Problems using an HP 1050 pump with glycerol as mobile phase
Posted: Tue Feb 18, 2014 5:47 pm
Hello,
First, let me say the title may be a bit misleading. I am not doing HPLC, but I am trying to use an HP1050 HPLC pump to pump glycerol into a reaction system. The pump works fine using water, methanol, etc but is having some problems pumping glycerol. I am trying to flow at 0.333 ml/minute into a system at vacuum. At first, I tried heating the glycerol in the solvent bottle to help lower the viscosity, to no avail. The high surface area/volume ratio of the smaller diameter tubings caused the sample to cool down before it even reached the piston block.
Then, I thought the problem may have been that the tubing was unable to deliver glycerol to the first piston, even if the first piston was pulling full vacuum pressure in the piston chamber. I addressed this by pressurizing (in a rated pressure vessel) the headspace of the glycerol feed bottle to 160 psi. This allowed the pump to flow some glycerol, but eventually the pump maxed out on pressure.
To address the maxing out on outlet pressure, I removed the glass filter frit on the outlet valve, and it brought the pressure down to a reasonable level.
Then, I noticed the pumping rate was not linear with respect to indicated pumping rate. For instance, at 0.5 ml/min the pump put out a droplet of glycerol every 5.5 seconds. At 0.25 ml/min the pump put out a droplet every 7.5 seconds. The droplets have roughly the same volume, and are a good estimate of volumetric flow.
Tl;dr : Does anyone have any suggestions on how to use this pump with a very viscous solution such as glycerol, and get a good correspondance between indicated flow/actual flow? Thanks.
First, let me say the title may be a bit misleading. I am not doing HPLC, but I am trying to use an HP1050 HPLC pump to pump glycerol into a reaction system. The pump works fine using water, methanol, etc but is having some problems pumping glycerol. I am trying to flow at 0.333 ml/minute into a system at vacuum. At first, I tried heating the glycerol in the solvent bottle to help lower the viscosity, to no avail. The high surface area/volume ratio of the smaller diameter tubings caused the sample to cool down before it even reached the piston block.
Then, I thought the problem may have been that the tubing was unable to deliver glycerol to the first piston, even if the first piston was pulling full vacuum pressure in the piston chamber. I addressed this by pressurizing (in a rated pressure vessel) the headspace of the glycerol feed bottle to 160 psi. This allowed the pump to flow some glycerol, but eventually the pump maxed out on pressure.
To address the maxing out on outlet pressure, I removed the glass filter frit on the outlet valve, and it brought the pressure down to a reasonable level.
Then, I noticed the pumping rate was not linear with respect to indicated pumping rate. For instance, at 0.5 ml/min the pump put out a droplet of glycerol every 5.5 seconds. At 0.25 ml/min the pump put out a droplet every 7.5 seconds. The droplets have roughly the same volume, and are a good estimate of volumetric flow.
Tl;dr : Does anyone have any suggestions on how to use this pump with a very viscous solution such as glycerol, and get a good correspondance between indicated flow/actual flow? Thanks.
