[Prof.Zzz]

How to make 20% Ethyl Acetate solution?
Is it 20mL ethyl acetate and 80mL Hexane?
or 1mL ethyl acetate and 5mL hexane?
I know this sound ridicules, but I can't find on the web how to prepare such mixture for chromatography.
Also 9:1, is it 90%??

[Babcock_Hall]

Assuming that 20% refers to volume-to-volume (v/v) and assuming that the other solvent is hexane, then your first answer is correct.

[billnotgatez]

@Babcock_Hall
Is the second answer also correct?
Or is my powers of perception being fooled?

[Dan]

@Babcock_Hall
Is the second answer also correct?
Or is my powers of perception being fooled?

I fear they are - second answer was 1:5, or 17% v/v

In the context of chromatography eluent it's almost certainly % v/v - I've never seen anyone weighing out their column solvents! 

[billnotgatez]

Duh smacking head against wall
1mL ethyl acetate and 5mL hexane
change to
1mL ethyl acetate and 4mL hexane
Is that better or am I losing it.

[AlphaScent]

Its ok, I had one of those days too...

[Babcock_Hall]

Dan,

Well over 99% of the time, I am sure people use volumes, so point taken.  Nevertheless, I still think when communicating with other scientists, one should specify whether one is using volumes or mass (this is my pet peeve).  In HPLC the ion pair reagent trifluoroacetic acid (TFA) may either be measured by volume or by mass.  Given its rather high density, 0.1 % TFA by mass versus by volume are quite different concentrations.  http://www.nestgrp.com/pdf/Vapp/AN9804.pdf

[Dan]

Dan,

Well over 99% of the time, I am sure people use volumes, so point taken.  Nevertheless, I still think when communicating with other scientists, one should specify whether one is using volumes or mass (this is my pet peeve). 

I agree completely!