No base line separation in Most validated methods.... why ?

[eight2015]

Hi guys, I have read some of EPA methods, Application papers from WATER, Thermo , Agilent, papers from scientific journals for separation and validation of nearly ( 20 compounds, some 15 compounds etc). In all these I found 20% peaks were not baseline seperated.

So I read in many books ( snyder, troubleshhoting book by John Dolan etc ) and it seems it is the basic knoweledge not to validate the peak untill you get baseline seperated for each peak and the resolution must be at least 1.5.

Why I am seeing many papers validated without base line seperated for their peaks. See attached example from EPA



Kindly press the link for example of seperation that validated

http://postimg.org/image/45yv90p17/

[kubowicz.tomasz]

Hello

You'll find a lot of information about it in chromatography literature...just look more carefully
And think about MS detection - you can have one peak and 3 compounds (co-elution). You can still quantitate them using specific ions (SIM and Scan)
Good luck

Regards

Tomasz Kubowicz

[Pepter]

Re: eight2015
The figure that you have posted is total ion chromatogram (TIC).
Basically its all signal intensities (all mass pekas) for one scan added together to obtain TIC (some way of data presentation).

[eight2015]

Thanks, I am familiar with GC-FID. So, shall i say:
a) In GC-MS if all peaks are baseline seperated then use the peak area from ( the total ion chromatogram.

b) if some co-elute in GCMS then use SIM and Scan

Is that true? Could you please just provide me with just any nice paper to understand this ,,, i searched a lot but lost into the details ,,, god bless u .

[eight2015]

Any more help ,, thanks

[tangaloomaflyer]

Thanks, I am familiar with GC-FID. So, shall i say:
a) In GC-MS if all peaks are baseline seperated then use the peak area from ( the total ion chromatogram.

b) if some co-elute in GCMS then use SIM and Scan

Is that true? Could you please just provide me with just any nice paper to understand this ,,, i searched a lot but lost into the details ,,, god bless u .

a) you would get better responses using the TIC, but you will have problems if you have matrix peaks that co-elute with your target analyte. The benefit of GCMS is you can quantitate the EIC which is much more selective.

b) Better to use SIM if you know what you are looking for and you don't have too many analytes in your target list, but for EPA 8260 or 8270 scan is more practical as there are too many analytes to set up that many SIM windows.

[eight2015]

Thanks , let me ask you:

1) in all mode ( scan , SIM whatever) using the peak area is it the only method of quntitation?. The reason i am asking this because i am worry if there is some cases in which we can not use peak area. Some one might say nooooo why you use peak area here you should use istope dilution or ion calculation because although you see peak this is not FID

Please recommend me some practical book in GCMS , i bought some but they are deadly theoritical and can not understand it

I feel my level is too bad so please help

[James_Ball]

Thanks , let me ask you:

1) in all mode ( scan , SIM whatever) using the peak area is it the only method of quntitation?. The reason i am asking this because i am worry if there is some cases in which we can not use peak area. Some one might say nooooo why you use peak area here you should use istope dilution or ion calculation because although you see peak this is not FID

Please recommend me some practical book in GCMS , i bought some but they are deadly theoritical and can not understand it

I feel my level is too bad so please help

Almost all GCMS quantitation is done using peak area of a single extracted mass, that is the most specific and accurate way to do it. Most modern integrators can handle even bad shaped peaks well and reproducibly, where old software had trouble if peaks had shoulders or flat tips or tails ect. Complete separation is nice, but when you have an analysis like volatiles where there are 100 analytes in a single standard run, there is no way to baseline separate every compound in the TIC. I have even done a LCMSMS analysis where we had over 300 pesticides in a single standard mix with less than a 30 minute run time. A lot of overlapping compounds, but easily separated with the MRMs.

Once you get experience in the field, you will find there is a big difference between what is best in theory and what is practical in application. Finding the sweet spot between the two is the mark of a good analyst