linearity: Assess the linearity of a calibration curve

In jranke/chemCal: Calibration Functions for Analytical Chemistry

Assess the linearity of a calibration curve

Description

A function to create diagnostic plots for the assessment of the linearity of calibration data based on their point-to-point slope or the curvature. The underlying methods follow ISO 84 66-1:2021 and DIN 32 402-51:2017 (German Industrial Norm).

Usage

linearity(x, y, method = c("slope", "curvature"), tolerance = 0.1)

Arguments

x	numeric vector of independent values (usually concentrations).
y	numeric vector of dependent values (usually the signal of the analytical device).
method	character string. Supported methods are "slope" and "curvature".
tolerance	numeric value between 0 and 1, describing the acceptable deviation from the median of the slopes or the signal-to-concentration ratio. The default tolerance is 10%.

Details

The point-to-point slope method is based on the assumption that the slope between two points should not vary greatly within the linear range.

The curvature method is similar to the point-to-point slope method. Here, the ratio between the instrument signal and the concentration of the calibration standard is assumed not to vary greatly within the linear range.

The use of the Mandel test is discouraged due to its limitations in the identification of non-linear behaviour of calibration curves (Andrade and Gomes-Carracedo, 2013).

Value

returns a diagnostic plot

Author(s)

Anıl Axel Tellbüscher

References

ISO 8466-1:2021. Water quality — Calibration and evaluation of analytical methods — Part 1: Linear calibration function

J. M. Andrade and M. P. Gomez-Carracedo (2013) Notes on the use of Mandel's test to check for nonlinearity in laboratory calibrations. Analytical Methods 5(5), 1145 - 1149.

Examples

# Continuous Flow Analysis (CFA) data
data(din38402b1)

# Point-to-point slope plot
linearity(din38402b1$conc, din38402b1$ext, method = "slope")

# Curvature plot
linearity(din38402b1$conc, din38402b1$ext, method = "curvature")

jranke/chemCal documentation built on Jan. 27, 2025, 8:52 a.m.