User guide

Multimode Source for 6100 Series Single Quad LC/MS User Guide 59

Reference 3

Guidelines for multimode source settings in MM-APCI mode

Nebulizer pressure Start at 20 psi. The signal decreases with higher nebulizer

pressure.

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

Drying gas temperature Just set to 350°C. Remember you want the vaporizer

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

Vaporizer Start at 250°C. APCI is gas phase chemistry. A higher temperature

usually works better. The vaporizer will compensate for flow rate or solvent

composition.

Corona current Set to 5 µA positive or negative. The corona voltage will be

~4000 V at 6 µA.

Vcap Set to 2000 V. The lower voltage works better for fast switching. The

APCI response is usually better at the higher end of the Vcap range.

Charging Voltage Set to 2000.

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

The above set of parameters is provided as a starting point and should yield good response

for many analytes. To obtain a specific response, i.e., high sensitivity detection of a

compound or class of compounds, or a balanced response to a wide variety of compound

classes, these parameters and the LC mobile phase composition should be examined

further using traditional techniques for optimizing a method. The four most important

parameters and the suggested optimization order are: vaporizer temperature, then capillary

voltage, then nebulizer pressure, and then corona current.