Skip to contents

UV Detector Processing for SEC

Source: R/step_sec_uv.R
step_sec_uv.Rd

step_sec_uv() creates a specification of a recipe step that processes UV detector signals for SEC analysis, including application of extinction coefficients for concentration determination.

Usage

step_sec_uv(
  recipe,
  measures = NULL,
  extinction_coef = NULL,
  extinction_column = NULL,
  wavelength = 280,
  path_length = 1,
  output_col = NULL,
  role = NA,
  trained = FALSE,
  skip = FALSE,
  id = recipes::rand_id("sec_uv")
)

Arguments

recipe

A recipe object.

measures

Character vector of UV detector column names to process. If NULL, will look for columns containing "uv" in the name.

extinction_coef

Extinction coefficient in mL/(mgcm) or L/(gcm). Can be:

  • A single numeric value applied to all samples

  • NULL to skip normalization (signal remains in AU)

extinction_column

Character name of a column containing sample-specific extinction coefficients. Overrides extinction_coef if provided.

wavelength

UV detection wavelength in nm. For documentation only.

path_length

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

output_col

Name for the output column. Default is to modify in place.

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 UV detector measures absorbance according to the Beer-Lambert law:

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

where:

  • A is absorbance (AU)

  • epsilon is the molar extinction coefficient in mL/(mg*cm)

  • c is the concentration (mg/mL)

  • l is the path length (cm)

This step can convert UV absorbance to concentration-proportional signals by dividing by the extinction coefficient and path length.

Common UV applications in SEC:

  • Proteins at 280 nm (aromatic amino acids)

  • Nucleic acids at 260 nm

  • Conjugated polymers

  • UV-active end groups or labels

UV vs RI for concentration:

  • UV is more sensitive for chromophore-containing analytes

  • UV response depends on chemical composition (may vary with MW)

  • RI is more universal but less sensitive

  • For accurate MW, combine both detectors

See also

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

Examples

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

# Apply fixed extinction coefficient
rec <- recipe(~., data = sec_triple_detect) |>
  step_measure_input_long(uv_signal, location = vars(elution_time), col_name = "uv") |>
  step_sec_uv(extinction_coef = 1.0, wavelength = 280) |>
  prep()

# Use sample-specific extinction coefficients
rec <- recipe(~., data = sec_triple_detect) |>
  step_measure_input_long(uv_signal, location = vars(elution_time), col_name = "uv") |>
  step_sec_uv(extinction_column = "ext_coef") |>
  prep()
} # }