APPLICATIONS
Isotope Dilution Analysis (IDA)
Current Uses of Enriched Isotopes
- Precise Quantification: To accurately measure elements or chemical species, particularly when sample preparation may cause losses or interconversions, such as in the case of mercury or chromium speciation.
- Investigation of the reactivity and fate of chemical species: To investigate the reactivity and fate of chemical species, isotopically enriched species can be useful to observe the bioaccumulation, reactivity, metabolic pathways, and fate.
What is isotope dilution analysis?
Isotope Dilution Analysis (IDA) is an advanced analytical technique that offers several benefits over traditional methods. Unlike conventional methods that rely on calibration curves, IDA is considered a primary measurement method because it is directly traceable to the International System of Units (SI), ensuring high metrological accuracy. IDA involves introducing a compound enriched in a specific isotope (known as a tracer or spike) into the sample. The change in isotopic composition allows for accurate measurement of the analyte.
Advantages and requirements of isotope dilution
IDA provides several advantages compared to other methodological calibrations.
Advantages
- Minimized Sensitivity Variations: Variations in sensitivity due to instrumental instabilities do not affect the final concentration measurement in the sample.
- Error Compensation: Once isotopic equilibrium is reached between the natural element and the added enriched tracer, any losses during sample preparation do not impact the final results.
Requirements
- Analyte Losses: Any loss of the analyte or the enriched tracer before achieving isotopic equilibrium can be a sources of error.
- Spike Performance: Once the isotopic equilibration is achieved, the enriched spike act identically to the natural element throughout the analytical process.
- Interference-Free Measurement: Measurements of isotopic peak areas must be free from spectral interferences to ensure accuracy.
- Spike Quantity: The amount of added enriched compound must be within a specified range relative to the natural compound.
Isotope Dilution Analysis (IDA) provides a robust method for improving quantification accuracy and reducing uncertainty, particularly by compensating for systematic errors during sample preparation. While it significantly enhances measurement reliability, it is limited to elements with more than one isotope and requires careful management of potential issues like contamination and spectral overlap.
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