Thermo Finnigan LCQ Deca XP Plus, Руководство по оборудованию

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Functional Description
_________________________________________________________________ API Source
__________________ LCQ Deca XP Plus Hardware Manual __________________
1-9
The sheath gas is inner coaxial dry nitrogen that sprays (nebulizes) the
sample solution into a fine mist as it exits the sample tube. The auxiliary gas
is other dry nitrogen that can be used to assist in nebulizing the sample
solution and in drying the spray chamber. The sweep gas is nitrogen gas that
helps to improve the ruggedness of your API source. Sweep gas is also useful
for reducing solvent adducts and chemical noise when using Full-scan MS or
Data Dependent experiment types. The solution exiting the APCI nozzle
forms a fine mist. The droplets in the mist then enter the vaporizer. The
vaporizer flash vaporizes the droplets at temperatures up to 600
°
C.
Typical vaporizer temperatures are 350 to 400
°
C for flow rates of
100
µ
L/min, 450 to 500
°
C for 1 mL/min (normal APCI flow rate), and 550 to
600
°
C for 2 mL/min. The sample vapor is swept toward the corona discharge
needle by the flow of the sheath gas and auxiliary gas.
The corona discharge needle assembly is mounted on the APCI flange. The
assembly positions the tip of the corona discharge needle near the vaporizer.
A small screw can be used to adjust manually the position of the needle into
or out of the assembly. A high potential (typically
±
3 to
±
5 kV) is applied to
the corona discharge needle to produce a corona discharge current of up to
10
µ
A. (A typical value of the corona discharge current is 5
µ
A.) The corona
discharge from the needle produces a reagent ion plasma primarily from the
solvent vapor. The sample vapor is ionized by ion-molecule reactions with the
reagent ions in the plasma.
APCI requires a constant source of electrons for the ionization process. Thus,
the corona discharge current is set and regulated. The potential applied to the
corona discharge needle varies, as needed, to provide the required current
Refer to Table 1-2 for specific guidelines for LC/APCI/MS operation.
Table 1-2. Guidelines for LC/APCI/MS Operation
LC Flow Rate Ion Transfer
Capillary
Temperature Vaporizer
Temperature Sheath Gas Auxiliary Gas
LC at flow rates
from 0.2 to
2 mL/min Typical setting:
150 to 225
°
C
Typical setting:
400 to 550
°
C
Required
Typical setting:
50 to 100 units
Not required, but
usually helps to reduce
solvent background
ions
Typical setting:
0 to 20 units