Stage 6. Calibration¶
In this stage, we will be calibrating your data. We will do this by creating a calibration curve for each element, based on SRMs measured throughout your analysis session, and a table of known SRM values.
You can either calculate a single calibration from a combination of all your measured standards, or generate a time-sensitive calibration to account for sensitivity drift through an analytical session. The latter is achieved by creating a separate calibration curve for each element in each SRM measurement, and linearly extrapolating these calibrations between neighbouring standards.
Parameters¶
There are three parameters that can be modified to subtly alter the behaviour of this function.
- Drift correct
- Whether to interpolate calibration parameters between SRM measurements
- Force zero intercept
- Whether to force calibration lines through zero (y = mx) or not (y = mx + c).
- Minimum points
- The minimum number of data points an SRM measurement must have to be included. Default value is 10.
In this tutorial, our analytical session is very short, so we are not worried about sensitivity drift. Make sure that the Drift correct check box is unticked.
We will however tick the Force Zero Intercept check box, which fits a polynomial calibration line to the data that is forced through zero.
SRMs used contains the list of SRMs measured throughout the analysis. These are automatically detected by LAtools based on your configuration.
To apply the changes, click on Calculate Calibration, then Apply Calibration. LAtools will now calculate a calibration curve for each analyte based on your measured and known SRM values, and apply the calibration to all samples.
To view the calibration lines for each analyte, click on Plot in popup. Each panel in this plot shows the measured counts/count (x axis) vs. known mol/mol (y axis) for each analyte with associated errors, with the fitted calibration line, equation and R2 of the fit. The axis on the right of each panel contains a histogram of the raw data from each sample, showing where your sample measurements lie compared to the range of the standards.
