Detection and quantification capabilities and the evaluation of low-level data: Some international perspectives and continuing challenges

The minimum amounts or concentrations of an analyte that may be detected or quantified by a specific measurement process (MP) represent fundamental performance characteristics that are vital for planning experiments and designing MPs to meet external specifications. Following many years of conceptual and terminological disarray regarding detection and quantification limits, the International Union of Pure and Applied Chemistry(IUPAC, 1995)(1) and the International Organization for Standardization (ISO, 1997)(2) developed a harmonized position and documents that provide a basis for international consensus on this topic. During the past year, the International Atomic Energy Agency (IAEA) has developed a TECDOC on Quantifying Uncertainty in Nuclear Analytical Measurements that treats "Uncertainty in Measurements Close to Detection Limits" from the perspective of the IUPAC and ISO recommendations.(3) The first part of this article serves as a review of these international developments during the last quinquennium of the twentieth century. Despite the achievement of international consensus on these contentious matters, many challenges remain. One quickly discovers this in the practical world of high stakes, ultra-trace analysis, where complications are introduced by the nature and distribution of the blank, the variance function (sigma vs. concentration), non-linear models, and hidden algorithms and data evaluation/reporting schemes. Some of these issues are illustrated through a multidisciplinary case study of fossil and biomass burning aerosol at extremely low levels in the polar atmosphere and cryosphere, and by biased reporting practices for "non-detects."