Chromatography – Frequently Asked Questions

Got a Question?

Our Engineers Get These Questions the Most

Chromatography and purification are at the heart of analytical and preparative chemistry. Whether you're working with HPLC, flash chromatography, or column purification, getting consistent, high-quality results depends on understanding the fundamentals and troubleshooting common challenges. This FAQ answers the questions we hear most often - from choosing the right stationary phase to optimizing yields and improving reproducibility.

General

When Should Column Parameters be Reconsidered? If maintaining separation requires repeated adjustment of flow rates, gradients, or loading, it may indicate that operating conditions would benefit from being redefined at the column level.

How Does Packing Uniformity Affect Performance? Packing uniformity influences flow distribution and efficiency. Variations can affect separation behaviour, selectivity, and reproducibility across runs.

What Should be Prioritised in Column Design? Maintaining stable flow, pressure, and packing behaviour across the expected operating range is central to supporting consistent performance.

How do you scale chromatography columns from pilot to commercial manufacturing?

Chromatography scale up starts with maintaining the required linear velocity, residence time, bed height and resin performance.

As column diameter increases, volumetric flow rises significantly. This affects pumps, valves, piping, pressure drop, buffer supply and facility integration.

For that reason, the column should not be selected as an isolated vessel. It should be evaluated as part of the full downstream process and the surrounding chromatography system.

How do I select the correct chromatography column diameter?

Column diameter is selected based on batch volume, resin capacity, target linear velocity, bed height, pressure drop and required process time.

A larger diameter can reduce cycle time, but it also increases volumetric flow and utility demand. The right diameter is therefore a balance between process performance, system capability and facility fit.

What is a dynamic axial compression chromatography column?

A dynamic axial compression column uses a movable piston to apply controlled axial compression to the packed bed.

This helps maintain contact between the packed bed and distributor during packing and operation. In large scale chromatography, dynamic axial compression can support bed stability and reproducible performance when the process is correctly designed and operated.

What does DAC solve in process chromatography?

DAC mainly supports bed compression control, reproducible packing and packed bed stability.

It does not solve every chromatography issue by itself. Resin selection, slurry preparation, packing method, pressure profile, distributor design and process conditions still determine the final column performance.

What is the best packing procedure for large scale chromatography columns?

A good packing procedure defines slurry concentration, filling method, packing flow, pressure profile, compression level, bed height target and acceptance criteria.

For large columns, the procedure must be repeatable and documented, because small variations in slurry handling or compression can become more visible at process scale.

How can channeling in chromatography columns be prevented?

Channeling is reduced by correct slurry preparation, controlled packing flow, stable bed compression, suitable distributor design and careful monitoring of pressure and performance data.

If channeling occurs, the cause may be related to packing, resin condition, distributor performance, frit blockage or process conditions. Diagnosis should therefore follow a structured troubleshooting approach.

Why does pressure increase during a chromatography run?

Pressure increase can come from resin compression, fouling, blocked frits, high viscosity buffers, particles, microbial growth, valve issues or changes in the flow path.

The first step is to compare the pressure profile with baseline data and determine whether the change is related to the system, the process fluid, the column hardware or the packed bed.

How do you troubleshoot high back pressure in a chromatography column?

High back pressure should be investigated systematically.

A practical approach is to check the system without the column, then evaluate buffers, filters, valves, tubing, frits, resin condition and packed bed performance.

This reduces the risk of repacking the column when the actual root cause is outside the packed bed.

When should a chromatography column be repacked?

A chromatography column should be considered for repacking when performance tests show unacceptable plate count, asymmetry, resolution or pressure behaviour compared with defined acceptance criteria.

Repacking should not be the first reaction to every deviation. Pressure trends, process changes, resin condition and system checks should be reviewed first.

What qualification documentation is required for GMP chromatography equipment?

GMP chromatography equipment normally requires design documentation, material documentation, certificates, FAT and SAT documentation, IQ and OQ protocols, calibration records, software documentation where relevant and user manuals.

The documentation package should match the intended GMP use, the site validation strategy and the level of automation in the system.

How do I compare chromatography column suppliers?

Supplier comparison should go beyond price and delivery time.

Relevant evaluation points include column design, pressure rating, cleanability, hydraulic concept, distributor and frit design, documentation quality, service model, spare parts strategy, GMP experience and ability to support scale up.

The best supplier is the one that reduces technical and project risk across the full equipment lifecycle.

Column Packing

What is early sedimentation during column packing preparation?

Early sedimentation occurs when chromatography resin begins to settle before or during transfer to the column. This can happen during slurry preparation, waiting time, transfer or filling if the resin is no longer kept sufficiently suspended in the liquid.

Can early sedimentation cause a column packing result to fall outside acceptance criteria? Early sedimentation can be one possible upstream contributor, but it should not be treated as the automatic cause. A packing result can fall outside defined acceptance criteria for many reasons, including packing method, pressure and flow settings, piston movement, media handling, distributor condition or frit condition.

Why does slurry homogeneity matter before column filling? The slurry entering the column should be sufficiently uniform for the intended filling sequence. If solids distribution changes during transfer, the first and last slurry portions entering the column may not contain the same solids content. This can create a less controlled starting point for consolidation and compression.

Does hardware design change how fast the resin settles? No. Hardware does not change the intrinsic settling behaviour of the media. Settling depends on the media, particle size distribution, density difference between solid and liquid, packing liquid and slurry concentration. Hardware can, however, influence how much time the slurry spends outside active suspension and how consistently the transfer and filling sequence is carried out.

Which hardware interfaces matter when troubleshooting early sedimentation? Relevant interfaces include the slurry unit, homogenisation approach, transfer line, connection size, valve sequence, low points, dead volume, slurry inlet, displacement route, piston starting position, distributor, frit, pressure measurement and flow measurement.

Does DAC packing correct early sedimentation? No. In a DAC column, controlled piston movement can bring the bed to the defined packed state, but it does not remix a slurry that has already entered the column with an uneven solids distribution. Early sedimentation should therefore be reviewed before compression, especially around slurry condition at filling, transfer time, displacement route and piston starting position.

Why does early sedimentation become more visible in larger columns? Larger columns often involve larger slurry volumes, longer transfer paths and longer transfer times. Facility layout also has more influence on where the slurry unit is placed and how the transfer line is routed. This gives early sedimentation more time and distance to affect the delivered slurry.

What should be reviewed if early sedimentation is suspected? The review should include whether the slurry was sufficiently suspended before transfer, how long the wait and transfer steps took, whether low points or dead volumes were present, whether the column was primed with buffer, whether the displacement route was defined, whether the piston starting position matched the planned slurry charge, and whether pressure and flow response followed the expected pattern.