(please forgive the repetition - I emailed this message to your Inbox, but I decided to post it anyway because others may also find it useful).
I can think of 3 ways to help you with this purification:
1) Are you familiar with cyano-functionalised silica gel? Silica gel that has been functionalised with cyano (CN, otherwise known as “carbonitrile” groups) has the exceptional property of being both a “normal” AND a “reverse” phase. The polarity of this sorbent is exactly half way between the polar and non-polar phases, therefore it can behave as a normal sorbent or a reverse phase sorbent depending on the solvent system that you employ. The beauty of CN-functionalised silica gel is that it is the least retentive sorbent in either situation; in other words, your amine would move down the column much faster and more readily than with regular silica gel. The only downside of using cyano-functionalised silica gel is that it is potentially quite expensive – slightly more expensive than C18 reverse phase silica, in fact.
2) The second choice, which happens to be much more affordable, is to use Florisil®. The Florisil® sorbent is a magnesia-silica gel that has been activated at high temperature. It is great for lipids, fatty acids, cholesterol esters, amines, basic compounds, natural products and alkaloids, nitrogen-containing heterocycles etc. It is slightly basic in its nature and it would allow an amine to flow fast and efficiently down the column. Since no real fictionalisation is involved with Florisil® the cost of the sorbent is low; however, it is not as “flexible” in its use as CN-silica gel, which can be used as both a normal and a reverse phase sorbent.
3) Last but not least, you have the option of doing some “catch and release” purification. To do this, you will need a functionalised silica gel that is a “strong cation exchanger”: for example propylsulfonic acid-functionalised silica gel, or tosic acid-functionalised silica gel. If you pass your solution through a column containing the cation exchanger, your product will be “caught” by the silica gel and you can wash off the non-basic impurities. Then, you can pass ammonia-methanol through the silica gel, and your compound will be released.