Contaminated? or NOT Contaminated?

Jane Rothert
Illinois State Water Survey,
Champaign, IL USA

Is the sample contaminated or is it not? That is the question. This poster looks at artificial samples with known contaminants added and addresses two different issues: Is the CAL seeing all of the contaminants that come into the lab and are they correctly identifying them and how do these contaminants actually affect the sample concentration? Samples of deionized water were sent to the laboratory disguised as real samples. Known contaminants had been placed in some of them (others were left clean) to determine whether the contamination screening process in the laboratory was accurate and uniform across all analysts. At the preliminary report review, the samples were renumbered as QA samples and their chemistry and the lab contamination reviewed. The dirtiest sample was one containing an insect with Cl concentration = 2.544 ppm and Ca concentration = 1.506 ppm. The other analyte concentrations were equally high.