AutoProbe
TM
A58
T
he AutoProbe components are shown below. A CTC liq-
uid autosampler loads samples onto the replaceable
probe tip via a syringe. The probe tip is attached to a
probe rod attached to a servo linear actuator that automatically
drives the probe through an isolation valve and into the mass spec-
trometer source.
Before (or during) analysis, the operators prepare individual
sample vials containing samples dissolved in suitable solvent and
place these on the sample tray.
For each sample in an analysis sequence, the autosampler
starts by loading 0.125 to 1.0 µl of sample and accurately injects it
onto the platinum DEP probe wire filament.
A small initial current is then passed through the DEP filament
wire to evaporate the solvent from the sample.
An isolation valve (bottom left) permits the introduction of the
probe into the mass spectrometer without compromising the MS
vacuum. When the probe is inserted into the first probe seal of the
isolation valve, a vacuum valve opens to allow the accessory vac-
uum pump to evacuate the probe inlet. A vacuum gauge measures
this vacuum, and when the vacuum reaches approximately 200
millitorr, the probe is advanced to a second seal. This vacuum
gauge acts as a safety feature to prevent the probe from being
inserted into the MS source should a vacuum problem occur any-
where in the system. Afterward, a pneumatically controlled ball
valve opens to permit the probe to be inserted through the isolation
valve and into the mass spectrometer.
Once the probe has been inserted into the mass spec source,
a small current (typically 10 to 1000 mA) is passed through the plat-
inum wire to heat the wire and desorb the sample for analysis. This
DEP probe filament can be set to a constant current, or the current
can be programmed in up to three ramp steps to obtain the opti-
mum results depending on the sample being analyzed.
After the sample analysis is complete, the probe tip is retracted
slightly from the MS source, and a high filament current is passed
through the wire coil to burn off any sample remaining on the fila-
ment wire coil. This assures that the filament wire is clean and
ready for the next sample.
AutoProbe Software and PC Control
T
he AutoProbe is controlled by PC software that is fully
integrated within the ThermoTM XcaliburTM MS software.
The AutoProbe operates as any other standard Xcalibur
virtual instrument, which means that the AutoProbe is configured,
started, stopped and monitored entirely within the Xcalibur user
interface. AutoProbe method settings, such as filament current
ramps within the three heating steps, are stored within the MS
method. (See figure below.)
The AutoProbe may optionally be used in the Xcalibur "Open
Access
TM
" mode of operation. This permits the chemist or technician
to log samples into the system using a very simple and locked-
down interface. With no subsequent user interaction, the samples
are analyzed automatically when the system becomes available,
and the results are computed and reported back to the chemist in a
printout or e-mail. This results in increased productivity from the
mass spectrometer lab.
DEP Probe Tip Wire Coil
Automated Isolation Valve
Vacuum Gauge
To MS
Rotary Ball
Valve
First
Vacuum
Valve
To Probe Vacuum Pump
Syringe Needle Guide
Syringe Needle
Platinum DEP Coil
DEP Probe Tip
AutoProbe Method Setup Screen
Xcalibur "Open Access" Log In Screen
Scientific Instrument Services, Inc.
TM
Phone: 908-788-5550
www.sisweb.com/catalog/08/A58
tip...
