Unusual High backpressure with organic solvent?

Question

Hello, it's 2 days my HPLC show strange back pressure in gradient mode when organic % increase, the method is 
 
 Zorbax C8 
 0 min - 1L/min - 40% Metanol / 60 % water PRESSURE 140 bar 
 10 min - 1L/min - 40% Metanol / 60 % water PRESSURE 140 bar 
 20 min - 1L/min - 90% Metanol / 10 % water PRESSURE 200 bar 
 
 with a mountain signal out of the detector 220nm 
 
 This happen also with blank injection

what could happened?

abasdeo · Accepted Answer

Hello, 
 On the initial part of the gradient when you get 140 bar, is that normal and expected? If yes, then you don't have a clog in the system because the pressure would be higher then. Methanol/water combination has a peculiar pressure profile in that it rises into a "hump" as the percentage of Methanol increases then slowly comes back down. So it's possible there may not be anything wrong. You are changing from 40% to 90% Methanol and if you watch the pressure profile, you are going to see that slow increase then decrease over time.

Unusual High backpressure with organic solvent?

Top Replies