Zineb is released from antifouling paints in the form of ionic ethylene-bis(dithiocarbamate) which is unstable in the marine environment. This part of ISO 15181 describes a method for converting the released species into a stable degradation product, ethylenethiourea, and determining its concentration in the treated artificial seawater samples, and gives the final calculation for the release rate of zineb under the specified laboratory conditions.
This part of ISO 15181 is designed to generally allow the concurrent determination of zineb and other biocides that can be released by a given antifouling paint (for example, copper) through the analysis of separate sub-samples of an artificial seawater extract generated in accordance with the procedure given in ISO 15181-1.
When used in conjunction with ISO 15181-1, the practical limits on the quantitative measurement of release rates by this method are from 2,9 micrograms per square centimetre per day to 500 micrograms per square centimetre per day. The quantitative measurement of release rates below this range will require the use of an analytical method with a lower limit of quantitation for ethylenethiourea.