Analytical Coverage Research Articles

42.3 METABOLOMICS APPROACHES TO STUDY METABOLIC CO-MORBIDITIES IN PSYCHOTIC DISORDERS

BackgroundPsychotic patients are at high risk for developing obesity, metabolic syndrome and type 2 diabetes. These metabolic co-morbidities are hypothesized to be related to both treatment side-effects as well as to metabolic changes occurring during the psychosis. Earlier metabolomics studies have shown that blood metabolite levels are predictive of insulin resistance and type 2 diabetes in the general population as well as sensitive to the effects of antipsychotics. Here we aimed to identify the metabolite profiles predicting future weight gain and other metabolic abnormalities in psychotic patients.MethodsWe applied metabolomics to investigate serum metabolite profiles in a prospective study setting in 36 first-episode psychosis patients during the first year of the antipsychotic treatment and 19 controls. Two analytical platforms with broad analytical coverage were used. Molecular lipids were analysed by ultra-high performance liquid chromatography coupled to time-of-flight mass spectrometry (UHPLC_QTOFMS) and polar metabolites were analysed by two-dimensional gas chromatography coupled to TOFMS (GCxGC-TOFMS). Ongoing prospective metabolomics studies ae focusing on the subjects in at-risk mental state.ResultsWhile corroborating several earlier findings when comparing cases and controls and the effects of the antipsychotic medication, we also found that prospective weight gain in psychotic patients was associated with increased levels of triacylglycerols with low carbon number and double-bond count at baseline and independent of obesity, that is, lipids known to be associated with increased liver fat.DiscussionThe first-episode psychotic patients who rapidly gain weight in the follow-up have early metabolic disturbances which are associated with insulin resistance and fatty liver. Our studies suggest that metabolite profiles may be used to identify the psychotic patients most vulnerable to develop metabolic co-morbidities, and may point to a pharmacological approach to counteract the antipsychotic-induced weight gain.

Use of dielectric barrier discharge ionization to minimize matrix effects and expand coverage in pesticide residue analysis by liquid chromatography-mass spectrometry

Although electrospray ionization (ESI) remains the gold standard ionization source for LC-MS, it exhibits two main limitations: the occurrence of matrix effects and the limited ionization coverage towards nonpolar compounds. Dielectric barrier discharge ionization (DBDI) has gained attraction in recent years as a versatile ionization method in different applications and formats. Here, we report a thorough evaluation of DBDI as ionization interface for LC-MS, which reveals attractive advantages over ESI and atmospheric pressure chemical ionization (APCI) provided its singular ionization mechanism versatility. A suite of 80 pesticides across a wide range of physicochemical properties were selected and the results were compared with both ESI and APCI sources. Using a helium plasma operated in homogeneous regime with square-wave AC waveform and relatively low voltages (2.5 kV), not only DBDI was able to ionize compounds only amenable so far by GC-MS (eg. organochlorine species), but also offered a competitive performance in terms of sensitivity when contrasted with the commercial electrospray ionization source under equivalent conditions. Unlike ESI, DBDI mechanism occurs in the gas-phase, so the method is less affected by liquid-phase surface phenomena that yield ion suppression in ESI. Data collected in the positive ion mode revealed negligible matrix effect values (<10% suppression) for most of the studied compounds in different complex matrix extracts such as wastewater, orange or olive oil. This is also consistent with the absence of adduct formation whereas with ESI source, Na adduct formation is quite common with these species. In general, both sensitivity and average limits of quantitation for DBDI were similar to those obtained by ESI and better than APCI. Results showed that analyte coverage with DBDI is enhanced with respect to ESI and APCI sources being able to effectively analyze organochlorine compounds.

Sailing and Sailing Rigs in the Ancient Mediterranean: implications of continuity, variation and change in propulsion technology

Ships and boats form the foundations of the maritime connectivity that is a central part of our understanding of the ancient Mediterranean. While the general chronological sequence of sail and sailing-rig development is well established, the implications are less-well discussed. This article sets out how sails and sailing rigs developed in antiquity, with emphasis on the Greco-Roman world. Subsequently, instances of innovation are defined. Why specific pieces of maritime technology were, or were not, widely adopted is considered. Long-term technological continuity can be comprehended, and a shared maritime culture of sailing in the ancient Mediterranean is suggested.

MALDI MS Guided Liquid Microjunction Extraction for Capillary Electrophoresis-Electrospray Ionization MS Analysis of Single Pancreatic Islet Cells.

The ability to characterize chemical heterogeneity in biological structures is essential to understanding cellular-level function in both healthy and diseased states, but these variations remain difficult to assess using a single analytical technique. While mass spectrometry (MS) provides sufficient sensitivity to measure many analytes from volume-limited samples, each type of mass spectrometric analysis uncovers only a portion of the complete chemical profile of a single cell. Matrix-assisted laser desorption/ionization (MALDI) MS and capillary electrophoresis electrospray ionization (CE–ESI)-MS are complementary analytical platforms frequently utilized for single-cell analysis. Optically guided MALDI MS provides a high-throughput assessment of lipid and peptide content for large populations of cells, but is typically nonquantitative and fails to detect many low-mass metabolites because of MALDI matrix interferences. CE–ESI-MS allows quantitative measurements of cellular metabolites and increased analyte coverage, but has lower throughput because the electrophoretic separation is relatively slow. In this work, the figures of merit for each technique are combined via an off-line method that interfaces the two MS systems with a custom liquid microjunction surface sampling probe. The probe is mounted on an xyz translational stage, providing 90.6 ± 0.6% analyte removal efficiency with a spatial targeting accuracy of 42.8 ± 2.3 μm. The analyte extraction footprint is an elliptical area with a major diameter of 422 ± 21 μm and minor diameter of 335 ± 27 μm. To validate the approach, single rat pancreatic islet cells were rapidly analyzed with optically guided MALDI MS to classify each cell into established cell types by their peptide content. After MALDI MS analysis, a majority of the analyte remains for follow-up measurements to extend the overall chemical coverage. Optically guided MALDI MS was used to identify individual pancreatic islet α and β cells, which were then targeted for liquid microjunction extraction. Extracts from single α and β cells were analyzed with CE–ESI-MS to obtain qualitative information on metabolites, including amino acids. Matching the molecular masses and relative migration times of the extracted analytes and related standards allowed identification of several amino acids. Interestingly, dopamine was consistently detected in both cell types. The results demonstrate the successful interface of optical microscopy-guided MALDI MS and CE–ESI-MS for sequential chemical profiling of individual, mammalian cells.

Development of a HS-SPME-GC/MS protocol assisted by chemometric tools to study herbivore-induced volatiles in Myrcia splendens

A headspace solid phase microextraction (HS-SPME) method combined with gas chromatography-mass spectrometry (GC/MS) was developed and optimized for extraction and analysis of volatile organic compounds (VOC) of leaves and galls of Myrcia splendens. Through a process of optimization of main factors affecting HS-SPME efficiency, the coating divivnilbenzene-carboxen-polydimethylsiloxane (DVB/Car/PDMS) was chosen as the optimum extraction phase, not only in terms of extraction efficiency, but also for its broader analyte coverage. Optimum extraction temperature was 30°C, while an extraction time of 15min provided the best compromise between extraction efficiencies of lower and higher molecular weight compounds. The optimized protocol was demonstrated to be capable of sampling plant material with high reproducibility, considering that most classes of analytes met the 20% RSD FDA criterion. The optimized method was employed for the analysis of three classes of M. splendens samples, generating a final list of 65 tentatively identified VOC, including alcohols, aldehydes, esters, ketones, phenol derivatives, as well as mono and sesquiterpenes. Significant differences were evident amongst the volatile profiles obtained from non-galled leaves (NGL) and leaf-folding galls (LFG) of M. splendens. Several differences pertaining to amounts of alcohols and aldehydes were detected between samples, particularly regarding quantities of green leaf volatiles (GLV). Alcohols represented about 14% of compounds detected in gall samples, whereas in non-galled samples, alcohol content was below 5%. Phenolic derived compounds were virtually absent in reference samples, while in non-galled leaves and galls their content ranged around 0.2% and 0.4%, respectively. Likewise, methyl salicylate, a well-known signal of plant distress, amounted for 1.2% of the sample content of galls, whereas it was only present in trace levels in reference samples. Chemometric analysis based on Heatmap associated with Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) provided a suitable tool to differentiate VOC profiles in vegetal material, and could open new perspectives and opportunities in agricultural and ecological studies for the detection and identification of herbivore-induced plant VOC emissions.

The New Russian Nationalism: Imperialism, Ethnicity and Authoritarianism 2000-2015

This useful and timely volume covers the growth of Russian nationalism from 2000 to 2015. It was in the process of completion during the annexation of Crimea in March 2014 and thus most of the chapters refer largely to events prior to that date, with some analytical coverage of how Russian nationalism has shaped public opinion of the annexation and subsequent Eastern Ukrainian conflict. It is thoroughly researched and yet accessible to the general reader, though with a few minor issues. Read here.

Inside-out and outside-in: Applying the concept of conventions in the analysis of policy implementation through sport clubs

The aim of this article is to enrich theoretically the analysis of processes of policy implementation through sport clubs. Subsequent to reviewing previous theoretical contributions on this topic, we make the case that available conceptualizations are marked by an inside-out perspective and that they conceptually and empirically stop short at the end implementer, i.e. the sport club. Consequently, analyses of policy implementation through sport clubs have not taken into account the fact that sport clubs are distinctly local phenomena. As such, past, current and potential future participants, volunteers and local inter-organizational relationships are found in a sport club’s local community. Because of this, there is a need for a concept that provides analytical coverage of an outside-in perspective, i.e. a concept that takes into account outside actors’ conceptions of the implementing sport club and the impact their views have on the implementation process. In relation to this need, we propose the application of the concept ‘convention’. In addition to describing the concept, we exemplify the methodological and analytical implications of its use in sport policy implementation analysis.

Analytical Coverage Probability Framework and Spectrum Sharing Prohibition Zone in Heterogeneous Cellular Networks with Sectored-FFR

Analytical Coverage Probability Framework and Spectrum Sharing Prohibition Zone in Heterogeneous Cellular Networks with Sectored-FFR

Black phosphorus-assisted laser desorption ionization mass spectrometry for the determination of low-molecular-weight compounds in biofluids.

Quantitative analysis of small molecules by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been a challenging task due to matrix-derived interferences in low m/z region and poor reproducibility of MS signal response. In this study, we developed an approach by applying black phosphorus (BP) as a matrix-assisted laser desorption ionization (MALDI) matrix for the quantitative analysis of small molecules for the first time. Black phosphorus-assisted laser desorption/ionization mass spectrometry (BP/ALDI-MS) showed clear background and exhibited superior detection sensitivity toward quaternary ammonium compounds compared to carbon-based materials. By combining stable isotope labeling (SIL) strategy with BP/ALDI-MS (SIL-BP/ALDI-MS), a variety of analytes labeled with quaternary ammonium group were sensitively detected. Moreover, the isotope-labeled forms of analytes also served as internal standards, which broadened the analyte coverage of BP/ALDI-MS and improved the reproducibility of MS signals. Based on these advantages, a reliable method for quantitative analysis of aldehydes from complex biological samples (saliva, urine, and serum) was successfully established. Good linearities were obtained for five aldehydes in the range of 0.1-20.0μM with correlation coefficients (R (2)) larger than 0.9928. The LODs were found to be 20 to 100nM. Reproducibility of the method was obtained with intra-day and inter-day relative standard deviations (RSDs) less than 10.4%, and the recoveries in saliva samples ranged from 91.4 to 117.1%. Taken together, the proposed SIL-BP/ALDI-MS strategy has proved to be a reliable tool for quantitative analysis of aldehydes from complex samples. Graphical Abstract An approach for the determination of small molecules was developed by using black phosphorus (BP) as a matrix-assisted laser desorption ionization (MALDI) matrix.

On-Tissue Derivatization via Electrospray Deposition for Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging of Endogenous Fatty Acids in Rat Brain Tissues.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) is used for the multiplex detection and characterization of diverse analytes over a wide mass range directly from tissues. However, analyte coverage with MALDI MSI is typically limited to the more abundant compounds, which have m/z values that are distinct from MALDI matrix-related ions. On-tissue analyte derivatization addresses these issues by selectively tagging functional groups specific to a class of analytes, while simultaneously changing their molecular masses and improving their desorption and ionization efficiency. We evaluated electrospray deposition of liquid-phase derivatization agents as a means of on-tissue analyte derivatization using 2-picolylamine; we were able to detect a range of endogenous fatty acids with MALDI MSI. When compared with airbrush application, electrospray led to a 3-fold improvement in detection limits and decreased analyte delocalization. Six fatty acids were detected and visualized from rat cerebrum tissue using a MALDI MSI instrument operating in positive mode. MALDI MSI of the hippocampal area allowed targeted fatty acid analysis of the dentate gyrus granule cell layer and the CA1 pyramidal layer with a 20-μm pixel width, without degrading the localization of other lipids during liquid-phase analyte derivatization.

Analytical Coverage Probability of a Typical User In Heterogeneous Cellular Networks

In a Poisson Point Process (PPP) network model, in which the locations of Base Stations (BSs) are randomly distributed according to a Spatial Poisson Process, has been recently used as a tractable stochastic model to analyse the performance of downlink Heterogeneous Cellular Networks (HCNs). The HCN is modelled as a multi-tier cellular network where each tier is characterised by the transmission power level, propagation path loss exponent and density of BSs. The current works on HCN enabling Intercell Interference Coordination (ICIC) technique usually deal with Strict Frequency Reuse (FR) or Soft FR with a reuse factor of $\Delta=1$ in a Rayleigh fading channel. It has been assumed that all Base Stations (BSs) transmit continuously which leads to a reduction on the impact of number of users and RBs on network performance. In this paper, the performance of Soft FR with a reuse factor of $\Delta>1$ in Rayleigh-Lognormal fading channel is evaluated. The impact of the number of users and Resource Blocks (RBs) on Intercell Interference (ICI) are presented for Round Robin scheduling and indicator functions. The results show that there are opposite trends between coverage probability of Cell-Center User (CCU) and Cell-Edge User (CEU).

Capturing in Vivo Plant Metabolism by Real-Time Analysis of Low to High Molecular Weight Volatiles

We have deployed an efficient secondary electrospray ionization source coupled to an Orbitrap mass analyzer (SESI-MS) to investigate the emissions of a Begonia semperflorens. We document how hundreds of species can be tracked with an unparalleled time resolution of 2 min during day-night cycles. To further illustrate the capabilities of this system for volatile organic compounds (VOCs) analysis, we subjected the plant to mechanical damage and monitored its response. As a result, ∼1200 VOCs were monitored displaying different kinetics. To validate the soundness of our in vivo measurements, we fully characterized some key compounds via tandem mass spectrometry (MS/MS) and confirmed their expected behavior based on prior gas chromatography/mass spectrometry (GC/MS) studies. For example, β-caryophyllene, which is directly related to photosynthesis, was found to show a periodic day-night pattern with highest concentrations during the day. We conclude that the capability of SESI-MS to capture highly dynamic VOC emissions and wide analyte coverage makes it an attractive tool to complement GC/MS in plant studies.

Chess-Boxing Around the Rule of Law Polish Constitutionalism at Trial

The 2015/16 dispute over composition and organisational design of the Constitutional Court in Poland (Pol. Trybunal Konstytucyjny – Constitutional Tribunal) involved two major political parties (Law and Justice – PiS, and Civic Platform – PO) taking partisan stance and involving into political rent-seeking, though with varying revolutionary zeal and different levels of subtlety in their attempts to by-pass or outrightly trespass constitutional constraints. The article provides factual and analytical coverage of the constitutional crisis resulting from the conflict that arose around the Constitutional Tribunal. It also presents nuances of the course and dynamics of the conflict as well as its immediate run-up, including the role of the Tribunal and its justices themselves. The paper provides analytical take on the legal and political nexus underpinning and propelling the conflict, as seen against the background of the societal divide and a “tribal” nature of the split among the people of Poland with regard to their appraisal of the socio-economic order that emerged from the Round Table Talks of 1989.

Warpgroup: increased precision of metabolomic data processing by consensus integration bound analysis

Current informatic techniques for processing raw chromatography/mass spectrometry data break down under several common, non-ideal conditions. Importantly, hydrophilic liquid interaction chromatography (a key separation technology for metabolomics) produces data which are especially challenging to process. We identify three critical points of failure in current informatic workflows: compound specific drift, integration region variance, and naive missing value imputation. We implement the Warpgroup algorithm to address these challenges. Warpgroup adds peak subregion detection, consensus integration bound detection, and intelligent missing value imputation steps to the conventional informatic workflow. When compared with the conventional workflow, Warpgroup made major improvements to the processed data. The coefficient of variation for peaks detected in replicate injections of a complex Escherichia Coli extract were halved (a reduction of 19%). Integration regions across samples were much more robust. Additionally, many signals lost by the conventional workflow were 'rescued' by the Warpgroup refinement, thereby resulting in greater analyte coverage in the processed data. I: MPLEMENTATION: Warpgroup is an open source R package available on GitHub at github.com/nathaniel-mahieu/warpgroup. The package includes example data and XCMS compatibility wrappers for ease of use. Supplementary data are available at Bioinformatics online. nathaniel.mahieu@wustl.edu or gjpattij@wustl.edu.

Thermal mineralization behavior of PFOA, PFHxA, and PFOS during reactivation of granular activated carbon (GAC) in nitrogen atmosphere.

Waste disposal site is one of the important sinks of chemicals. A significant amount of perfluoroalkyl and polyfluoroalkyl substances (PFASs) such as perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and perfluorohexanoic acid (PFHxA) have been brought into it. Because of their aqueous solubility, PFASs are released to landfill effluent waters, from which PFASs are efficiently collected by adsorption technique using granular activated carbon (GAC). The exhausted GAC is reactivated by heating processes. The mineralization of PFASs during the reactivation process was studied. Being thermally treated in N2 atmosphere, the recovery rate of mineralized fluorine and PFC homologues including short-chained perfluorocarboxylic acids was determined. If the reagent form of PFOA, PFHxA, and PFOS were treated at 700°C, the recovery of mineralized fluorine was less than 30, 46, and 72%, respectively. The rate increased to 51, 74, and 70%, if PFASs were adsorbed onto GAC in advance; moreover, addition of excess sodium hydroxide (NaOH) improved the recovery to 74, 91, and 90%. Residual PFAS homologue was less than 1% of the original amount. Steamed condition did not affect destruction. The significant role of GAC was to suppress volatile release of PFASs from thermal ambient, whereas NaOH enhanced destruction and retained mineralized fluorine on the GAC surface. Comparing the recovery of mineralized fluorine, the degradability of PFOS was considered to be higher than PFOA and PFHxA. Whole mass balance missing 9~26% of initial amount suggested formation of some volatile organofluoro compounds beyond analytical coverage.

Mass Spectrometry Imaging and GC-MS Profiling of the Mammalian Peripheral Sensory-Motor Circuit.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) has evolved to become an effective discovery tool in science and clinical diagnostics. Here, chemical imaging approaches are applied to well-defined regions of the mammalian peripheral sensory-motor system, including the dorsal root ganglia (DRG) and adjacent nerves. By combining several MSI approaches, analyte coverage is increased and 195 distinct molecular features are observed. Principal component analysis suggests three chemically different regions within the sensory-motor system, with the DRG and adjacent nerve regions being the most distinct. Investigation of these regions using gas chromatography-mass spectrometry corroborate these findings and reveal important metabolic markers related to the observed differences. The heterogeneity of the structurally, physiologically, and functionally connected regions demonstrates the intricate chemical and spatial regulation of their chemical composition.

Solid-phase extraction and nanoflow liquid chromatography-nanoelectrospray ionization mass spectrometry for improved global urine metabolomics.

Global urine metabolomics is a rapidly expanding field with the potential to discover biomarkers of disease and exposure. To date, most methods focus on rapid sample preparation, using neat or diluted urine, together with high-throughput analyses, and are poorly suited for detection of low abundance metabolites present in urine samples. In this study, novel methods have been developed to analyze urine by splitless nanoflowUHPLC-nanoESI-TOFMS (nUHPLC-nESI-TOFMS) after preconcentration by solid-phase extraction (SPE), thus enabling significant improvements in analytical sensitivity and coverage of the urinary metabolome. In initial work, urine samples were extracted by both anion and cation exchange mixed-mode polymeric SPE cartridges and qualitatively compared with those using conventional sample preparations using UHPLC-ESI-TOFMS analyses. Compared with neat or diluted urine samples, SPE concentration of urine resulted in detection of additional metabolites including bile acids, lipids, pharmaceuticals, and markers of lifestyle, with little loss of other components of the metabolome. Analyses of SPE preparations by nUHPLC-nESI-TOFMS revealed excellent retention time repeatability with <1% coefficient of variation (CV) for 96% of analyzed peaks. The repeatability of the MS response was <30% CV for >79% of MS features in both negative and positive nESI modes. Compared with UHPLC-ESI-TOFMS, analysis by the nanoplatform enabled detection of signaling molecules important in disease processes including sex steroids, glucocorticoids, eicosanoids, and neurotransmitter metabolites. The significant improvement in sensitivity arising from use of splitless nUHPLC-nESI-TOFMS analyses of SPE-concentrated samples represents a step change in coverage of the urinary metabolome, thereby increasing the potential for biomarker discovery.

Polarimetric Plasmonic Sensing with Bowtie Nanoantenna Arrays

We propose a polarimetric plasmonic biosensor based on bowtie nanoantenna array transducers. Through numerical simulations, based on the finite element method (FEM), we study the phase retardation between the components of light polarized parallel and perpendicular to the major axis of the bowties within the arrays. From a design for high volumetric sensitivity at a wavelength of 780 nm, sensitivities ∼5 rad/RIU is obtained, corresponding to a detection limit of ∼10−7 when using a polarimetric readout platform. Similarly, surface sensitivity of the same array is evaluated by simulating the phase retardation changes induced by the coverage of bioreceptors and analytes of the metallic nanostructures.

Silver dopants for targeted and untargeted direct analysis of unsaturated lipids via infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI).

Unsaturated lipids play a crucial role in cellular processes as signaling factors, membrane building blocks or energy storage molecules. However, adequate mass spectrometry imaging of this diverse group of molecules remains challenging. In this study we implemented silver cationization for direct analysis by infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) to enhance the ion abundances for olefinic lipids and facilitate peak assignment. Trace amounts of silver nitrate were doped into the electrospray solvent of an IR-MALDESI imaging source coupled to an Orbitrap mass analyzer. Calcifediol was examined as a model compound to demonstrate the effect of silver dopants on sensitivity and assay robustness. Dried human serum spots were subsequently analyzed to compare Ag-doped solvents with previously described solvent compositions. Mass differences as well as ion abundance ratio filters were employed to interpret results based on the characteristic isotopic pattern of silver. Olefinic lipids were readily observed as silver adducts in IR-MALDESI analyses. Silver cationization decreased the limit of detection for calcifediol by at least one order of magnitude and was not affected in complex biological matrices. The ion abundance ratio and mass difference of [M + (107) Ag(+)](+) and [M + (109) Ag(+)](+) were successfully applied to facilitate the spectral assignment of silver adducts. Overall, silver cationization increased the analyte coverage in human serum by 43% compared with a standard IR-MALDESI approach. Silver cationization has been shown to enhance IR-MALDESI sensitivity and selectivity for unsaturated lipids, even when applied to complex samples. Increased compound coverage, enhanced robustness as well as the developed tools for peak assignment and mapping of isotopic patterns will clearly benefit future mass spectrometry imaging studies.

A new approach for plasma (xeno)metabolomics based on solid-phase extraction and nanoflow liquid chromatography-nanoelectrospray ionisation mass spectrometry

Current metabolite profiling methods based on liquid chromatography-mass spectrometry (LC-MS) platforms do not detect many of the components present at trace concentrations in extracts of plasma due to their low ionisation efficiency or to interference from highly abundant compounds. Nanoflow LC-nanospray MS platforms, which are commonly used in proteomics, could overcome these limitations and significantly increase analytical sensitivity and coverage of the plasma (xeno)metabolome (i.e., metabolites and xenobiotics), but require small injection volumes (<0.5μL). In this study, we developed sample preparation methods to remove ion suppressive phospholipids and concentrate remaining components of the plasma (xeno)metabolome in order to analyse sub-microliter volumes of plasma extracts for nanoflow ultra-high-performance liquid chromatography-nanoelectrospray ionisation-time-of-flight mass spectrometry (nUHPLC-nESI-TOFMS). These methods use phospholipid filtration plates in combination with polymeric or mixed mode exchange solid-phase extraction (SPE). The phospholipid filtration plates removed >94% of the predominant phospholipid/lysophospholipid species from plasma, whilst absolute recoveries of 63 selected (xeno)metabolites from spiked plasma were generally between 60 and 104%. After a further SPE step, recoveries of test compounds were between 50 and 81%. Studies revealed that both the sample preparation methodology and nUHPLC-nESI-TOFMS analyses gave acceptable repeatability. A qualitative comparison of SPE methods revealed that sample concentration by either polymer or mixed mode ion-exchange SPE gave comprehensive metabolite coverage of plasma extracts, but the use of cation exchange SPE significantly increased detection of many cationic compounds in the sample extracts. Method detection limits for steroid, eicosanoid and bile metabolites were <1.0ng/mL plasma and for pharmaceutical contaminants were between 0.01 and 30ng/mL plasma. Comparison of the phospholipid removal/cation exchange SPE and the classical protein precipitation (PPT) sample preparation methodologies revealed that both methods detected the same range of (xeno)metabolites. However, unlike PPT extracts, the SPE preparations allowed direct injection of more concentrated plasma extracts onto the nUHPLC-nESI-TOFMS platform without blockage of the nanocolumn or nanospray, thus resulting in a wider coverage of the (xeno)metabolome. This is the first work to demonstrate the significantly enhanced sensitivity arising from the use of concentrated SPE sample preparations and direct nUHPLC-nESI-TOFMS analysis for untargeted profiling of plasma samples and constitutes a step forward for identifying mixtures of chemical stressors accumulated in blood as well as the disruption of key metabolite pathways in the same sample.