When verification is required, extra analyses are conducted.

In the same laboratory, different methods may be used. For example, one laboratory may analyze metals in the same sample with inductively coupled plasma and emission spectrometry. The results of the two methods are compared as a verification.

In different laboratories, the same or different methods of analysis may be used to analyze portions of the same sample.

To verify methods, NIST sells samples of accurately determined composition. NIST also distributes portions of the same sample to many laboratories and pools the data for verification of methods. This data is pooled data from a steel sample that NIST distributed to several laboratories for validation of their methods.

*AA is atomic absorption. *ICP is inductively coupled plasma.
*Emission is emission spectrometry.