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Mechanistic Modeling

Mechanistic chromatography models predict separation behavior from physical equations rather than empirical correlations. By describing the underlying physics: convection, diffusion, and adsorption, into mathematical differential equations, these models can extrapolate beyond the conditions used to calibrate them.

What is a Mechanistic Chromatography Model?

A mechanistic model describes a chromatography process using mass-balance partial differential equations (PDEs) that account for each physical mechanism occurring inside the column. Unlike empirical plate-count or regression-based approaches, mechanistic models resolve how solute concentrations evolve in both space and time inside the column, making them powerful tools for process development and optimization.

∂c∂t=−u∂c∂z⏟convection+D∂2c∂z2⏟dispersion−βdqdt⏟binding\frac{\partial c}{\partial t} = \underbrace{-u \frac{\partial c}{\partial z}}_{\text{convection}} + \underbrace{D \frac{\partial^2 c}{\partial z^2}}_{\text{dispersion}} - \underbrace{\beta \frac{dq}{dt}}_{\text{binding}}

Why use Mechanistic Modeling?

  • Predictive power: Once calibrated, the model can predict chromatograms under new operating conditions like different flow rates, load concentrations, gradient shapes, without additional experiments.
  • Physical insight: Model parameters map directly to physical properties (e.g. porosity, diffusion coefficients, binding constants), providing deeper understanding of the separation.
  • In-silico optimization: Thousands of virtual experiments can be run to screen process parameters and optimize yield, purity, or productivity computationally.

How Efflux Implements It

Efflux assembles a simulation from modular unit operations (inlets, tubings, mixers, columns, and detectors) connected in a flow graph. Each column is governed by a column model that describes solute transport, paired with a binding model that captures adsorption kinetics. The resulting system of differential-algebraic equations is then solved by the simulation engine.

To see how this works in practice, visit the chromatography simulator page.

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