Dear Colleagues,

The unique identification and quantification of molecular species becomes problematic when it comes to trace analysis. Trace analysis is concerned with the identification of very small amounts of chemicals. The concentration of each such chemical may go down into the sub-ppm range. Despite the very small quantities, analysis is highly relevant for analyzing wastewater streams, drinking water quality, forensics, toxicity studies (when we do not know what it is, how to access tox, and tox levels) and quality of specific chemical and pharmaceutical (by-)products. Whereas higher quantities can be easily identified and quantified by, e.g., NMR techniques, trace analysis is still often a problem. Often, we are told that chromatography with a subsequent detector, e.g., a UV detector, does the job, but that could not be further from the truth. Such approaches only work well when we already know, or assume, which species are present. True unknowns form a massive problem as they cannot be identified/quantified that way. This often does not only refer to low quantities but, normally, a much larger number, up to hundreds or thousands, of species that also need to be identified and quantified and separated. In this Special Issue, we provide the reader with an overview of the status of trace chemical identification and quantification, completed with some suggestions for future improvements.

Trace analysis of molecules comprises identification and quantification. Identification can be regarded as consisting of two elements: identification of the chemical formula and identification of the chemical structure. Before the chemical formula can be determined, uniquely, we may need separation, possibly GC or LC multidimensional separation approaches. The chemical formula can otherwise be determined, uniquely for molecular weights of 500–600, using mass spectrometry, more specifically FT–ICR–MS. Structure elucidation may involve several approaches. When the concentration is too low, we need concentration methods. An important issue is the selectivity of concentration methods or, in other words, how much of the absolute quantity is truly retained/recovered for further analysis. 

N.B. There is an obvious connection to the topic of “Contaminants of Emerging Concern in Water: Occurrence, Fate and Removal”. The current Special Issue is concerned with techniques to identify and quantify such contaminants.

Prof. Dr. Robert J. Meier
Guest Editor

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• instrument analysis
• chemical formula identification
• structure elucidation
• quantification
• high-resolution LC–MS and GC–MS
• NMR techniques
• N-detector (LC)
• S-detector (GC)
• multidimensional chromatography
• concentrate
• absorbants