peak shoulder

[Mark Tracy]

Since the detection is at 375 nm, you have a lot of freedom to select your buffer system. It is reasonable to assume that the rate of acid-induced degradation is directly proportional to [H+]; in other words a factor of 10 for each pH unit. You can use formate (pH 3-4) or acetate (pH 4-5) buffers for your mobile phase and diluent to reduce the decomposition of the sample.

[Chem1]

I got the peak shoulder problem solved by using Phenomenex brand column instead of Zorbax column.
Thank you for all your helps.

[DR]

Is the Phenomenex <5µ? That was going to be my suggestion - that you could use the same dimensions for column jacket with a smaller particle size. If what you were seeing was poor resolution of cis-trans isomers, that should help.

[Rob Burgess]

I have seen this kind of affect before i.e. changing just the column brand having a significant impact on the baseline of your gradient.

Are there any rational reasons for this that anyone could suggest ?!?

[Chem1]

DR,
I did not have cis-tran separation problems. My problem was my reference standard peak had a shoulder (please see my first post). I got it fixed by changing column brand only. It worked! . But I don’t understand why it worked.

Thanks,