User guide

Multimode Source for 6100 Series Single Quad LC/MS User Guide 9

Basic Operation and Maintenance 1

To create a method for positive/negative mixed mode operation

1 Open the MSD Spray Chamber dialog box by clicking the Instrument > Set

Up MSD Signals in the Method and Run Control view.

2 Select MM-ES_APCI from the Method Spray Chamber drop-down list.

3 Check that Installed Spray Chamber is also set to MM-ES+APCI.

4 Make any other changes that are necessary for your method.

5 Click the OK button.

6 Open the Set up MSD Signals dialog box by clicking the Instrument > MSD

Spray chamber in the Method and Run Control view.

7 Modify the settings so that Signal 1 has Positive polarity and Signal 2 has

Negative polarity as shown in Figure 1.

8 Make any other changes that are necessary for your method.

9 Click the OK button.

Rapid polarity switching is a very useful technique but it requires time for the

ion chemistry to be established and the optics path to refill with ions. The gas

density plays a role in the speed of refilling the ion path. The gas density is

affected by source temperature. For a method running positive/negative

switching, it is advised to use a lower vaporizer temperature (150 to 200°C)

and a lower Vcap (approximately 1000 V). These will greatly affect the quality

of the results in positive/negative switching experiments.