8270E benzidine/pcp tailing

[MichaelVW]

Benzidine and pentachlorophenol tailing factors need to be <= to 2.

The method doesn't seem clear on whether to do this using the main quant ions, or if you can/should use the TIC. I think I've always had it pass both ways but maybe I'm making it harder than it has to be. Any thoughts?

[lmh]

What's the point of having a mass spec and using the TIC? The peak shape that matters is the shape of the peak that you quantify. In my view, it doesn't make sense to contaminate the chromatogram that you quantify by including masses unrelated to the chemical you're measuring. So I quantify an EIC or a sum of a couple of ions, and expect the peak shape of the EIC to pass muster.

The analogy is in HPLC-PDA, where everyone quite naturally picks the wavelength at which they want to quantify things; I've never heard of anyone quantifying on total absorbance from 200-600nm.

[cjm]

We just evaluate tailing of the quant ion. With 8270E, the analyst no longer needs to perform these evaluations on a daily basis, however we typically run a tune every day as it's a great indicator of inlet cleanliness and we like to monitor dftpp tune drift.

[MichaelVW]

Thanks for your feedback. I'm 90% convinced, but to be devil's advocate...

t doesn't make sense to contaminate the chromatogram that you quantify by including masses unrelated to the chemical you're measuring.

Benzidine isn't a chemical I'm measuring.

And I know I can improve benzidine's peak shape by increasing the oven's ramp rate, but so far doing so makes analytes that I actually care about preform worse. In this particular case, DDT breakdown is < 2% and Pentachlorphenol - which is an analyte of interest - has a tailing factor of about 1.

I'd prefer guidance on tailing factor for analytes I care about. But I guess it would have been overkill for the method to specify a maximum tailing factor for every possible analyte, so they just picked a couple compounds. They probably were using the EIC for the primary M/Z when they came up with "2.0" for a limit. Maybe they would have picked 1.9 of they had used the EIC, or 2.1 if they had used a different ion. But who knows... that was ancient history: the example calculation in Table 1 measures peak height in millimeters.