Sample Enrichment by Solid-Phase Extraction for Reaching Parts per Quadrillion Levels in Environmental Analysis

Determination of parts per quadrillion (ppq) levels of various pollutants, contaminants, or background species in environmental samples is a challenging task for analytical chemistry. Among them, dioxins, perfluoroalkylated acids, organophosphorus and organochlorine pesticides, herbicides, and nitrosamines are found in the environment and consequently they must be determined at ppq levels. Analytical techniques alone are not able to reach these concentration levels, and they can be utilized only if sample enrichment is applied. This review is based on the literature reporting analytical methods based on solid-phase extraction or related techniques that are applied to determine ppq levels or have quantitation limits below the parts per trillion (ppt) range. Some other important aspects of the analytical process, such as calibration, precision, recovery, uncertainty, environmental matrix certified reference materials, or interlaboratory comparison, are discussed in the context
of this analytical research.