Modifier Concentrations

[thiazole]

Often times people will use a wide range of modifier concentrations in HPLC. For example, you might see a range of 0.01 to 0.1% TFA for a C18 modifier. I've always wondered what makes someone decide to use 0.01% one time and 0.1% the next. What are the advantages and disadvantages to using more concentrated or more dilute modifier concentrations.

[tom jupille]

If the method was developed systematically, the modifier concentration should have been studied and optimized (usually, this means finding the lowest level that is effective).

All too often, however, it is "whatever worked on last week's method".

[djacqo]

[quote="whatever worked on last week's method".[/quote]

So true. Choosing the right modifier is the important thing, I don't ever modify the amounts. I keep them at 0.1%