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D4282-15 – Standard Test Method Technical Guide
🧪 Scope and Application
ASTM D4282 – 15 (Reapproved 2022) establishes a standardized test method for the determination of free cyanide in water and wastewater. Under this method, free cyanide is precisely defined as the cyanide species that diffuses as hydrogen cyanide (HCN) from a solution buffered at pH 6 and held at room temperature. The method is validated for the concentration range of 10 to 150 µg/L; samples exceeding this upper limit must be diluted appropriately to bring the analyte level within the validated scope.
It is critical to recognize the specific limitations of the method. It does not determine cyanide from complexes that resist dissociation, including hexacyanoferrates and gold cyanide, nor does it include thiocyanate or cyanohydrin. The method has undergone rigorous collaborative testing in accordance with Practice D2777. All values are stated in SI units, and users bear the responsibility for establishing appropriate safety, health, and environmental practices.
⚠️ Critical Safety Advisory: The standard explicitly states it does not purport to address all safety concerns. Specific hazard statements are provided in Sections 8.6, 8.9, Section 9, and 12.2.1. Users must thoroughly review and implement all safety protocols before handling cyanide-containing samples or reagents.
⚙️ Test Method Summary and Procedure
The analysis is conducted entirely within a sealed microdiffusion cell. The sample is first treated with cadmium ion, which serves to selectively precipitate potentially interfering hexacyanoferrate complexes. Following this pretreatment, the pH of the solution is adjusted to 6.0. At this pH and at room temperature, free cyanide diffuses out of the sample matrix as gaseous HCN and is collected