Chromatography Forum

I am currently using the following mobile phases to try and separate an anion compound with HPLC:

A) 0.005M tetrabutyl ammonium phosphate in methanol
B) PIC A reagent in water


With 90% (A) and 10% (B) mixture, pressure seems to be fine and stabilises at around 80 bar at 1ml/min;

But with increase of (B) percentage as little as 20% causes pressure to shoot up as far as 300bar! I found the mixture to be quite viscous as well.

The above was tested without the sample, just the mobile phases washing through the column alone.

Does anyone experienced with similar problems before? Or is this quite abnormal?

Thanks in advance!

Looks like a precipitation of the reagent due to the high methanol content. Disconnect the column, change to water and wash out the precipitated reagentform the instrument. Then reconnect the column and flush it with water at low flow until the pressure goes down.