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Get More Uptime with Restek’s Long-Life ESI Electrode for Sciex Turbo V Sources

  • Same LC-MS/MS performance as original equipment.
  • Rugged electrode lasts longer and requires fewer replacements.
  • Ensures more instrument uptime for sample analysis.

Electrospray ionization is the primary technique that LC-MS/MS labs use to convert the LC column effluent into ions for the detector. However, the high temperature, high voltage, acidic mobile phases, and elements (such as salts) in the sample create a corrosive environment in the MS source that can eat away at metal components. No part of the ionization flow path is more affected by this harsh environment than the capillary electrode. This delicate tube, typically made from stainless steel, is only a few thousandths of an inch thick. The constant flow, temperature, and voltage encountered in a high-throughput laboratory wear away the tip of the electrode as the spray emerges (Figure 1). Eventually, the tip will corrode to the point of failure and the uniform spray that had ensured a steady, sensitive signal will become deformed. When this occurs, the instrument will lose sensitivity, runs will fail, and sample throughput will cease while the instrument is taken offline for troubleshooting and maintenance. To help labs overcome this obstacle, Restek has developed the Long-Life ESI electrode (for use with Sciex Turbo V sources) that outlasts original equipment electrodes as demonstrated by the experiments shown here.

Figure 1: Corroded electrode tips produce poorly focused spray streams that result in decreased instrument sensitivity.

New vs Corroded Electrodes

Longer Lifetime Means Higher Productivity

The lifetime of an ESI electrode can vary widely based on the mobile phases and additives used, frequency of operation, and nature of samples injected. So, how can you determine if one electrode will outlast another? We did it by testing both the original equipment electrode and a Restek Long-Life ESI electrode under an accelerated degradation protocol that pushed the limits of the electrodes quickly while still being relevant to actual operating conditions. We used an aqueous mobile phase with relatively high concentrations of trifluoroacetic acid and salt, then set the ion source temperature and voltage at maximum. A stock electrode from the original equipment manufacturer (OEM) was tested first. Everything was installed to the manufacturer’s specifications and we inspected the electrode periodically for evidence of corrosion. At 100 hours, the OEM electrode did not show overt signs of corrosion, but at 120 hours extreme corrosion was observed and the electrode failed. Next, the Long-Life ESI electrode was tested, and it remained unchanged throughout the entire experiment. The final assessments are shown in Figure 2: the OEM electrode was irreparably damaged at 120 hours, while the Long-Life ESI electrode still appeared to be in new condition—even after 180 hours of exposure to the tough experimental conditions.

Figure 2: Restek Long-Life ESI electrodes for Sciex Turbo V sources last longer than OEM electrodes, so more samples can be analyzed with less downtime for maintenance.

Accelerated Degeneration Testing

Equivalent Chromatography Ensures the Same Performance

Longer electrode lifetime is only beneficial if the instrument performs as well as with the original part. To evaluate chromatographic performance, we compared our Long-Life ESI electrode to an OEM electrode by initially examining polypropylene glycol (PPG) ionization in all modes (positive, negative, Q1, and Q3), assessing both calibration ions and full scans. Results were very comparable (see example in Figure 3), so we injected an evaluation standard through the LC-MS/MS next. As shown in Figure 4, equivalent results were obtained. Because the Long-Life ESI electrode performed as well as the original electrode, analysts can now obtain the same LC-MS/MS performance they are accustom to on a more robust system that will stay up and running longer.

Figure 3: Electrode comparison: polypropylene glycol analysis (ESI+, Q1, full scan with calibration ions shown in insets).

OEM Electrode

OEM Electrode: Polypropylene Glycol (Q1, Full Scan with Calibration Ions in Insets)
LC_GN0599
Column
SamplePos PPG 1x10-5 M
Conc.:1x10-5 Molar
Mobile Phase
Flow: mL/min
DetectorAPI 4000
Ion Source:Electrospray
Ion Mode:ESI+
Mode:MS scan
InstrumentApplied Biosystems/MDS Sciex LC-MS/MS System
NotesOriginal equipment ESI electrode

Long-Life ESI Electrode

Long-Life ESI Electrode: Polypropylene Glycol (Q1, Full Scan with Calibration Ions in Insets)
LC_GN0600
Column
SamplePos PPG 1x10-5 M
Conc.:1x10-5 Molar
Mobile Phase
Flow: mL/min
DetectorAPI 4000
Ion Source:Electrospray
Ion Mode:ESI+
Mode:MS scan
InstrumentApplied Biosystems/MDS Sciex LC-MS/MS System
NotesLong-Life ESI electrode

Figure 4: Electrode comparison: PFAS reference standard analysis (ESI-, MRM).

ESI Electrode Comparison: PFAS on Raptor C18 (Standard Sciex Electrode)
LC_GN0595
ColumnRaptor C18 (cat.# 9304552)
Dimensions:50 mm x 2.1 mm ID
Particle Size:5 µm
Pore Size:90 Å
Temp.:40 °C
SamplePFAS mix
Diluent:96:4 Methanol:water
Conc.:5-10 ng/mL
Inj. Vol.:2 µL
Mobile Phase
A:5 mM Ammonium acetate in water
B:Methanol
Time (min)Flow (mL/min)%A%B
0.000.47525
8.000.41090
8.010.47525
10.000.47525
DetectorAPI 4000
Ion Source:Electrospray
Ion Mode:ESI-
Mode:MRM
InstrumentApplied Biosystems/MDS Sciex LC-MS/MS System

In summary, testing shows that Restek Long-Life ESI electrodes for Sciex Turbo V sources provide equivalent ionization and chromatographic performance to original equipment manufacturer electrodes over significantly longer lifetimes. Because they perform the same and are less susceptible to corrosive conditions in the MS source, Long-Life ESI electrodes ensure more instrument uptime for sample analysis and are a particularly good choice for high-throughput laboratories.

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