Published: 4th June 2021 | © Anthias Consulting Ltd
Imagine you have a sample with an unknown concentration of target analyte in a very difficult matrix that you know could lead to signal suppression or which might conversely, artificially enhance the target response upon analysis.
You don’t have the time for a full method validation and you don’t have many samples, so what do you do ?
You can use the quantitative method Standard Addition (SA) in order to eliminate the matrix effect. A series of analyses are carried out where, after sample homogenisation, equal volumes of the initial sample are taken then all but one are separately ‘spiked’ with known and different amounts of the target analyte, all are then diluted to the same volume and analysed in a sequence. The instrument signals are then determined for all these solutions and the results plotted.
Multiple calibration points are used and on construction of the calibration curve of the concentration against the response (e.g. area of the peak), a trend line is added and the absolute value of the point of intercept on the x-axis indicates the concentration of analyte in the original sample as shown in Figure 1. The red arrow points to -0.75 which indicates an original concentration of 0.75 concentration units.
Quantitation using standard addition has pros and cons, like all methods. It gives very accurate quantitation and takes into account any effects of the sample matrix in an analysis which could skew results. However, there must be enough sample to analyse at multiple levels (need at least 2 points), the sample must be homogenous and a new calibration curve must be constructed for each sample to get accurate results, which is time-consuming. When very accurate results are required and especially when the matrix is varying from sample to sample, then it is worth the effort whether for a one-off analysis or routinely!
To learn more about Standard Addition attend:
- Practical Essentials of GC and GC-MS data analysis and sample preparation
- Practical Essentials of LC and LC-MS columns, detectors and data analysis
- Practical Essentials of Elemental Analysis spectrometers, detectors, mass spectrometers, and data analysis
For more information about data analysis visit our data analysis training courses page.
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