Decreased surrogate response

[eauchem]

I am running 524.2 on a 6890/5973N + Tekmar Stratum concentrator. I purge 25mL with a Vocarb 3000 trap. I am using a 30m DB-VRX column. (Not sure if all of this pertains to my question)...

I have seen a significant decrease in the reponse of one of my surrogates.
I use Fluorobenzene as the ISTD and 4-BFB and 1,2-dichlorobenzene-d4 as surrogates. I spike all of these at 5ppb, but lately my 4-BFB concentration has been below 4ppb? The 1,2-DCB-d4 is running low, but at least above 4ppb (passes QC limits).

Has anybody else encountered this (by the way - I did open a new vial of standard, they are all in the same mix) - it didn't help.

Thanks!

[Bigbear]

Water "activating" the source. Been there, done that. Do a search of this forum as this has been discussed in the past.

[helmi]

Hi, using the same instrument as eauchem but using method 8260c. i have problem with my purge & trap. i have follow the same instruction that i get from teledyne instrument web. my instrument have inject the vial but doesn't suck the sample (which i use the new septa, to avoid pressure decreased). can you help me to solve this problem, because before this i used tekmar 3100, that i can adjust their pressure - to make sure the autosampler sucks the sample and go to sparger. but stratum ptc, doesn't have criteria to adjust its pressure. It is because there are something that blocked the vial and its lines/tubing? could you help me in solving this problem, please?