Diode Array Detector Processing for SEC

step_sec_dad() creates a specification of a recipe step that processes diode array detector (DAD) signals across multiple wavelengths. It can apply wavelength-specific extinction coefficients and optionally compute ratios to a reference wavelength.

Usage

step_sec_dad(
  recipe,
  measures = NULL,
  wavelengths = c(254, 280, 220),
  extinction_coefs = NULL,
  reference_wavelength = NULL,
  output_prefix = "uv",
  path_length = 1,
  role = NA,
  trained = FALSE,
  skip = FALSE,
  id = recipes::rand_id("sec_dad")
)

Arguments

recipe

A recipe object.

measures

Character vector of DAD/UV measure columns. If NULL, the step searches for measure columns containing "dad" or "uv".

wavelengths

Numeric vector of wavelengths (nm) aligned with measures. If NULL, attempts to parse wavelengths from measures names.

extinction_coefs

Extinction coefficients by wavelength. Accepts a named numeric vector (names are wavelengths), an unnamed vector aligned with wavelengths, or a data frame with columns wavelength and extinction_coef.

reference_wavelength

Optional wavelength used as denominator for ratio calculations.

output_prefix

Prefix used to name output columns (e.g., uv_254).

path_length

Path length of the flow cell in cm. Default is 1.0.

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

For each wavelength, the signal can be normalized using the Beer-Lambert law:

$$A = \varepsilon \times c \times l$$

where A is absorbance (AU), epsilon is the extinction coefficient, and l is the path length. When reference_wavelength is provided, the step additionally creates ratio columns for each wavelength vs the reference.

See also

Other sec-detectors: step_sec_concentration(), step_sec_dls(), 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(uv_254, location = vars(elution_time), col_name = "uv_254") |>
  step_measure_input_long(uv_280, location = vars(elution_time), col_name = "uv_280") |>
  step_sec_dad(
    measures = c("uv_254", "uv_280"),
    wavelengths = c(254, 280),
    extinction_coefs = c(`254` = 1.2, `280` = 1.0),
    reference_wavelength = 280
  ) |>
  prep()
} # }