We have designed a versatile and sensitive liquid chromatographic (LC) system, featuring a monolithic trap column and a very narrow (10 μm ID) fused silica open tubular liquid chromatography (OTLC) separation column functionalized with C₁₈-groups, for separating a wide range of molecules (from small metabolites to intact proteins). Compared to today’s capillary/nanoLC approaches, our system provides significantly enhanced sensitivity (up to several orders) with matching or improved separation efficiency, and highly repeatable chromatographic performance. The chemical properties of the trap column and the analytical column were fine-tuned to obtain practical sample loading capacities (above 2 μg), an earlier bottleneck of OTLC. Using the OTLC system (combined with Orbitrap mass spectrometry), we could perform targeted metabolomics of sub-μg amounts of exosomes with 25 attogram detection limit of a breast cancer-related hydroxylated cholesterol. With the same set-up, sensitive bottom-up proteomics (targeted and untargeted) was possible, and high-resolving intact protein analysis. In contrast to state-of-the-art packed columns, our platform performs chromatography with very little dilution and is “fit-for-all”, well suited for comprehensive analysis of limited samples, and has potential as a tool for challenges in diagnostics.

Performing Quantitative Determination of Low-Abundant Proteins by Targeted Mass Spectrometry Liquid Chromatography | InTechOpen, Published on: 2017-06-07. Authors: Tore Vehus

Selecting interior wood materials requires balancing functional and aesthetic demands with indoor air quality, as wood can emit volatile organic compounds (VOCs) and very volatile organic compounds (VVOCs) that either peak shortly after installation or persist over time. This study investigated time-resolved VOC and VVOC accumulation concentrations from untreated pine, spruce, aspen, and oak, representing wood species commonly used in Norway. Concentrations of VOCs and VVOCs were monitored for 25–28 days under low-ventilation, worst-case chamber conditions using Proton Transfer Reaction–Time-of-Flight Mass Spectrometry (PTR-TOF-MS). Emission behaviour was assessed using peak concentration, decay rate, half-time, stabilised concentration, cumulative exposure (AUC₂₈), and available health-based thresholds. Clear species-dependent differences were observed. Pine was the dominant VOC source, with the highest peak concentration, stabilised concentration, and AUC₂₈, mainly due to monoterpenes, which remained above the health-based threshold throughout the test period. Oak showed the second-highest VOC burden and a distinct acetate-dominated profile, with acetic acid showing the longest predicted exceedance duration. Aspen and spruce had lower VOC burdens, but their cumulative VVOC exposure exceeded VOC exposure. VVOCs generally peaked earlier than VOCs, although persistence varied by species. Overall, the concentration of VOCs and VVOCs was controlled by species, compound chemistry, volatility, and internal transport, supporting species- and compound-specific ventilation and material-selection strategies.

Electron beam-induced current (EBIC) microscopy can provide spatially resolved electrical information that conventional probe methods and local scanning probes often miss in nanoparticulate thin films. Here we present a practical EBIC methodology to qualitatively assess conductivity uniformity and electrical continuity in thin films spanning two electrodes inside a scanning electron microscope (SEM) using TiO2 nanoparticulate films as a model system. The approach combines a purpose-built insulating holder with embedded electrodes and a measurement configuration to visualize current pathways and identify electrically disconnected regions that may not be apparent from morphology alone. EBIC line scans and 2D maps enable rapid screening of film quality, highlighting cracks, and poor particle connectivity. The workflow is designed for reproducibility and can be adapted to other semiconducting or weakly conducting thin films where microscale continuity is critical to device performance.

Blood has a complex proteome with a huge span of protein abundances, and we are currently exploring sample preparation strategies addressing this potential challenge. We first evaluated the possibility to simply reduce complexity by fractionating blood samples (prior to targeted proteomics), using combinations of centrifugal filters that are promoted as having differing molar mass (M _M ) selectivity. However, systematic fractionation was not possible, as the units had surprisingly unpredictable M _M filtration profiles. Hence, labeling implying M _M selectivity of centrifugal filters shouldn’t be taken literally. One filter combination (100+50K) however appeared to reduce human serum albumin (HSA) compared with much of the proteome (assessed using gel electrophoresis and staining). However, for our target protein beta-catenin, a “dilute-and-shoot” approach (without any attempt to remove high abundant proteins) was what enabled identification of beta-catenin in blood with nano liquid chromatography mass spectrometry (nano-LC-MS). Thus, minimal sample preparation can be an option in targeted blood proteomics. All blood samples prepared and analyzed (using ultrafast nano-LC-MS) were of considerable complexity, and we document the importance of using external standard spiking and minimum three MS/MS transitions to confirm the presence of target proteins.