Chromatography Forum

Dear all,
I'm a new guy in this forum. I need for someone to solved this: I'm analizing a cough and could syrup, with phenylephrine and clhorpheniramine. I have a good HPLC Platform in order to see the degradation of each component, 0.1% = QL. But I getting crazy because the syrup has carboxymethylcellulose, this excipient stuck in the C18 column, causing high back pressure and loss of eficiency on the column.
I tried to eliminate the CMC by using SEP technique (SAX) but for the highly viscous solution obtained is a nigthmare to pass througth the SEP. Also precipitate the CMC by adittion of ETOH, but my analite has some affinity for the CMC-precipitate, and I have deficient accuracy for the phenylephrine.
Someone has an idea to eliminate the CMC of a solution?

Thank you all!

G

I find the answer: Use an acidic ETOH (0.025N HCL) In this situation the phenylephrine don't be adsorbed by the precipitate of CMC, surely because at that pH the carboxylic goups are protoned.
Thank you all for taking the time to read this...

G

Hi gtvofigo; Yes ucing low pH is a good way; what is hapening is the protonation of the Secondary amine' ta low ph it's protonates.

For this reason and for the future I do not think that would be the best way. since the chlorpheniramine and phenyllephrine have basic gorups the bes is retain them at low pH using Cation xchange not SAX; you retain your analytes at low pH and then you elute them at high pH (once amine groups desprotonates)