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Correct Inter-Detector Volume Delays

Source: R/step_sec_detector_delay.R
step_sec_detector_delay.Rd

step_sec_detector_delay() creates a specification of a recipe step that corrects for volume delays between detectors in multi-detector SEC systems.

Usage

step_sec_detector_delay(
  recipe,
  reference = NULL,
  targets = NULL,
  delay_volumes = NULL,
  delay_times = NULL,
  flow_rate = 1,
  method = c("shift", "interpolate"),
  role = NA,
  trained = FALSE,
  skip = FALSE,
  id = recipes::rand_id("sec_detector_delay")
)

Arguments

recipe

A recipe object.

reference

Character name of the reference detector column (typically RI). All other detectors will be aligned to this reference.

targets

Character vector of detector column names to shift. If NULL, all measure columns except the reference will be shifted.

delay_volumes

Named numeric vector of delay volumes in mL. Names should match the target column names. Positive values indicate the detector sees the sample after the reference.

delay_times

Named numeric vector of delay times in minutes. Alternative to delay_volumes. Requires flow_rate to be specified.

flow_rate

Flow rate in mL/min. Required if using delay_times.

method

Method for shifting signals:

  • "shift" (default): Simple index shift (fastest, slight edge effects)

  • "interpolate": Linear interpolation (smoother, preserves signal shape)

role

Not used by this step.

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

In multi-detector SEC systems, detectors are connected in series and separated by tubing. This causes each detector to see the same analyte at different times. For accurate molecular weight calculations that combine signals from multiple detectors (e.g., RI + MALS for absolute MW), these delays must be corrected.

Typical detector order and delays:

  • UV detector: Often first, minimal delay

  • RI detector: Common reference detector

  • MALS detector: Often has 0.1-0.3 mL delay from RI

  • Viscometer: May have 0.2-0.5 mL delay

Determining delay volumes:

  1. Inject a narrow standard and record all detector signals

  2. Measure the time offset between peak maxima

  3. Convert to volume: delay_volume = time_offset × flow_rate

See also

Other sec-chromatography: step_sec_band_broadening(), step_sec_baseline(), step_sec_exclude_regions(), step_sec_integration_window(), step_sec_mw_averages(), step_sec_mw_distribution(), step_sec_mw_fractions(), step_sec_peaks_deconvolve(), step_sec_peaks_detect(), step_sec_peaks_refine()

Examples

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

# Correct UV and MALS signals relative to RI
rec <- recipe(~., data = sec_triple_detect) |>
  step_measure_input_long(ri_signal, location = vars(elution_time), col_name = "ri") |>
  step_measure_input_long(uv_signal, location = vars(elution_time), col_name = "uv") |>
  step_measure_input_long(mals_signal, location = vars(elution_time), col_name = "mals") |>
  step_sec_detector_delay(
    reference = "ri",
    delay_volumes = c(uv = -0.05, mals = 0.15)
  ) |>
  prep()
} # }