Chromatography Forum

All , I've been having trouble with rising pressure on my hplc - 1 mL/min for water once generated less than 3000 psi and now is generating 4000 psi and rising on a daily basis. There have been relatively little increases in pressures with acetonitrile , so why is it that water itself is generating so much pressure?

Could it be that something's plugged up inside of the water pump ? I've checked the outside connections and all of them seem fine , I've taken them apart and then reconnected everything. My concern is on whether something on the inside has been plugged up in sections that pertain to the workings of the pump for water.

I'm cleaning the column with 10 minutes of water at 1 mL/min and 10 minutes of acetonitrile at 3 mL/min. Perhaps I should be cleaning more with a stronger polar solvent or vice versa a stronger nonpolar solvent. Perhaps I'm using too high of a flow rate for acetonitrile which is destroying the column.

Any advice would be appreciated.

Column type?

Chances are you are building up something on the column head. Typically, executing a cleaning routine w/ the column reversed will help (at least a little). Also, better sample clean-up may be in order. Without column and sample details, we can't tell for sure.

PS - straight water is not a very good idea for many common column types, a minimum of ~5% ACN would probably be better.

Column type?

Chances are you are building up something on the column head. Typically, executing a cleaning routine w/ the column reversed will help (at least a little). Also, better sample clean-up may be in order. Without column and sample details, we can't tell for sure.

PS - straight water is not a very good idea for many common column types, a minimum of ~5% ACN would probably be better.

it's a restek biphenyl column ... the sample is biocide in quaternary surfactants. I need to find the right solvent types to get rid of both nonpolar and polar substances that are building in the column , so far most people have suggested thf and methanol.

is acetonitrile an appropriate solvent for storing the column after shutdown?