OCENA NIEPEWNOŚCI OZNACZEŃ WSKAŹNIKÓW CHEMICZNYCH WÓD NA PODSTAWIE GRANICY WYKRYWALNOŚCI (LOD) I PRAKTYCZNEJ GRANICY WYKRYWALNOŚCI (PLOD)

Abstract

UNCERTAINTY OF WATER CHEMICAL INDICATORS DETERMINATION ON THE BASE OF LIMIT OF DETECTION (LOD) AND PRACTICAL LIMIT OF DETECTION (PLOD)Abstract. Authors describe examples of implementation of limit of detection (LOD) and practical limit of detection (PLOD) for the estimation of uncertainty involved in sampling and analytical processes during drinking water quality monitoring. Practical limit of detection is one of the most important parameters characterising performance of laboratory methods used during drinking water quality monitoring. According to drinking water directive (98/83/EC) laboratory must be capable of measuring concentrations equal to theparametric value with trueness, precision and limit of detection that is usually equal 10% of parametric value. As examples results of 4 metal monitoring results were used (Al, Mn, Cu, Pb). Two series of samples were taken. Achieved practical limits of detection for Cu and Mn are significantly lover from required (by 2–3 orders of magnitude). In case of lead practical limit of detection is determined, in one set of samples, fails to comply with required precision, which may suggest possible problems with sampling process quality. Sampling process is very often important source of uncertainty influencing final result and in general quality of results achieved. Practical limit of detection is (PLOD) a very useful tool for assessment of quality of whole monitoring procedure starting from sampling through samples preservation and transportation and laboratory procedures.