How can I improve the EI/CI filament performance and lifetime on an EI GCMS instrument? - WKB62805

ENVIRONMENT

• AutoSpec Premier
• AutoSpec Ultima
• GCT Classic
• GCT Premier
• Quattro Micro GC
• EI/CI

ANSWER

You can improve the filament performance and lifetime by taking the following precautions.

1. Carefully remove new filament from packaging to prevent damage to filament shield.

2. Cut filament legs to appropriate length prior to fitting filament to inner source.

3. Conditioning a filament will anneal it in the position in which it was manufactured and inspected. This ensures that the coils are unaffected (for example, will not droop, open, or close up when used. See WKB62609.

4. Set a high solvent trip level that still allows data acquisitions. The source vacuum on the AutoSpec needs to improve 3x from the trip level before the instrument is allowed into Operate mode and filament current allowed to flow.

5. As much as possible, reduce the oxygen progress into the source housing, either by air leaks, GC syringe injections, reference (PFK/Heptacosa/Metri) injections, or during solid sample introduction. Re-tighten new ferrule seals within the GC oven/transfer line after a few oven temperature ramps.

6. Allow Outer Source to cool <100 °C (monitored using the readback) before venting Source housing.

7. Inspect and optimize filament alignment across the entrance hole to the Inner Source.

8. Confirm that the trap contact, Inner Source block, and Ion Repeller within the Inner Source are clean and correctly located.

9. Set instrument to Standby after a sample run using the Startup/Shutdown option in MassLynx.

ADDITIONAL INFORMATION

1. The filament (if left constantly on) will establish an approximate temperature of @160 °C to 180 °C with no help from the source heaters.

2. Waters recommends that filaments slowly raise the trap current in 50mA jumps to the desired setting when the instrument is left in Standby >1 hour.