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"Lock mass"

Missael Antonio Arroyo Negrete, Kazimierz Wrobel, Francisco Javier Acevedo Aguilar, Eunice Yanez Barrientos, Alma Rosa Corrales Escobosa, Katarzyna Wrobel
OBJECTIVE: The goal of this work was to set up a high throughput procedure for the determination of fatty acid methyl esters (FAMEs) in cosmetic castor oils using flow injection - electrospray ionization - high resolution mass spectrometry, and to demonstrate the need of such analysis for the quality control purposes. METHODS: The sample aliquot was mixed with isooctane:chloroform (1:1) and submitted to transesterification; the obtained FAMEs were appropriately diluted using water:isopropanol:acetonitrile (20:50:30) with addition of sodium formate which served as an internal standard, lock mass calibrant and promoted the formation of sodium adducts during electrospray ionization (ESI)...
May 9, 2018: International Journal of Cosmetic Science
Jian Wang, Daniel Leung, Willis Chow, James Chang, Jon W Wong
This paper presents a multi-class target screening method for the detection of 105 veterinary drug residues from 11 classes in milk using ultra-high performance liquid chromatography electrospray ionization quadrupole Orbitrap mass spectrometry (UHPLC/ESI Q-Orbitrap). The method is based on a non-target approach of full mass scan and multiplexing data-independent acquisition (Full MS/mDIA). The veterinary drugs include endectocides, fluoroquinolones, ionophores, macrolides, nitroimidazole, NSAIDs, β-lactams, penicillins, phenicols, sulfonamides, and tetracyclines...
February 5, 2018: Analytical and Bioanalytical Chemistry
Toshinobu Hondo, Kirk R Jensen, Jun Aoki, Michisato Toyoda
A simple, effective accurate mass assignment procedure for a time-of-flight mass spectrometer is desirable. External mass calibration using a mass calibration standard together with an internal mass reference (lock mass) is a common technique for mass assignment, however, using polynomial fitting can result in mass-dependent errors. By using the multi-turn time-of-flight mass spectrometer infiTOF-UHV, we were able to obtain multiple time-of-flight data from an ion monitored under several different numbers of laps that was then used to calculate a mass calibration equation...
December 2017: European Journal of Mass Spectrometry
Jian Wang, Willis Chow, James Chang, Jon W Wong
A semiautomated qualitative method for target screening of 448 pesticide residues in fruits and vegetables was developed and validated using ultrahigh-performance liquid chromatography coupled with electrospray ionization quadrupole Orbitrap high-resolution mass spectrometry (UHPLC/ESI Q-Orbitrap). The Q-Orbitrap Full MS/dd-MS(2) (data dependent acquisition) was used to acquire product-ion spectra of individual pesticides to build a compound database or an MS library, while its Full MS/DIA (data independent acquisition) was utilized for sample data acquisition from fruit and vegetable matrices fortified with pesticides at 10 and 100 μg/kg for target screening purpose...
January 18, 2017: Journal of Agricultural and Food Chemistry
Hajime Miyaguchi
An improved version of a polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method for genotyping toxic pufferfish species by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) is described. DNA extraction is carried out using a silica membrane-based DNA extraction kit. After the PCR amplification using a detergent-free PCR buffer, restriction enzymes are added to the solution without purifying the reaction solution. A reverse-phase silica monolith column and a Fourier transform high resolution mass spectrometer having a modified Kingdon trap analyzer are employed for separation and detection, respectively...
September 20, 2016: Journal of Visualized Experiments: JoVE
María Del Mar Contreras, Isabel Borrás-Linares, María Herranz-López, Vicente Micol, Antonio Segura-Carretero
When using the Caco-2 intestinal model, the low uptake, intracellular presence at low levels as well as generation of trace metabolites may limit the analysis of flavonoids. To overcome these limitations, we performed a simple but sensitive methodology based on nano-LC-TOF-MS, using an on-line trapping step. The analytical method was validated for quercetin, quercetin 3-O-glucoside, and quercetin 3-O-glucuronide and the reliability for characterization using lock-mass calibration was also assessed along the linear range...
April 2016: Electrophoresis
Purva Kulkarni, Filip Kaftan, Philipp Kynast, Aleš Svatoš, Sebastian Böcker
Mass spectrometry imaging (MSI) has become widely popular because of its potential to map the spatial distribution of thousands of compounds in a single measurement directly from tissue surfaces. With every MSI experiment, it is important to maintain high mass accuracy for correct identification of the observed ions. Many times this can be compromised due to different experimental factors, leading to erroneous assignment of peaks. This makes recalibration a crucial preprocessing step. We describe a lock mass-free mass spectra recalibration method, which enables to significantly reduce these mass shift effects...
October 2015: Analytical and Bioanalytical Chemistry
Qingkai Wang, Yu Chen, Lili Miao, Guobao Jiang, Shuqing Chen, Jun Liu, Xiquan Fu, Chujun Zhao, Han Zhang
Topological insulators have been theoretically predicted as promising candidates for broadband photonics devices due to its large bulk band gap states in association with the spin-momentum-locked mass-less Dirac edge/surface states. Unlike the bulk counterpart, few-layer topological insulators possess some intrinsic optical advantages, such as low optical loss, low saturation intensity and high concentration of surface state. Herein, we use a solvothermal method to prepare few-layer Bi₂Te₃ flakes. By sandwiching few-layer Bi₂Te₃ flakes with polymethyl methacrylate (PMMA) polymer, a novel light modulation device had been successfully fabricated with high chemical and thermal stabilities as well as excellent mechanical durability, originating from the contribution of PMMA acting as buffer layers that counteract excessive mechanical bending within the fragile Bi₂Te₃ flakes...
March 23, 2015: Optics Express
María del Mar Contreras, David Arráez-Román, Alberto Fernández-Gutiérrez, Antonio Segura-Carretero
A new method based on nano-liquid chromatography coupled to time-of-flight mass spectrometry (nano-LC-TOF-MS) using lock-mass calibration was developed to facilitate the accurate and routine characterization and quantification of phenolic compounds. Thus, it was applied to study cranberry syrups, in which, using negative ionization mode, a total of nine phenolic compounds were unequivocally identified using standards and 38 tentatively taking into account their retention time, accurate mass (errors<5 ppm) data and isotope pattern, as well as literature...
January 2015: Talanta
Sara Kildgaard, Maria Mansson, Ina Dosen, Andreas Klitgaard, Jens C Frisvad, Thomas O Larsen, Kristian F Nielsen
In drug discovery, reliable and fast dereplication of known compounds is essential for identification of novel bioactive compounds. Here, we show an integrated approach using ultra-high performance liquid chromatography-diode array detection-quadrupole time of flight mass spectrometry (UHPLC-DAD-QTOFMS) providing both accurate mass full-scan mass spectrometry (MS) and tandem high resolution MS (MS/HRMS) data. The methodology was demonstrated on compounds from bioactive marine-derived strains of Aspergillus, Penicillium, and Emericellopsis, including small polyketides, non-ribosomal peptides, terpenes, and meroterpenoids...
June 2014: Marine Drugs
Jian Wang, Piero R Gardinali
This study described an analytical method for the identification of common phase II pharmaceutical metabolites in reclaimed water using liquid chromatography high resolution Orbitrap mass spectrometry after solid phase extraction (SPE). Orbitrap mass spectrometer was operated at resolution of 70000 in MS mode and 35000 in data-dependent MS/MS mode, without using lock mass. Firstly, parent drugs and their metabolites were tentatively identified based on accurate mass using a mass tolerance of 5 ppm. A detailed examination of the extracted ion chromatograms (XICs) for all potential metabolites revealed the presence of two phase II metabolites of sulfamethoxazole, acetylsulfamethoxazole and sulfamethoxazole glucuronide in reclaimed water...
July 2014: Chemosphere
An Staes, Jonathan Vandenbussche, Hans Demol, Marc Goethals, Şule Yilmaz, Niels Hulstaert, Sven Degroeve, Pieter Kelchtermans, Lennart Martens, Kris Gevaert
The use of internal calibrants (the so-called lock mass approach) provides much greater accuracy in mass spectrometry based proteomics. However, the polydimethylcyclosiloxane (PCM) peaks commonly used for this purpose are quite unreliable, leading to missing calibrant peaks in spectra and correspondingly lower mass measurement accuracy. Therefore, we here introduce a universally applicable and robust internal calibrant, the tripeptide Asn3. We show that Asn3 is a substantial improvement over PCM both in terms of consistent detection and resulting mass measurement accuracy...
November 19, 2013: Analytical Chemistry
J L Kuiper, J S W Lind, H J M Groen, J Roder, J Grigorieva, H Roder, A M C Dingemans, E F Smit
BACKGROUND: The serum proteomic test VeriStrat has been shown to be able to classify advanced non-small cell lung cancer (NSCLC) patients for overall survival (OS) after treatment with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). In this study, VeriStrat was evaluated as a pre-treatment stratification tool in patients with advanced stage NSCLC for treatment with the combination of erlotinib and sorafenib, considering both OS and progression-free survival (PFS) as end points...
November 20, 2012: British Journal of Cancer
Emmie N M Ho, W H Kwok, April S Y Wong, Terence S M Wan
A recent trend in the use of high resolution accurate mass screening (HRAMS) for doping control testing in both human and animal sports has emerged due to significant improvement in high resolution mass spectrometry in terms of sensitivity, mass accuracy, mass resolution, and mass stability. A number of HRAMS methods have been reported for the detection of multi-drug residues in human or equine urine. As blood has become a common matrix for doping control analysis, especially in equine sports, a sensitive, fast and wide coverage screening method for detecting a large number of drugs in equine blood samples would be desirable...
July 2013: Drug Testing and Analysis
Chang Ho Sohn, Heather D Agnew, J Eugene Lee, Michael J Sweredoski, Robert L J Graham, Geoffrey T Smith, Sonja Hess, Gregg Czerwieniec, Joseph A Loo, James R Heath, Raymond J Deshaies, J L Beauchamp
We present novel homobifunctional amine-reactive clickable cross-linkers (CXLs) for investigation of three-dimensional protein structures and protein-protein interactions (PPIs). CXLs afford consolidated advantages not previously available in a simple cross-linker, including (1) their small size and cationic nature at physiological pH, resulting in good water solubility and cell-permeability, (2) an alkyne group for bio-orthogonal conjugation to affinity tags via the click reaction for enrichment of cross-linked peptides, (3) a nucleophilic displacement reaction involving the 1,2,3-triazole ring formed in the click reaction, yielding a lock-mass reporter ion for only clicked peptides, and (4) higher charge states of cross-linked peptides in the gas-phase for augmented electron transfer dissociation (ETD) yields...
March 20, 2012: Analytical Chemistry
Ying Zhang, Zhihui Wen, Michael P Washburn, Laurence Florens
Several methods to obtain low-ppm mass accuracy have been described. In particular, online or offline lock mass approaches can use background ions, produced by electrospray under ambient conditions, as calibrants. However, background ions such as protonated and ammoniated polydimethylcyclosiloxane ions have relatively weak and fluctuating intensity. To address this issue, we implemented dynamic offline lock mass (DOLM). Within every MS1 survey spectrum, DOLM dynamically selected the strongest n background ions for statistical treatments and m/z recalibration...
December 15, 2011: Analytical Chemistry
Jürgen Cox, Annette Michalski, Matthias Mann
Mass accuracy is a key parameter in proteomic experiments, improving specificity, and success rates of peptide identification. Advances in instrumentation now make it possible to routinely obtain high resolution data in proteomic experiments. To compensate for drifts in instrument calibration, a compound of known mass is often employed. This 'lock mass' provides an internal mass standard in every spectrum. Here we take advantage of the complexity of typical peptide mixtures in proteomics to eliminate the requirement for a physical lock mass...
August 2011: Journal of the American Society for Mass Spectrometry
Arjen Lommen, Arjen Gerssen, J Efraim Oosterink, Harrie J Kools, Ainhoa Ruiz-Aracama, Ruud J B Peters, Hans G J Mol
A strategy, detailed methodology description and software are given with which the mass accuracy of U-HPLC-Orbitrap data (resolving power 50,000 FWHM) can be enhanced by an order of magnitude to sub-ppm levels. After mass accuracy enhancement all 211 reference masses have mass errors within 0.5 ppm; only 14 of these are outside the 0.2 ppm error margin. Further demonstration of mass accuracy enhancement is shown on a pre-concentrated urine sample in which evidence for 89 (342 ions) potential hydroxylated and glucuronated DHEA-metabolites is found...
March 2011: Metabolomics: Official Journal of the Metabolomic Society
Ramón Díaz, María Ibáñez, Juan V Sancho, Félix Hernández
Hybrid quadrupole time-of-flight mass spectrometry (QTOF MS) has gained wide acceptance in many fields of chemistry, for example, proteomics, metabolomics and small molecule analysis. This has been due to the numerous technological advances made to this mass analyser in recent years. In the environmental field, the instrument has proven to be one of the most powerful approaches for the screening of organic pollutants in different matrices due to its high sensitivity in full acquisition mode and mass accuracy measurements...
January 30, 2011: Rapid Communications in Mass Spectrometry: RCM
Kimberly A Lee, Chris Farnsworth, Wen Yu, Leo E Bonilla
The positive role and application of highly accurate mass measurements in proteomics is well documented. The new generation of hybrid FTMS and Q-TOF instruments, including the LTQ-Orbitrap (OT), is remarkable in their ability to routinely produce single-digit to subppm statistical mass accuracy while maintaining high analytical sensitivity. The use of mass calibrants (lock masses) to reduce the systematic error of mass-to-charge measurements has also been reported and, in some cases, incorporated in the instrument control software by the instrument manufacturers...
February 4, 2011: Journal of Proteome Research
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