Free Cyanide Methods

Oct 1

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10/1/2014 3:37 PM  RssIcon

Approved methods for cyanide previously only measured total cyanide or weak acid-dissociable (WAD) cyanides. These methods typically overestimate the amount of free cyanide in the sample. EPA has acknowledged the challenges of cyanide analysis and sample preservation and in May 2012 amended 40 CFR Part 136 to add additional methods for free cyanide analysis (see page 5 of 90, 29761, C. 5.).

Free Cyanide Methods

  • ASTM D7237-10
  • OIA-1677-09 *
  • ASTM D4282-02

Revised cyanide sample handling instructions and sample preservation procedures are included in the May 2012 amendment to 40 CFR Part 136 and are detailed in ASTM Standard Practice D7365-09a. Samples that are not analyzed within 15 minutes are to be preserved using sodium hydroxide at pH>10 instead of the previous pH>12. The lower pH may reduce some sample preservation related false positives.

* Weck Laboratories received CDPH NELAP approval for test method OIA-1677-09 on November 14th, 2013. Free cyanide is analyzed on the same instrument as total cyanide using flow injection and amperometric detection. See previous accuracy and precision study for total cyanide.

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