Dimensionless plate height is unsuitable for comparing chromatographic columns.

Area of Science:

• Analytical Chemistry
• Chromatography Science

Background:

• Dimensionless plate height (h) is defined differently for various column internal structures (open, packed, monolithic, pillar array).
• The plate height (H) and kinetic performance are primarily influenced by flow channel dimensions, not external parameters like particle or domain size.
• Current metrics for h are subjective and unmeasurable from external column analysis, limiting their utility.

Purpose of the Study:

• To demonstrate the limitations of dimensionless plate height (h) in evaluating column performance across different structures.
• To introduce and evaluate objective performance metrics: the kinetic performance factor (q) and the quality factor (q_max).
• To provide a reliable method for comparing the performance of differently structured chromatography columns.

Main Methods:

• Analysis of how internal column structure dimensions affect flow channels and overall kinetic performance.
• Evaluation of the previously introduced kinetic performance factor (q) and quality factor (q_max).
• Comparison of practically achievable performance for various column types, considering factors beyond q_max.

Main Results:

• Dimensionless plate height (h) is shown to be an unmeasurable and subjective metric that does not accurately reflect column performance.
• Increasing domain size (d_dom) independently of flow channel dimensions (d_chan) can artificially decrease h without improving kinetic performance.
• The quality factor (q_max) is identified as a suitable objective metric for comparing differently structured columns.

Conclusions:

• Dimensionless plate height (h) is inadequate for comparing columns with diverse internal structures.
• Objective metrics like the quality factor (q_max) provide a more reliable basis for column comparison.
• Practical column performance depends on q_max alongside other factors such as pressure tolerance and achievable flow channel dimensions.