Mass Measurement Errors Research Articles

Damage detection in ship hull by structural parameters estimation based on wavelet transform data

ABSTRACT This paper develops a structural model updating method in the time-scale domain based on the wavelet transform of the correlation function and seeks its implementation for damage detection of the ship hull. The quasi-exact sensitivity equation based on the wavelet transform coefficients are used to identify the damage as well as to overcome the drawbacks of incomplete data measurement. Different types of mother wavelets have been studied to select the best wavelet to identify structural damages. The abilities of the method is numerically examined through several damage cases. The robustness of the method against mass measurement and modeling errors is evaluated numerically using Monte Carlo analysis and error-contaminated data. This method proves to be strong against both types of errors for detecting of the damage in shell structures.

Accuracy of Smart Scales on Weight and Body Composition: Observational Study

BackgroundSmart scales are increasingly used at home by patients to monitor their body weight and body composition, but scale accuracy has not often been documented.ObjectiveThe goal of the research was to determine the accuracy of 3 commercially available smart scales for weight and body composition compared with dual x-ray absorptiometry (DEXA) as the gold standard.MethodsWe designed a cross-sectional study in consecutive patients evaluated for DEXA in a physiology unit in a tertiary hospital in France. There were no exclusion criteria except patient declining to participate. Patients were weighed with one smart scale immediately after DEXA. Three scales were compared (scale 1: Body Partner [Téfal], scale 2: DietPack [Terraillon], and scale 3: Body Cardio [Nokia Withings]). We determined absolute error between the gold standard values obtained from DEXA and the smart scales for body mass, fat mass, and lean mass.ResultsThe sample for analysis included 53, 52, and 48 patients for each of the 3 tested smart scales, respectively. The median absolute error for body weight was 0.3 kg (interquartile range [IQR] –0.1, 0.7), 0 kg (IQR –0.4, 0.3), and 0.25 kg (IQR –0.10, 0.52), respectively. For fat mass, absolute errors were –2.2 kg (IQR –5.8, 1.3), –4.4 kg (IQR –6.6, 0), and –3.7 kg (IQR –8.0, 0.28), respectively. For muscular mass, absolute errors were –2.2 kg (IQR –5.8, 1.3), –4.4 kg (IQR –6.6, 0), and –3.65 kg (IQR –8.03, 0.28), respectively. Factors associated with fat mass measurement error were weight for scales 1 and 2 (P=.03 and P<.001, respectively), BMI for scales 1 and 2 (P=.034 and P<.001, respectively), body fat for scale 1 (P<.001), and muscular and bone mass for scale 2 (P<.001 for both). Factors associated with muscular mass error were weight and BMI for scale 1 (P<.001 and P=.004, respectively), body fat for scales 1 and 2 (P<.001 for both), and muscular and bone mass for scale 2 (P<.001 and P=.002, respectively).ConclusionsSmart scales are not accurate for body composition and should not replace DEXA in patient care.Trial RegistrationClinicalTrials.gov NCT03803098; https://clinicaltrials.gov/ct2/show/NCT03803098

МЕТОДИКА РОЗРАХУНКУ ПАРАМЕТРІВ НАПРУЖЕНО-ДЕФОРМОВАНОГО СТАНУ ПЛИТ КРАНОВИХ ВАГ

The article shows that the improvement of technological processes of metallurgical production, which aims to improve the quality of metal structures, increase the yield of suitable product, stabilize its parameters, is not possible without a balanced accounting system of raw materials, semi-finished products and other cargo in all areas. In the conditions of fast-moving processes of mass continuous production with an extensive network of cargo flows, electronic-tensometric weighing complexes are becoming more and more common, which make it possible to fully automate the process of technological weighing, ensuring documented registration of its results, increasing the objectivity of weight information. The analysis of design features of lifting mechanisms of cranes became the basis for the development of proposals for the installation of the load-receiving unit of crane scales for automatic determination of the mass of liquid cast iron in the pouring-bucket section of the foundry shop. Based on the developed methodology and calculations of the parameters of the pressure base plates of the load-receiving unit, recommendations for optimizing the design of the plates, locations and number of sensors are issued. The data obtained as a result of the calculations and experimental studies confirm the validity of the hypothesis, which was the basis of the method of calculating the slab of the load-receiving unit, which was that the calculation of slabs in the form of a beam on two hinged supports in the same plane does not reproduce the real process of slab bending in the space that passes as a result of the loading of the load-receiving unit in the built-in crane scales. The aim of the work is to develop a new method for calculating the load bearing plates of crane scales, thanks to which it will be possible to determine the parameters of the stress-strain state of the load bearing plate under the influence of the main types of mechanical loads that affect the design of the weighing device in operation, which will lead to a decrease in the mass measurement error and thereby will optimize the cost of related materials in foundry technology and improve the quality of the final product.

Digital ion trap mass analysis of high mass protein complexes using IR activation coupled with ion/ion reactions

Native mass spectrometry (MS) focuses on measuring the masses of large biomolecular complexes and probing their structures. Large biomolecular complexes are readily introduced into mass spectrometers as gas-phase ions using electrospray ionization (ESI); however, the ions tend to be heavily adducted with solvent and salts, which leads to mass measurement errors. Various solution clean-up approaches can reduce the degree of adduction prior to introduction to the mass spectrometer. Gas-phase activation of trapped ions can provide additional adduct reduction, and charge reduction ion/ion reactions increase charge state separation. Together, gas-phase activation and charge reduction can combine to yield spectra of well separated charge states for improved mass measurements. A simple gas-phase collisional activation technique is to apply a dipolar DC (DDC) field to opposing electrodes in an ion trap. DDC activation loses its efficacy when ions are trapped at low q values, which is true of the high m/z ions generated by charge reduction ion/ion reactions. Digital ion trapping (DIT) readily traps high m/z ions at higher q values by varying trapping frequency rather than amplitude, but the low frequencies used to trap high m/z ions also decreases the efficacy of DDC activation. We demonstrate here using ions derived from GroEL that IR activation of ions shows no discrimination against high m/z ions trapped with DIT, because they can be focused equally well to the trap center to interact with the IR laser beam. Following pump out of excess background gas, IR activation can also induce efficient dissociation of the GroEL complex. This work demonstrates that IR activation is an effective approach for ion heating in native MS over the unusually wide range of charge states accessible via gas-phase ion/ion reactions.

High-Performance Molecular Imaging with MALDI Trapped Ion-Mobility Time-of-Flight (timsTOF) Mass Spectrometry.

Imaging mass spectrometry (IMS) enables the spatially targeted molecular assessment of biological tissues at cellular resolutions. New developments and technologies are essential for uncovering the molecular drivers of native physiological function and disease. Instrumentation must maximize spatial resolution, throughput, sensitivity, and specificity, because tissue imaging experiments consist of thousands to millions of pixels. Here, we report the development and application of a matrix-assisted laser desorption/ionization (MALDI) trapped ion-mobility spectrometry (TIMS) imaging platform. This prototype MALDI timsTOF instrument is capable of 10 μm spatial resolutions and 20 pixels/s throughput molecular imaging. The MALDI source utilizes a Bruker SmartBeam 3-D laser system that can generate a square burn pattern of <10 × 10 μm at the sample surface. General image performance was assessed using murine kidney and brain tissues and demonstrate that high-spatial-resolution imaging data can be generated rapidly with mass measurement errors <5 ppm and ∼40 000 resolving power. Initial TIMS-based imaging experiments were performed on whole-body mouse pup tissue demonstrating the separation of closely isobaric [PC(32:0) + Na]+ and [PC(34:3) + H]+ (3 mDa mass difference) in the gas phase. We have shown that the MALDI timsTOF platform can maintain reasonable data acquisition rates (>2 pixels/s) while providing the specificity necessary to differentiate components in complex mixtures of lipid adducts. The combination of high-spatial-resolution and throughput imaging capabilities with high-performance TIMS separations provides a uniquely tunable platform to address many challenges associated with advanced molecular imaging applications.

Combating selective ionization in the high resolution mass spectral characterization of complex mixtures.

Direct "dilute and shoot" mass spectral analysis of complex naturally-occurring mixtures has become the "standard" analysis in environmental and petrochemical science, as well as in many other areas of research. Despite recent advances in ionization methods, that approach still suffers several limitations for the comprehensive characterization of compositionally complex matrices. Foremost, the selective ionization of highly acidic (negative electrospray ionization ((-) ESI)) and/or basic (positive electrospray ionization ((+) ESI)) species limits the detection of weakly acidic/basic species, and similar issues (matrix effects) complicate atmospheric pressure photo-ionization (APPI)/atmospheric pressure chemical ionization (APCI) analyses. Furthermore, given the wide range of chemical functionalities and structural motifs in these compositionally complex mixtures, aggregation can similarly limit the observed species to a small (10-20%) mass fraction of the whole sample. Finally, irrespective of the ionization method, the mass analyzer must be capable of resolving tens-of-thousands of mass spectral peaks and provide the mass accuracy (typically 50-300 ppb mass measurement error) required for elemental composition assignment, and thus is generally limited to high-field Fourier transform ion cyclotron mass spectrometry (FT-ICR MS). Here, we describe three approaches to combat the above issues for (+) ESI, (-) ESI, and (+) APPI FT-ICR MS analysis of petroleum samples. Each approach relies on chromatographic fractionation to help reduce selective ionization discrimination and target either specific chemical functionalities (pyridinic and pyrrolic species (nitrogen) or carboxylic acids (oxygen)) or specific structural motifs (single aromatic core (island) or multi-core aromatics (archipelago)) known to be related to ionization efficiency. Each fractionation method yields a 2-10-fold increase in the compositional coverage, exposes species that are undetectable using direct "dilute and shoot" analysis, and provides coarse selectivity in chemical functionalities that can both increase the assignment confidence and optimize ionization conditions to maximize compositional coverage.

A family of metric gravities

.The goal of this paper is to take a completely fresh approach to metric gravity, in which the metric principle is strictly adhered to but its properties in local space-time are derived from conservation principles, not inferred from a global field equation. The global field strength variation then gains some flexibility, but only in the regime of very strong fields (2nd-order terms) whose measurement is now being contemplated. So doing provides a family of similar gravities, differing only in strong fields, which could be developed into meaningful verification targets for strong fields after the manner in which far-field variations were used in the 20th century. General Relativity (GR) is shown to be a member of the family and this is demonstrated by deriving the Schwarzschild metric exactly from a suitable field strength assumption. The method of doing so is interesting in itself because it involves only one differential equation rather than the usual four. Exact static symmetric field solutions are also given for one pedagogical alternative based on potential, and one theoretical alternative based on inertia, and the prospects of experimentally differentiating these are analyzed. Whether the method overturns the conventional wisdom that GR is the only metric theory of gravity and that alternatives must introduce additional interactions and fields is somewhat semantical, depending on whether one views the field strength assumption as a field and whether the assumption that produces GR is considered unique in some way. It is of course possible to have other fields, and the local space-time principle can be applied to field gravities which usually are weak-field approximations having only time dilation, giving them the spatial factor and promoting them to full metric theories. Though usually pedagogical, some of them are interesting from a quantum gravity perspective. Cases are noted where mass measurement errors, or distributions of dark matter, can cause one theory to mimic another implying that such estimates or distributions should be first obtained from weak-field measurements before being used to discriminate verification candidates. By this method theorists gain insight into the local constraints on space-time, and GR verification gains strong-field comparative objectives.

A generalized flexibility matrix-based model updating method for damage detection of plane truss and frame structures

Nowadays, many non-destructive damage detection methods for determining the location and severity of damage in the field of health monitoring are considered in order to reduce the cost of maintenance and improve safety and reliability of structure. In this paper, damage specification is obtained by sensitivity-based updating approach. By applying changes on sensitivity matrix and using measured flexibility data, it is concluded that the results of proposed method are more accurate and efficient than the old modal flexibility methods. The mass modeling error and measurement error of flexibility and natural frequency are calculated in order to ensure the accuracy and robustness of proposed method for 2-D finite element truss and frame model. Close index, measuring the performance of the method, and the coefficient of variation, which represents the distribution of response, are used. Compared with Wang method, the proposed method is capable of accurately localizing and quantifying damage in all scenarios.

An Empirical Mass Function Distribution

Abstract The halo mass function, encoding the comoving number density of dark matter halos of a given mass, plays a key role in understanding the formation and evolution of galaxies. As such, it is a key goal of current and future deep optical surveys to constrain the mass function down to mass scales that typically host galaxies. Motivated by the proven accuracy of Press–Schechter-type mass functions, we introduce a related but purely empirical form consistent with standard formulae to better than 4% in the medium-mass regime, . In particular, our form consists of four parameters, each of which has a simple interpretation, and can be directly related to parameters of the galaxy distribution, such as . Using this form within a hierarchical Bayesian likelihood model, we show how individual mass-measurement errors can be successfully included in a typical analysis, while accounting for Eddington bias. We apply our form to a question of survey design in the context of a semi-realistic data model, illustrating how it can be used to obtain optimal balance between survey depth and angular coverage for constraints on mass function parameters. Open-source Python and R codes to apply our new form are provided at http://mrpy.readthedocs.org and https://cran.r-project.org/web/packages/tggd/index.html respectively.

Black hole mass function from gravitational wave measurements

We examine how future gravitational-wave measurements from merging black holes (BHs) can be used to infer the shape of the black-hole mass function, with important implications for the study of star formation and evolution and the properties of binary BHs. We model the mass function as a power law, inherited from the stellar initial mass function, and introduce lower and upper mass cutoff parametrizations in order to probe the minimum and maximum BH masses allowed by stellar evolution, respectively. We initially focus on the heavier BH in each binary, to minimize model dependence. Taking into account the experimental noise, the mass measurement errors and the uncertainty in the redshift dependence of the merger rate, we show that the mass function parameters, as well as the total rate of merger events, can be measured to $&lt;10%$ accuracy within a few years of advanced LIGO observations at its design sensitivity. This can be used to address important open questions such as the upper limit on the stellar mass which allows for BH formation and to confirm or refute the currently observed mass gap between neutron stars and BHs. In order to glean information on the progenitors of the merging BH binaries, we then advocate the study of the two-dimensional mass distribution to constrain parameters that describe the two-body system, such as the mass ratio between the two BHs, in addition to the merger rate and mass function parameters. We argue that several years of data collection can efficiently probe models of binary formation, and show, as an example, that the hypothesis that some gravitational-wave events may involve primordial black holes can be tested. Finally, we point out that in order to maximize the constraining power of the data, it may be worthwhile to lower the signal-to-noise threshold imposed on each candidate event and amass a larger statistical ensemble of BH mergers.

THE VELOCITY DISTRIBUTION FUNCTION OF GALAXY CLUSTERS AS A COSMOLOGICAL PROBE

ABSTRACT We present a new approach for quantifying the abundance of galaxy clusters and constraining cosmological parameters using dynamical measurements. In the standard method, galaxy line-of-sight velocities, v, or velocity dispersions are used to infer cluster masses, M, to quantify the halo mass function (HMF), , which is strongly affected by mass measurement errors. In our new method, the probability distributions of velocities for each cluster in the sample are summed to create a new statistic called the velocity distribution function (VDF), . The VDF can be measured more directly and precisely than the HMF and can be robustly predicted with cosmological simulations that capture the dynamics of subhalos or galaxies. We apply these two methods to realistic (ideal) mock cluster catalogs with (without) interlopers and forecast the bias and constraints on the matter density parameter Ω m and the amplitude of matter fluctuations σ 8 in flat ΛCDM cosmologies. For an example observation of 200 massive clusters, the VDF with (without) interloping galaxies constrains the parameter combination and shows only minor bias. However, the HMF with interlopers is biased to low Ω m and high σ 8 and the fiducial model lies well outside of the forecast constraints, prior to accounting for Eddington bias. When the VDF is combined with constraints from the cosmic microwave background, the degeneracy between cosmological parameters can be significantly reduced. Upcoming spectroscopic surveys that probe larger volumes and fainter magnitudes will provide clusters for applying the VDF as a cosmological probe.

Left Ventricular Hypertrophy in Asymptomatic Nonsevere Aortic Stenosis

Increased biomechanical stress on cardiomyocytes because of outflow obstruction secondary to aortic stenosis (AS) is thought to induce reexpression of the fetal gene program, which modifies myocyte efficiency, sarcomere composition, and regulation of extracellular matrix, as well as various nuclear signal transduction pathways resulting in autocrine production and secretion of cytokines, neurohormones and growth factors that ultimately promote ventricular hypertrophy.1,2 See Article by Gerdts et al The traditional view of adaptative concentric left ventricular hypertrophy (LVH) because of parallel replication of new sarcomeres is that wall thickness increases to normalize LV systolic wall stress and preserve systolic performance. This view, accepted for the past 40 years3 and perhaps counterintuitively expected to mitigate the effects of LV pressure overload on cardiovascular morbidity and mortality, has begun to be challenged by new clinical data, suggesting that moderate or severe LVH may be associated with adverse outcomes in AS4,5 and that inappropriately increased LV mass, found in 17% of patients with mild to moderate AS6 and in 67% of patients with asymptomatic severe AS, was associated with a 4.5-fold increased risk of cardiovascular events.7 Conversely, the absence of hypertrophy in one third of the patients with severe AS seems to have no adverse effects on systolic function or survival.8,9 Experimental studies in genetically modified animal models are consistent with clinical observations.10 In addition, no association was found between AS severity and the magnitude or pattern of LVH using cardiac magnetic resonance.11 Thus, it seems that the presence, severity, and the geometric pattern of LVH in AS vary widely, are …

Scientific workflow optimization for improved peptide and protein identification.

BackgroundPeptide-spectrum matching is a common step in most data processing workflows for mass spectrometry-based proteomics. Many algorithms and software packages, both free and commercial, have been developed to address this task. However, these algorithms typically require the user to select instrument- and sample-dependent parameters, such as mass measurement error tolerances and number of missed enzymatic cleavages. In order to select the best algorithm and parameter set for a particular dataset, in-depth knowledge about the data as well as the algorithms themselves is needed. Most researchers therefore tend to use default parameters, which are not necessarily optimal.ResultsWe have applied a new optimization framework for the Taverna scientific workflow management system (http://ms-utils.org/Taverna_Optimization.pdf) to find the best combination of parameters for a given scientific workflow to perform peptide-spectrum matching. The optimizations themselves are non-trivial, as demonstrated by several phenomena that can be observed when allowing for larger mass measurement errors in sequence database searches. On-the-fly parameter optimization embedded in scientific workflow management systems enables experts and non-experts alike to extract the maximum amount of information from the data. The same workflows could be used for exploring the parameter space and compare algorithms, not only for peptide-spectrum matching, but also for other tasks, such as retention time prediction.ConclusionUsing the optimization framework, we were able to learn about how the data was acquired as well as the explored algorithms. We observed a phenomenon identifying many ammonia-loss b-ion spectra as peptides with N-terminal pyroglutamate and a large precursor mass measurement error. These insights could only be gained with the extension of the common range for the mass measurement error tolerance parameters explored by the optimization framework.

Correcting systematic bias and instrument measurement drift with mzRefinery.

Motivation: Systematic bias in mass measurement adversely affects data quality and negates the advantages of high precision instruments.Results: We introduce the mzRefinery tool for calibration of mass spectrometry data files. Using confident peptide spectrum matches, three different calibration methods are explored and the optimal transform function is chosen. After calibration, systematic bias is removed and the mass measurement errors are centered at 0 ppm. Because it is part of the ProteoWizard package, mzRefinery can read and write a wide variety of file formats.Availability and implementation: The mzRefinery tool is part of msConvert, available with the ProteoWizard open source package at http://proteowizard.sourceforge.net/Contact: samuel.payne@pnnl.govSupplementary information: Supplementary data are available at Bioinformatics online.

Simultaneous detection and identification of precursors, degradation and co-products of chemical warfare agents in drinking water by ultra-high performance liquid chromatography–quadrupole time-of-flight mass spectrometry

Environmental markers of chemical warfare agents (CWAs) comprise millions of chemical structures. The simultaneous detection and identification of these environmental markers poses difficulty due to their diverse chemical properties. In this work, by using ultra-high performance liquid chromatography–quadrupole time-of-flight mass spectrometry (UHPLC–QTOF), a generic analytical method for the detection and identification of wide range of environmental markers of CWAs (including precursors, degradation and co-products of nerve agents and sesqui-mustards) in drinking water, was developed. The chromatographic analysis of 55 environmental markers of CWAs including isomeric and isobaric compounds was accomplished within 20min, using 1.8μm particle size column. Subsequent identification of the compounds was achieved by the accurate mass measurement of either protonated molecule [M+H]+ or ammonium adduct [M+NH4]+ and fragment ions. Isomeric and isobaric compounds were distinguished by chromatographic retention time, characteristic fragment ions generated by both in-source collision induced dissociation (CID) and CID in the collision cell by MS/MS experiments. The exact mass measurement errors for all ions were observed less than 3ppm with internal calibration. The method limits of detection (LODs) and limits of quantification (LOQs) were determined in drinking water and found to be 1–50ngmL−1 and 5–125ngmL−1, respectively. Applicability of the proposed method was proved by determining the environmental markers of CWAs in aqueous samples provided by Organization for the Prohibition of Chemical Weapons during 34th official proficiency test.

Constructing a mass measurement error surface to improve automatic annotations in liquid chromatography/mass spectrometry based metabolomics

Estimation of mass measurement accuracy is an elementary step in the application of mass spectroscopy (MS) data towards metabolite annotations and has been addressed several times in the past. However, the reproducibility of mass measurements over a diverse set of analytes and in variable operating conditions, which are common in high-throughput metabolomics studies, has, to the best of our knowledge, not been addressed so far. A method to automatically extract mass measurement errors from a large data set of measurements made on a quadrupole time-of-flight (QTOF) MS instrument has been developed. The size of the data processed in this study has enabled us to use a statistical data driven approach to build a model which reliably predicts the confidence interval of the absolute mass measurement error based on individual ion peak conditions in a fast, high-throughput manner. We show that our model predictions are reproducible in external datasets generated in similar, but not identical conditions, and have demonstrated the advantage of our approach over the common practice of fixed mass measurement error limits. Outlined is an approach which can promote a more rational use of MS technology by automatically evaluating the absolute mass measurement error based on the individual peak conditions. The immediate application of our method is integration in high-throughput peak annotation pipelines for database searches.

Simultaneous determination of 10 unapproved sedative drugs in feeds by ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry

A new analytical method using ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS) was developed for screening and confirmation of 10 unapproved sedative drugs in feeds. The samples were extracted using the solution of methanol-0.1 mol/L HCl (9:1, v/v), and the extracts were centrifuged and then directly purified through MCX cartridges. The identification and detection were achieved in positive electrospray ionization (ESI) mode using Q-TOF-MS. The potential of UPLC-Q-TOF MS for confirmatory analysis was shown by determining the accurate mass of all the compounds and fragment ions upon collision-induced-dissociation (CID) at different energies. The extra mass measurement errors for all the sedative drugs were found to be within 5 ppm. The calibration graphs were linear in the concentration range of 5-100 microg/L with the correlation coefficients more than 0.99 for the 10 drugs. The limits of quantification (LOQ, S/N = 10) were 8 microg/kg for nitrazepam, zolpidem and thioridazine; 10 microg/kg for thriazolam, estazolam, diazepam, promethazine, chlorpromazine and midazolam; 20 microg/kg for clozapine. The recoveries for all the compounds in feeds were 60.6%-108.5% with the relative standard deviations less than 10% at the spiked levels of LOQ, 2LOQ and 4LOQ.

Use of theoretical peptide distributions in phosphoproteome analysis.

The high mass accuracy and resolution of modern mass spectrometers provides new opportunities to employ theoretical peptide distributions in large-scale proteomic studies. We used theoretical distributions to study noise filtering and mass measurement errors and to examine mass-based differentiation of phosphorylated and nonphosphorylated peptides. Only the monoisotopic mass of the experimental precursor ion was necessary for this analysis. We found that peak deviations can be used to characterize the modification states of peptides in a sample. When applied to large-scale proteomic data sets, the peak deviation distribution can be used to filter chemical/electronic noise for singly charged species. Using peak deviation distributions, it is possible to separate the phosphorylated peptides from the nonphosphorylated peptides, enabling evaluation of the phosphoproteome content of a sample. Because this approach is simple, with light computational requirements, the analysis of theoretical peptide distributions has a significant potential for application to phosphoproteome analyses. For our studies we used publicly available data sets from three large-scale proteomic studies.

Identification of New Apolipoprotein-CIII Glycoforms with Ultrahigh Resolution MALDI-FTICR Mass Spectrometry of Human Sera

Apolipoprotein-CIII (apoCIII) is an abundant blood glycoprotein associated with lipoprotein particles. Three different glycoforms have been described, all containing a mucin-type core-1 O-glycosylation with either zero, one or two sialic acids. Changes in the relative abundance of these glycoforms have been observed in a variety of different pathologies. In this study, ultrahigh resolution 15T MALDI Fourier transform ion cyclotron resonance (FTICR) MS was used to analyze apoCIII isoforms in serum protein profiles. For this purpose, serum proteins were purified using both a fully automated RPC18-based magnetic bead method and an RPC4 cartridge-based solid phase extraction method. Six new apoCIII isoforms were identified with low-ppm mass measurement errors and ultrahigh precision. These were characterized by more complex glycan moieties that are fucosylated instead of sialylated. To confirm the glycan moiety and localize the glycosylation site, top-down ESI-FTICR-MS/MS and bottom-up LC-ion trap MS/MS were used. A large variation in the presence and abundance of the fucosylated isoforms was found in a set of 96 serum samples. These findings of fucosylated apolipoprotein-CIII isoforms warrant further research to elucidate the implications these glycoforms may have for the plethora of studies where alterations in apoCIII have been linked to the development of many different pathologies.

Simultaneous determination of 12 β-agonists in feeds by ultra-high-performance liquid chromatography–quadrupole-time-of-flight mass spectrometry

A new analysis method using ultra-performance liquid chromatography (UPLC)–quadrupole-time-of-flight mass spectrometry (Q/TOF MS) was developed for screening and confirmation of 12 β-agonists in feeds. Under the optimized gradient elution conditions, it takes only 6min to separate all 12 β-agonists, and the critical pair of Ractopamine and Isoxsuprine isomers was almost completely separated. Based on the over 10,000 full-width at half maximum (FWHM) mass resolution and high mass accuracy features of TOF MS with 20mDa mass window, accurate mass chromatograms were reconstructed for individual compounds. The fragmentation pathways of 12 β-agonists were also studied using Q-TOF MS. The potential of UPLC–Q/TOF MS for confirmatory analysis was shown by determining the accurate mass of all compounds and fragment ions upon collision-induced-dissociation (CID) at different energies. The extra mass measurement errors for all β-agonists were found to be within 5ppm. The limits of detection (LODs) and limits of quantitation (LOQs) were determined for all β-agonists in feeds and found to be 1–5ng/mL and 5–50μg/kg, respectively. The method of UPLC–Q/TOF MS developed in this study was initially applied to the research of feeds for analysis of 12 β-agonists and proved to be accurate, sensitive, convenient and practical.