is this integration scintifically accepted ?

[Newchromatographer]

Hi , folks

I usually try to fix slope , width etc numbers in Lc solution software ( shimadzue company software ) then keep every thing without manual integration but the peak looks like this ( 6.230 i mean )



i feel the result much much trustable when i repeat the injection better when i do that manulally


Any help will be much a ppreciated , god bless you all

[bisnettrj2]

What does a blank injection look like? Can you overlay the two and show what the blank baseline and the baseline showing the peak look like together?

[tom jupille]

The integration shown for the peak at 6.230 minutes is incorrect. It may be reproducible, but it *is* incorrect, and grossly overestimates the area of the peak. Computer algorithms often perform poorly when you have a small peak on the tail of a huge peak, as in this case.

[Newchromatographer]

What does a blank injection look like? Can you overlay the two and show what the blank baseline and the baseline showing the peak look like together?

Thank .The blank injecion shows a straight line begine from zero with no peaks at all , appologise for not show the chromatogram here as i am far at present .

Thanks

[Newchromatographer]

The integration shown for the peak at 6.230 minutes is incorrect. It may be reproducible, but it *is* incorrect, and grossly overestimates the area of the peak. Computer algorithms often perform poorly when you have a small peak on the tail of a huge peak, as in this case.

Thanks for a very short concentrated knwledgable answer . But , how can i integrate the peak without using manual injection as i understood you hint in using manual integration in this case .

I feel that manual integration especially at lower concentration tend to loss the certainty in the result , not sure i am just asking ?

[unmgvar]

you should have the possibility to use 2 parameters in order to get a more precise integration, maybe it is named differently in your software

1. tangent/rider peak- this is used in order to integrate peaks that are very small compare to a huge peak and are at the front or tail of it.
2. baseline point- your chromatogram is tailing so much that you might need to tell the software how to handle this baseline

can you tell what you are looking for?
probably many possibilities, but this looks like a food application, something like:
Histamines in fish or something like that

your main problem is sample matrix and how bad it "smears" on the column. have you looked into sample prep solutions? SPE?

[bisnettrj2]

I meant, can you post a matrix blank (not an instrument/mobile phase blank). I apologize for the lack of clarity. I wanted to have a visual to confirm what Tom wrote - the integration looks incorrect. I would rather go with an integration that resembles the later peak at 13.25 minutes, if you're stuck with this sample preparation.

[Victor]

If you are particularly interested in the peak at 6.23 min. then try turning the integrator function off until about ? 5.7 min. The system will ignore the previous stuff. Or try turning the integration off until about 4 min and then you might get a decent integration of the previous peak too. I have no experience of Shimadzu software but I am sure this is possible in any software.

[dblux_]

I would suggest green peak area.
[/img]

[Bruce Hamilton]

My solution would be to fix the chromatography, change chromatographic conditions so the small peak of interest doesn't elute on tail. Such a peak is very susceptible to changes in the large peak.

However, your question was about the integration, and I would use Victor's suggestion as the fastest solution, except I would set software to start at about 4 mins to catch first small peak as well.

One superior solution is to adjust the parameters for tail skimming to catch the peaks - as suggested by several others above.

Manual integration should not be needed, as the peak is clearly well above noise, and most software can catch minor peaks on tails - provided baseline, peak width and peak detection sensitivity parameters are anywhere near optimal.

Please keep having fun,

Bruce Hamilton

[Newchromatographer]

Thanks Guys all of you that's great .

Thank bisnettrj2 , this is the matrix blank ( soil mix with water) .The method is just determining how much from my compound adsorbs into the soil assuming that no adsorption occurs in the system . see figure 1 and 2 just replicate injection . Figure 3 is done in the same condition but in this time I include my analyte .The intresting peak comes around 13 min but the earlier peaks just i ask about integration if small peak as internal add after it

Thank also for victor and others for remind me to look at matrix effect which really draw to my mind lots of question especially when I just use filtration technique to separate the analyte from the soil ( I feel it works ok not sure )

Figure 1


Figure 2



Figure 3