In this article, the chemical forms of selected essential elements - non-metals and metals - in plants, medicinal plant raw materials and plant extracts, are discussed. The introduction contains the description of basic terms used within the text, such as speciation, speciation analysis, hyphenated techniques, as well as provides the information on the reason of the studies on the chemical forms of selected elements [1-5]. In the Chapters 1, 2 and 3, the characterization of three essential non-metallic elements - nitrogen, phosphorus and sulphur, is presented. The importance of non-metals for life, especially their involvement in ATP, ADP, nucleic acids, proteins, phospholipides and sulpholipides, is highlighted. From the analyzed chemical forms of nitrogen, the most important from the point of speciation analysis, are nitrite and nitrate form of this element. Within the Chapter 1, the studies on the former are reviewed, with the accent on their analysis (Table 1) in medicinal plant raw materials and in herbal drugs [29-35]. Chapter 2 describes the investigation on chemical forms of phosphorus, from them the most important - inorganic phosphate phosphorus [38-41, 46]. The chemical forms of nitrogen and phosphorus are related also to the indexes of ADI and RDA, to give the knowledge on their potential impact on human's health. Chapter 3 is focussed on sulphur and its chemical forms - inorganic and organic sulphur in plant material [53, 54]. Special attention to potentially dangerous for human chemical form of sulphur - SO2 in several Chinese herbs [59] is paid on. Chapter 4 concerns the analysis of chemical forms of iron, selected as characteristic example of an essential metallic elements, and is based on the studies of Fe and other metals concentration in crude drugs as well as in infusions, decoctions and herbal teas (Table 2), providing also evaluation of the extraction efficacy of iron with the comparison with the other important elements [65, 66]. In the Chapter 5, the examples of speciation studies of other metals (Mn, Zn, Mg, Pt and other) are discussed [82-101]. The analytical methodology, including speciation scheme for selected metals, especially in plant materials used in medicine, is given. Hyphe-nated techniques, such as HPLC with combination of different detection techniques (spectroscopic, electrochemical) applied for the speciation analysis of metals in plant material, are reviewed. The Summary contains the final remarks and conclusions on the described examples of speciation studies of nitrogen, phosphorus, sulphur, iron and other selected metallic elements important for life, as well as perspectives for the further development of analysis of their chemical forms in the future.
