fractional abundance of liquid solution


How to determine fractional abundance of liquid solution?

Can you say some tag words that might lead to me to read about what you are asking?  It isn't (those terms) in my body of knowledge but am curious.  With the words 'fractional abundance' I think of fractions taken off of a chromatography column or a distillation.  So different fractions would have different abundances of the compounds you are separating.  Is that right?  Any more tag words for me to find this?