This part of ISO 15181 specifies the apparatus and analytical method for determining the amount of copper (based) biocide that has been released from an antifouling paint into artificial seawater in accordance with the procedure given in ISO 15181-1. It determines the copper-ion concentration and gives the final calculation for the release rate of copper under the specified laboratory conditions. This part of ISO 15181 is designed to generally allow the concurrent determination of copper ions and other biocides that might be released by a given antifouling paint through the analysis of separate sub-samples of an artificial seawater extract generated in accordance with the procedure given in ISO 15181-1, and analysed in accordance with the procedures given in other parts of this International Standard. When used in conjunction with ISO 15181-1, the practical limits on the quantitative measurement of release rates by this method are from 1,8 µg·cm–2·d–1 to 500 µg·cm–2·d–1. The quantitative measurement of release rates below this range will require the use of an analytical method with a lower limit of quantitation for copper in artificial seawater than the limit specified in 5.1.