Troubleshooting Pressure Increase with Shodex NH2P Columns

Record: 928

Category: Instrument
Product: NH2P
Sample: N/A

Question

Why does system backpressure increase immediately after the first injection when using NH2P columns? Even when running a blank injection, the pressure increase remains.

Answer
If column pressure increases immediately after the first injection and persists even with blank runs, the cause is usually not the column itself. Possible sources include:

• HPLC injector: sample valve or rotor seal leakage can introduce particulates or cause blockages.

• Instrument plumbing: restrictions in tubing, frits, or inline filters. Confirm all connections use 1/16″ tubing with standard 10-32 screw-type fittings to avoid dead volumes or partial blockages at the column inlet.

• Mobile phase: impurities or particulates in solvents can deposit early in the run.

Recommended steps:

• Disconnect the column and run the system with a union to confirm whether the pressure increase is from the HPLC system or the column.

• If pressure still rises without the column, the issue lies with the injector or HPLC system.

• If pressure is stable without the column, flush the column in the recommended regeneration solvent to rule out precipitation inside the packing.

In this case, the persistent pressure increase was determined to be related to the injector/HPLC system rather than the NH2P column.

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