1.1 This Recommendation provides requirements for defining, testing and verifying the performance of atomic absorption spectrometer (AAS) systems when used for measuring metal pollutants in water as mandated by national laws and regulations. It does not intend to exclude any other equivalent means of measuring metal pollutants in water. An AAS system can be applied simply and rapidly for the determination of a variety of metals in potable, ground, surface and saline waters as well as domestic and industrial wastewaters. An AAS system of this type may be applied for the determination of metal concentrations in other matrices such as soil, etc. References [1] – [4] give a description of the AAS system and some applications. 1.2 The flame and electrothermal atomization (furnace) types of AAS atomizers are covered by this Recommendation. The hydride generation and the cold vapor techniques are also briefly described. The conditions of operation described for each system type are intended to cover applications for trace analysis. 1.3 It is possible that the performance of an instrument can exceed the minimum criteria prescribed in this Recommendation for these applications. Higher accuracy and repeatability of measurements can be accomplished by careful attention to the optimization of the performance of each of the instrument’s components. In such cases, success may also depend on the knowledge, skill, and experience of the analyst, as well as the quality of instrument manufacture. 1.4 A sample usually needs to undergo a specific preparation technique prior to analysis with an AAS system. Sampling techniques, methods of analysis and impact of interfering components are beyond the scope of this Recommendation. As appropriate, the relevant international, regional or national sampling techniques and reference methods of analysis should be applied. 1.5 This Recommendation does not address requirements and tests that may be necessary for operator safety. Therefore, users should determine whether an instrument meets the safety and labeling requirements specified in national regulations.