1) On the GC front panel, you will set up the program method
Build/Modify, method 1, enter
Activate, method 1
Status
2) On the computer, hit esc utill you come to the main menu. Press I for Instr Control. Edit these parameters:
Mass range 45 to 200 amu (this can be edited by clicking on “SCAN RANGE” or by clicking directly on the number boxes below “Lo mass” and “Hi mass”)
Scan time 1 second (this can be edited by clicking on the “Control” drop down menu and selecting “Set Scan Rate”)
Mult voltage 1500 V (this can be edited directly on the screne by clicking on the number box below “MULT”)
Background Mass 45 amu (Automatic Gain Control)(this can be edited by clicking on the “Setup” drop down menu and selecting “AGC Prescan Parameters”)
3) Data Acquisition
Press ESC until you are on the first page.
Press A (Analysis)
Enter data file name and comment.
Go to Control Menu and select Acquire Current Entry
Wait for the parameters to download to the mass spec
NOTE: Comment should include the name of the sample and important conditions.
**Please do not change any parameters that have been preset on this screen.
Use bottle labeled "hexane for washing" to wash the syringe at least 5 times before each run (please do not contaminate the stock solution). Inject the standard sample (1 uL injection only). You will be shown how to do this effectively.
The syringe must be inserted all the way to hit the switch on the injector - this starts data collection.
Hit any key to get back to the main menu. The acquisition status bar will show when the scan is finished running. To view your scan at any time, hit F to load your file. You must use the arrow keys to highlight your file and press enter to load it. Press F2 to see your chromatogram. Plot scan from 1 to 2000.
If you wish to stop your data acquisition, you must be on the Analysis Status window. To get there, select U on the home page. Once on this window, Ctrl Q with stop the acquisition.
When the acquisition is completes, press Reset on the 3400 gas chromatography (make sure both ready light is green and column temp. is back to initial temp. 40 C before starting another run.)
4) Analyze data (when run is complete, approx. 9-12 mins.)
To view your scan, hit F to load your file. You must use the arrow keys to highlight your file and press enter to load it. Press F2 to see your chromatogram. Plot scan from 1 to 2000. You can print your chromatogram by hitting Alt H.
the arrow keys to see the MS for a peak of interest. Hit F1. Alt H will print your spectrum.
5) Perform library search on your sample
Press L when you have the spectrum displayed and go directly to the library.
Make sure you are in the correct library (NIST05.LBR) and change the molecular weight range (W [MW of parent ion]) or the mass range as seen in the spectrum (X) if desired.
Press ENTER (you can also press R to see the first 10 choices of the library fit).
Press F1-F10 to cycle through the first 10 choices.
There are three types of fit that the library search uses: Purity, Fit and Reverse Fit. Read the handout at the mass spec to familiarize yourself with the different types of fit and their uses.
6) Repeat procedure for the other standard samples and unknown mixtures
7) You are required to turn in as part of your report:
Standards
A good chromatogram of each standard sample.
A mass spectrum of each standard, that is, 6 total (with labeled peaks).
A library fit print out of each known, that is, 6 total.
Unknowns (mixture containing 2 or more of the known standards)
Chromatographs and mass spectra of all 3 unknown mixtures.
Identify each unknown and report.