List of FacultyMass SpectrometryGeneral Laboratory Information Expansion of the Department of Chemistry Mass Spectrometry Laboratory began in 1998 to better support research activities of faculty within the Chemistry Department and throughout the University of Virginia. The Laboratory is located in room 157 of the Chemistry Building, McCormick Road. Contact Information Laboratory Director: |
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Overview
Samples are analyzed on a fee-for-service basis. At present, a number of ionization methods are available, including: atmospheric pressure chemical ionization (APCI); methane chemical ionization (CI); electrospray ionization (ESI); electron impact ionization (EI). All analyses are performed at unit resolution. A detailed description of current instrumentation is given below. Instruments scheduled for future installation include matrix assisted laser desorption ionization (MALDI) and secondary ion mass spectrometry (SIMS).
Sample Submission
A sample submission table and request forms are located across the hall from the lab. Samples may be submitted in solution or crystalline forms. For samples submitted in solution form, use the minimum solvent required to dissolve the analyte. Note that any unused sample is returned to the submission table after completion of analysis. The Mass Spectrometry Laboratory cannot effectively dispose of the wide range of compounds submitted for analysis; as a result, the submitter must remove any remaining sample when data is retrieved. Special sample submission requirements (dry ice, oxygen-free, etc.) are the responsibility of the submitter; these issues must be addressed by laboratory personnel prior to sample submission.
When submitting samples, please take care to provide as much information as possible on the submission sheet. The requested information is vital to ensure that your samples are analyzed properly. When calculating the analyte mass, please use the most abundant, mono-isotopic mass for the constituent elements. This is particularly important for compounds containing elements with two or more abundant isotopes (e.g., Br, Cl, and a wide range of transition metals). Please see www.shef.ac.uk/chemistry/chemputer (select "Isotope Patterns") for an easy-to-use mass calculator. In addition, if the sample consists of positive and negative counter-ions, please list the mass of each in the space provided.
Sample quantity requirements are given below with descriptions of available ionization modes. Results are generally provided within 24 hours, but of course turnaround time increases when multiple analyses are required.
Mass Spectrometers
Finnigan
(Model LCQ Classic) quadrupole ion trap mass spectrometer. This instrument
has an upper mass-to-charge (m/z) limit of 2000, and can be configured
with either atmospheric pressure chemical ionization (APCI) or electrospray
ionization (ESI) interfaces. APCI generally produces [M+H]+ and [M-H]-
molecular ions (where M is the neutral analyte mass) in positive and negative
ion modes respectively. ESI is particularly amenable to biological samples
(proteins, peptides, etc.) and will produce [M+zH]z+ and [M-zH]z- species
(where z = 1,2,3…) in positive and negative ion modes respectively.
Note that the mass spectrometer measures mass-to-charge ratios (m/z), such
that an ion of neutral mass 998 which picks up 2 protons during electrospray
ionization (z = 2) will show a mass-to-charge ratio (m/z) of 500. Generally
speaking, sample injections with a concentration range of 0.5 - 50 nanogram/microliter
(10 microliters total injected volume) provide satisfactory results for
both ESI and APCI analyses.
Finnigan (Model Voyager) gas chromatograph single quadrupole mass spectrometer. The upper mass-to-charge (m/z) limit of this mass analyzer is 1000, but the practical limit is determined by the GC column. Larger analytes (> 500) and/or those with polar functional groups, may irreversibly bind to the GC column. This instrument is configured for electron impact (EI) and methane chemical ionization (CI). Electron impact ionization (EI) produces radical cations [M· ]+ in addition to fragment ions which may be useful for structural elucidation. Methane chemical ionization (CI) will produce mostly [M+H]+ and [M-H]- in positive and negative ion modes respectively. Typically, sample injections of 0.01 - 1 nanogram (in 1-10 microliters total injected volume) produce satisfactory results.
Future mass spectrometers. Several other mass spectrometers are in the laboratory and efforts are underway to make these available for sample analysis. A matrix-assisted laser desorption ionization (MALDI) time-of-flight mass spectrometer (Finnigan Model Vision 2000) is being installed and should be available for sample analysis in the near future. In addition, two triple quadrupole mass spectrometers (Finnigan Models TSQ 700 and 7000) are scheduled for installation in the coming months. These instruments will be fitted with ionization sources to complement those already present in the laboratory. Additional information will be provided as installation nears completion.