Total Cyanide Field Spikes for Industrial Wastewater Samples Verify Successful Sample Integrity, Preservation,...

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. For 257 industrial wastewater effluent samples collected at a wide variety of Greater Boston industries, 237 (92.2%) had usable field spike recoveries, averaging 86.2% recovery. Field spike recoveries for problematic industries that had very high or very low field spike recoveries were useful to show when alternative preservations and field dilutions were successfully preserving total cyanide. The field spike approach is general and should also work in a similar manner for raw and treated drinking water samples.