This International Standard specifies two methods for the determination, by atomic absorption spectrometry, of one or more of cadmium, chromium, cobalt, copper, lead, manganese, nickel and zinc, in aqua regia extracts of soil obtained in accordance with ISO 11466. The choice of method for any element depends on the amount of that element expected to be in a sample, and both methods might be needed to cover all the elements in one sample. The methods are applicable when the extractable element content is above or below the amount given in Table 1 (as milligrams per kilogram, dry matter), as appropriate. The two methods are described separately as follows: Method A — Determination of cadmium, chromium, cobalt, copper, lead, manganese, nickel and zinc by flame atomic absorption spectrometry. Method B — Determination of cadmium, chromium, cobalt, copper, lead, manganese, nickel and zinc by electrothermal atomic absorption spectrometry. Many of the procedures and reagents are common to both methods, and to the different elements within each method. Users are advised, however, to read the whole standard carefully before embarking on any of the procedures. Table 1 — Indicative limits of soil contents (mg/kg dry matter) for elements extractable in aqua regia in accordance with ISO 11446 Element Method A (flame AAS) Method B (electrothermal AAS) Cadmium > 2 < 2 Chromium > 12 < 12 Cobalt > 12 < 12 Copper > 5 < 5 Lead > 15 < 15 Manganese > 2 < 2 Nickel > 12 < 12 Zinc > 2 < 2 NOTE 1 Indicative limits given in Table 1 are appropriate to the equipment and techniques avaiable at the time of publication of this International Standard. Technical improvements may change this position in the future. NOTE 2 This International Standard refers specifically to the use of atomic absorption spectrometry. Users of this International Standard are advised to operate their laboratories to accepted quality control procedures. Certified Reference Materials (CRM) should be used to establish the amounts of the relevant elements in in-house reference materials. The latter can be used for routine quality control of the procedures given in this International Standard. Results should be established with control charts, for each element, within the laboratory. No result should be accepted which falls outside an agreed limit. Quality control procedures based on a widely accepted statistical technique should be used to establish such limit, to ensure that these are stable and that no long-term drift is occurring. Certified Reference Materials should be used regularly to maintain the integrity of the in-house reference materials and, thereby, the quality control system.