How do you make and use (certified) reference materials?
The mole and the International System of Units (SI)

As mentioned above, the difficulty of tracing measurements in chemistry has led metrologists to develop various strategies specific to the field. Primary operating procedures (or primary analysis methods) are one such strategy. However, they require very heavy and expensive technical resources, generally deployed by expert laboratories. Other methods, though less elaborate, remain perfectly acceptable and accepted alternatives. These include

• Certified Reference Materials (CRM). This is the best-known and most satisfactory technique for conducting validation, which explains the interest shown in it by analysts. These materials are sold with an assigned or reference value, established by a certifying...