By fred on Wednesday, June 5, 2002 - 06:47 am:
Hello,
I want to replace the methanol in an elution buffer (30% methanol) by acetonitrile (ACN). Would somebody know where I can find a table comparing the "elution strength" of different organic modifiers or indicate whether a thumbrule exists to calculate the percentage of acetonitrile that has the same effect than 30% methanol?
Thank you very much for considering this question.
By Anonymous on Wednesday, June 5, 2002 - 08:14 am:
Usually a smaller percentage of acetontitrile will match; try 25% or 20% ACN to start. THF instead of methanol will also require a smaller percentage.
By Tom Mizukami on Wednesday, June 5, 2002 - 08:42 am:
Fred,
The very rough thumbrule is that 50% Methanol is about as elutropic as 40% ACN. So like Anon. said, about 25%.
Here is a link to a nomograph by MacMod; http://www.mac-mod.com/tr/00111-tr.html
By Einar Pontén on Tuesday, June 11, 2002 - 01:32 pm:
Snyder & Kirkland presented some data in "Introduction to..."
These makes it easy to maintain the capacity but manipulating selectivity by a new organic modifier.
Thus to keep the solvent strength of the eluent S(eluent) you need some data on pure solvent S(solvent) and the ratio X(solvent).
S(eluent) = S(solvent) x X(solvent) + S(water) x X(water)
For reversed phase (rel. scale)
S acetonitrile = 3.2
S methanol = 2.6
S ethanol = 3.6
S i-propanol = 4.2
S water = 1
The rule of thumb above seems to be good.
Einar Pontén
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