EPA 524.2 Internal Standard/Surrogate Issue

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I've been running Purge and Trap GCMS for about a year now and am seeking answers to a problem that I've been having. When I run samples my internal standard (Fluorobenzene) and surrogates (BFB and D4) are for the most part consistent. However when I run calibration standards (0.5ppb to 20 ppb) and LFB (4ppb) my internal standard and surrogate responses increase. So much so that my surrogate recoveries for my samples sit between 50-70%. Currently, my internal standard response for samples is around 80,000 and my surrogate responses are around 18,000. My internal standard response for my LFB/CCV is around 108,000 and surrogate response is around 40,000. Also, I noticed that if I have a high concentration of a specific analyte in a sample it will cause the internal standard/or surrogates to increase depending on where the analyte elutes (For example I had a high abundance of THF come out of a sample and it only increased the internal standard and not the surrogates. I believe it's because THF elutes close to Fluorobenzene, which is causing it to be effected). Has anyone else had this problem/found a solution to it?
The equipment used includes: Aquatek 100, Lumin Concentrator (using VOCARB K Trap), 7890B GC, and 5977A MSD.
There have been several threads on this forum about increasing response overall for internal standards with increasing concentration of target analytes.

It is a common problem for me when I analyze nasty samples (water with visible creosote or a beads of PCE appear in some of my projects). The cure is to clean out the entire path from the vial to the GC inlet and the MS source.
The instrument was installed in May of 2016 and this problem has been going on from the start.
If you increase the split ratio, does the problem decrease?
Steve Reimer wrote:
There have been several threads on this forum about increasing response overall for internal standards with increasing concentration of target analytes.

It is a common problem for me when I analyze nasty samples (water with visible creosote or a beads of PCE appear in some of my projects). The cure is to clean out the entire path from the vial to the GC inlet and the MS source.
I agree with Steve. Its probably an active sites problem. It happens with metals analysis also. You can run a concentrated potassium signal and then rinse it down to nearly nothing. Then aspirate a high sodium standard and suddenly you have potassium showing up again.
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