Mass Spec Procedure

This manual is meant to complement your training and is not intended to replace on-the-job training.

Last Updated

5/1/2015

OPERATING PROCEDURE

Set-up of MS Software

1) On the desktop select .

2) When prompted, press OK to continue.

3) After waiting a minute for the system to come on-line, a SEM voltage window will appear. Select “Run Uncalibrated” or click “Auto adjust” and wait for the SEM voltage to be calibrated.

At this point, there are two different types of Mass Spec scan that can be done:

1. Bargraph scans will detect all masses within a certain range (for example, 1-200amu). This is useful if you do not know what mass fragments will be coming off of your TGA sample. The resolution is not as good as a trend scan, but it can aid in identifying what sort of compound is being lost during the TGA run.

2. Trend scans are useful for monitoring the gases evolved during a TGA run with good resolution. The mass spec will only look for those fragment masses that you select. It can cycle through them much faster, resulting in more data points per unit time, and therefore higher resolution. The drawback is that the mass spec can only detect the masses that you select, and so you must know which fragment ions you are looking for before you set up a trend scan. It also takes longer and is more complicated to set up a Trend scan.

Running a Bargraph Scan:

• Confirm that the pump button is illuminated, and press the “heater” button on the MS. The temperature set point should be 150°C.

• Connect the mass spec attachment to the TGA (instructions are in a separate page of this manual). Wait for the temperature to reach 150°C before continuing...

• Under TG-Triggered Runs select “Run Bargraph Scan".

• Under “File Manager” create a file name under your own data folder and press “Open.” Enter the “Start Mass” when data should start being collected and the “End Mass” when it should stop. Atomic Mass Values here can not exceed 300 with this instrument.

• Type in a file name for your new method file and click Open.

• If the file does not already exist, the software will prompt you to confirm that you wish to create a new file. Click Yes to create a new file, or No to go back and select an existing file to edit.

• The new window that opens will allow you to select the masses you wish to detect, as well as some other options. Each of the columns represents one “channel” or one mass fragment to detect. By default, all of the channels are disabled. Right click where it says “OFF” to enable a channel. Start with channel 0 and use each channel in order from left to right as needed. Leave any channels you do not need in the “OFF” position.

• Once you have enabled a channel, you can set the mass that will be detected on that channel. Right click in the “Mass” row to enter a mass for each channel. Press Enter to set the mass.

• When all of the masses you wish to detect have been assigned to a channel, you can click on the Display tab at the bottom of the window, and then right-click in the color row to change the color that will be displayed for each channel. This is completely optional.

• The mass fragments will be displayed in the data file in the order they were entered into the channels. So when you open the data file, the mass for channel 0 will be at the top of the list, and each channel will be displayed in order after that, regardless of what mass it is. You can sort the masses that you have entered by going into the Edit menu and selecting Sort Mass. This will put the lowest mass in Channel 0 and so on. You do not need to do this, but it can make it easier to look at your data.

• When you have finished, save the method file with a unique name so that you can find it easily later.

II. Running a Trend Scan from an Existing Method File

• Open the software as normal. On the main selection screen under TG-Triggered Runs, select Run Trend Scan.

• Use the first File Manager button to select the method file that you created in section 1. You cannot run a trend scan without a method file.