurate detection of this potentially transferrable carbapenemase gene in the clinical setting is critical. This study developed a loop-mediated isothermal amplification (LAMP) assay targetting multiple alleles of blaOXA-51-like genes. Specifically, an alignment-based primer design, in silico primer screening, and in vitro assay confirmation were conducted. Both in silico and in vitro results revealed the tolerance of the LAMP assay to up to five primer-template mismatches outside the 3′-end primer regions. Within 90 min, the LAMP assay also detected the gene targets in other Gram-negative bacteria with known and novel blaOXA-51-like genes. Finally, it showed a superior limit of detection (as low as 101 CFU/mL) compared with polymerase chain reaction, and high specificity against non-targets. This study developed a highly adaptable LAMP assay to monitor blaOXA-51-like genes in the clinical setting and provided important insights into LAMP primer design and screening.

Manganese tetraphenylporphyrin and carbon nanocoil interface-based electrochemical sensing of tyrosine.

Tyrosine is one of the essential metabolites present in the human body for nutritional maintenance and normal physiological functioning. Its concentration in the body is crucial in predicting various hereditary, emotional, and physiological disorders. Therefore, quantitative monitoring of tyrosine in clinical samples is indispensable. We state the use of carbon nanocoils/manganese tetraphenylporphyrin convened glassy carbon electrode (CNC/MnTPP/GC) for the streamlined electrochemical sensing of tyrosine. Cutting-edge analytical techniques were employed to perform a comprehensive physicochemical analysis of the synthesized materials. To investigate the electrochemical properties, various techniques such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy, and chronocoulometry were employed. CNC/MnTPP/GC displayed an optimal response at pH 5 and exhibited remarkable linearity within the concentration range of 0.05 to 100 μM for tyrosine. Using DPV, it demonstrated a low limit of detection (21 nM ± 1.17) and a sensitivity of 0.12 μA μM-1 cm-2. CNC/MnTPP/GC displayed excellent performance in terms of repeatability, reproducibility, and stability for up to 30 days, making it suitable for real-time analysis, particularly in the analysis of tyrosine in blood serum. Notably, CNC/MnTPP/GC showcased a superior detection limit compared to previously reported methods.

Iodide based electrochemical gold quantification method for lateral flow assays

The lateral flow assay (LFA) is an ideal technology for at-home medical diagnostic tests due to its ease of use, cost-effectiveness, and rapid results. Despite these advantages, only few LFAs, such as the pregnancy and COVID-19 tests, have been translated from the laboratory to the homes of patients. To date, the medical applicability of LFAs is limited by the fact that they only provide yes/no answers unless combined with optical readers that are too expensive for at-home applications. Furthermore, LFAs are unable to compete with the state-of-the-art technologies in centralized laboratories in terms of detection limits. To address those shortcomings, we have developed an electrochemical readout procedure to enable quantitative and sensitive LFAs. This technique is based on a voltage-triggered in-situ dissolution of gold nanoparticles, the conventional label used to visualize target-specific signals on the test line in LFAs. Following the dissolution, the amount of gold is measured by electroplating onto an electrode and subsequent electrochemical quantification of the deposited gold. The measured current has a low noise, which achieves superior detection limits compared to optical techniques where background light scattering is limiting the readout performance. In addition, the hardware for the readout was developed to demonstrate translatability towards low-cost electronics.

Synthesis and fluorescence properties of a two-dimensional Cd-complex for the ratiometric fluorescence detection of Zn2+ ions

The two-dimensional complex [Cd3(L)(2,2'-bpy)2]n (1) was synthesized solvothermally from 4,5-di(3,5-dicarboxylphenoxy)phthalic acid (H6L) and 2,2'-bipyridine (2,2'-bpy) and fully characterized by elemental analysis, infrared spectroscopy, single crystal and powder X-ray diffraction. Complex 1 displays high stability in water and resistance towards acidic and basic media. Fluorescence studies revealed that it may be acted as a ratiometric fluorescence probe to detect Zn2+ ions in water with a superior detection limit of 3.48 nM. The fluorescence recognition mechanism stems from weak interactions between Zn2+ ions and complex 1. Its pronounced stability and recyclability suggest that the new material may be used for high-precision detection of Zn2+ ions in real-life aqueous samples, even under acidic and basic conditions.

Timescale correlation of shallow trap states increases electrochemiluminescence efficiency in carbon nitrides

Highly efficient interconversion of different types of energy plays a crucial role in both science and technology. Among them, electrochemiluminescence, an emission of light excited by electrochemical reactions, has drawn attention as a powerful tool for bioassays. Nonetheless, the large differences in timescale among diverse charge-transfer pathways from picoseconds to seconds significantly limit the electrochemiluminescence efficiency and hamper their broad applications. Here, we report a timescale coordination strategy to improve the electrochemiluminescence efficiency of carbon nitrides by engineering shallow electron trap states via Au-N bond functionalization. Quantitative electrochemiluminescence kinetics measurements and theoretic calculations jointly disclose that Au-N bonds endow shallow electron trap states, which coordinate the timescale of the fast electron transfer in the bulk emitter and the slow redox reaction of co-reagent at diffusion layers. The shallow electron trap states ultimately accelerate the rate and kinetics of emissive electron-hole recombination, setting a new cathodic electrochemiluminescence efficiency record of carbon nitrides, and empowering a visual electrochemiluminescence sensor for nitrite ion, a typical environmental contaminant, with superior detection range and limit.

Colorimetric detection of circulating tumor cells in breast cancer based on ladder-branch hybridization chain reaction and DFs/AuNCs nanozyme

Breast cancer is the most common malignant tumor in women, which accounts for 6.9% of all cancer-related deaths. Early diagnosis is crucial for making the best clinical decision and improving the prognosis of patients. Circulating tumor cells (CTCs) have been regarded as significant tumor biomarkers. Herein, we designed a colorimetric biosensor for breast cancer CTCs quantification based on ladder-branch hybridization chain reaction (HCR) and DNA flowers/gold nanoclusters (DFs/AuNCs) nanozyme. With the assistance of complementary DNA labeled on magnetic beads (MBs), the cleavage products of RNA-cleaving DNAzymes (RCDs) could be rapidly captured, subsequently triggering ladder-branch HCR. In addition, the DFs/AuNCs nanozyme was applied for colorimetric analysis, which further improved the sensitivity for the detection of target CTCs. Benefiting from specific RCDs, ladder-branch HCR and DFs/AuNCs, we achieved a superior detection limit of 3 cells/mL as well as a broad linear range of 10 cells/mL to 104 cells/mL. Conclusively, this colorimetric biosensor achieved sensitively and selectively detection of breast cancer CTCs without the participation of enzymes at room temperature, which might provide new insight into the early detection of breast cancer.

Atomically dispersed Ag implanted zeolitic imidazolate Frameworks-8 for Visible-Light enhanced plasmonic opto-chemical sensor

A reliable and highly sensitive gas sensor is regarded as an indispensable approach for monitoring and ensuring human health and safety. Herein, a wet-chemical synthesis strategy is developed to fabricate a Agx/ZIF-8 heterostructure, in which Ag is encapsulated in porous zeolitic imidazolate frameworks-8 (ZIF-8). The size of Ag is highly tunable and precisely controllable in the range of single atom to 50 nm. Agx/ZIF-8 samples are found to be particularly useful in gas sensors for triethylamine (TEA) detection, and their sensing performance can be further enhanced via downsizing the Ag nanoparticle (NPs) into the atomical level, thus realizing the maximum utilization of Ag element as well as achieving the most outstanding sensing performance. As a result, the optimal sample Ag(SAs-1mL)/ZIF-8 with the atomic Ag, shows relatively lower operating temperature (290 °C), high response (142), superior detection limits (0.41 ppm), and ultra-fast response/recovery time (4/15 s), which are significantly better than the sample Ag(0.5nm-0.25mL)/ZIF-8 with Ag nanoclusters (ca. 0.5–1 nm in size) and other Agx/ZIF-8 samples with larger Ag nanoparticles (range from ca. 2 nm to 50 nm in diameter). Moreover, benefiting from the localized surface plasmon resonance (LSPR) effect, the response of Ag(SAs-1mL)/ZIF-8 sensor is greatly increased by as much as 440 % when it illuminated with the 405 nm LED, where the light wavelength resonates with the plasmon frequency of Ag. This work highlights the crucial role of size effect of noble metal, proves the LSPR effect of atomic level Ag, and offering an attractive strategy to improve sensitivity and stability of gas sensors based on single atoms.

Chemiluminescence and electrochemiluminescence of water-soluble iridium(III) complexes containing a tetraethylene-glycol functionalised triazolylpyridine ligand

BackgroundIridium(III) complexes, exhibiting high luminescence quantum yields and a wide range of emission colours, are promising alternatives to tris(2,2ʹ-bipyridine)ruthenium(II) for chemiluminescence (CL) and electrochemiluminescence (ECL) detection. This emerging class of reagent, however, is limited by the poor solubility of many iridium(III) complexes in aqueous solution, and lack of understanding of their remarkably variable selectivities towards different analytes. ResultsSeven [Ir(C^N)2(pt-TEG)]+ complexes, exhibiting a wide range of reduction potentials and emission energies, were examined with six model analytes. For CL, cerium(IV) was used as the oxidant. The alkylamine analytes generally produced greater CL and ECL with the more readily oxidised Ir(III) complexes (C^N = piq, bt, ppy), predominantly through the ‘direct’ pathway requiring oxidation of both metal complex and analyte. Aniline derivatives that did not also contain secondary or tertiary alkylamines elicited CL from the less readily oxidised complexes (C^N = df-ppy-CF3, df-ppy) via energy transfer. The most difficult to oxidise complexes (C^N = df(CF3)-ppy-Me, df(CN)-ppy) gave poor responses due to the limited potential window of the solvent and inefficiency of energy transfer to their high energy excited states. Greater CL and/or ECL intensities were generally obtained for each analyte with at least one Ir(III) complex than with [Ru(bpy)3]2+; superior limits of detection for two analytes were demonstrated. SignificanceThis exploration of CL/ECL in which the properties of luminophore, analyte and oxidant are all varied provides a new understanding of the influence of the metal-complex potentials and excited state energy on the light-producing and quenching pathways, and consequently, their distinct selectivity towards different analytes. These findings will guide the development of water-soluble Ir(III) complexes as CL and ECL reagents.

A Performance Comparison Between Organic Electrochemical Transistor and Electrode Configurations for Enzymatic Sensing

AbstractOrganic electrochemical transistors (OECTs) excel at biosensing due to their high amplification factor, which allows for detecting low analyte concentrations and picking up weak physiological signals. One prominent use of OECT is in enzymatic metabolite sensing, with the OECT claimed to have a superior low limit of detection and enhanced sensitivity compared to conventional two or three electrode‐based setups. However, there has yet to be a direct comparative study on the performance metrics of these sensor configurations under unified conditions. Here, the glucose sensing performance of an enzyme‐immobilized electrode is systematically examined in two types of devices that have the same geometrical relations: the first one is a traditional 2‐ or 3‐electrode configuration where the sensing electrode is the working electrode, and in the second one, the enzymatic electrode serves as the gate electrode of an OECT. While benchmarking the performance of OECT technology for enzyme‐based metabolite sensing, this study provides insights into the operation mechanism of OECT‐based enzymatic sensors. These results can help to design more efficient OECT‐based circuits to transduce biological events that involve redox reactions.

Synthesis of Fluorescent Pyrazoline Sensors as Versatile Tool for Zinc ion Detection: A Mini-Review.

Zinc ions are one of the 2nd most abundant mineral after iron and it is important for immune system, enzymatic catalysis, DNA synthesis, and maintaining structural integrity in humans. But, monitoring the Zn levels in human body poses more challenges. This review paper investigates (paper from 2010 to 2023) the synthesis of pyrazoline derivatives by different methods, including conventional methods and green chemistry protocol. These Pyrazoline derivatives highlighted for their potential application as chemo-sensor for Zn2+ ions recognition. Pyrazoline compounds exhibit excellent sensitivity & selectivity and emitting blue-light with high quantum yields and electroluminescence, along with a superior limit of detection. These derivatives are stable bioactive molecule, with well-known diverse biological activities. This review not only gives valuable insights into the essential role of Zinc in human physiology but also provides a practical method for accurate Zinc detection in various samples. Which holds the potential for advancements in health diagnostics and environmental monitoring. Because of their significant biological application and selectivity as sensors, researchers have much more attention to prepare green environmentally-friendly pyrazoline derivatives.

A ratiometric fluorescence nanosensor for glutathione detection based on spatially confined dual-emission of α-lipoic acid-modified gold nanoclusters and silicon nanoparticles.

The development of dual-emission ratiometric fluorescent probes with aggregation-induced emission enhancement (AIEE) overcomes the limitations of gold nanocluster (Au NC)-based probes, particularly their weak intrinsic fluorescence, in real-world applications. These AIEE probes also exhibit superior detection limits and enhanced sensitivity. A novel combination for the reliable fluorometric detection of glutathione (GSH) was proposed, utilizing aggregation-induced emission enhancement (AIEE) facilitated by electrostatic interaction and spatial confinement. The probe consists of a ratiometric combination of negatively charged α-lipoic acid-modified Au NCs (LA@Au NCs) and positively charged silicon nanoparticles (SiNPs). The addition of SiNPs causes aggregation of LA@Au NCs, enhancing the fluorescence of LA@Au NCs through the AIE effect under electrostatic interaction and spatial confinement. The addition of Cu2+ quenched the emission of LA@Au NCs as a result of charge transfer. The fluorescence emissions of LA@Au NCs were restored upon the addition of GSH due to the interaction between GSH and Cu2+. Simultaneously, the emission signal of SiNPs remains unchanged, serving as an internal reference signal during GSH measurement. It was found that the fluorescence ratio (F680/F465) is directly proportional to the concentration of GSH in the range of 0.05-100 μM, with a detection limit of 1.7 nM (S/N = 3). The proposed system was applied to detect GSH in real samples, including dietary supplements, human serum, and saliva samples. This work opens new avenues for constructing novel sensors based on AIEE for detecting biomolecules.

Electrochemical sensor with electrohydrodynamic-printed microelectrodes for the detection of low concentration of tea polyphenols

The accurate quantification of tea polyphenols plays a crucial role in the quality inspection of tea and various food products. With the advantages of high sensitivity and selectivity, electrochemical method has gained widespread utilization in detecting tea polyphenols. The accuracy of electrochemical detection heavily relies on the dimensions of the microelectrodes utilized. In the present work, six microelectrode systems with varying diameters (70, 200, 300, 500, 800, and 1000 µm) were manufactured by electrohydrodynamic printing method and integrated into sensors to detect low concentration of tea polyphenols. The performances of sensors were evaluated in terms of detection limits, sensitivity, and linear range. The results demonstrated that sensors with minor microelectrodes exhibited superior detection limits and sensitivity. The sensor featuring a 70 µm microelectrode demonstrated a linear range of 1–70 μmol/L and a low detection limit of 0.22 μmol/L. Average recovery rates of sensors ranging from 95.2% to 105.0% were obtained in detecting tea polyphenols in green tea, confirming the remarkable potential for rapid and accurate detection of low concentration of tea polyphenols in real samples.

Measurable Residual FLT3-ITD before Allogeneic Transplant for Acute Myeloid Leukemia

Background: In the past year, multiple studies have demonstrated the drastically increased risk of relapse and death in patients with Acute Myeloid Leukemia (AML) who have persistent FLT3 internal tandem duplication (ITD) mutations detectable in clinical remission by next generation sequencing (NGS). Translating this evidence into a change in clinical practice requires both widely available testing and a clear understanding of the clinical implications of FLT3-ITD detection at defined threshold levels. In the largest of the recent studies (Pre-MEASURE, PMID: 36881031), we performed FLT3-ITD MRD detection in blood DNA collected from 608 patients at the time of first remission (CR1) prior to allogeneic hematopoietic cell transplant (alloHCT). To evaluate cross-assay comparability and the impact of residual disease burden levels, we performed analysis on this cohort using a commercially available FLT3-ITD MRD NGS assay. Methods: Of the 608 patients aged 18 or older from the Pre-MEASURE study who received an alloHCT for FLT3-ITD mutated AML during CR1 at a CIBMTR reporting site in the USA between the years of 2013-2019, patients not experiencing non-relapse mortality and with sufficient DNA from pretransplant blood available were included in this analysis. A commercially available testing kit (IVS, Invivoscribe, San Diego, CA), which can detect FLT3-ITD MRD by NGS for up to 21 patients on one Illumina MiSeq flow cell, was used to establish a workflow following clinical testing standards and validated to detect ITDs down to a variant allele fraction (VAF) of at least 0.005%. Results were compared to those previously reported using an anchored multiplex PCR-based (AMP) targeted NGS assay. Overall survival (OS) and cumulative incidence of relapse were estimated with the day of transplant as time 0 using Kaplan-Meier estimation (log-rank tests) and Cox proportional hazards models. Results: A total of 451 patients were included in this study, of which 173 (38%) experienced relapse (median: 5.2 months; range 0.7-52.1) and 133 (29%) died (median: 10.7 months; range 2-53.8) post-alloHCT. The IVS assay identified 232 FLT3-ITD variants with a median VAF of 0.005% (range 0.0002-44%) and length of 51bp (range 5-228). IVS positive patients had a median of 1 FLT3-ITD variant (range 1-15) and median maximum VAF of 0.01% (range 0.0003-44%). Utilizing the same VAF cutoff of 0.01% for MRD positivity for the IVS test as used in the Pre-MEASURE study, patients testing positive prior to alloHCT exhibited higher rates of relapse (79% vs 31%, p<0.0001) and decreased survival (29% vs 77%, p<0.0001) at 3 years compared to testing negative. These results closely align with those previously reported using the AMP assay (Figure A). The IVS test has a superior limit of detection compared with the AMP test, allowing investigation of alternative VAF thresholds. In total, 151 patients (33.5%) were FLT3-ITD MRD positive by IVS of which only 75 (17%) had VAF ≥0.01%. A threshold-free approach for the IVS test improved the ability to identify patients at risk of relapse, predicting 63% of relapses within 6 months of transplant compared to 43% with the 0.01% cutoff, but resulted in decreased specificity as 42% of all positive patients relapsed within 6 months vs. 57% with the 0.01% VAF cutoff. In multivariable analysis, IVS FLT3-ITD MRD status was associated with both relapse and overall survival (Figure B). Additionally, stratifying patients by their level of residual FLT3-ITD disease burden prior to alloHCT revealed a dose-dependent increase in risk for death (Figure B) and relapse. Any detectable level of residual FLT3-ITD over 0.001% VAF exhibited increased risk, with VAFs ≥0.01% being the highest. Conclusions: In this analysis of patients with AML from the Pre-MEASURE study, we show cross-assay evidence that the detection of residual FLT3-ITD variants in pre-transplant blood during CR1 is associated with significantly increased risk of relapse and death after alloHCT. The highly sensitive assay used in this study could identify ~2/3 of patients who relapsed within 6 months and demonstrated that a dose-dependent correlation between residual FLT3-ITD level and adverse clinical outcomes exists, with VAF ≥0.01% representing the highest risk. This evidence provides strong justification for NGS-based AML MRD clinical testing for persistent FLT3-ITD prior to alloHCT to identify patients at high risk of post-transplant relapse and death.

Application of high-performance liquid chromatography in determining saturates and aromatic hydrocarbons along with polars/additives in automotive finished and used lubricating oils

Lubricating oils help an internal combustion engine function effectively by reducing friction and wear on the engine's moving parts. They typically consist of petroleum-derived base oil and various additives to achieve the desired characteristics in automotive engine oils. Determination of aromatics and polar additives in the finished and used lubricating oils is not possible with existing methods hence their development is significant from the perspectives of environment and reuse/re-refining of used lubricating oils. This study reports the development of a new HPLC method to determine additives in the finished lubricating oils and/or polars in the used engine oils. The proposed method is simple, fast (runtime of 13 min), does not require sample pre-treatment, and exhibits high precision and superior limits of detection and quantification. The method demonstrated good linear response ranging from 0.1 to 30 mass for total aromatics and 0.1 to 20 % for additives. The method validation was carried out by analyzing brand-new commercial two and four-wheeler lubricants with used automotive lubricants. Based on the proposed method, the aromatics and additives concentration ranges in the studied finished lubricants were estimated between 0.20–1.70 % (mass) and 0.20–3.50 % (mass), respectively. Similarly, for used lubricants, the aromatics and additives were estimated to be 1.00–6.10 % and 0.60–2.40 % (mass), respectively.

Ultrafast Electrochemical Sensor Based on Electrical Potential-Assisted Hybridization for Non-Amplification Determination of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) by Differential Pulse Voltammetry (DPV)

A highly ultrafast and sensitive electrochemical sensor based on electrical potential-assisted hybridization was developed for the determination of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The electrode was modified with multi-walled carbon nanotubes (MWCNTs) and Au nanoparticles (AuNPs) for excellent electrochemical performance. The constant electric field was applied to rapidly and efficiently enrich the capture probes to the electrode surface in 60 s. Meanwhile, pyrene as the backfill reagent resulted in a significant reduction of nonspecific adsorption. The electrochemical properties of the modified electrode were investigated via electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The analytical response was measured by differential pulse voltammetry (DPV). The sensor achieved the ultrafast hybridization of nucleic acids at the electrode interface within 90 s, substantially reducing the reaction time from hours to minutes. Under optimal conditions, the sensor exhibited a superior detection limit of 60 fM and showed satisfactory specificity toward single-base mismatch. Additionally, the proposed sensor realized sensitive determination of SARS-CoV-2 in throat swabs. The enzyme-free and non-amplification sensing strategy showed promising potential for application in point-of-care testing (POCT).

Electrochemical Studies of Nanoflakes like ZnMnO3 Perovskites for the Determination of Priority Organic Pollutant N-hydroxysuccinimide

Surfactant assisted co-precipitation method active for preparing ZnMnO3 perovskites. The as- synthesized nanoflakes are well characterized by using numerous microscopic and spectroscopic methods which confirmed that ZnMnO3 has high crystalline nature, desired functional groups with nanoflakes like morphology. The synthesized ZnMnO3 were fabricated as the electrode material to determine biologically important as well as priority organic pollutant N- hydroxysuccinimide (NHS). The improved sensing performance of ZnMnO3 towards NHS with outstanding sensitivity, and selectivity in the presence of a 50-fold excess concentration of metal ions and amino acids. The NHS sensor at ZnMnO3/GCE exhibits wide dynamics ranging from 0.01 μM to 530.6 μM with a superior detection limit of 0.04 μM. Furthermore, the proposed sensor has utilized by practical applicability of NHS detection in the spiked urine samples that achieved better recoveries.