Dynamic Light Scattering Processing for SEC

step_sec_dls() creates a specification of a recipe step that processes dynamic light scattering (DLS) correlation data to estimate diffusion coefficient and hydrodynamic radius (Rh).

Usage

step_sec_dls(
  recipe,
  measures = NULL,
  temperature = 25,
  viscosity = NULL,
  laser_wavelength = 633,
  angle = 90,
  solvent_ri = 1.333,
  rg_col = "rg",
  output_cols = c("rh", "diffusion_coef"),
  role = NA,
  trained = FALSE,
  skip = FALSE,
  id = recipes::rand_id("sec_dls")
)

Arguments

recipe

A recipe object.

measures

Character vector of DLS measure columns. If NULL, the step searches for measure columns containing "dls" or "corr".

temperature

Temperature in degrees Celsius.

viscosity

Solvent viscosity in mPa*s. If NULL, uses a water approximation based on temperature.

laser_wavelength

Laser wavelength in nm. Default is 633.

angle

Scattering angle in degrees. Default is 90.

solvent_ri

Solvent refractive index. Default is 1.333 (water).

rg_col

Optional Rg measure column from MALS for Rg/Rh ratio.

output_cols

Output column names for Rh and diffusion coefficient.

role

Role for generated columns.

trained

Logical indicating if the step has been trained.

skip

Logical. Should the step be skipped when baking?

id

Unique step identifier.

Value

An updated recipe with the new step added.

Details

The DLS correlation function g2(tau) is approximated as: $$g2(\tau) = 1 + \beta e^{-2 \Gamma \tau}$$ where Gamma is the decay rate. The diffusion coefficient is calculated as D = Gamma / q^2 with q determined from the scattering angle and wavelength. Rh is then obtained from the Stokes-Einstein equation.

See also

Other sec-detectors: step_sec_concentration(), step_sec_dad(), step_sec_intrinsic_visc(), step_sec_lals(), step_sec_mals(), step_sec_rals(), step_sec_ri(), step_sec_uv(), step_sec_viscometer()

Examples

if (FALSE) { # \dontrun{
library(recipes)
library(measure)

rec <- recipe(~., data = sec_triple_detect) |>
  step_measure_input_long(dls_corr, location = vars(lag_time), col_name = "dls") |>
  step_sec_dls(measures = "dls", temperature = 25, viscosity = 0.89) |>
  prep()
} # }