column bleed

[pah_2015]

I am performing a Full Scan of hexane and air and in both chromatograms I observe a column bleed. I tried to clean the liner and the septum, and performed a column conditioning, but these are the results. Do you think my column is unusable, I need to change it or there is any other thing I can do?

[Peter Apps]

Change your carrier gas scrubbers, and make sure that the system is leak-tight - oxygen and water in carrier gas aggravates column bleed.

Peter

[James_Ball]

I noticed the scale is Relative Abundance, but what is the Raw Abundance?

Also what is the spectra of the column bleed?

With it set to relative abundance it could be minimal bleed but just look huge since it is scaling everything to a small maximum peak.

[pah_2015]

I think it is relative abundance because the scale is related to the highest paek of the chromatogram, which has the value of 100. I tried to change the scale to absolute and still got the same high bleed. This is a picture of the carrier gas scrubber attached to the gas cylinder. We have a second scrubber parallel to the internal valves, but it is still good, not even half saturated. That's my air - water scan. Are the N2 and O2 peaks to high, signal of a leak?

[James_Ball]

Nitrogen intensity of 150,000 counts could be either high or normal depending on the sensitivity of the instrument. If m/z 69 is 1,000,000 counts when the tune gas is on, then you are at 15% which is above normal (5% could be considered good for most systems) If the 69 m/z is 10,000,000 counts then you are at 1.5% which is great, on the other hand if 69 m/z is only 100,000 then you are at 150% which is really bad.

With 18 m/z being as high or higher than 28 m/z, it would mean you have really high humidity if it is an air leak. It may be closer to normal if it is just the residuals in a tank that are showing up.

[Bigbear]

Do you have a "no injection chromatogram" when this column was just installed? Comparing the two would tell yu if the column is shot.