Chromatography Forum

I am analyzing a mixture of three lipids by HPLC with ELSD detection. I get good separation on a C-18 column but the %RSD for one of the components is large (~15%) but the other two lipids show good reproduciblity (%RSD < 2%). This component is a PEGylated lipid and is the second peak to elute.

The problem is not carryover from a previous injection because injecting a blank after the sample results in no peaks in the blank injection.

Is this a problem inherent to using ELSD detection with PEGylated compounds?

is it the only one with PEG?
if yes then
one possibility is of your procedure of doing the pegylation
how do you know that it is going well?

PEGs are sticky. Try adding a small amount (10ppm) of glycerin to your sample

Carls, thanks for the idea, I will need to order glycerin but will do so and will report back.

Unmgvar, we purchase the PEG lipid so if it is variable pegylation, we will need to find an alternate supplier.