Chromatography Forum

Hi,
If i purchase a new HPLC column (Any RP,IEC,SEC or HIC), vendor provide all the information with the column. I have a doubt if in the insert of the column say max pressure limit is 40 bar and if i am runing my related hplc method without the column and it shows 10 bar pressure, so what could be the my max limit keep in my same HPLC method. is it 40 bar or 50 bar?
Thanks & Regards
:lol:

Hi,
If i purchase a new HPLC column (Any RP,IEC,SEC or HIC), vendor provide all the information with the column. I have a doubt if in the insert of the column say max pressure limit is 40 bar and if i am runing my related hplc method without the column and it shows 10 bar pressure, so what could be the my max limit keep in my same HPLC method. is it 40 bar or 50 bar?
Thanks & Regards

I am not sure if there's something misunderstood here because max pressure of 40 bar is too low for an analytical HPLC column. For a new 4.6 x 150 x 3um, it's easy to build up 100bar with 1ml/min flow.

Apart from 40 bar being a very low pressure I think you may have 50 bar when the 10 extra bar coming from the system before the column, so running without the detector. The the pressure on column will be 40 bar.

Hi,
If i purchase a new HPLC column (Any RP,IEC,SEC or HIC), vendor provide all the information with the column. I have a doubt if in the insert of the column say max pressure limit is 40 bar and if i am runing my related hplc method without the column and it shows 10 bar pressure, so what could be the my max limit keep in my same HPLC method. is it 40 bar or 50 bar?
Thanks & Regards
:lol:

I am not sure if there's something misunderstood here because max pressure of 40 bar is too low for an analytical HPLC column. For a new 4.6 x 150 x 3um, it's easy to build up 100bar with 1ml/min flow.

actually this is my IEX HPLC column Tosho 75 x 7.5 mm. and the specification given with this column is 40 bar max limit but there is not mehtioned with system or without system.

The manufacturers man exactly what they say: The pressure is the maximum ON the column. If your 10 bar system pressure is on the detector and you run the pumps at 50 bar then the pressure on the column is 50 bar. If your 10 bar system pressure is between the pump and column then 50 bar at the pump will put 40 bar on the column.

actually this is my IEX HPLC column Tosho 75 x 7.5 mm. and the specification given with this column is 40 bar max limit but there is not mehtioned with system or without system.

So you can check where pressure drop is. Without the column and detector disconected, if the pressure is 10 bar, so pressure drop is at the front of the column -> it's harmless to the column. If the pressure drop rises when you connect to the detector, it's after the column and you should count it to the total column tolerance as HW Mueller has mentioned.

It is irrelevant where the extra-pressure is as long as it is not the differential pressure over the column bed. The differential pressure over the column bed is what should not exceed 40 bar. If you have a post column pressure of 100 bar, it does not do anything...

Before everybody screams at me: in GPC/SEC it is common to specify a pressure for an individual column. In classical GPC/SEC you put six columns in series, and then the total pressure will be rather high, but the differential pressure on each column remains low.

Hm, so I had a wrong concept carried around with me for some 40 years? It makes a lot of sense that the manufacturers mean differential pressure, though. But: I am still holding on to "absolute" pressure playing some role also, for instance, polymeric columns swell when contacting solvent, pressure tends to reverse that, etc.

Uwe's explanation is similar to voltage drop across resisters in series