J. A. Stone

Queen's University, Kingston, Ontario, Canada

Are you J. A. Stone?

Claim your profile

Publications (15)21.67 Total impact

  • International Journal of Mass Spectrometry. 01/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: A paper spray ion source was combined with a drift tube operating at ambient pressure for mobility measurements of ions derived from pharmaceutical solutions. Paper spray ionization with solvent alone resulted in a mixture of ions convolved to a single peak with a reduced mobility of 2.19cm2/Vs in the mobility spectrum. These were mass-identified principally as m/z 157, (MeOH)2(HCOOH)2H+ and m/z 129, (MeOH)4(H2O)H+ while pharmaceuticals with nitrogen bases formed MH+ product ions. The duration of response was governed by the volume of liquid added to the paper source and was limited by evaporation of solvent in gas at 58°C venting the drift tube. Quantitative variation was attributed in part to morphologic changes in the tip of the paper spray source. This was associated with mass flow in the electrical discharge and not due alone to cycles of wetting and drying of the paper. Mobility spectra of chlorpromazine in urine, exhibited a single product ion peak and linear response was 30 to 500ng with an estimated limit of detection of 1.5ng. Ion flux could be prolonged by continuous addition of liquid and findings portend a combination of paper spray ionization IMS with paper chromatography. KeywordsPaper spray ionization–Ion mobility spectrometry–Morphology–Evaporation rate–Memory effect
    International Journal for Ion Mobility Spectrometry 09/2011; 14(2):51-59.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A planar differential mobility spectrometer has been used to study the ions formed at atmospheric pressure by a series of n-alkyl carboxylic acid esters (M). MH+ and M2H+ ions were present at low temperature. The combination of thermal energy and energy derived from collisional heating by acceleration in the asymmetric electric field caused ion decomposition at an effective temperature (Teff) higher than ambient. The products were the protonated carboxylic acids, F+. The electric field thresholds for the first observation of F+ decreased as the temperature of the supporting gas atmosphere was increased and the rate, 1.5°C per Townsend, was the same for all the esters. A measurable mass dependence for thresholds existed where the higher the molar mass for the ester of a given acid, the higher the required field. Although MH+ is the well-established precursor of the protonated acid, an apparent direct formation of F+ from M2H+ was observed even though no MH+ was present in the spectrum. This is ascribed to Teff being mass dependent. A field sufficient to raise a M2H+ to Teff for dissociation to MH++M, raises MH+ to a higher Teff, leading to its immediate decomposition.
    International Journal of Mass Spectrometry - INT J MASS SPECTROM. 01/2011; 303(2):181-190.
  • Source
    G.A Eiceman, E.G Nazarov, J.A Stone
    [Show abstract] [Hide abstract]
    ABSTRACT: Positive ion mobility spectra for three compounds (2,4-dimethylpyridine (2,4-DMP, commonly called 2,4-lutidine), dimethyl methylphosphonate (DMMP) and 2,6-di-t-butyl pyridine (2,6-DtBP)) have been studied in air at ambient pressure over the temperature range 37–250 °C with (H2O)nH+ as the reactant ion. All three compounds yield a protonated molecule but only 2,4-dimethylpyridine and dimethyl methylphosphonate produced proton-bound dimers. The reduced mobilities (K0) of protonated molecules for 2,4-dimethylpyridine and DMMP increase significantly with increasing temperature over the whole temperature range indicating changes in ion composition or interactions; however, K0 for the protonated molecule of 2,6-di-t-butyl pyridine was almost invariant with temperature. The K0 values for the proton-bound dimers of 2,4-dimethylpyridine and DMMP also showed little dependence on temperature, but could be obtained only over an experimentally smaller and lower temperature range and at elevated concentrations. Chemical standards will be helpful as mobility spectra from laboratories worldwide are compared with increased precision and 2,6-di-t-butyl pyridine may be a suitable compound for use in standardizing reduced mobilities. The effect of thermal expansion of the drift tube length on the calculation of reduced mobilities is emphasized.
    Analytica Chimica Acta 01/2010; · 4.39 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ion mobility spectra for a series of mono-substituted toluenes and a series of mono-substituted anilines were obtained using three different methods of atmospheric pressure ionization including photoionization, chemical ionization from a (63)Ni source, and chemical ionization from a corona discharge source. The product ion peak intensities were measured as functions of analyte concentration at 323 K in a purified air atmosphere. Two, and sometimes three, product ion peaks were observed in spectra from chemical ionization with the (63)Ni source and it is suggested that the major peak, due to the protonated molecule, arose in both series by proton transfer from H3O+(H2O)n. The second peak with diminished intensity and longer drift time than the protonated molecule can be seen with the toluenes and was understood to be the NO+ adduct, formed from the reactant ion NO+(H2O)n. Electron transfer from the anilines to the latter ion yields the molecular ions, identified by having the same reduced mobility coefficients as the molecular ions produced by photoionization. The structure of these product ions was determined by investigations using the coupling of ion mobility spectrometry with atmospheric pressure photoionization and mass spectrometry (APPI-IMS-MS). The relative abundances of both the NO+ adducts with the toluenes and the molecular ions with the anilines are enhanced with a corona discharge source where relatively more NO+(H2O)n is produced than in a (63)Ni source. Ab initio calculations show that only the protonated anilines of all the product ions are significantly hydrated with 1 ppm(v) of moisture in the supporting atmosphere of the ion mobility spectrometer.
    Talanta 07/2009; 78(4-5):1464-75. · 3.50 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Mixtures of n-alkanethiols, in solution with equi-molar amounts from 0.5 to 360ng per compound, were determined using gas chromatography (GC) with a differential mobility spectrometer, operated with a flow of air at ambient pressure, as the GC detector. A homologous series of n-alkanethiols with carbon number from two to six showed baseline resolution in the GC separation and positive and negative ion chromatograms were produced simultaneously for the alkanethiols. Differential mobility spectra showed compensation voltages characteristic of each alkanethiol and plots of ion intensity, retention time, and compensation voltage yield contour plots illustrating the second dimension of analytical selectivity provided by the detector. Another yet undeveloped dimension of analytical information was found in the dependence of mobility coefficients on electric field. Mass-analysis of ions from thiols showed a hydrogen abstracted ion, protonated monomers, and proton bound dimers. Linear ranges were narrow and the minimum detectable limits were ~1ng. Response in positive polarity provided a ten-fold improvement in detection limits though spectra were more complex than for negative ions. In a methane-rich air atmosphere, intended to simulate ambient air or the detection of leaks from natural gas pipelines, the response to thiols with negative ions was not degraded by the methane up to 50% v/v, the highest level tested.
    International Journal for Ion Mobility Spectrometry 01/2009; 12(3):81-90.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Protonated ammonia and hydrazines (MH(+)) form complexes with ketones and the differences in masses and mobilities of the resulting ions, MH(+)(ketone)(n), are sufficient for separation in an ion mobility spectrometer at ambient pressure. The highest mass ion for any of the protonated molecules is obtained when the ketone is present at elevated concentrations in the supporting atmosphere of both the source and drift regions of the spectrometer so that an ion maintains a discrete composition and mobility. The sizes of the ion-molecule complexes were found to depend on the number of H atoms on the protonated nitrogen atom--four for ammonia, three for hydrazine, two for monomethylhydrazine, and one for 1,1-dimethylhydrazine, and the drift times of these ions were proportional to the size of the ion-molecule complex. Unexpected side products, including protonated hydrazones and azines, and associated ketone clusters, were isolated to a single drift tube containing ceramic parts and could not, from CID studies, be attributed to gas-phase ion chemistry. These findings illustrate that mobility resolution of ions in IMS and IMS/MS experiments can be enhanced through chemical modification of the supporting gas atmosphere without changes in the core ion.
    Journal of the American Society for Mass Spectrometry 06/2007; 18(5):940-51. · 3.59 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The rate constants for the dissociations, A2H+ → AH+ + A, of the symmetrical proton bound dimers of 2,4-dimethylpyridine and dimethyl methylphosphonate have been determined using an ion mobility spectrometer operating with air as drift gas at ambient pressure. Reaction time was varied by varying the drift electric field. The rate constants were derived from the mobility spectra by determining the rate at which ions decomposed in the drift region. Arrhenius plots with a drift gas containing water vapor at 5 ppmv gave the following activation energies and pre-exponential factors: 2,4-dimethylpyridine, 94 ± 2 kJ mol−1, log A (s−1) = 15.9 ± 0.4; dimethyl methylphosphonate, 127 ± 3 kJ mol−1, log A (s−1) = 15.6 ± 0.3. The enthalpy changes for the decompositions calculated from the activation energies are in accord with literature values for symmetrical proton bound dimers of oxygen and nitrogen bases. The results for dimethyl methylphosphonate were obtained over the temperature range 478–497 K and are practically independent of water concentration (5–2000 ppmv). The activation energy for 2,4-dimethylpyridine, obtained over the temperature range 340–359 K, decreased to 31 kJ mol−1 in the presence of 2.0 × 103 ppmv of water. At the low temperature, a displacement reaction involving water may account for the decrease. The reduced mobilities of the protonated molecules and the proton bound dimers have been determined over a wide temperature range. While the values for the dimers are essentially independent of the water concentration in the drift gas, those of the protonated molecules show a strong dependence.
    International Journal of Mass Spectrometry. 09/2006;
  • H. Borsdorf, J.A. Stone, G.A. Eiceman
    [Show abstract] [Hide abstract]
    ABSTRACT: The ionization pathways and drift behavior were determined for sets of constitutional isomeric and stereoisomeric non-polar hydrocarbons (unsaturated monocyclic terpenes, unsaturated and saturated bicyclic terpenes) using ion mobility spectrometry (IMS) with different techniques of atmospheric pressure chemical ionization (APCI) to assess how structural and stereochemical differences influence ion formation. Depending on the structural features, different ions were observed for constitutional isomers using ion mobility spectrometry with photoionization (PI) and corona discharge (CD) ionization. Photoionization provides ion mobility spectra containing one major peak for saturated compounds while at two peaks were observed for unsaturated compounds, which can be assigned to product ions related to monomer and dimer ions. However, differences in relative abundance of product ions were found depending on the position of the double bond. Although IMS using corona discharge ionization permits the most sensitive detection of non-polar hydrocarbons, the spectra are complex and differ from those obtained using photoionization. Additional cluster ions and fragment ions were detected. Only small differences in ion mobility spectra were observed for the diastereomers while the enantiomers provide identical spectra. The structure of the product ions formed was checked by investigations using the coupling of ion mobility spectrometry with mass spectrometry (IMS–MS).
    International Journal of Mass Spectrometry. 01/2005;
  • G A Eiceman, J A Stone
    Analytical Chemistry 12/2004; 76(21):390A-397A. · 5.82 Impact Factor
  • G. A. Eiceman, J. A. Stone
    Analytical Chemistry - ANAL CHEM. 10/2004; 76(21).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The electric field dependence of the mobilities of gas-phase protonated monomers [(MH+(H2O)n] and proton-bound dimers [M2H+(H2O)n] of organophosphorus compounds was determined at E/N values between 0 and 140 Td at ambient pressure in air with moisture between 0.1 and 15 000 ppm. Field dependence was described as alpha (E/N) and was obtained from the measurements of compensation voltage versus field amplitude in a planar high-field asymmetric waveform ion mobility spectrometer. The alpha function for protonated monomers to 140 Td was constant from 0.1 to 10 ppm moisture in air with onset of effect at approximately 50 ppm. The value of alpha increased 2-fold from 100 to 1000 ppm at all E/N values. At moisture values between 1000 and 10 000 ppm, a 2-fold or more increase in alpha (E/N) was observed. In a model proposed here, field dependence for mobility through changes in collision cross sections is governed by the degree of solvation of the protonated molecule by neutral molecules. The process of ion declustering at high E/N values was consistent with the kinetics of ion-neutral collisional periods, and the duty cycle of the waveform applied to the drift tube. Water was the principal neutral above 50 ppm moisture in air, and nitrogen was proposed as the principal neutral below 50 ppm.
    The Journal of Physical Chemistry A 06/2003; 107(19):3648-54. · 2.77 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Mobility spectra for positive ions, created from a 63Ni foil in purified air at ambient pressure (660 Torr) with 0.15 ppm moisture, were obtained with a drift tube with a discrete drift ring design at 250 °C as electric fields for components were individually and independently varied. Peak area, peak width, baseline intensity, drift times, and reduced mobilities (Ko) were used to measure the function and performance of each component and findings were interpreted using a model for the transport of thermalized ions in weak electric fields at ambient pressure. Transit times and intensities for ions in drift tubes at ambient pressure can be understood through a detailed knowledge of the fields local to a component and derivations from theory of ion transport. Prolonged ion residence in the drift region resulted in ion transformations even for highly purified gases of low moisture at high temperature. These findings suggest that mobility spectra may be obtained with uniformly high quality and reproducibility only under conditions when ion residence time is the primary point of reference in obtaining spectra. Other regions of the drift tube were optimized and newly observed chemistry occurred in the aperture to detector region. The sampling of ions by such an ion shutter was found to inherently bias the ion distributions and alter actual lengths of drift regions. Consequently, drift lengths measured from physical configurations of drift tubes will be inadequate for precise measurements of drift times. These studies establish baseline measurements for evaluating drift tubes that should be generally applicable for optimizing performance in other drift tubes with discrete drift ring designs. Also, these results demonstrate that precise measurements in ion mobility spectrometry (IMS) will require attention to detail not heretofore carefully regarded in modern analytical IMS. © 2001 American Institute of Physics.
    Review of Scientific Instruments 08/2001; 72(9):3610-3621. · 1.60 Impact Factor
  • R G Ewing, G A Eiceman, J A Stone
    [Show abstract] [Hide abstract]
    ABSTRACT: Gaseous oxygen and nitrogen bases, both singly and as binary mixtures, have been introduced into ion mobility spectrometers to study the appearance of protonated molecules, and proton-bound dimers and trimers. At ambient temperature it was possible to simultaneously observe, following the introduction of molecule A, comparable intensities of peaks ascribable to the reactant ion (H2O)nH+, the protonated molecule AH+ and AH+ H2O, and the symmetrical proton bound dimer A2H+. Mass spectral identification confirmed the identifications and also showed that the majority of the protonated molecules were hydrated and that the proton-bound dimers were hydrated to a much lesser extent. No significant peaks ascribable to proton-bound trimers were obtained no matter how high the sample concentration. Binary mixtures containing molecules A and B, in some cases gave not only the peaks unique to the individual compounds but also peaks due to asymmetrical proton bound dimers AHB+. Such ions were always present in the spectra of mixtures of oxygen bases but were not observed for several mixtures of oxygen and nitrogen bases. The dimers, which were not observable, notable for their low hydrogen bond strengths, must have decomposed in their passage from the ion source to the detector, i.e. in a time less than approximately 5 ms. When the temperature was lowered to -20 degrees C, trimers, both homogeneous and mixed, were observed with mixtures of alcohols. The importance of hydrogen bond energy, and hence operating temperature, in determining the degree of solvation of the ions that will be observed in an ion mobility spectrometer is stressed. The possibility is discussed that a displacement reaction involving ambient water plays a role in the dissociation.
    International Journal of Mass Spectrometry and Ion Processes 11/1999; 193(1):57-68.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A tandem ion mobility spectrometer with two sequential differential mobility spectrometry (DMS) drift tubes and with detectors at ambient pressure is described and modes of operation are demonstrated. Separate but coordinated electronic control for each drift tube allows several modes of operation including: all ions passing; compensation voltage (CV) scanning; and ion selection over a narrow CV range. Any of these modes can be applied to each drift tube allowing several combinations of analytical measurements, analogous to tandem mass spectrometry, with ions entered into a gas atmosphere containing reagents between the mobility regions. Ions may be changed by cluster or displacement reactions and characterized in the second DMS analyzer. Proton bound dimers of compounds appearing near 0 V CV in DMS1 were isolated in DMS1, introduced into 1 % isopropanol vapors, and resolved at characteristic CV values in the DMS2. This is achieved with analyzer dimensions little greater than a single DMS instrument.
    International Journal for Ion Mobility Spectrometry 15(3).

Publication Stats

168 Citations
21.67 Total Impact Points

Institutions

  • 1999–2014
    • Queen's University
      • Department of Chemistry
      Kingston, Ontario, Canada
  • 2001–2011
    • Queens University of Charlotte
      • Chemistry
      New York, United States
  • 1999–2011
    • New Mexico State University
      • Department of Chemistry and Biochemistry
      Las Cruces, New Mexico, United States
  • 2009
    • Helmholtz-Zentrum für Umweltforschung
      • Department Monitoring- und Erkundungstechnologien
      Leipzig, Saxony, Germany