Overpressure, using products with amines and amides in C18

[usuchrom]

I have several years working in preparative chromatography and this not happened to me so far. I use Phenomenex columns (Luna and Gemini, C18 media) and I have watched in recent months a considerable increase of pressure to purify compounds with amine radicals (active and disabled) and amides. One of these products made that a Luna "died" in a week (basic aqueous phase: pH 7.4. Organic phase MeCN-MeOH)
The dimensions of columns are 100x21.2mm 5um.
I use a pre-column guard.
The amount of sample injected is 25-50mg.
Is there a specific column for these compounds?
Is the problem of the column, or compounds?
Could the problem have been generated by the by-products of the reaction?

I wish you can help me,
thanks

[Uwe Neue]

It is usually not the product that you are purifying, but gunk in the sample that is clogging up columns. Try to figure out what this is, and then think about elution schemes.

What does the column manufacturer recommend you to do?

[usuchrom]

Following the recommendations of the manufacturer, the column wash back flush (pure water, MeCN, THF, CH2Cl2, THF, water-MeCN 50%, mobile phase)
But pressure has not improved. They also recommended inject 20 mg, but this was to continue blocking the column. I have tried injections of 4ml and 8ml, but the result is the same.

[usuchrom]

More information about the sample preparation: the sample was dissolved with the mobile phase.
I also tried to purify it using an aqueous acid (0.1% formic acid), but the result was increased pressure to the overpressure.

[ym3142]

1, how did your Gemini behave?

2, I wish you could see if the peak shape was changing so that you know if the column was actually fouling

3, what was in your sample?

4, does the residual radical cause polymerization of something? if so the polymer may clog your column;

5, some vendors admit their C18 column foul quickly at pH 7 or above

[usuchrom]

1, Gemini endured more about this product, but the column is currently working around 140Bar, when usually work around 60Bar.
2, There was no change in peak shape that tells me nothing unusual. Since the first injection (just endured two injections Luna, in Gemini the rest: about 20) until the end, I always got the same kind of peak.
3, Pentane ring and an aromatic ring (let's call them 1 and 2) with a carboxylic acid in 2 (position 1) and a carbonyl in 2 (position 6). In 2, in position 3, SEA contains alkyl amines and amides.
4, I do not know if there was a polymerization. How could I know it?
5, The pH range is 2-10 in Luna (although about 2, lasts a very short life). In Gemini, pH 1-14. I always use Luna with pH around 7 to 8.

[HW Mueller]

Clean up your act as Uwe already told you.

[ym3142]

if the junk was from the sample it should have block both Luna and Gemini the same way. Since Gemini is lasting longer than Luna it seems to me your sample actually was reacted with stationary phase.

Why and how? Of course it is challenging question. Usuchrom is the only person who may have the answer.

[usuchrom]

I think the problem was the pH. Because I tried to purify with Gemini and also, the pressure incresing. Al the examples that I told before was with a basic pH (around 7.5). At least I have to purify with Formic Acid 0.1%, in Gemini, and the pressure decreased (not too much).