5890 vs 6890 chromatography

[NBchemist]

Ok,
this sounds like a pretty weird question, but has anyone ever tried to translate methods from an older 5890 system to a newer 6890 system and experienced a significant change in chromatography? I am trying to set up a method where I have example chromatograms for, given by the EPA. My older system (5890) is able to reproduce the picture, but when running the method on a newer instrument (equipped with a 6890) the elution order changes as well as the whole retention "picture".
I ran the method in constant flow and then also constant pressure (since the 5890 runs it on const p) but apart from the RTs nothing changes. I also ran it on a different 6890 to make sure that at least the two identical instruments are consistent, and they are.

Anyone got any ideas?

[aldehyde]

The two systems should give very comparable results. I wouldn't be surprised by slight changes in response but the design of the inlet and detector should be very close. If you are using the same column, flow rate, carrier gas, oven program, and inlet temperature your chromatography should be identical.

What kind of analysis is this? Pestacides? What analytes?

[NBchemist]

Hi,

we have just solved the mystery. I have switched back to the old system and it turns out that something has happened to the column. Which is odd nevertheless. The peakshape is good (no tailing or any other indication of column breakdown) but the separation and elution order has changed. Now the old system is giving the same results (which are not the ones desired) as the new one. I have ordered a new column and will see what happens at the end of the week.

Thanks

[aldehyde]

Very interesting, what kind of column is it?

[NBchemist]

SPB Octyl from Supelco