How to perform a standard addition calculation in TargetLynx - WKB113046

OBJECTIVE or GOAL

Calculate the concentration in a sample by the standard addition method. This procedure can also be used when a compound is present endogenously but a matrix-matched calibration curve is required for calculation of other samples. The standard addition method is then used to recalculate the actual concentrations of the calibration curve. This is explained in more detail in the "Additional Information" section.

ENVIRONMENT

• MassLynx
• TargetLynx

PROCEDURE

The "Additional Information" section below gives an explanation of what standard addition actually is.

For this procedure to work effectively, a sample (blank matrix) is analyzed as well as the sample spiked with the compound or compounds of interest at one or more concentration levels. 

1. Within the sample list, set the sample type of the sample to "standard" and set the concentration to "0".
2. Spiked samples should also be set to sample type "standard", and the spiked concentration should be included in the concentration column. The sample list may look as follows:
   
3. In the processing method, the standard addition setting should be activated in the calibration section of the method:
   
   When this option is not visible, it can be shown by right-clicking in the screen and selecting "Use standard addition?".
   
4. After data is processed, the standard addition concentration shows in the header of the calibration curve window:
   
   The standard addition concentration can also be shown by adding the column "standard addition concentration" to the summary table.

ADDITIONAL INFORMATION

For this procedure to work effectively, a sample (blank matrix) is analyzed as well as the sample spiked with the compound or compounds of interest at one or more concentration levels. This is shown visually below with the added concentrations labeled below each container:

When these samples are analyzed, the following calibration is obtained:

The concentration in the sample (blank matrix) is calculated by extrapolating the calibration curve to y=0, and the resulting x value is mirrored on the y axis, which shows the endogenous concentration:

When multiple samples (within the same matrix) must be calculated using this calibration curve, the concentration should be changed in the sample table, corrected for the calculated "blank matrix" concentration. In this example, all concentration levels should be incremented with 20, meaning the initial concentrations of 0, 10, 20, and 30 are now 20, 30, 40, and 50. These concentrations should be used for the calculation of other samples.