Chromatography Forum

I'm not sure if I'm articulating myself well enough, but here's my problem: I have a current HPLC system, where we typically have backpressure readouts of around 15 MPa. We are looking to get a new HPLC, and the rep said its DAD detector has a maximum pressure of 6 MPa. My questions are:

- Is the pressure at the pump outlet the same as the pressure at the column inlet and outlet?
- What pressure is actually being shown on the system readout when looking at the pump? (I'm assuming just the pressure at the pump outlet)
- Is the pressure at the detector usually significantly less than at the pump outlet?
- Assuming everything transfers from one system to our new one, and we end up with the same types of backpressures, will I have issues with this new detector?

No, the pressure is not the same in the whole system.
The pressure basically is the backpressure created by the column. Simplified, the pressure displayed is the pressure between pump and column. In the column, there is a pressure gradient, i.e. the pressure is decreasing from inlet to outlet. After the column, i.e. before the detector and in the detector flow cell, the pressure is much lower. In a coventional HPLC system, this pressure is usually next to nothing. In modern UHPLC equipment, with narrower tubings and low-volume flow-cells, there can be considerable back pressure after the column, but it will still be much lower than 6 MPa.
You only have to be careful if you want to put another detector in-line after the DAD...this might create more backpressure on the DAD's flow-cell.

Thanks, HPLCaddict. That's all I needed to know. Your help is much appreciated.