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- Posts: 2
- Joined: Wed Mar 14, 2012 10:22 am
Hi all!
I´m doing a work regarding free porphyrins in bacteria and I´m evaluating what solvent that is preferred after a elution from an C18-SPE. The standard I´m using contains 6 different porphyrins with carboxylic acid side chains ranging from 2 to 8 (fully substituted). This leads to a linear relationship in polarity and amount of carboxylic acid chains, were 8 carboxylic acid chains are the most hydrophillic (log P = -27) and the one with two carboxylic acid chains are the most lipophillic (log P = 7). I have some problem to choose a proper eluent solvent from the SPE since a more polar solvent (6M formic acid) give high response for the more polar porphyrins and less polar solvents (acetonitrile) results in low responses for polar porphyrins. What do you do when the standard have that a large spread in log P?
I´m doing a work regarding free porphyrins in bacteria and I´m evaluating what solvent that is preferred after a elution from an C18-SPE. The standard I´m using contains 6 different porphyrins with carboxylic acid side chains ranging from 2 to 8 (fully substituted). This leads to a linear relationship in polarity and amount of carboxylic acid chains, were 8 carboxylic acid chains are the most hydrophillic (log P = -27) and the one with two carboxylic acid chains are the most lipophillic (log P = 7). I have some problem to choose a proper eluent solvent from the SPE since a more polar solvent (6M formic acid) give high response for the more polar porphyrins and less polar solvents (acetonitrile) results in low responses for polar porphyrins. What do you do when the standard have that a large spread in log P?
