Total Cyanide Field Spikes for Industrial Wastewater Samples Verify Successful Sample Integrity, Preservation, Pre-Treatment and Testing.

Obtaining accurate and precise results for total cyanide concentrations in wastewater samples is fraught with positive and negative interferences. Even the United States Environmental Protection Agency has acknowledged that it may be difficult or impossible to adequately mitigate all interferences. We demonstrated that a field spike of complex cyanide can be successfully used to demonstrate when sampling, preservation, pre-treatment, and analysis techniques are working adequately to retain any cyanide present in the sample without causing false positives or false negatives.

False cyanide formation during drinking water sample preservation and storage.

Carefully controlled bench-scale and on-site experiments demonstrated that cyanide can form in the treated drinking water sample container during preservation and storage. In the bench-scale experiment, treated tap water samples were collected on 20 days over six months. The tap water samples were split and some of the splits were spiked with formaldehyde, a known ozone disinfection byproduct, held for three hours and tested for cyanide.

Evaluation and testing of analytical methods for cyanide species in municipal and industrial contaminated waters.

Total cyanide analysis by distillation is used most commonly to assess cyanide content of water samples. This manual method is robust but slow and provides no information about cyanide speciation, a significant limitation in that cyanide species have substantially different toxicity characteristics. Seven alternative methods for the analysis of cyanide species or groups of species were evaluated in reagent water and five different contaminated water matrices, including five species-specific methods--weak acid dissociable (WAD) cyanide, free cyanide by microdiffusion, available cyanide, automated WAD cyanide by thin film distillation, metal cyanides by ion chromatography--and two automated techniques for total cyanide--total cyanide bythin film distillation and total cyanide by low-power UV digestion.