Negative peaks like the one in the image are always present when samples (and mobile phase as blank) are injected into columns with cross-linked polystyrene-divinylbenzene matrix. RI is used as a detector. It always happens at the same times according to the method; it has varied temperature, flow and the peaks run equally. Dirt from the columns has already been discarded. The columns were tested in another HPLC using the same method and in this other equipment the negative peaks do not appear, therefore damage to the columns is ruled out. It is also not about the initial injection peak.
The methods are operated correctly, parameters and suitable mobile phase (deionized water).
Thanks!!
Perhaps overload of the detector by some strong signal: some electronic amplifiers tend to reverse polarity when heavily overloaded..
Hi yuliana,
Did you already have a look at earlier post on Researchgate to get directions for troubleshooting?
https://www.researchgate.net/post/Why_I_am_getting_negative_peaks_on_HPLC
Best, Hendrik
Thanks Nikolay Pavlov and Hendrik-Jan Brouwer !
According to the protocol we are following, everything seems to indicate that the problem is in the injector. We have already injected the same mobile phase as a sample blank and the problem persists. We have also prepared the mobile phase on different occasions and with deionized water from other laboratories and the problem continues.
The post shared by Hendrik-Jan Brouwer confirmed my suspicions.
Thank you very much to both.
Hi Cruz.
Check this out:
https://support.waters.com/KB_Inst/Chromatography/WKB67342_Negative_peaks_observed_using_Refractive_Index_Detector
I have solved my negative peaks problem regulating the valve.
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