Affinity Complex Titration

General remarks

  • The first component is the mobile phase modulator.

  • This first component must be non-binding.

  • The ACT implementation currently supports at most one bound state per component.

  • The first component can be specified either as a negative logarithmic concentration (\(\mathrm{pH}\), \(\mathrm{pNa}\), …) or as a raw ion concentration.

  • To convert an existing ACT setup from ACT_USE_ION_CONC = False to ACT_USE_ION_CONC = True while keeping exactly the same model response:

    1. Replace the first component value \(\mathrm{pIon}\) by \(c_{\mathrm{ion}} = 10^{-\mathrm{pIon}}\).

    2. Replace ACT_PKAA by ACT_CMID_A = 10^{-\mathrm{ACT\_PKAA}}.

    3. Replace ACT_PKAG by ACT_CMID_G = 10^{-\mathrm{ACT\_PKAG}}.

    4. Keep ACT_KA, ACT_KD, ACT_QMAX, ACT_ETAA, and ACT_ETAG unchanged.

Group /input/model/unit_XXX/particle_type_ZZZ/adsorption – ADSORPTION_MODEL = AFFINITY_COMPLEX_TITRATION

For information on model equations, refer to Affinity Complex Titration.

IS_KINETIC

Selects kinetic or quasi-stationary adsorption mode: 1 = kinetic, 0 = quasi-stationary. If a single value is given, the mode is set for all bound states. Otherwise, the adsorption mode is set for each bound state separately.

Type: int

Range: {0,1}

Length: 1/NTOTALBND
ACT_USE_ION_CONC

Selects how the mobile phase modulator concentration is interpreted.

  • False: the first component concentration is on a negative logarithmic axis, for example \(\mathrm{pH}\) or \(\mathrm{pNa}\). Use ACT_PKAA and ACT_PKAG.

  • True: the first component is the raw ion concentration \(c_{\mathrm{ion}}\). Use ACT_CMID_A and ACT_CMID_G.

Default is False.

These two cases are equivalent when

\[\mathrm{p}K_{a,A,i} = -\log_{10}(c_{\mathrm{mid},A,i}), \qquad \mathrm{p}K_{a,G,i} = -\log_{10}(c_{\mathrm{mid},G,i}).\]

Type: bool

Range: {False, True}

Length: 1
ACT_KA

Adsorption rate constants.

Unit: \(m_{MP}^3\,mol^{-1}\,s^{-1}\)

Type: double

Range: \(\ge 0\)

Length: NCOMP
ACT_KD

Desorption rate constants.

Unit: \(s^{-1}\)

Type: double

Range: \(\ge 0\)

Length: NCOMP
ACT_QMAX

Maximum binding capacities before modulation by the ACT capacity gate.

Unit: \(mol\,m_{SP}^{-3}\)

Type: double

Range: \(> 0\)

Length: NCOMP
ACT_ETAA

Hill-type coefficients controlling how strongly the apparent binding capacity changes with the modulator concentration.

Unit: \(1\)

Type: double

Range: \(\mathbb{R}\)

Length: NCOMP
ACT_ETAG

Hill-type coefficients controlling how strongly the apparent affinity changes with the modulator concentration.

Unit: \(1\)

Type: double

Range: \(\mathbb{R}\)

Length: NCOMP

Group /input/model/unit_XXX/particle_type_ZZZ/adsorption – ACT_USE_ION_CONC = False

Use these parameters only when the first component is given as \(\mathrm{pIon}\) (for example \(\mathrm{pH}\)).

ACT_PKAA

Midpoint of the binding capacity transition on the negative logarithmic ion axis.

Unit: \(1\)

Type: double

Range: \(\mathbb{R}\)

Length: NCOMP
ACT_PKAG

Midpoint of the affinity (equilibrium constant) transition on the negative logarithmic ion axis.

Unit: \(1\)

Type: double

Range: \(\mathbb{R}\)

Length: NCOMP

Group /input/model/unit_XXX/particle_type_ZZZ/adsorption – ACT_USE_ION_CONC = True

Use these parameters only when the first component is given as a raw ion concentration. CADET internally converts them to the same negative logarithmic axis used by the ACT_PKAA / ACT_PKAG form.

ACT_CMID_A

Midpoint ion concentration for the binding capacity transition. Must be non-negative and should use the same concentration unit as the first liquid-phase component.

Recommended unit: \(mol\,m_{MP}^{-3}\)

Type: double

Range: \(\ge 0\)

Length: NCOMP
ACT_CMID_G

Midpoint ion concentration for the affinity (equilibrium constant) transition. Must be non-negative and should use the same concentration unit as the first liquid-phase component.

Recommended unit: \(mol\,m_{MP}^{-3}\)

Type: double

Range: \(\ge 0\)

Length: NCOMP