Removal of SDS in order to analyze by LC/MS

[MarkFG]

I am currently analyzing an ophthalmic drug product that has been photodegraded in order to generate an impurities profile. I'd like to collect fractions of several of the observed peaks for LC/MS analysis. However, my diluent and mobile phase is a 58% aqueous solution of sodium dodecyl sulfate with 0.6% H3PO4 mixed with 42% acetonitrile. Is there any extraction technique available to removed the SDS in order to make the samples more LC/MS friendly?

[Mark Tracy]

If you plan to re-analyze by LC/MS then you can just let the LC separate them. If you plan to just do an infusion into the ESI source, then you need to remove both the SDS and phosphate. For that, try a weak anion exchange SPE cartridge. Use a compatible volatile acid like formic for elution.