June 18, 2021, 10:58:18 PM
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Topic: Blank samples calibration curve show analyte peak  (Read 182 times)

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Offline ss2905

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Blank samples calibration curve show analyte peak
« on: June 07, 2021, 03:03:45 AM »
Hi, I am performing a LC-MS analysis for the quantification of an androgen. The androgen peak is clearly visible at all concentrations that are used for the calibration curve. The only problem is that this peak is also visible in my blank and double blank samples. Also, the intensity of the peak in the blank samples is relatively high.
How do I get rid of the peak in these samples? What could be the problem in this case? Please help. I washed the column many times, but it did not resolve the problem.

Thanks in advance!

Offline Babcock_Hall

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Re: Blank samples calibration curve show analyte peak
« Reply #1 on: June 07, 2021, 12:14:24 PM »
I am not an analytical chemist.  However, I would be tempted to look for other possible sources of contamination, such as the solvent.  What is you protocol for cleaning the column?

Offline jeffmoonchop

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Re: Blank samples calibration curve show analyte peak
« Reply #2 on: June 07, 2021, 12:36:41 PM »
Your blank solvent is contaminated, perhaps you took the blank sample from a blank solution that you already used to prepare your samples. Always use fresh blank to vial before you prep samples. Other causes may be carryover from the needle, maybe your needle wash needs to be changed. Normally I would inject blanks first, then a std, then the blank again and you will be able to tell if there is carryover from the previous injection. This can be a problem throughout your run if you are adding carryover from the previous samples your results won't be accurate.

If it is your column, maybe your runtime isnt long enough, does your peak return to baseline for long enough before the next injection? Anyway it sounds to me like your column is not the problem.

Offline DangerousBill

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Re: Blank samples calibration curve show analyte peak
« Reply #3 on: June 08, 2021, 07:55:50 PM »
Have you run just your solvent?

Could it be that the ion source is contaminated?

Offline Asim

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Re: Blank samples calibration curve show analyte peak
« Reply #4 on: Today at 04:11:23 PM »
I think your analyt curve is not present. You are seeing only curve obtained in blank..
You must try to change the mobile phase.
And clean apparatus by tap water and rinse by De-ionised water at the end.

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