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Has the pressure in your preparative liquid chromatograph suddenly risen significantly compared to before?
Created on 05.11
**Author:Orginal from Internet
Has the pressure in your preparative liquid chromatograph suddenly risen significantly compared to before? Can’t find the cause? The following methods may help you troubleshoot the issue!
Potential points of blockage in liquid chromatography: online filters, purge valve inserts, injector needle holders, columns, column ovens and flow cells.If the pressure becomes too high, you should immediately open the purge valve to relieve the pressure, then close the purge valve again before checking each component in turn.
I. Remove the chromatographic column and slowly increase the flow rate to observe changes in pressure.
I. If there is no pressure after removing the chromatographic column, this indicates that the blockage is in the column or the flow cell:
1. Connect the front end of the chromatographic column and disconnect the rear end.
①. If the pressure is high, this indicates a blockage at the front end of the column. Investigate the mobile phase recently used with this column (salts precipitation; use a high-water-phase ratio and increase the column temperature to flush at a low flow rate) and the solubility of the sample being analyzed (if the sample has poor solubility and has precipitated, backflush with a highly soluble solvent at a low flow rate without connecting the detector);
②. Consider switching to a less viscous mobile phase (you may also slightly increase the column temperature or reduce the flow rate);
③. Column temperature is too low: On cold winter mornings, before the laboratory heating has warmed up, room temperature is very low, which increases the viscosity of the mobile phase. This can cause a significant rise in column pressure and slow down the mixing of the mobile phase. It is best to wait until the room temperature has stabilised before commencing the experiment.
2. If the column pressure is low, this indicates a blockage in the flow cell between the rear end of the column and the detector.
Remove the column, connect a two-way connector, and disconnect the tubing from the detector outlet (to prevent the detector from being damaged by overpressure caused by a blockage in the outlet tubing). If the pressure is high, the flow cell is blocked (flush with a low flow rate); if the pressure is low, the waste line downstream of the flow cell is blocked.
II. If the pressure remains high after removing the chromatographic column.
1. Disconnect the tubing upstream of the column oven (to check for blockages inside the column oven or in the connecting tubing);
2. If the pressure remains high, disconnect the tubing upstream of the injector (to check for blockages in the injector needle seat tubing);
3. If the pressure remains high, disconnect the tubing upstream of the purge valve (to check for blockages in the purge valve or the tubing).
4. If the pressure in the HPLC system exceeds 3 MPa without a column connected, it is highly likely that the purge valve core (filter element) is contaminated and requires replacement;
5. If the pressure remains high, this indicates a blockage in the tubing upstream or downstream of the pump/mixer or in the in-line filter.
Once a blockage in a component or section of tubing has been identified, it can be replaced or flushed:
1.If the blockage is caused by salt precipitation, it can be flushed with hot water;
2.If the blockage is caused by particulate matter, it can be flushed after ultrasonic cleaning;
3. If the blockage is caused by sample precipitation, it can be flushed with a solvent in which the sample is soluble after ultrasonic cleaning.
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