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Connection Between LC and MS Detector
API Sources
Electrospray Ionization (ESI)
Thermo Scientific
The connection between the liquid chromatograph and the Surveyor MSQ Plus MS detector
is a PEEK union. This union is located behind the front door of the MS detector to the left of
the source block cover. See
Figure 14. Connection between LC and MS detector
0.005-in. ID red,
PEEK tubing from LC
Flow
The atmospheric pressure ionization (API) source forms gas phase sample ions from sample
molecules that are contained in solution. The API source also serves as the sample interface
between the LC and the MS detector. A catch on the left side of the source enclosure door
shuts off the high voltage supply if the door is opened.
You can operate the API source using the following techniques:
•
Electrospray Ionization (ESI)
•
Atmospheric Pressure Chemical Ionization (APCI)
The sample, consisting of preformed ions in solution, enters the source through a stainless
steel insert capillary held at a voltage of ± 1 to 5 kV. The insert capillary is surrounded by a
tube that directs a concentric flow of nitrogen nebulizing gas past the droplets of liquid
forming at the tip of the probe. The action of the nebulizing gas and the high voltage
produces an aerosol of liquid droplets containing sample ions and solvent ions. A second
concentric flow of nitrogen gas, referred to as the sheath gas. assists the ion evaporation
process. This highly efficient desolvation process close to the entrance cone enables the
routine use of high LC flow rates (up to 2 mL/min) with the ESI technique.
Drawn in by the low vacuum produced by the forepump, the desolvated ions enter the
M-Path region through the entrance cone. As the ions exit the focusing region, they pass into
the RF/dc prefilter. See
Figure
Figure
14.
port 2 of Rheodyne
micro-injection valve
15.
2
0.005-in. ID red,
PEEK tubing to
Surveyor MSQ Plus Hardware Manual
Functional Description
MS Detector
Flow
23
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