HPLC analysis - Retention time of a API and its salt form

[rickmartink]

Dear all

In HPLC analysis will the Base and Its salt form of a API have the Same RT or different RT. Eg. Omeprazole and Omeprazole Magnesium with these two have same RT during HPLC run or different RT.

Pl. advice

[prepcolumn]

it will be same

[rickmartink]

it will be same

Thanks
then how do i differentiate or know in a blind sample ( placebo mixture containing either omeprazole or omeprazole Magnesium) whether it has omeprazole mag. or Omeprazole.

[tom jupille]

Measure Mg++

[Vlad Orlovsky]

You need to quantify both counter-ions and calculate content of free base and salt. Actually you molecule is basic and Mg ion is basic. Is it part of formulation?

You can do both using reversed-phase cation-exchange column. You will need ELSD/CAD for Mg determination:
http://www.sielc.com/upload/file/pdf/SI ... y_2009.pdf