Analysys of potassium sorbate and sorbic acid in RP-HPLC

[Subject0]

Good morning!

I analyze some preservatives in cosmetic products using ACN and 0.1% phosphoric acid in water as mobile phase in gradient elution.

My standards (some parabens, sorbic acid, phenoxyethanol, sodium dehydroacetate) are dissolved in 1% phosphoric acid/methanol and then diluted in the same solvent, and so are my samples.

Now I need to analyze and quantify potassium sorbate. Will be the acidic composition of my mobile phase be enough to convert potassium sorbate into sorbic acid? How would you approach it? Do i need to dissolve it in water and then adjust pH?

Thank you

[Consumer Products Guy]

Now I need to analyze and quantify potassium sorbate. Will be the acidic composition of my mobile phase be enough to convert potassium sorbate into sorbic acid?

Yes.

How would you approach it? Do i need to dissolve it in water and then adjust pH?

I'd just let the acidity in your dilution mix do its job. Use potassium sorbate as your standard.

By the way, in the 1970s we assayed for potassium sorbate by packed-column GC after converting to sorbic acid.