Scott T. Quarmby

University of Florida, Gainesville, Florida, United States

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Publications (2)5.83 Total impact

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    ABSTRACT: A novel and practical technique for performing both parent and neutral loss (P&NL) monitoring experiments on a quadrupole ion trap mass spectrometer is presented. This technique is capable of performing scans analogous to the parent and neutral loss scans routinely applied on tandem-in-space instruments and allows for the screening of a sample to detect analytes of a specific compound class on a chromatographic time-scale. Acylcarnitines were chosen as the model compound class to demonstrate the analytical utility of P&NL monitoring because of their amenability to electrospray ionization (ESI), their unique and informative MS/MS fragmentation pattern, and their importance in biological functions. The [M + H]+ ions of all acylcarnitines dissociate to produce neutral losses of 59 and 161 amu and common product ions at m/z 60, 85, and 144. Both the neutral loss monitoring of 59 amu and the parent ion monitoring of m/z 85 are shown to be capable of identifying acylcarnitine [M + H]+ ions in a synthetic mixture and spiked pig plasma. The neutral loss monitoring of 59 amu is successful in detecting acylcarnitines in an unspiked pig plasma sample.
    Analytical Chemistry 12/2002; 74(22):5799-806. DOI:10.1021/ac026073d · 5.83 Impact Factor
  • Scott T. Quarmby, Richard A. Yost
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    ABSTRACT: The quadrupole ion trap is a highly versatile and sensitive analytical mass spectrometer. Because of the advantages offered by the ion trap, there has been intense interest in coupling it to ionization techniques such as electrospray which form ions externally to the ion trap. In this work, simulation and experiment were employed to study the injection of electrosprayed ions into the quadrupole ion trap in a Finnigan MAT LCQ LC/MSn mass spectrometer. SIMION v6.0 was chosen for the simulation studies because it allowed the actual ion trap electrode geometry including endcap holes to be simulated. The endcap holes weaken the rf trapping field in the region near the holes; this distortion of the field is important when ions have large axial excursions as they do in ion injection. In addition, the field penetrates out the endcap holes and affects ions as they approach the ion trap. The results of simulating ions started outside the ion trap agreed well with experimentally obtained ion injection data of the effect of qz during injection. From these simulations, a model for the process by which injected ions are trapped was developed. Injected ions can be trapped even with the modest helium buffer gas pressures commonly used (≈1 mTorr) because ions naturally oscillate for long times (and therefore distances) at certain qz values and initial rf phases. This allows enough collisions to occur to damp the ions’ excess kinetic energy.

Publication Stats

24 Citations
5.83 Total Impact Points

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  • 2002
    • University of Florida
      • Department of Chemistry
      Gainesville, Florida, United States