3. What materials should you test?

3.1 What types of materials are suitable for proficiency testing?

There are several types, depending on the analytical field in which CIL is used. Artificial materials can be used for simple purposes, where little sample preparation is involved.

• Verification standard solutions: these do not detect matrix effects, but are independent of the analysis method. They are inexpensive. There are also such solutions, certified either by a metrology organization or by a reagent supplier.

• Samples with dosed additions: these are samples to which a known quantity (absolute or relative) of the analyte has been added. They represent a realistic substitute for the matrix, but do not allow all sources of error to be...