EPA 8015 by GCMS using ChemStation

[DReggio]

Hello, we are trying to switch our GCMS TVH processing method to ChemStation. While it works great for 8260 we have been having trouble building a method that gives reliable results for 8015.

Does anyone have a working processing method they could send or know a source of an example one?

The version of ChemStation we are using is E.02.00.493

Thank you,
Damien

[Steve Reimer]

Are you trying to integrate the TIC?
I do that for TPH-G. It does mean careful manual integrations and no baseline rise or roll.

[DReggio]

Are you trying to integrate the TIC?

Not sure what you mean by trying to integrate the tentatively identified compound. We take the total area of the peaks for the retention time range and then subtract the internal standards/surrogates.

[James_Ball]

TIC = Tentatively Identified Compound
TIC = Total Ion Chromatogram

Even in some EPA methods they use the exact same acronym for both things which becomes very confusing.

If you are trying to integrate hydrocarbons on a MS file like you would on an FID file you just choose TIC instead of Target Ion in the "Quant signal " box in Edit Compounds. Also you can use the H Compound Type to designate it as a Hydrocarbon which allows for integration over a broad area instead of a single peak. You then set the Extract signal from boxes to the beginning and ending time for the Hydrocarbon range you want to integrate as a single area. (set by using the center of the range RT and putting a + and - minutes to give the time span needed)

[DReggio]

Thanks James,

I have the quant signal set to total ion, the compound type H and the subtraction method set to "extended Area Quant." Do you use the chemstation integrator or RTE? Do you use any macros to assist in getting consistent results?

Thanks,
Damien

[James_Ball]

I normally use RTE integrator simply because after using it since before Chemstation was on Windows I still know what all the settings do.

I never could figure out how to automatically remove the areas of the internal standard or surrogate so I chose different compounds. Since I was working with external standard calibration I just had to move to using 1-methylnaphthalene which elutes just past the normal end of the gasoline range. I quantify the surrogate using the Target ion. If your surrogate has to elute during the window for your target compounds you could spike it at a very low level so that it still gives a good signal for the target ion but does not contribute enough to the total ion chromatogram of the low standard to effect the overall quantitation or response factor. If your low standard gives 100,000 area counts TIC and the surrogate and internal standard only contribute 1000 area counts TIC each then the low standard will only be 2% higher than it should be and keeping these compounds constant throughout the calibration curve would have even less effect on the rest of the standards and you could probably mitigate the 2% on the low calibration through curve weighting.

[DReggio]

I never could figure out how to automatically remove the areas of the internal standard or surrogate.

If the type is set to H chemstation will automatically subtract surrogates and internal standards (type S and I) that fall within the range. You will need to combine coeluting surrogates or internal standards to avoid double subtracting. A problem I have noticed is that integrating the internal standard does not change the area that is subtracted, it just subtracts the area that was initially quantitated.

Unfortunately we are running 8260 and then reanalyzing the data to add TPHg so changing the surrogates is not an option.

I'm getting ready to give up on trying to use chemstation for TIC ranges. I'm beginning to think it might be easier to switch to openchrom or export the .ms into something ezchrom can read.

[Yama001]

I had to fix the issue with changed IS and S peaks by having the QEdit macro run the TPH macro again upon exit. This fixes that issue, but you cannot manually intergate the tph range, as it reset to the default integration. If you are good with altering the macros, you can set things up so manual integration of the range is rarely needed.

[DReggio]

I had to fix the issue with changed IS and S peaks by having the QEdit macro run the TPH macro again upon exit. This fixes that issue, but you cannot manually intergate the tph range, as it reset to the default integration. If you are good with altering the macros, you can set things up so manual integration of the range is rarely needed.

Thanks Yama! I had no idea there whas a TPH macro, I am looking at in now.

The main problem with the default integration for me is that it just takes whatever point is at the start of the RT and connects that to the end of the RT creating a ridiculous baseline.

[LALman]

I never could figure out how to automatically remove the areas of the internal standard or surrogate.

If the type is set to H chemstation will automatically subtract surrogates and internal standards (type S and I) that fall within the range. You will need to combine coeluting surrogates or internal standards to avoid double subtracting. A problem I have noticed is that integrating the internal standard does not change the area that is subtracted, it just subtracts the area that was initially quantitated.

Unfortunately we are running 8260 and then reanalyzing the data to add TPHg so changing the surrogates is not an option.

I'm getting ready to give up on trying to use chemstation for TIC ranges. I'm beginning to think it might be easier to switch to openchrom or export the .ms into something ezchrom can read.

Thread resurrection...
I've run TVH[GRO] for many years on my Agilent 6890N/5973. I have it in both my routine BTEX/MTBE and my full 8260 methods. I have my report sheets in Excel set up so I can either check it or uncheck it depending on customer request. I use Flurorbenzene as the internal standard and calibrate using 1,2,3,4,5,10,20,30, and 40 thousand ppb for the cal curve. I use the "H" type and you can further specify FLAT in the A1 user number but I don't bother with that. I've found that Internals and Surrogates are subtracted just fine but that you don't want to sum quant ions on any of the internal standards or surrogates in that range or you get a double subtraction that tilts the cal curve so the low end becomes inaccurate. Response Factor calibration fit is typically 3-5% RSD. My 3sigma recovery for a 5000 ppb check standard is 84.7-115.3% with 3sigma RSD of 15.3%