Chromatography Forum

Hi,

Please can someone explain the differences in the chemistry between these two HPLC columns:

Agilent ZORBAX RRHD Eclipse Plus C18 (50 mm x 2.1 mm, 1.8µm)

Waters Acquity UPLC BEH C18 column (50 mm × 2.1 mm, 1.7 μm)

I'm getting very little retention with the ZORBAX, even with 100% aqueous isocratic flow. I've seen some reports of others having success with the Acquity column, for the same compound as I'm developing a method for. I just want to understand the differences between these two columns before I buy one. Thank you.

Difficult to say,

both brands are excellent, They use a different base silica, and different silanes, a different way to do the endcapping.
I your case I would try a HILIC column.

Agilent ZORBAX RRHD Eclipse Plus C18 - carbon load 9 %.
Waters Acquity UPLC BEH C18 - carbon load 18 %.
Poor retention with 100 % aqueous MP may be due to dewetting of the stationary phase. To avoid this, try to wash the column with 30-50 % ACN in water at your working flow rate, then switch to your 100 % aqueous MP without stopping the flow, and inject the analyte solutions.

Also of note, the Agilent has a 95angstrom pore size while the Waters has a 130angstrom pore size.

This can make a difference in how the water interacts with the phase and with the resolution. It isn't a huge difference but combined with the carbon loading maybe will be noticeable.

Thanks for the tips everyone