ISO 15181-3:2007

Overview - ISO 15181-3:2007 (zineb / ETU release rate)

ISO 15181-3:2007 defines a laboratory method for determining the release rate of the zinc ethylene‑bis(dithiocarbamate) biocide (zineb) from antifouling paints. Because zineb is released as an unstable ionic species in seawater, the standard specifies a controlled degradation step to convert the released species to the stable degradation product ethylenethiourea (ETU) and then quantifies ETU to calculate the zineb release rate under prescribed laboratory conditions. The method is intended for repeatable quality‑assurance testing and material selection, not as a direct substitute for in‑service environmental release measurements.

Key topics and technical requirements

• Principle: Convert released zineb species to ETU, determine ETU concentration, calculate zineb release rate.
• Analytical method: High‑performance liquid chromatography (HPLC) or an alternative instrument with a limit of quantitation (LOQ) for ETU in artificial seawater of ≤ 6 µg/L. Calibration requires linear regression with correlation coefficient ≥ 0.999.
• Sample treatment: Reflux 10 mL extract with 0.1 M NaOH for 30 minutes, acidify, dilute and filter (0.45 µm PVDF), then analyze. Samples may be stored at 2–4 °C up to 7 days or –5 °C up to 1 month.
• Apparatus highlights: HPLC system (isocratic pump, UV detector @233 nm, autosampler, C18 column), reflux apparatus, volumetric flasks, syringes and PVDF syringe filters.
• Calibration and QC: Triplicate determinations, discard individual results that deviate >10% from the triplicate mean and re‑analyse. Cleaning of reusable glassware with hydrochloric acid is specified.
• Quantitative range: When used with ISO 15181‑1 extraction procedure, practical measurement limits are 2.9 µg·cm⁻²·d⁻¹ to 500 µg·cm⁻²·d⁻¹. Lower release rates require more sensitive ETU analysis than specified.

Practical applications and users

• Who uses it: Paint and varnish manufacturers, independent testing laboratories, quality control (QC) teams, research labs studying antifouling formulations, and supply‑chain quality personnel.
• Use cases: Product development and comparative testing of antifouling coatings, factory QC of zineb‑containing paints, laboratory benchmarking of biocide release behavior, and concurrent testing for multiple biocides (e.g., copper) from the same extract using sub‑samples.
• Limitations: Results are standard laboratory release rates under fixed temperature, salinity and pH and do not directly represent in‑service environmental release; apply correction factors when extrapolating to real‑world exposures.

Related standards

• ISO 15181‑1: General method for extraction of biocides (required procedural complement).
• ISO 15181‑2 / -4 / -5: Companion parts cover copper, PTPB and other biocides and related calculation methods.
• ISO 3696: Water for analytical laboratory use (reagent quality).

Keywords: ISO 15181‑3:2007, zineb release rate, ethylenethiourea (ETU), antifouling paints, HPLC, artificial seawater, biocide release testing, release rate µg·cm⁻²·d⁻¹.