EFFECT OF WATER SAMPLE TRANSPORTATION CONDITIONS ON THE REPORTED ANALYTICAL RESULTS OF CYANIDE

The need to accurately determine contaminant concentrations of groundwater and surface water sources is essential to properly evaluate human health risks. Analysis of these water supplies requires that they must arrive for analysis within designated holding times and temperatures. Cyanide is an example of a contaminant where the concentration can diminish based on the storage conditions and may result in a non-detection (false negative) result. A false negative result can lead to underestimation of health risks for individuals that use this water. Certain conditions can cause the cyanide anion to convert to hydrogen cyanide gas and dissipate into the sample vial headspace prior to analysis. Sample storage conditions while in transit to the laboratory must be controlled to prevent this cyanide degradation. During shipment of samples from remote locations around the world to laboratories in the United States or other developed nations it is not always possible to meet these standards.

The goal of this research is to identify the contributing factors during water sample shipment that could lead to biased or false negative results being reported for cyanide. These conditions include storage temperature and extended time prior to analysis that exceed EPA standards, and the possibility of not being preserved in accordance with EPA requirements. Temporal relationships were established to determine the rate that each factor contributes to the decrease of cyanide during these situations. Additional analyses were performed utilizing field test kits in order to determine if under some conditions they are more accurate than laboratory analysis under suboptimal transportation conditions. Analysis of these factors allows for a better understanding of both the impact of the storage conditions experienced by samples awaiting analysis and the reliability of the currently reported data. Preliminary results indicate that the temperature and duration that a sample is held prior to analysis impacts the laboratory result less than the preservation technique used, specifically pH adjustment.