Using the Widener University VG-70 SE


Overview of instrument

General Diagram:

Source Region:

Collision Cell:

Electrostatic Analyzer:

Detector:


Power on computer, electronics, and heaters

  1. Electronics on
    1. Power on to electronics cabinet (rockerswitch on back of instrument)
    2. Power On (switch on front of console, shown below)
    3. Set the magnet energy to IB

  2. Heaters and ion gauges
    1. Set inlet reservoir and transfer line heaters.
      1. S REEN Transfer line feedthrough °200 C
      2. S RES Inlet Reservoir 200 °C (max temp achieved)
    2. Set the source temp, 200 °C for typical operation, 300 C max, gauge reads higher than setpoint
    3. Turn on Ion gauges to "Read" (switch analyzer gauge first, shown below)

  • Computer on
    1. turn on power strip (behind GC)
    2. LOGIN VG
    3. PASSWORD analysis
    4. to load opus software from menu select: applications; decterm
    5. NOTE: When entering a value in a window, always use the enter key so that value is accepted.


    Operate

    1. Electron Ionization (controls shown below)
      1. Operate, turns on electron filament & high voltage
      2. Set the electron beam energy
      3. The emission current should be ca 2 mA
      4. Set the electron multiplier, 3 to 4 kV

    2. In opus window, click on instrument icon to see settings for
      1. acceleration voltage (8 kV)
      2. electric sector voltage (8 kV)
      3. magnet (m/z to transmit, 69 is good starting point)

    3. Observe signal with scope (controls shown below)
      1. use span and mv/div to observe peak on scope
      2. set filter to 0.3
      3. use keyboard to enter approximate mass in box for the magnet in the opus instrument window
      4. use L & R arrow keys to shift settings so peak is on scope
      5. calculate resolution as: 106/span (in ppm at 5% peak height from scope)


    To load sample. (1 ul will last ca 1 hr)

    1. For solids probe Tmax = 350 °C
    2. Direct inlet reservoir
      1. The sample reservoir has 2 valves (see diagram below)
        1. Pump out reservoir open both valves (Right valve first)
        2. Run sample close right valve
        3. Open reservoir close both valves
      2. Valves are on/off, no control or needle
      3. Right side valve goes to the pump
      4. Left side valve goes to chamber


    Tune instrument

    1. Tune Source to maximize signal. adjust corse, fine, & deflect. controls are interactive.
      1. 1 is source
      2. 2 is collision cell

    2. Adjustments
      1. analyzer
        1. y, z, z1, z2, zfocus and deflect
      2. before magnet
        1. Curve 1
        2. Rotate 1
      3. after magnet
        1. Curve 2
        2. Rotate 2
      4. change slits as needed
        1. Close CCW to turn up
        2. Open CW to turn down

    3. Tune at low resolution
      1. Open up beam restrictors
        1. Open the source slit
        2. Open up collector slit so peak has flat top
        3. Open alpha slit, and z restrictors
      2. Tune for maximum intensity
      3. Close collector to obtain peak shape at ca 70% intensity and tune

    4. For high resolution
      1. Open collector to flat top
      2. Close source to ca 10% intensity (3 clicks in mV) and tune
      3. Close collector to ^ peak and tune curve, y-focus & rotation

    Calibration

    1. Experiment
      1. Set Limits
      2. For exact mass scan very slowly, suggest Time = 20 s for scan from m/z 10 to 300.
      3. For exact mass set to continuum mode.
      4. Blank out current calibration (>> Button)

    2. Inject 1 uL PFK PFK Spectrum or Table
    3. Acquire data
      1. File: Cal File Name
      2. Data: Location Data
      3. Overwrite
      4. Load
      5. Start

    4. Calibration window comes up
    5. REF, directory, select PFK
    6. Get a good PFK Scan for calibration reference, need good S/N
    7. Majority of peaks should be close
    8. Major peaks are shown in spectrum below
    9. Adjust low and High values so peaks match close to expected values
      1. Change
      2. Return
      3. Automatic
      4. Adjust location and predict values to increase number of peaks found.

    10. When adjusted Overwrite; Accept

    Acquiring High Resolution Data

    1. Experiment settings. Same as setup for calibration, any changes require recalibration.
      1. Set Limits
      2. For exact mass scan very slowly, suggest Time = 20 s
      3. For exact mass set to continuum mode.

    2. Acquire
      1. File Name
      2. Text Box, add description of experiment
      3. Overwrite
      4. Load
      5. Start

    3. Acquire 10 scans with just PFK
    4. Inject sample
    5. For realtime data
      1. File; open, select file
      2. chromatagram (total ion current)
      3. click on clock for reatime data
      4. click on chromatagram for mass spectrum

    6. To stop acquisition, acquire; stop
    7. Bring up data with Histogram button

    Processing High Resolution Data

    1. File: Open
    2. Click on Chromatogram
    3. Note for mouse movement
      1. Middle Drag to average sample + PFK
      2. Left drag to average background (PFK)
      3. Right click to subtract and display
    4. On Spectrum
      1. Annotate
      2. Modify
      3. Decimal Places (set to 4)
    5. To set calibration
      1. In chromatagram, middle drag on PFK and right click to send to spectrum
      2. Histogram data, Spectrum; utilities; peak detect
      3. Utility; Calibrate
      4. Change calibration file name (use filename_1)
      5. Auto calibrate
      6. overwrite
      7. accept
    6. In opus window, Analysis; Mass Measure
    7. Select Reference Compound (PFK)
    8. Select calibration file named above
    9. Click Accurate
    10. Set Windows
      1. Initial ppm 400
      2. Final PPM 200
    11. To analyze sample, middle drag on sample, left drag on PFK, right click to display spectrum
    12. Histogram data, Spectrum; utilities; peak detect (for close peaks set minimum width to 1 in peak detect options)
    13. Number peaks, Annotate; modify.
    14. zoom in on peak of interest
    15. For elemental analysis
      1. In opus window, Analysis; elemental
      2. Control; elements (select elements to search and specify allowed range and isotopic abundance)
      3. Control; show (to select minimum and maximum abundance for peaks to analyze)
      4. graph; display range to calculate elemental composition of peaks in spectrum.
      5. Printing does not currently work from this window.
    16. Exact mass calculator from SIS
    17. Exact mass of elements from SIS
    18. PFK reference spectrum from SIS
    19. If you receive a data error message, close and reopen OPUS

    To power down Instrument

    1. Set to electronics to Standby
    2. Source temp to 0 C
    3. Inlet & Transfer line to 75 C
    4. Ion Gauges OFF
    5. Pump out sample reservoir (open right valve)
    6. Power off
    7. To Shutdown Computer
      1. Close opus software
      2. from session manager window, menu select: session; end session
      3. login as
        1. LOGIN system
        2. PASSWORD security
      4. to shutdown select: application; decterm; 13
      5. AT <<< Prompt turn off power strip to computer
    8. Power off to electronic console

    This page is maintained by
    Scott Van Bramer
    Department of Chemistry
    Widener University
    Chester, PA 19013

    Please send any comments, corrections, or suggestions to svanbram@science.widener.edu.

    This page has been accessed 4068 times since 5/30/97.
    Last Updated Wednesday, October 11, 2000 21:27:33