Four Points Lead to Elevated HPLC Column Pressure in the Liquid Chromatography
1. Replacement is not complete when replacing the mobile phase
When the mobile phase system is changed, incomplete replacement causes the different nature and immiscible mobile phases to existing in one system, which also causes the pressure to rise.
2. Precipitation of salt crystals
After using a buffer or a mobile phase with a buffer added, the inorganic salt component of the buffer may remain in the system. They will precipitate out due to reduced solubility in the new mobile phase system, causing increased fluid resistance and increased pressure.
3. Precipitation of the sample
When the solvent used in the sample does not match the mobile phase, the sample entering the HPLC column may sometimes precipitate due to reduced solubility, causing an increase in pressure.
4. Pressure pulse
During the operation, a sudden rise and fall of the pressure inside the system sometimes occur. For example, when the injection valve is rotated, the action is too slow, and the liquid flow is blocked and then released instantaneously; the pressure difference at the instant of starting is higher. The pressure pulses thus formed cause collapse of the porous filler and minor changes in the structure of the bed. The long-term accumulation of filler fines may also increase the resistance of the HPLC column bed.