How do masking agents prevent interfering substances from being extracted?

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Viking 1 on Mars — sample preparation Viking 1's sample scoop, poised to extract material from the surface of Mars.

In analytical chemistry, masking agents prevent interfering substances from being extracted by reacting with them in the sample solution to convert them into a non-extractable form.1

These agents function primarily through complexation, where the masking agent selectively binds with the potential interferent to form a stable complex that remains in the solution and does not participate in the extraction process. In some cases, masking agents may also facilitate the precipitation of interfering elements, effectively removing them from the pool of substances available for extraction. By chemically altering the nature of these interferences, masking agents ensure that they do not impede the subsequent isolation, manipulation, or measurement of the target analyte.231