By Anonymous on Tuesday, January 14, 2003 - 11:45 pm:
Hello Friends
While doing chomatographic purity on HPLC when diluted solution (i.e 0.003%w/v)injecting I am getting two peak, one of solvent peak and other is peak of intrest but when I am injecting concentration solution (i.e 3.0%w/v). My problem is solvent peak in concentration solution chromatogram is very big compare to solvent peak in diluted solution why it happening any one could answer ? Injection volume same for both solution (i.e 20 microlitre) and both sample prepared in Mobile phase.
By Michele on Wednesday, January 15, 2003 - 04:41 am:
I want to make sure that I understand. The area of your solvent front peak increases as the concentration of your analyte peak increases? It sounds like your analyte contains an impurity that is very soluble in your mobile phase, perhaps a salt, eluting with the solvent front.
By Anonymous on Wednesday, January 15, 2003 - 10:30 am:
Have you injected a blanco solution, with the same sample preparation, but no active ingredients?
By Anonymous on Thursday, January 16, 2003 - 09:53 pm:
Thanks Michele
I agree with you that it might be impurity but when we doing TLC no secondary sopt obsereved with drug. You mention that it might salt you mean to say citrate salt ?
Thanks Anonymous
Yes I injected blank also we found that solvent peak response is same as obsereved in diluted sample.
By Anonymous on Friday, January 17, 2003 - 08:04 am:
Can you supply more informations about your analysis - detection, eluent composition, column type, sample type? Is your solvent peak area proportional to sample concentration?
By Anonymous on Saturday, January 18, 2003 - 10:19 am:
My chromatographic condition as follows
detection : 220nm
Eluent composition :1%w/v KH2PO4:Methanol (90:10)
Column : micro Bondapack waters column
Sample : Diethylcarbamazine Citrate
No solvent peak area not proprotional to sample concentration.
By Anonymous on Saturday, January 18, 2003 - 02:35 pm:
At 220 nm you see a lot of things as an unretained peak. You will see the citrate peak. You will also see the differences between your sample and the mobile phase (even if you are making the sample in the mobile phase, there is likely to be some difference from sample handling and evaporation). You may see junk from the caps of your vials. You may see the solvent that is used for your needle wash, if you have such a thing. Lots of things.... Why do you worry about it?
By Daren on Tuesday, January 21, 2003 - 06:57 am:
why don't you just inject a sample of sodium citrate in your solvent at the same concetration of the citrate counter ion in your concentrated sample and compare peak areas. This will at least provide some added confidence that it is the salt you're seeing.
By Anonymous on Wednesday, January 22, 2003 - 04:29 am:
Most probably the increase in so called solvent peak is due to either citrate or residual solvents present in your sample.