ACS Measurement Science Au最新文献

Fourier-transformed alternating current voltammetry (FTacV) is a technique utilizing a combination of a periodic (frequently sinusoidal) oscillation superimposed onto a staircase or linear potential ramp. The advanced utilization of a large amplitude sine wave induces substantial nonlinear current responses. Subsequent filter processing (via Fourier-transformation, band selection, followed by inverse Fourier-transformation) generates a series of harmonics in which rapid electron transfer processes may be separated from non-Faradaic and competing electron transfer processes with slower kinetics. Thus, FTacV enables the isolation of current associated with redox processes under experimental conditions that would not generate meaningful data using direct current voltammetry (dcV). In this study, the enhanced experimental sensitivity and selectivity of FTacV versus dcV are illustrated in measurements that (i) separate the Faradaic current from background current contributions, (ii) use a low (5 μM) concentration of analyte (exemplified with ferrocene), and (iii) enable discrimination of the reversible [Ru(NH₃)₆]^3+/2+ electron-transfer process from the irreversible reduction of oxygen under a standard atmosphere, negating the requirement for inert gas conditions. The simple, homebuilt check-cell described ensures that modern instruments can be checked for their ability to perform valid FTacV experiments. Detailed analysis methods and open-source data sets that accompany this work are intended to facilitate other researchers in the integration of FTacV into their everyday electrochemical methodological toolkit.

Large-scale plasma proteomics studies have been transformed due to the multiplexing and automation of sample preparation workflows. However, these workflows can suffer from reproducibility issues, a lack of standardized quality control (QC) metrics, and the assessment of variation before liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis. The incorporation of robust QC metrics in sample preparation workflows ensures better reproducibility, lower assay variation, and better-informed decisions for troubleshooting. Our laboratory conducted a plasma proteomics study of a cohort of patient samples (N = 808) using tandem mass tag (TMT) 16-plex batches (N = 58). The proteomic workflow consisted of protein depletion, protein digestion, TMT labeling, and fractionation. Five QC sample types (QC_std, QC_dig, QC_pool, QC_TMT, and QC_BSA) were created to measure the performance of sample preparation prior to the final LC–MS/MS analysis. We measured <10% CV for individual sample preparation steps in the proteomic workflow based on data from various QC sample steps. The establishment of robust measures for QC of sample preparation steps allowed for greater confidence in prepared samples for subsequent LC–MS/MS analysis. This study also provides recommendations for standardized QC metrics that can assist with future large-scale cohort sample preparation workflows.

Electrosynthesis traditionally requires dedicated reactor systems and an added electrolyte, although some paired electrosynthesis processes are possible at interdigitated microband electrodes simply immersed in solution and without an intentionally added electrolyte. Here, 1,1′-ferrocenedimethanol oxidation and activated olefin electro-hydrogenation reactions are investigated as model processes at a Pt–Pt interdigitated microband array electrode with 5 μm width and with 5 μm interelectrode gap. Voltammetric responses for electro-hydrogenation are discussed, and product yields are determined in methanol (MeOH) in the presence/absence of an added electrolyte (LiClO₄). An isotope effect is observed in CH₃OD solvent, leading to olefin monodeuteration linked to a fast EC-type process close to the cathode surface (in the cathode reaction zone) rather than to charge annihilation in the interelectrode zone. A finite element simulation is employed to visualize/discuss reaction zones and to contrast the rate of charge annihilation processes with/without a supporting electrolyte.

Recent advancements in mass spectrometry (MS) have revolutionized quantitative proteomics, with multiplex isotope labeling emerging as a key strategy for enhancing accuracy, precision, and throughput. This tutorial review offers a comprehensive overview of multiplex isotope labeling techniques, including precursor-based, mass defect-based, reporter ion-based, and hybrid labeling methods. It details their fundamental principles, advantages, and inherent limitations along with strategies to mitigate the limitation of ratio-distortion. This review will also cover the applications and latest progress in these labeling techniques across various domains, including cancer biomarker discovery, neuroproteomics, post-translational modification analysis, cross-linking MS, and single-cell proteomics. This Review aims to provide guidance for researchers on selecting appropriate methods for their specific goals while also highlighting the potential future directions in this rapidly evolving field.

Portable electrochemical analytical devices such as cholesterol sensors are widely used for disease diagnosis. However, these tools are bulky and require bioreceptors for the specific detection of cholesterol. Herein, a novel 3D electrochemical paper-based analytical device (3D-ePAD) combined with a near-field communication (NFC) potentiostat was developed and applied to the nonenzymatic detection of cholesterol. This 3D-ePAD platform was designed so that all working operations are performed on a single device, which is separated into an origami PAD (oPAD) and an inset PAD (iPAD). β-Cyclodextrin (β-CD), which is immobilized on oPAD, is used as a specific material for the nonenzymatic detection of cholesterol. Through this device, cholesterol detection is integrated with a battery-free NFC potentiostat on a smartphone. The concentration of cholesterol was examined through a [Fe(CN)₆]^3-/4- current signal as a redox indicator, which was previously stored in the detection part of an iPAD. Under optimal conditions, 3D-ePAD/NFC exhibited a linear detection efficiency of 1–500 μM and a maximum detection limit of 0.3 μM for cholesterol detection. Moreover, the proposed sensor was successfully used to measure cholesterol in real serum samples from humans, and the results were consistent with those of a commercial cholesterol meter. Therefore, the new NFC-operated 3D-ePAD platform can be used as an alternative tool for the nonenzymatic quantification of various biomarkers. In addition, 3D-ePAD/NFC can support the diagnosis of other diseases in the future, as the device is inexpensive, portable, and disposable and functions with low sample volumes.

This study investigated the occurrence of ibuprofen, naproxen, sulfamethoxazole, trimethoprim, and efavirenz in water resources (river, estuarine, and sea waters) of the East London coastline, South Africa. These pharmaceuticals were previously reported to be dominant in wastewater and inland rivers of South Africa. Hence, it is important to monitor their occurrence in the coastal and marine environment. The pharmaceuticals of interest were extracted with a solid-phase extraction method and analyzed by using a liquid chromatography-quadrupole time-of-flight mass spectrometry instrument. The analytical method was validated by spiking the environmental samples with a mixture of pharmaceuticals at two concentration levels (5 and 15 μg L^–1). The analytical method yielded acceptable recoveries ranging from 75 to 107%, with method quantitation limits from 0.16 to 9.44 ng of L^–1. All five targeted pharmaceuticals were detected in seawater samples, with ibuprofen recording the highest concentration of 90 ng L^–1. However, it was efavirenz and sulfamethoxazole with the highest concentrations of 572 and 60 ng L^–1, respectively, in the Gonubie River that showed high ecotoxicological risks toward the aquatic organisms. There were no risks associated with the occurrence of other targeted pharmaceuticals. The suspect screening showed the occurrence of 57 additional pharmaceuticals in samples, with antibiotics being more dominant. The results of the present study demonstrate a need to perform a more robust investigation on the occurrence of a wide range of pharmaceuticals along the South African coasts.