Abstract: The International Union of Pure and Applied Chemistry (IUPAC) definition of a chemical species is a “specific form of an element defined as to isotopic composition, electronic or oxidation state, and/or complex or molecular structure.” The composition and structure of the specific forms determine their properties, including their toxicity. This has important social consequences at the level of international guidelines. The quantitative determination or qualitative assessment of chemical species requires one to develop sufficiently sensitive and selective methods. All analytical methods have their specific advantages and disadvantages for species detection and quantifications. However, in most cases, separation methods like chromatography are required. A serious problem of validating an analytical method for chemical speciation is the scarce availability of reference materials. Another problem is the stability of species during sample treatment. Strategies for validation are spike and recovery assays as well as mass balance coherence. The validation of analytical methods for speciation analysis would be much simpler and more reliable if the analytical techniques had sufficient sensitivity and selectivity and were available to determine molecular and redox forms of an element directly on solid and liquid samples. Currently, technological efforts are being made in these directions, and thus the future looks promising. Graphical abstract: [Figure not available: see fulltext.].