Carry over problems with the PTV inlet

Chromatography Forum: GC Archives: Carry over problems with the PTV inlet
Top of pagePrevious messageNext messageBottom of pageLink to this message  By Dita on Monday, September 1, 2003 - 03:52 am:

I'm using a GC-MS method with a PTV inlet for the determination of amines.The bad thing is that I have a lot of carry over.
I think the PTV inlet causes the problems. Is this a known disadvantage of a PTV? What can I do to dissolve this problem?

Using a Agilent PTV in the solvent vent mode.
liner: 1.5 mm I.D. 150 l volume deactivated multi baffle liner.
Inlet temp: 40C (0.90 min) -->700C/min to 300C (8 min)


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Tuesday, September 2, 2003 - 02:02 pm:

You don't give the split ratio programming. The usual way to do PTV is high split during injection for solvent evaporation, splitless during heating for maximum sensitivity, then split again to flush residues from the liner. With the information given I suspect the second split time is too short or the split ratio is too low to flush the liner properly


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Dita on Wednesday, September 3, 2003 - 06:27 am:

De vent flow I use is 2.5 ml/min. That is very low but when I raise the vent flow the abundance of the chromatographic peaks decrease a lot.
The purge flow is 100 ml/min at 3.0 min.
Gassaver 20 ml/min at 15.0 min.

Because we analyse at very low levels the carry over is a big problem.

Regards, Dita


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Wednesday, September 3, 2003 - 04:11 pm:

If the analytes decrease significantly with a higher flow, then the temperature of the inlet is too high. Lower the temperature of the liner, then see if you can vent the solvent efficiently. I am not really sure if it is possible with the Agilent design, but is sounds as if there may be solution from the injector getting it areas where it doesn't belong because of the relatively high temperature and low flow rate.

Based on conversations I have had with users, I would try a lower purge flow, say about 40 ml/min and would not use the gas saver. I personally have not seen problems with the gas saver, but I would try a few runs without it to see if it makes any difference.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Friday, January 30, 2004 - 05:34 am:

Are you injecting 150ul at once? or speed controlled. If you use a liner with an ID of 1.5mm and you want to inject 150ul. This doesn't fit in the liner. I think you have an explosion in the liner resulting in carry over.
Go to www.atasgl.com to learn more about LVI.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By s on Thursday, March 4, 2004 - 05:54 pm:

i agree it .


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