User guide

Multimode Source for 6100 Series Single Quad LC/MS User Guide 61

Reference 3

Guidelines for positive/negative polarity switching in mixed mode

The following settings are a good starting point when you are doing

positive/negative polarity switching in MM-ES+APCI mode.

Drying gas flow Always set to 5 L/min (IR does the drying).

Nebulizer pressure Start at 40 psi. You will use the nebulizer pressure and the

corona current to balance ESI and APCI. A higher nebulizer pressure results

in more ESI. A lower nebulizer pressure results in more APCI.

Drying gas temperature Set to 250°C. Remember you want the vaporizer to

control the drying and to be able to maintain the set point.

Vaporizer Start at 150°C. A higher temperature usually works better for

MM-APCI. MM-ESI is usually unaffected except for sodium adduction. The

vaporizer will compensate for flow rate or solvent composition.

Capillary Voltage Set to 1000 V. The lower voltage works better for fast

switching. You are balancing ESI and APCI response.

Corona current Set to 1 µA for positive or negative polarity. The corona

voltage will be approximately 3500 at 2 µA. More corona current will reduce

the ESI signal and increase the APCI signal.

Charging Voltage Set the charging voltage to 2000 V.

NOTE

Click Instrument > MSD Spray Chamber to set the Method Spray Chamber to

MM-ES+APCI before you edit the Set Up MSD Signals dialog box.

NOTE

Refer to “To create a method for positive/negative mixed mode operation” on page 9 for

additional information.