Chromatography Forum

We are using headspace to analyse Xylene, Toluene, Benzene and methanol content in our finished product. Recently during validation we found problem that the Peaks are very small in height (usually DMF comes around 7000 and now came at 4000) so we investigated and found vial pressure is 93 instead of 14-15. so we tried to turn the vial pressure knob and found not working so we called for a breakdown maintenance from Agilent and they are working for 20 days till not rectified. last Friday, They said they changed all the spare parts and now the instrument is good and working satisfactorily. After that today we performed a calibration and the peaks are not satisfactory and found peaks like the following. Please let me know what is happening and what may be the solution for this problem.



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[img]322cea97-3c23-47a3-b536-d78c2c8810eb[/img]

I presume your matrix is some sort of polymer that is soluble in DMF. Is that correct? Please try to repost your images. Whatever you pasted in the post above is not a link so I can't access the images.

Hello

First of all...20 days to solve problem by the vendor is really weird (think about quality of service). Back to your problem :

You mentioned knob for vial pressure valve so I'm assuming we're talking about Agilent HS 7694

1.There are two valves: vent valve and pressurization valve - really easy to make diagnostic test (which one is leaking). In worst scenario just replace them.
2. I'd recommend to replace sample loop (especially it you have DMF - it tends to stick inside)

Regards

Tomasz Kubowicz

Thanks for all the replies. I tried something new yesterday and that's working now (somewhat)

I replaced the vial pressure valve to new one and Removed the gc removables including Jet assembly. sonicated and refitted.

I changed the flow from constant pressure to constant flow and kept 1.5 ml per minute and checked.

Its actually working with the minor changes. Peak heights become lower But sharp. RT shift observed.

Anyway I did an inhouse calibration and Working till now.

Thanks