Liuhatfield4592

Graphene oxide cannot be completely reduced by electrochemical methods, thus the rGO-Cu probe can enrich the analytes through the huge surface area of the graphene thin layer, as well as the hydrogen bond and the electrostatic absorption of the surface oxygen-containing groups. Seven AD related neurotransmitters and sixteen biomarkers in PC12 single cells and twelve metabolites in serum of AD rats were successfully analyzed by using FPESI-MS, and this method is expected to be used in the rapid detection of metabolites in biological samples and living organism. Accuracy of reference values obtained by the reference method is essential to ensure the quality of a near-infrared (NIR) model. The purpose of this study was to assess the accuracy of a newly developed NIR analytical method for the determination of water content in a freeze-dried meningococcal vaccine by evaluating not only uncertainties associated with the calibration model and NIR measurement procedures but also systematic error arising from the reference Karl-Fischer method. An experimental design based on the standard addition method (SAM) in freeze-dried vaccines is proposed for total error assessment of the NIR analytical system. The accuracy profile showed that the NIR model successfully determined water content over the 1.0-6.7% range. The SAM enabled overall proportional error assessment, which yielded a slope of 1.01. The present study confirmed the suitability of the proposed NIR analytical method for the determination of water content in the freeze-dried meningococcal vaccine. Furthermore, assessment of the overall proportional error proved that the NIR analytical method could be used to accurately estimate differences in water content, therein surpassing the reference method as the method of choice for determining intra- or interbatch variability as well as stability. This study demonstrates a newly developed PDMS/DVB/PDMS fiber's suitability for the determination of pesticides in soy milk via direct-immersion solid-phase microextraction (SPME) combined with gas chromatography-mass spectrometry, eliminating the need for extensive sample pre-treatment procedures. Fouling accumulation on the coating surface was further minimized by implementing rapid and effective pre- and post-desorption cleaning steps. Under optimum conditions, the fiber was used to perform over 120 extractions while maintaining RSD values of less than 24.5% for 10 extracted pesticides. By comparison, the RSD values ranged from 8.4% to 42.8% over 80 extractions using a commercial PDMS/DVB fiber. The optimized conditions were used to fully validate a quantitative method for the targeted analytes by matrix-matched calibration and isotopically labeled internal standard correction. Significantly, the proposed method was able to achieve limits of quantitation (1-2.5 μg/kg) for the targeted analytes that were below the Maximum Residue Levels mandated for soy-based products. Accuracy, intra- and inter-day repeatability were also satisfactory. The proposed PDMS/DVB/PDMS fiber dramatically improved repeatability and suitability for direct-immersion SPME in soy milk, and represents a good alternative to other extraction methods for high-throughput quantitative analysis of pesticide residues in soy-based products. Herein, an electrochemical label-free biosensor designed for the detection of glycated albumin (GA) using reduced graphene oxide/Au nanoparticles (RGO/AuNPs) modified by anti-GA aptamer. For fast and simple modification of the electrode, the aptamer chain was thiolated. Transition electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) techniques were used to the characterization of synthesized materials. Structural analysis of nanomaterials shows that graphene sheets were synthesized very fine by average thickness of 2.5 nm and Au nanoparticles distributed on the surface of graphene sheets uniformly. Cyclic voltammetry (CV) square wave voltammetry (SWV) and impedance spectroscopy (EIS) were used to electrochemical study of the decorated electrode. Electrochemical studies described the potential of fabricated rGO/AuNPs-aptamer electrode to selectively determine GA properly in buffer solution at the range of 2-10 μg mL-1 by the detection limit of 0.07 μg. mL-1 for GA. V.Barium sulfate-coated CsPbBr3 perovskite nanocrystals (CsPbBr3 NCs@BaSO4) was successfully synthesized that exhibited stable and intense fluorescence property in aqueous buffer. selleck inhibitor With the CsPbBr3 NCs@BaSO4 as signal readout, an ultrasensitive fluorescence nanosensor was developed for turn-on determination of melamine by the manipulation of inner filter effect of citrate-protected gold nanoparticles (AuNPs). The fluorescence of the CsPbBr3 NCs@BaSO4 was remarkably quenched by the AuNPs due to inner filter effect. This inner filter effect could be weakened by the addition of melamine as a result of melamine-triggering aggregation of the AuNPs and subsequently led to a recovery in the fluorescence of the CsPbBr3 NCs@BaSO4. The recovery ratio was proportional to the concentration of melamine in the range of 5.0-500.0 nmol/L. The limit of detection was 0.42 nmol/L and the relative standard deviation was 4.0% for the repetitive determination of 500.0 nmol/L melamine solution (n = 11). The nanosensor was successfully applied to analysis of melamine in dairy product samples. Methylphosphonic acid (MPn) is suspected to play an important role in aquatic systems like rivers or the open ocean. To gain more insights into the importance of MPn, e.g., for the aquatic phosphorus cycle, an analytical method for its quantitative determination was developed. The method is based on the use of an isotopically-labelled internal standard and sample preparation including solid-phase extraction (SPE). Instrumental detection was done using GC-MS after derivatisation of MPn with N-tert-Butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA). The study compares different isotopically-labelled compounds as well as different SPE-materials. As water samples with high salt content decrease the recovery of the chosen SPE-material, a desalting procedure using electrodialysis was implemented. Finally, water samples from different aquatic systems located at the German Baltic Sea coastal area were analysed to gain first insights into the relevance of MPn in these systems. MPn-concentrations in the low μg/L-range were detected.