Ifenprodil is not very solubile in aqueos solutions. However, because it has an amine group, it can be made a solubile salt when mixed with an organic acid such as tartaric acid.
Here is our recipe (February 2008):
(Note that we have a final solution with 1% tartaric acid, and most people seem to end up with 0.1%. Probably I was just impatient and so used a high concentration of tartaric acid to guarantee dissolution.)
Prepare 10% tartaric acid made in distilled water,
- e.g. 1 g tartaric acid in 10 ml final volume.
Dissolve ifenprodil in 10% tartaric acid at 10x the desired final concentration
- e.g. if you want a final concentration of 3 mg/ml, then dissovle 30 mg ifenprodil in 1 ml of 10% tartaric acid.
Then add 0.1M Phosphate buffer, 0.15M NaCl to bring the solution to the desired final concentration
- e.g. add 9 ml of PBS to 30 mg ifenprodil dissolved in 1 ml of 10% tartaric acid
Bring the pH of the solution from ~pH 4 to ~ pH 7 by added a small amount of 10 N NaOH
- e.g., add 10 N NaOH only 10 microliters at a time, checking pH with pH paper until the solution is neutralized.
- it takes about 100 microliters of 10N NaOH to neutralize 10 ml of 1% tartaric acid, but add the NaOH bit by bit and check pH frequently.
Prepare vehicle of 0.1M PBS, 1% tartaric acid and pH to 7.0 as above.
- e.g. mix 1 ml of 10% tartaric acid and 9 ml of 0.1M PBS, use 10 N NaOH to bring to pH 7.0.
Figure From: J. Allen, A synthesis of DL-erythro-2-(4-benzylpiperidino)-1-(4-hydroxyphenyl)-[1-14C]propan-1-OL L-(+)-tartrateJournal of Labelled Compounds and Radiopharmaceuticals Volume 17, Issue 6 , Pages 785 - 792