Rapid Method For Determination Research Articles

In vitro fitness of SARS-CoV-2 variants as assessed by competition experiments followed by ddRT-PCR and whole genome sequencing.

To develop a new method for reliable and rapid determination of the fitness of SARS-CoV-2 variants of concern. Competition experiments between two SARS-CoV-2 variants were performed in cells of the upper (nasal human airway epithelium) and lower (Calu-3 cells) respiratory tracts followed by quantification of variant ratios by droplet digital reverse transcription (ddRT)-PCR. In competition experiments, the delta variant outcompeted the alpha variant in both cells of the upper and lower respiratory tracts. A 50/50% mixture of delta and omicron variants indicated a predominance of omicron in the upper respiratory tract whereas delta predominated in the lower respiratory tract. There was no evidence of recombination events between variants in competition as assessed by whole gene sequencing. Differential replication kinetics were shown between variants of concern which may explain, at least partly, the emergence and disease severity associated with new SARS-CoV-2 variants.

Detection of Abnormal Wall Shear Stress and Oscillatory Shear Index via Ultrasound Vector Flow Imaging as Possible Indicators for Arteriovenous Fistula Stenosis in Hemodialysis.

The arteriovenous fistula (AVF) is an essential vascular access for hemodialysis patients. AVF stenosis may occur at sites with abnormal wall shear stress (WSS) and oscillatory shear index (OSI), which are caused by the complex flow in the AVF. At present, an effective method for rapid determination of the WSS and OSI of the AVF is lacking. The objective of this study was to apply an ultrasound-based method for determination of the WSS and OSI to explore the risk sites of the AVF. In this study, the ultrasound vector flow imaging technique V Flow was applied to measure the WSS and OSI at four different regions of the AVF to detect and analyze the risk sites: (i) anastomosis region, (ii) curved region, (iii) proximal vein and (iv) distal vein. Twenty-one patients were included in this study. The relative residence time was calculated based on the measured WSS and OSI. The curved region had the lowest WSS; the anastomosis region had a significantly higher OSI (p < 0.05) compared with the venous regions, and the curved region had a significantly higher RRT (p < 0.05) compared with the proximal vein region. V Flow is a feasible tool for studying WSS variations in AVF. The possible risk site in the AVF may be located in the anastomosis and curved regions, where the latter could present a higher risk for AVF stenosis.

New approaches for rapid setpoint determination and uninterrupted tracking in non-invasive continuous blood pressure monitoring based on volume-clamp method

The volume-clamp method (VCM) is a widely used non-invasive continuous blood pressure (BP) monitoring technique, but determining the volume setpoint (V0) in the open-loop phase can be time-consuming and may cause finger tissue displacement. Additionally, frequent interruptions in BP measurement are required during the closed-loop phase to reset V0. We proposed two new approaches: the proportional value method (PVM) for rapid V0 determination in the open-loop phase and the uninterrupted V0 tracking method (UVTM) in the closed-loop phase. PVM adaptively searches for V0 by analyzing the shape index (Prop) of the plethysmographic (PG) signal under constant cuff pressure, while UVTM introduces a new vascular compliance calculation method in closed-loop phase to track changes in V0 without interrupting BP measurement. We describe the non-invasive continuous BP monitor (NC-BPM) based on these methods. Experimental results show that PVM can accurately determine V0, with a mean arterial pressure error of −1.72 ± 2.80 mmHg when compared to oscillometric method (OSCM). UVTM in NC-BPM produced a mean absolute error (MAE) of 2.44 ± 2.91 mmHg for mean arterial pressure (MAP) in induced BP fluctuation test compared to the Nexfin monitor. In the clinical study with invasive reference, the MAE in measuring MAP by NC-BPM was 4.69 ± 5.39 mmHg. Our results show that PVM and UVTM are highly accurate and reliable, with the potential to integrate effectively into VCM-based BP monitoring devices that could benefit patients, healthcare providers, and researchers.

Rapid and accurate determination methods based on data fusion of laser-induced breakdown spectra and near-infrared spectra for main elemental contents in compound fertilizers

Compound fertilizer occupies a dominant position in the structure of fertilizer products in China. The contents of nitrogen, phosphorus and potassium are the key indicators affecting the fertilization efficiency and the price of compound fertilizers. Laser-induced breakdown spectroscopy (LIBS) and near-infrared spectroscopy (NIRS) are two rapid analytical techniques suitable for online monitoring of the above components in compound fertilizer. However, accurate LIBS analysis needs to overcome matrix effects and interference from environmental elements, and NIRS also has the limitation of not being able to directly detect inorganic components in compound fertilizers. The combination of LIBS and NIRS techniques, namely LIBS-NIRS data fusion, has the potential to reduce interferences in the detection of single spectroscopic techniques and further improve the analysis accuracy. This study compared the LIBS-NIRS data fusion methods under different optimization conditions, and found that CARS-OPF (competitive adaptive reweighted sampling combined with outer product fusion) and CARS-EWF (competitive adaptive reweighted sampling combined with equal weight fusion) are two effective intermediate data fusion methods which can achieve better quantitative analysis results than single spectroscopic methods. The root mean square errors of prediction (RMSEP) for nitrogen, phosphorus, and potassium contents in compound fertilizers by using CARS-OPF are 0.901, 0.693, and 1.52, respectively, and the RMSEP for those indicators by using CARS-EWF are 0.934, 0.719, and 1.60, respectively. In these two methods, the LIBS and NIRS characteristic variables of compound fertilizers are firstly screened by CARS algorithm, and then intermediate data fusion was carried out by using equal weight fusion or outer product fusion. Redundant variables in the original data can be well removed in the data fusion process to ensure the accuracy of the analysis. Therefore, the combined methods of LIBS-NIRS based on CARS-OPF and CARS-EWF could be well applied to the rapid and accurate detection of main elemental contents in compound fertilizers.

Validated UPLC-MS/MS method for the determination of ivosidenib in rat plasma: Application to a pharmacokinetic study

AbstractIvosidenib (AG-120) is an unlisted, but estimated to be valid, oral inhibitor for isocitrate dehydrogenase 1 (IDH1) in the phase Ⅰ study of IDH1-mutated acute myeloid leukemia (AML) patients. This paper presents the investigation and validation of a rapid, effective, qualitative and quantitative determination method of ivosidenib in rat plasma by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The samples were treated using acetonitrile precipitation to remove protein influence. Then, the supernatant was extracted to analyze plasma concentration traits. In the UPLC system, acetonitrile and water containing 0.1% formic acid were selected as a cosolvent mobile phase, applying a gradient elution to isolate compounds in a C18 column. Mass detections were performed on a triple quadruple mass spectrometer in positive ion mode. Electroshock characteristic fragment ionization was used for m/z 583.95→214.53 for ivosidenib for quantitative determination, m/z 583.95→186.6 for qualitative determination, and m/z 492.06→354.55 for IS. The selectivity, linearity, stability, accuracy and precision were verified by reaching the guideline criteria from European Medicine Agency (EMA) and the Food and Drug Administration (FDA). The calibration curve was linear over the concentration range of 2–2,000 ng mL−1 for ivosidenib in rat plasma with a lower limit of quantification (LLOQ) of at least 2 ng mL−1. Additionally, there was no distinct matrix effect or carry-over phenomenon. The method was successfully established and applied to separate ivosidenib from plasma, with the entire analytical process being performed within 3 min for each sample, which shows high-efficiency and convenience for further studies of ivosidenib.

Trypsin Digestion Pretreatment of Kelp Samples and the Iodine Speciation Analysis of Iodate, Iodide, MIT, and DIT by HPLC-ICP-MS

The analysis of iodine content in kelp is mainly focused on determining total iodine content, which lacks a rapid and sensitive analytical method for iodine species corresponding to iodate, iodide, monoiodotyrosine (MIT), and diiodo-tyrosine (DIT). Based on exploring the pretreatment methods of enzymatic hydrolysis of kelp, a rapid determination method of high-performance liquid chromatography and inductively coupled plasma mass spectrometry (HPLC-ICP-MS) for different iodine species existed in kelp samples was established. The pretreatment method is trypsin hydrolysis of kelp samples treated at 50°C for 10 hours, then the extraction solution was obtained by centrifugation, and filtration was proved for the first time. A high-efficiency separation anion-exchange column (Dionex IonPac AS-14) for iodate, iodide, MIT, and DIT with 0.1 mol·L−1(NH4)2CO3 solution at pH = 9 as a mobile phase, a flow rate of 0.8 mL·min−1 for the first 1500 s, and 1.2 mL·min−1 for the last 1800 s was confirmed. The linear ranges of the standard calibrations on four iodine species are 1.0–150 μg·L−1, and the detection limits are 1.62, 1.02, 1.59, and 2.55 μg·L−1, respectively, while the RSD values of four iodine species are all less than 2%. Under the optimized conditions, the proposed method was successfully applied for the speciation analysis of iodine in kelp samples.

A novel electrochemical aptasensor based on eco-friendly synthesized titanium dioxide nanosheets and polyethyleneimine grafted reduced graphene oxide for ultrasensitive and selective detection of ciprofloxacin

Developing a rapid, sensitive, and efficient analytical method for the trace-level determination of highly concerning antibiotic ciprofloxacin (CIP) is desirable to guarantee the safety of human health and ecosystems. In this work, a novel electrochemical aptasensor based on polyethyleneimine grafted reduced graphene oxide and titanium dioxide (rGO/PEI/TiO2) nanocomposite was constructed for ultrasensitive and selective detection of CIP. Through the in-situ electrochemical oxidation of Ti3C2Tx nanosheets, TiO2 nanosheets with good electrochemical response were prepared in a more convenient and eco-friendly method. The prepared TiO2 nanosheets promote charge transferring on electrode interface, and [Fe(CN)6]3-/4- as electrochemical active substance can be electrostatically attracted by rGO/PEI. Thus, electrochemical detection signal of the aptasensor variates a lot after specific binding with CIP, achieving working dynamic range of 0.003–10.0 μmol L−1, low detection limit down to 0.7 nmol L−1 (S/N = 3) and selectivity towards other antibiotics. Additionally, the aptasensor exhibited good agreement with HPLC method at 95% confidence level, and achieved good recoveries (96.8–106.3%) in real water samples, demonstrating its suitable applicability of trace detection of CIP in aquatic environment.

Early leaf responses of cell physiological and sensor-based signatures reflect susceptibility of wheat seedlings to infection by leaf rust.

Leaf rust caused by Puccinia triticina Erikss. can have devastating effects on wheat (Triticum aestivum L.), causing severe economic losses. This comprehensive study serves to facilitate our understanding of the impact of carbohydrate and antioxidant metabolism in association with sensor-based phenotyping and leaf rust stress responses in wheat seedlings. After 24 h of inoculation (hai) very susceptible variety to leaf rust (Ficko) increased cell-wall invertase (cwInv; EC 3.2.1.26), compared to other varieties that significantly increased cwInv later. This could mean that the Ficko variety cannot defend itself from leaf rust infections once symptoms have started to develop. Also, Ficko had significantly decreased amounts of cytoplasmic invertase (cytInv; EC 3.2.1.26) at 8 hai. The downregulation of cytInv in susceptible plants may facilitate the maintenance of elevated apoplastic sucrose availability favoring the pathogen. The significant role of vacuolar invertase (vacInv; EC 3.2.1.26) in moderately resistant varieties was recorded. Also, a significant decrease of glucose-6-phosphate dehydrogenase (G6PDH; EC 1.1.1.49) and UDP-glucose pyrophosphorylase (UGPase; EC 2.7.7.9) in moderately resistant varieties might restrict normal development of leaf rust due to reduced sugar. During plant-pathogen interaction, when the invader spreads systemically throughout the plant, the main role of ascorbate peroxidase (APX; EC 1.11.1.11) activity in one moderately resistant variety (Olimpija) and catalase (CAT; EC 1.11.1.6) activity in another moderately resistant variety (Alka) is to protect the plant against oxidative damage in the early stages of infection. Non-invasive phenotyping with a sensor-based technique could be used as a rapid method for pre-symptomatic determination of wheat leaf rust resistance or susceptibility.

Rapid confirmation method of food poisoning caused by Bacillus cereus cereulide in rice and flour products

To develop a method for rapid determination of Bacillus cereus cereulide in rice and flour products by ultra-performance liquid chromatography-tandem mass spectrometry, providing emergency measures for food poisoning caused by cereulide. Single rice and flour samples were extracted with acetonitrile aqueous solution, salting out, after centrifuged and filmed, the organic phase was directly determined. The complex matrix samples fried rice and noodles were extracted with acetonitrile aqueous solution, cleaned up with HLB column, a ACQUITY UPLC Peptide BEH C_(18) 300Å column(2.1 mm×100 mm, 1.7 μm)was used for liquid chromatography separation, multiple reaction monitoring(MRM) mode was used for detection in electrospray ionization with positive ion mode, and quantified by the solvent standard curve method. At the spiked level of 0.5, 1.0 and 5.0 μg/kg, the recoveries of cereulide in negative steamed rice, steamed bread and noodles samples were 87.4%-98.3%, and the relative standard deviations were 1.4%-4.2%. At the spiking levels of 1.0, 2.0 and 5.0 μg/kg, the recoveries of cereulide in the negative samples such as fried steamed rice and fried noodles were 89.5%-99.3% with the relative standard deviations of 1.1%-7.5%(n=6). The detection limit of cereulide was 0.2-0.3 μg/kg, and the quantification limit was 0.5-1.0 μg/kg. The established method was applied to the detection of the actual samples causing food poisoning in a certain place in Beijing. The content of cereulide in poisoned food samples was 1287-7398 μg/kg, the content of cereulide in two raw materials cold noodles was 0.4 and 9.4 μg/kg. The method is simple, rapid, high sensitivity and accurate, and can realize the rapid treatment of food poisoning caused by cereulide.

Analytical method development and validation of secnidazole in its pure and pharmaceutical dosage form by using uv-visible spectrophotometric method

UV-spectrophotometry refers to absorption spectroscopy in the ultraviolet-visible spectral region. This method of analysis is gaining importance as it is rapid, simple, precise, less time consuming and accurate. The objective of present investigation was to develop an accurate, rapid and robust method for determination of Secnidazole in API and in pharmaceutical preparations by using UV spectrophotometric method. Secnidazole shows maximum absorbance at a wavelength of 305nm, which is used for this study. The method provides a linear response from a quantitation range of 06 µg/ml to 14 µg/ml in ethanol with regression equation y = 0.032x - 0.002 and r2 0.999 Interday precision and accuracy was found to be below 0.2 and above 99.00% respectively for the developed method. Thus the developed method suitably applied for regular quality control of Secnidazole in pure and pharmaceutical preparations.

Raman spectroscopy coupled with metaheuristics-based variable selection models: A method for rapid determination of extra virgin olive oil content in vegetable blend oils

Vegetable blend oils play a vital role in the daily human diet, but they have become the target of forgeries. This work proposes a method for the rapid on-site quantification of high-value pure vegetable oil (e.g., extra virgin olive oil (EVOO)) content in vegetable blend oils by combining Raman spectroscopy and metaheuristics-based variable selection models. First, the corn oil-EVOO and peanut oil-EVOO vegetable blend oil samples were prepared for Raman spectra measurement. Then, partial least squares regression and four metaheuristics-based variable selection models, including genetic algorithm combined moving window (GA-MW), particle swarm optimization combined moving window (PSO-MW), grey wolf optimizer combined moving window (GWO-MW), and whale optimization algorithm combined moving window (WOA-MW), were applied to the collected Raman spectra for a comparative study. The method developed in this work could accurately quantify the EVOO content in vegetable blend oil samples. In addition, the stability tests and limit of detection values verified the stability and sensitivity of the developed method. Finally, two-tailed paired t-tests identified that there was no significant difference between the gas chromatography–mass spectrometry method and the developed method. Therefore, the developed method provides a rapid and cost-effective strategy for quantitative authentication of vegetable blend oils.

Sensitive measurement of silver ions in environmental water samples integrating magnetic ion-imprinted solid phase extraction and carbon dot fluorescent sensor

Increasing use of silver in various fields has caused Ag+ pollution in water environment, taking great threats to people's health. As a consequence, establishing rapid and reliable methods for sensitive determination of Ag+ is of great significance. Fluorescent (FL) sensors based on carbon dots (CDs), an excellent carbonaceous nanomaterial with strong and stable fluorescence, have absorbed extensive attentions in analysis of pollutants due to its advantages of carbon sources being readily available, low cost, easy operation and fast response. Moreover, ion-imprinting is a better way to increase the selectivity of the proposed method. Present work described an effective method for the sensitive measurement of silver ion in water samples in combination with magnetic ion-imprinted solid phase extraction and CDs based fluorescent sensor, which took full advantages of easy separation and high enrichment of magnetic solid phase extraction, high selectivity of ion-imprinting technology, and sensitivity and rapid response of fluorescent sensor from CDs. Sulfur-doped CDs derived from dithizone and magnetic ion-imprinted nanomaterial were prepared, and characterized with Fourier transform infrared spectroscopy and transmission electron microscope, etc. Magnetic Ag+ imprinted nanomaterial based solid phase extraction was employed for separating and enriching Ag+ from water samples. The significant parameters were optimized in detail. Under the optimal conditions, the proposed method provided good linearity in the range of 0.01–0.4 µmol/L and low detection limit of 3 nmol/L. The reliability of the proposed method was validated with real water samples, and the results demonstrated that the proposed method was simple, robust, selective and sensitive detection tool for Ag+ in real water samples.

Rapid Multi-Residue Method for Simultaneous Determination of 1,3,5-Triazine Herbicides in Environmental Samples by Capillary GC-MS-EI Selective Ion Monitoring Method

A new multi-residue method using gas chromatography–mass spectrometry electron ionization selective ion monitoring mode (SIM) has been developed for the simultaneous determination of eight 1,3,5-triazine herbicides such as 1,3,5-triazine-2,4-diamine (atrazine), ametryn, prometryn, propazine, terbuthylazine, terbutryn, and simazine simetryn in water and soil samples. Quantification is done using lindane (gamma benzene hexachloride) as an internal standard. A specific Capillary DB-Wax column of 30 m length, 0.32 mm internal diameter, and 0.25 µm film thickness is used for the separation of eight 1,3,5-triazine-2,4-diamine. The method was applied for the determination of residues in groundwater and soil samples. The lowest detection limit by GC-MS-SIM (selective ion monitoring mode) is 0.1 pg/mL. Recovery in water samples is in the range of 93–103%, and in soil samples, 91–102% for different individual compounds. Forty-five groundwater and soil samples were collected in and around Kancheepuram district in Tamilnadu (India), and they were analyzed for the respective residues. A detailed discussion of the GC-MS analysis results has been presented.

Nickel Oxy-Hydroxy/Multi-Wall Carbon Nanotubes Film Coupled with a 3D-Printed Device as a Nonenzymatic Glucose Sensor.

A rapid and simple method for the amperometric determination of glucose using a nanocomposite film of nickel oxyhydroxide and multi-walled carbon nanotube (MWCNTs) was evaluated. The NiHCF)/MWCNT electrode film was fabricated using the liquid-liquid interface method, and it was used as a precursor for the electrochemical synthesis of nickel oxy-hydroxy (Ni(OH)2/NiOOH/MWCNT). The interaction between nickel oxy-hydroxy and the MWCNTs provided a film that is stable over the electrode surface, with high surface area and excellent conductivity. The nanocomposite presented an excellent electrocatalytic activity for the oxidation of glucose in an alkaline medium. The sensitivity of the sensor was found to be 0.0561 μA μmol L-1, and a linear range from 0.1 to 150 μmol L-1 was obtained, with a good limit of detection (0.030 μmol L-1). The electrode exhibits a fast response (150 injections h-1) and a sensitive catalytic performance, which may be due to the high conductivity of MWCNT and the increased active surface area of the electrode. Additionally, a minimal difference in the slopes for ascending (0.0561 µA µmol L-1) and descending (0.0531 µA µmol L-1) was observed. Moreover, the sensor was applied to the detection of glucose in artificial plasma blood samples, achieving values of 89 to 98% of recovery.

Rapid and sensitive determination of Se and heavy metals in foods using electrothermal vaporization inductively coupled plasma mass spectrometry with a novel transportation system.

Rapid, sensitive and simultaneous determination of trace multi-elements in various plant food samples such as grain, oilseed, vegetable and tea is always a challenge thus far. In this work, a rapid determination method for Se, Cd, As and Pb in food samples by inductively coupled plasma mass spectrometry (ICP-MS) using slurry sampling electrothermal vaporization (SS-ETV) was developed. To improve the analytical sensitivity and precision as well as eliminate the memory effect, a gas turbulator line and signal delay device (SDD) were for the first time designed for the graphite furnace (GF) ETV coupled with ICP-MS. The signal acquisition parameters of ICP-MS, ashing and vaporization conditions, and the flow rates of carrier gas and gas turbulator were investigated for Se, Cd, As and Pb in food samples. Under the optimized conditions, the limits of determination (LODs) for Se, Cd, As and Pb were 0.5 ng g-1, 0.3 ng g-1, 0.3 ng g-1 and 0.6 ng g-1, respectively; the limits of quantification (LOQs) for Se, Cd, As and Pb were 1.7 ng g-1, 1.0 ng g-1, 1.0 ng g-1 and 1.9 ng g-1, respectively; linearity (R2) in the range of 1 to 4,000 ng g-1 was >0.999 using the standard addition method. This method was used to analyze 5 CRMs including rice, tea and soybeans, and the concentrations detected by this method were within the range of the certified values. The recoveries of Se, Cd, As and Pb in plant food matrices including grain, oilseed, celery, spinach, carrot and tea samples were 86-118% compared to the microwave digestion ICP-MS method; and the relative standard deviations (RSDs) were 1.2-8.9% for real food sample analysis, proving a good precision and accuracy for the simultaneous determination of multi-elements. The analysis time was less than 3 min, slurry preparation time < 5 min without sample digestion process. The proposed direct slurry sampling ICP-MS method is thus suitable for rapid and sensitive determination of Se, Cd, As and Pb in food samples with advantages such as simplicity, green and safety, as well as with a promising application potential in detecting more elements to protect food safety and human health.

Calibration and Sensitivity Analysis of Macro and Meso Parameters of Discrete Element Model for Coal Measure Soil

The orthogonal test sequence of the meso parameters of the discrete element model was designed by using the orthogonal test method. The calculation method of directly determining the meso parameters from the macro mechanical parameters was established by using the test simulation calculation results and the multi factor nonlinear joint inversion method. The proposed method was applied to the discrete element numerical simulation of triaxial test of coal measure soil. The results show that the numerical simulation results are in good agreement with the stress-strain curves of the triaxial test of coal bearing soil. Through error analysis, it is found that the maximum error of the partial stress peak is 5.4%, the error of the cohesion is 2%, the error of the internal friction angle is 7%, and the error is all within 10%. It verifies that the method for rapid determination of the meso parameters proposed in this paper is feasible, and provides a new idea for the calibration of the meso parameters in the discrete element numerical simulation method.

Rapid method of arsenic estimation in geological samples by WD-XRF using a novel concept of As-Pb concentration equivalence.

The presence of arsenic in ground waters of many countries has been a subject of global concern due to its toxicity. Primary sources of arsenic are geogenic, i.e. weathering and erosion of rocks and soils containing arsenic. This paper presents a rapid method for determination of arsenic in solid geological samples by wavelength dispersive X-ray fluorescence spectrometer. To achieve the best LLD (lower limit of detection), the most intense X-ray fluorescence line Kα1,2 is preferably used for determination of elemental concentrations because it pertains to the most probable transition. But the greatest challenge in arsenic estimation is the serious line overlap of AsKα1,2 lines with the equi-energy PbLα1,2 lines. By using the conventional line overlap correction methods, uncertainty and detection limits in arsenic determination are degraded to an unacceptable degree in samples which contains high lead and low arsenic concentrations. The proposed method bypassesthe line overlap issue in employing a novel concept of arsenic-lead concentration equivalence factor for the cumulative peak of AsKα1,2 and PbLα1,2 fluorescence lines. The constancy of this factor for all geological matrices facilitates arsenic determination in samples universally irrespective of matrix elements. For the method validation, 22 international certified reference materials have been analysed and the results proved to be propitious wherein only one value out of 22 determinations showed relative error more than 20% of the certified values. This attests to the high accuracy of the proposed method which can effectively determine arsenic below 5mg/kg in the presence of high lead concentration up to 1000mg/kg.

Rapid detection of the biomarker for cystinuria by a metal-organic framework fluorescent sensor

Arginine (Arg) is considered a valuable biomarker for various diseases, including cystinuria, and its concentration level holds significant implications for human health. To achieve the purposes of food evaluation and clinical diagnosis, it is imperative to develop a rapid and facile method for selective and sensitive determination of Arg. In this work, a novel fluorescent material (Ag/Eu/CDs@UiO-66) was synthesized by encapsulating carbon dots (CDs), Eu3+ and Ag + into UiO-66. This material can serve as a ratiometric fluorescent probe for detecting Arg. It exhibits a high sensitivity with a detection limit of 0.74 μM and a relatively broad linear range from 0–300 μM. After dispersing the composite Ag/Eu/CDs@UiO-66 in an Arg solution, the red emission of Eu3+ center at 613 nm was significantly enhanced, while the characteristic peak of CDs center at 440 nm remained unchanged. Therefore, a ratio fluorescence probe could be constructed based on the peak height ratio of the two emission peaks to achieve selective detection of Arg. In addition, the remarkable ratiometric luminescence response induced by Arg results in a significant color transition from blue to red under UV-lamp for Ag/Eu/CDs@UiO-66, which was convenient for visual analysis.

Determination of cobalt and tungsten in human urine by inductively coupled plasma mass spectrometry

Objective: To establish a inductively coupled plasma mass spectrometry method for the determination of trace cobalt and tungsten in human urine. Methods: The authors used 1% nitric acid solution as diluent in October-December 2021, the sample dilution factor and internal standard element were optimized by single factor rotation experiment, and the difference between the working curve and the standard curve was compared. Results: The method uses working curve to determine cobalt and tungsten in urine, the linear range of this method was 0.0~10.0 μg/L, the correlation coefficient was 0.999 9, the detection limits respectively were 0.005 μg/L (cobalt) and 0.09 μg/L (tungsten), the recoveries of samples respectively were 87.0%~100.2% (cobalt) and 89.4%~104.8% (tungsten), the relative standard deviations respectively were 0.4%~4.4% (cobalt) and 0.6%~3.8% (tungsten) . Conclusion: A simple and rapid method for determination of cobalt and tungsten in urine has been established. This method has the advantages of simple operation, high sensitivity, low detection limit and good stability. It is suitable for determination of cobalt and tungsten in urine of all kinds of people.

Development of PREDAC-H1pdm to model the antigenic evolution of influenza A/(H1N1) pdm09 viruses

The Influenza A (H1N1) pdm09 virus caused a global pandemic in 2009 and has circulated seasonally ever since. As the continual genetic evolution of hemagglutinin in this virus leads to antigenic drift, rapid identification of antigenic variants and characterization of the antigenic evolution are needed. In this study, we developed PREDAC-H1pdm, a model to predict antigenic relationships between H1N1pdm viruses and identify antigenic clusters for post-2009 pandemic H1N1 strains. Our model performed well in predicting antigenic variants, which was helpful in influenza surveillance. By mapping the antigenic clusters for H1N1pdm, we found that substitutions on the Sa epitope were common for H1N1pdm, whereas for the former seasonal H1N1, substitutions on the Sb epitope were more common in antigenic evolution. Additionally, the localized epidemic pattern of H1N1pdm was more obvious than that of the former seasonal H1N1, which could make vaccine recommendation more sophisticated. Overall, the antigenic relationship prediction model we developed provides a rapid determination method for identifying antigenic variants, and the further analysis of evolutionary and epidemic characteristics can facilitate vaccine recommendations and influenza surveillance for H1N1pdm.