IS response EPA8260

[MicheleCAC]

Hi everyone, I am performing volatile compounds analysis with EPA 8260, I use autosampler OI4552 + P&T OI4660 + GC agilent 6850 + MSD5975C.
My problem is this, I have the IS response that changes from one day to the next, I perform BFB tuning before each session, already the day after calibration the CCV but with constant responses for the analytes but the IS response varies.
Thanks for your help

[James_Ball]

Do all the IS responses vary or does the 1,4-Dichlorobenzene vary more than the others?

[Steve Reimer]

If you put your IS solution in the other standard vial do you get the same variation? If it isn't adding the same volume each time look for leaks or a bad rotor seal in the valve. Especially if you are seeing a loss in the first internal standard over a day or two.
If it is just, or mostly, the dichlorobenzene clean everything in the path from the sparge tube to the inlet and try again.

[MicheleCAC]

If you put your IS solution in the other standard vial do you get the same variation? If it isn't adding the same volume each time look for leaks or a bad rotor seal in the valve. Especially if you are seeing a loss in the first internal standard over a day or two.
If it is just, or mostly, the dichlorobenzene clean everything in the path from the sparge tube to the inlet and try again.

In fact, I have the problem above all on the first IS (Fluorobenzene).
Thanks for the help

[MicheleCAC]

Do all the IS responses vary or does the 1,4-Dichlorobenzene vary more than the others?

not especially on the first IS (fluorobenzene)

[James_Ball]

Do all the IS responses vary or does the 1,4-Dichlorobenzene vary more than the others?

not especially on the first IS (fluorobenzene)

As Steve mentioned loss of the lower boiling would usually be from a leak around the internal standard seal, allowing the more volatile IS to evaporate first. If you have a leak detector check around the IS vial seal (assuming it is built into the autosampler) and see if it is leaking. If you are hand spiking, makes sure the IS vial is open as little as possible.

[MicheleCAC]

Do all the IS responses vary or does the 1,4-Dichlorobenzene vary more than the others?

not especially on the first IS (fluorobenzene)

As Steve mentioned loss of the lower boiling would usually be from a leak around the internal standard seal, allowing the more volatile IS to evaporate first. If you have a leak detector check around the IS vial seal (assuming it is built into the autosampler) and see if it is leaking. If you are hand spiking, makes sure the IS vial is open as little as possible.

Thanks for the advice!