Chromatography Forum

Dear all,
For the first time, I begin a method development with negative chemical ionisation with GC-MSMS (Waters QuattroMicro). As I'm not very familiar with NCI, could you tell me which parameters are critical and need absolutely to optimize?

We also observe very short life time of the filament using NCI! What could be the reason for that?

Thanks in advance. Best regards

Dear all,
For the first time, I begin a method development with negative chemical ionisation with GC-MSMS (Waters QuattroMicro). As I'm not very familiar with NCI, could you tell me which parameters are critical and need absolutely to optimize?

We also observe very short life time of the filament using NCI! What could be the reason for that?

Thanks in advance. Best regards

Source temperature can have a large impact on NCI sensitivity so you'll want to optimize that.

Are you running a lot of high concentration samples or frequent tunes? I know with our Agilent GC-MS NCI tuning frequently or injecting ppm level standards tends to quickly dirty up the source and reduce filament life, however I don't know how similar the Agilent and Waters systems are.

The pressure of buffer gas in the source is important for best results and should be optimized.

I don't know if Waters has special filaments for use with PCI and NCI, but some manufacturers do. The pressure is higher in the vacuum chamber when a reagent gas is used, and that can shorten filament life.