Identification of human calculi with time‐of‐flight secondary ion mass spectrometry

Time‐of‐flight secondary ion mass spectrometry was used to study four human calculi and to compare the results with those from twelve commercially available urinary calculi minerals including three organic compounds (L‐cystine, uric acid and sodium urate). Phase identification of calcium phosphate compounds was carried out by considering the relative ion abundances of [Ca₂O]⁺ and [CaPO₂]⁺. Deprotonated [M–H]^? and protonated [M+H]⁺ uric acid were detected and used for component recognition in pure uric acid and in the mixed samples of struvite, calcium oxalate and uric acid. Iodine related to the medical history of a patient was also detected. Copyright © 2009 John Wiley & Sons, Ltd.     

Detecting changes in arabidopsis cell wall composition using time‐of‐flight secondary ion mass spectrometry

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) was previously used to characterize lignocellulosic materials, including woody biomass. ToF‐SIMS can acquire both rapid spectral and spatial information about a sample's surface composition. In the present study, ToF‐SIMS was used to characterize the cell walls of stem tissue from the plant model organism, Arabidopsis thaliana. Using principal component analyses, ToF‐SIMS spectra from A. thaliana wild‐type (Col‐0), cellulose mutant (irx3), and lignin mutant (fah1) stem tissues were distinguished using ToF‐SIMS peaks annotated for wood‐derived lignocellulose, where spectra from the irx3 and fah1 were characterized by comparatively low polysaccharide and syringyl lignin content, respectively. Spatial analyses using ToF‐SIMS imaging furthermore differentiated interfascicular fiber and xylem vessels based on differences in the lignin content of corresponding cell walls. These new data support the applicability of ToF‐SIMS peak annotations based on woody biomass for herbaceous plants, including model plant systems like arabidopsis. Copyright © 2015 John Wiley & Sons, Ltd.     

Pharmaceutical metabolite profiling using quadrupole/ion mobility spectrometry/time‐of‐flight mass spectrometry

The use of hybrid quadrupole ion mobility spectrometry time‐of‐flight mass spectrometry (Q/IMS/TOFMS) in the metabolite profiling of leflunomide (LEF) and acetaminophen (APAP) is presented. The IMS drift times (T_d) of the drugs and their metabolites were determined in the IMS/TOFMS experiments and correlated with their exact monoisotopic masses and other in silico generated structural properties, such as connolly molecular area (CMA), connolly solvent‐excluded volume (CSEV), principal moments of inertia along the X, Y and Z Cartesian coordinates (MI‐X, MI‐Y and MI‐Z), inverse mobility and collision cross‐section (CCS). The correlation of T_d with these parameters is presented and discussed. IMS/TOF tandem mass spectrometry experiments (MS² and MS³) were successfully performed on the N‐acetyl‐p‐benzoquinoneimine glutathione (NAPQI‐GSH) adduct derived from the in vitro microsomal metabolism of APAP. As comparison, similar experiments were also performed using hybrid triple quadrupole linear ion trap mass spectrometry (QTRAPMS) and quadrupole time‐of‐flight mass spectrometry (QTOFMS). The abilities to resolve the product ions of the metabolite within the drift tube and fragment the ion mobility resolved product ions in the transfer travelling wave‐enabled stacked ring ion guide (TWIG) demonstrated the potential applicability of the Q/IMS/TOFMS technique in pharmaceutical metabolite profiling. Copyright © 2009 John Wiley & Sons, Ltd.     

Modern MALDI time‐of‐flight mass spectrometry

This paper focuses on development of time‐of‐flight (TOF) mass spectrometry in response to the invention of matrix‐assisted laser desorption/ionization (MALDI). Before this breakthrough ionization technique for nonvolatile molecules, TOF was generally considered as a useful tool for exotic studies of ion properties but was not widely applied to analytical problems. Improved TOF instruments and software that allow the full potential power of MALDI to be applied to difficult biological applications are described. A theoretical approach to the design and optimization of MALDI‐TOF instruments for particular applications is presented. Experimental data are provided that are in excellent agreement with theoretical predictions of resolving power and mass accuracy. Data on sensitivity and dynamic range using kilohertz laser rates are also summarized. These results indicate that combinations of high‐performance MALDI‐TOF and TOF‐TOF with off‐line high‐capacity separations may ultimately provide throughput and dynamic range several orders of magnitude greater than those currently available with electrospray LC‐MS and MS‐MS. Copyright © 2009 John Wiley & Sons, Ltd.     

Cationization of dendritic macromolecule adsorbates on metals studied by time‐of‐flight secondary ion mass spectrometry

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) was utilized to study dendritic macromolecules with various architectures, such as dendrons, dendrimers and hyperbranched polyesters prepared from bis‐(hydroxymethyl)propionic acid (Bis‐MPA) and a series of hyperbranched polyethers based on 3‐ethyl‐3(hydroxymethyl)oxetane. The measurements were performed on spin‐coated thin films of the branched molecules (D) onto silicon, chemically etched copper foil and silver‐coated wafers. They showed weak signatures of molecular ions by proton capture (D + H)⁺ in the high mass range of the spectra (m/z > 400). On the contrary, cationization of the intact molecules with alkali or transition metal ions such as Na⁺, Cu⁺ or Ag⁺ was observed. High‐intensity quasi‐molecular ions (D + M)⁺ (with M = Na⁺, Cu⁺ or Ag⁺) allowed the studied polymers to be identified. The whole molecular species were observed for Bis‐MPA dendrons and dendrimers up to 3000 Da for hydroxyl or acetonide‐terminated derivatives. The success of the so‐called cationization experiments with metal substrates compared with analysis of molecular adsorbates on silicon is highlighted. The ToF‐SIMS sensitivity appeared useful to provide information about the molecular end‐groups or to highlight incomplete reaction occurring during some deprotection step of the synthesis. Only uncationized fragments of low masses were detected for the hyperbranched polyesters. This result suggested the effect of molecular asymmetry and/or flattening of the molecules on the substrates, which hampered the molecule lift‐off efficiency. Nevertheless, the hyperbranched polyethers were characterized based on the peak distribution of intensities, which allowed estimation of their molecular weight average. This work was intended to illustrate the capabilities of ToF‐SIMS to analyse dendritic polymers on surfaces. Copyright © 2003 John Wiley & Sons, Ltd.     

Chemical discrimination of multilayered paint cross sections for potential forensic applications using time‐of‐flight secondary ion mass spectrometry

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) equipped with a bismuth imaging source and an argon gas cluster ion beam (GCIB) was used to image polished cross‐sections of four automotive multilayer paint samples. Secondary ion mass spectrometry chemical imaging of the individual layers was possible after a GCIB sputter ion dose of (7 × 10¹⁵) ions/cm² was applied for the removal of polishing residue, at which point the chemical composition of the individual clear coats could be distinguished using principal components analysis. For the differentiation of the four clear coat chemistries, only four secondary ion peaks were necessary; C₂H₅O⁺ (m/z 45.04), C₉H₉NO₂⁺ (m/z 163.09), and C₁₀H₁₁NO₂⁺ (m/z 177.10) that appeared to be fragments of the carbamate‐based clear coat, and C₇H₁₁⁺ (m/z 95.09) that was strongly associated with the polyurethane‐based clear coat. Clear identification of the four paint samples based on this short peak list highlights the strength of the SIMS technique as a potential forensic approach to discriminate automotive paints and suggests that many more variables could be included in the multivariate and statistical analysis to differentiate a wider range of clear coat chemistries.     

Thermal desorption characteristics of ammonium nitrate and potassium perchlorate inorganic salts using particle mapping time‐of‐flight secondary ion mass spectrometry

To help optimize ion mobility spectrometry (IMS) for the detection of inorganic explosives, time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) was used to study the thermal desorption behavior of ammonium nitrate (NH₄NO₃) and potassium perchlorate (KClO₄) particles on surface. This was carried out by ToF‐SIMS chemical imaging analysis to identify the change in the number of particles and their size before and after exposure to desorption temperatures of 150, 200, 250, 300, 350 and 400 °C for durations of 3, 6, 9 and 12 s. It was found that particles less than 7.2 µm in diameter contributed to more than 50% of both the number and mass of the particles desorbed from the surface. Combining ToF‐SIMS particle mapping with the vapor collection experiment revealed that the technique could be used also to determine the optimum desorption temperatures of explosive particles; this was found to be approximately 200 and 300 °C for NH₄NO₃ and KClO₄ particles, respectively. Although work remains to validate this number for KClO₄, experiments using variable desorption temperature IMS suggest the optimum temperature of NH₄NO₃ desorption to be approximately 200 °C. Published 2016. This article is a U.S. Government work and is in the public domain in the USA     

Photodegradation of poly(ether sulphone) Part 1. A time‐of‐flight secondary ion mass spectrometry study

An extensive study of the surface chemical changes to poly(ether sulphone) (PES) ultrafiltration membranes is made for the first time by the use of time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) after photoirradiation at 254 nm with irradiances varying from 10 to 300 mJ cm^?2 in a nitrogen atmosphere. Complementary information is provided by analysis with x‐ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR). The versatility, superior specificity and sensitivity of using ToF‐SIMS to investigate degradation phenomena are highlighted. The combined results demonstrate that photoirradiation causes a number of chemical changes to the surface: incorporation of oxygen; degradation of the benzene rings and formation of oxidized carbon species; depletion of carbon; reduction of ? SO₂? to some extent; formation of ? OH, C?O and ? SO₃H groups; and probable formation of ? C₆H₄? O? C₆H₅ end‐groups. In addition, no ? OSO₃H groups are formed and no formation of SO₂ is detected. Also, it is shown that chain scission dominates below an irradiation dose of ～200 mJ cm^?2 (at 254 nm in a nitrogen atmosphere). At higher doses, cross‐linking becomes dominant. Copyright © 2004 John Wiley & Sons, Ltd.     

Evaluation and validation of an ion mobility quadrupole time‐of‐flight mass spectrometry pesticide screening approach

An ion mobility quadrupole time‐of‐flight mass spectrometry‐based pesticide suspect screening methodology was developed and validated covering 20 plant‐derived food matrices deriving from six commodity groups of different complexity according to the actual European Commission document SANTE/11813/2017 applying a QuEChERS sample preparation protocol. The method combines ultra‐performance liquid chromatography, traveling wave ion mobility, and quadrupole time‐of‐flight mass spectrometry. Besides the determination of the physicochemical property collision cross‐section and the establishment of a corresponding scientific suspect screening database comprising 280 pesticides for several pesticides, different protomers, sodium adducts, as well as dimers were identified in ion mobility spectrometry traces. Additionally, collision cross‐section values were included in the validation requirements regarding chromatography and mass spectrometry for the detection of pesticides. A collision cross‐section value window was analyzed within a tolerable error of ±2%. For this cross‐matrix validation, screening detection limits were determined at concentration levels of 0.100 mg/kg (84% of the original pesticide scope), 0.010 mg/kg (56%), and 0.001 mg/kg (21%). By application of ion mobility spectrometry, the compound identification was improved due to independence of commodity of concern and concentration levels of analyte molecules, as false assignments are reduced by application of a collision cross‐section range.     

Optimization of a quadrupole ion storage trap as a source for time‐of‐flight mass spectrometry

Designs of a quadrupole ion trap (QIT) as a source for time‐of‐flight (TOF) mass spectrometry are evaluated for mass resolution, ion trapping, and laser activation of trapped ions. Comparisons are made with the standard hyperbolic electrode ion trap geometry for TOF mass analysis in both linear and reflectron modes. A parallel‐plate design for the QIT is found to give significantly improved TOF mass spectrometer performance. Effects of ion temperature, trapped ion cloud size, mass, and extraction field on mass resolution are investigated in detail by simulation of the TOF peak profiles. Mass resolution (m/Δm) values of several thousand are predicted even at room temperature with moderate extraction fields for the optimized design. The optimized design also allows larger radial ion collection size compared with the hyperbolic ion trap, without compromising the mass resolution. The proposed design of the QIT also improves the ion–laser interaction volume and photon collection efficiency for fluorescence measurements on trapped ions. Copyright © 2011 John Wiley & Sons, Ltd.     

Liquid chromatography time‐of‐flight mass spectrometry evaluation of fungicides reactivity in free chlorine containing water samples

Liquid chromatography (LC) combined with tandem mass spectrometry (MS/MS), based on the use of a hybrid quadrupole‐time‐of‐flight mass analyzer, was used to investigate the reactivity of nine fungicides in free chlorine‐containing water samples. Three of the selected compounds (fenhexamid, FEN; pyrimethanil, PYR; and cyprodinil, CYP) displayed a poor stability in presence of moderate chlorine levels; thus, the effects of different parameters on their half‐lives (t_1/2) were evaluated. Sample pH, bromide traces, and the water matrix affected their relative stabilities. Despite such variations, the three fungicides are degraded at significant rates not only in ultrapure, but also in surface water spiked with chlorine levels up to 2 µg ml^?1, and when mixed with chlorinated tap water, generating several transformation products (TPs). The time‐course of precursor species and their TPs was followed in the LC‐MS mode, using the information contained in accurate, full scan mass spectra (MS) to propose the empirical formulae of TPs. Thereafter, their ion product scan (MS/MS) spectra were considered to set their chemical structures; allowing, in some cases, to distinguish between isomeric TPs. The reaction pathway of FEN, the less stable fungicide, involved just an electrophilic substitution of hydrogen per chlorine, or bromine, and cleavage of the molecule to render an amide. PYR and CYP shared common reaction routes consisting of halogenation, hydroxylation, and condensation processes leading to complex mixtures of TPs, which were relatively stable to further transformations. Copyright © 2013 John Wiley & Sons, Ltd.