Chromatography Forum

Hi,

I'm having a problem in the middle of runs. The column had reached over the maximum limit of standard operation. I tried to wash the column using 100% ACN. At first the pressure is normal which below than 100 bar. But then over time it reached to 350 bar. I'm trying to consider about regenerating my column. But still have no proper procedure. I'm using capillary column C18 (0.5 mm) with silica beads. And mobile phase water,ACN, and acetic acid.

If the symptom is simply high pressure (i.e., no changes in retention or selectivity), the most probable causes are:
- precipitation of something from your samples or the mobile phase
- plugging of the inlet with particulate matter (again, from either the samples or the mobile phase).

If it's plugging, the only viable fix is to reverse-flush the column. Check with the column manufacturer to see if your particular column can be reverse-flushed; the procedure may damage some columns (but your column is already unusable, so how much worse can it get?).

If it's precipitation, reverse-flush may not help (the junk may have precipitated behind the inlet frit. In that case, the remedy is to reverse-flush the column with something that will redissolve the precipitate. That means you will have to make an educated guess about your samples and what might have precipitated.

To save time and money maybe it is time to purchase a new capillary?