Measurement and Results - Internal standard basics
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The following is available as part of our ICP Operations Guide, which is available on our website at https://www.inorganicventures.com/icp-operations-guide. Internal Standardization
The calibration curve technique is the most popular calibration technique. If the sample matrices are known and consistent then matrix matching the calibration standards to the samples is an excellent option. Even when matrix matching is an option, many analysts still use an internal standard. It is suggested that the analyst consider the following questions before using an internal standard:
As discussed in the last part of this series, the matrix can influence the plasma as well as the nebulizer. Internal standardization is very effective in correcting for nebulizer related effects and may be effective for correcting plasma related effects. It is obviously important that the matrix effect influence both the internal standard to the same extent as the analyte. This should be the case for nebulizer related effects but it may not be so for plasma related effects where the matrix influence is related to the excitation potential of the emission line (as discussed in Part 10). It may be difficult to find an internal standard that has a similar excitation potential as the analyte in measurements where several analytes are involved. The analyst is advised to confirm that the matrix influences the internal standard and analyte signal intensities proportionately. |