Application Note
Instrument: Pegasus BT ® Systems

EMPOWERING RESULTS®

StayClean Ion Source Stability
LECO Corporation; Saint Joseph, Michigan USA
Key Words: Pegasus BT, Pegasus BT 4D, Source Stability, Reproducibility, High Matrix

Introduction
Fouled ion sources and related issues are often time consuming to diagnosis and resolve. A definitive diagnosis can only
be achieved after other preventative maintenance steps (inlet maintenance, column trimming, etc.) have been tried andtested. Once the source has been pinpointed as the issue, users must remove, disassemble, clean, reassemble, reinstall
and test the source before proceeding. Even routine, scheduled preventative cleaning leads to system downtime and opens
the door to potential mistakes in source reassembly. In less controlled environments the incremental contamination of anion source may not be noticed until long past the point of compromised results or impacting the stability of the overallsystem. Worse still, tuning routines will typically compensate for the loss in signal by increasing various voltages, not theleast of which is at the detector. This decreases the detector's operational life, requiring additional maintenance time toresolve. For these reasons, LECO has specifically designed the Pegasus BT systems with an ion source that virtuallyeliminates the need for removal and cleaning. The purpose of this note is to provide significant evidence that the LECO
StayClean ion source actually stays clean.

Figure 1. The Pegasus BT 4D and a simplified drawing of the StayClean ion source. The source filaments can be quickly changed without
source disassembly, while the overall source design ensures maximum system stability and minimizes maintenance downtime.

As seen in Figure 1, the gridless, open-style EI source design differs significantly from traditional, closed-box style sources.
With the Pegasus BT's innovative design the metal source body components are relatively distant from the ionization
region. Additionally, this source format facilitates removal of neutrals and other contaminants into the vacuum and out of
the flight path. These improvements dramatically reduce source fouling while generating EI spectra with high fidelity tocommercially available GC-MS libraries. The only maintenance the source will require is periodic filament replacement,
which has also been simplified as part of the system's design. Minimization of system downtime was among the key
requirements of the Pegasus BT system design.

Experimental
A QuEChERS spinach extract spiked with various pesticides at 50 ppb was used as the test matrix. In each test round 100
spiked test matrix injections were made using parameters listed in Table 1. At the end of each round, the inlet liner andgold seal were replaced and 0.25 m was trimmed from the guard column. Following inlet maintenance, the system autotune was run and another 100 spiked test matrix injections followed. This sequence was repeated for a total of 400 matrix
injections.
Table 1. GC-TOFMS Conditions
Mass Spectrometer
Ion Source Temperature
Mass Range
Acquisition Rate
Transfer Line
Gas ChromatographInjection
Carrier Gas
Guard Column
ColumnLECO Pegasus BT
250 °C45-570 m/z
8 spectra/s
320 °C
Agilent 7890
1 µL Splitless, Inlet Temperature: 250 °C
He @ 1.4 mL/min, Corrected Constant Flow
2m, 0.25 mm i.d.(Phenomenex, Torrance, CA, USA)
Rxi-5ms, 30 m x 0.25 mm i.d. x 0.25 μm film (Restek, Bellefonte, PA, USA)

Figure 2. Total Ion Chromatogram (TIC) of the spiked spinach extract and Analytical Ion Chromatogram (AIC). The AIC is filtered to display
pesticide signals ONLY, and is multiplied by 10 for visualization purposes. The insert is an image of the QuEChERS spinach extract.

Results and Discussion
A typical injection is shown in Figure 2 where significant matrix is evident; the analytes of interest (pesticides) are at least afactor of ten less intense than the background. The examples in Figure 3 show a consistent response pattern for the spiked
pesticides in each of the sampling rounds. The signal degrades over the course of the 100 replicate injections, but returns
to the initial response after inlet maintenance and column clipping, without cleaning the ion source. This suggests the ion
source is not experiencing any signs of contamination even with a very dirty spinach matrix extract. All data wereprocessed with the same method settings and no changes were made to the software-determined peak integrations.

Figure 3. Response trends of four different pesticides showing signal recovery after only inlet maintenance and guard column trimming.

To verify that system tuning had not compensated for a fouling source, the tuning logs were reviewed. After the first roundof injections the detector increased 12V (~0.6% of the overall voltage) and remained static for all subsequent tunings.
Other values set during the automatic tuning were similarly consistent over the test period. Despite the heavy sample
matrix load, the ion source remained unaffected.

Conclusion
Fouled ion sources lead to problems with test accuracy and system stability. Resolving these issues takes time andresources away from your testing schedule. Fortunately, LECO's StayClean source resists fouling even after hundreds ofinjections of matrix heavy extracts. Combined with the system's excellent sensitivity, integrated data collection, and analysis
software, the Pegasus BT systems provide a superior testing platform for your most challenging samples.

LECO Corporation | 3000 Lakeview Avenue | St. Joseph, MI 49085 | Phone: 800-292-6141 | 269-985-5496
info@leco.com • www.leco.com | ISO-9001:2015 Q-994 | LECO is a registered trademark of LECO Corporation.
Pegasus, StayClean are registered trademarks of LECO Corporation.

Form No. 203-821-569

12/18—REV0© 2018 LECO Corporation