Journal of Planar Chromatography VOL. 16. JANUARY/FEBRUARY 2003 11 Summary This paper focuses on the use of complexation liquid chromatogra- phy (in its TLC mode) to investigate eleven monosulfides. In the study we made use of the fact that monosulfides molecules contain readily polarizable sulfur atoms, which enables complex formation. In an attempt to establish the most convenient working conditions for separation of the compounds, the stationary phase (silica) layer was impregnated with salts of selected metals. This procedure resulted in modification of the chemical nature of the active sites present on the stationary phase surface, enabling more efficient sep- aration of the analytes, although in this introductory study the monosulfides were chromatographed as individual chemical species only, to enable examination of their retention behavior unperturbed by the other components of a mixed sample. 1 Introduction In the work discussed in this paper an attempt has been made to demonstrate one of the numerous applications of complexation chromatography, a modern mode of chromatography that pro- vides a good chance of investigating chemical compounds. In this study we have investigated monosulfides, i.e. organic com- pounds containing sulfur atoms in their molecules. We chose these compounds because of their considerable practical impor- tance and use as, e.g., polymer stabilizers, accelerators in the vulcanization of Indian rubber, or as supplementary compounds added to oils and greases. Monosulfides are also important as biomimetics in biochemical processes. Because of their ability to form complexes, monosulfides can also be used for selective detection and efficient removal of toxic metals from man’s envi- ronment [1–5]. To devise an appropriate complexation chromatography system common adsorbents (e.g. silica layers) are often impregnated with the salts of transition metals, which changes the nature of the active sites on the adsorbent surface. Metals deposited on the surface of the matrix affect the properties of the silanol groups according to the reaction: mSi–OH + Me m+ - (Si–O) m Me + mH + Formation of complexes on the adsorbent surface is apparent, e.g., from changes of retention times compared with those mea- sured on the unmodified stationary [6]. In our study eleven monosulfides were analyzed (as single chem- ical species) with aid of a number of experimentally selected mobile phases. The specific chemical structure of the monosul- fides, a sulfur atom bonded to two hydrocarbon (alkyl or aryl) groups was particularly well suited for complexation chromatog- raphy, because the readily polarizable sulfur atom has a tendency to form coordination bonds (most frequently charge-transfer bonds) with metal cations. The strength of these bonds can differ from weak, with cations of alkaline metals, to strong, with cations of heavy metals. Impregnated silica was spiked with cations in the 2+ oxidation state – Cu(II), Co(II), Ni(II), and Mn (II) – and in the 3+ oxidation state – Al(III), Cr(III), and Fe(III). After development the respective R F values were calculated, enabling approximate evaluation of the effect of mobile phase composition on the chromatographic behavior of the monosulfides. 2 Experimental TLC was performed on plastic-backed plates precoated with sil- ica gel (Merck, Darmstadt, Germany; #1.05735) as stationary Use of Complexation TLC to Investigate Selected Monosulfides. Part I. Silica Impregnated with Cu(II), Co(II), Ni(II), Mn(II), Al(III), Cr(III), and Fe(III) Cations as Stationary Phase Gabriela Grygierczyk, Janusz Wasilewski, Magdalena Witkowska, and Teresa Kowalska* Key Words: Monosulfides Complexation chromatography Complex compounds Impregnation with metal cations G. Grygierczyk, M. Witkowska, and T. Kowalska, Institute of Chemistry, Silesian University, 9 Szkolna Str., 40-006 Katowice, Poland; and J. Wasilewski, Depart- ment of Biochemistry, University of Warmia and Mazury, 14 ¯o³nierska Str., 10- 561 Olsztyn, Poland. DOI: 10.1556/JPC.16.2003.1.2