Modified natural diatomaceous earth (DE) is a principal component of the stationary phase in normal thin-layer chromatography (TLC) applications and is mixed with commercial silica gel 60GF254 (Si-60GF254). Modification is carried out by flux calcination and refluxing with acid. Natural DE, modified DEs [flux calcinated (FC)DE and FCDE-I), and Si-60GF254 are characterized by scanning electron microscopy and Fourier-transform-IR spectroscopy. Particle size, specific surface area, pore distribution, pore volume, and surface hydroxyl group density parameters of materials are determined by various techniques. FCDE-I and Si-60GF254 are investigated for their usefulness in the stationary phase of TLC both individually and in composition. Commercially available red and blue ink samples are run on layers of Si-60GF254 and FCDE-I individually, and on various FCDE-I and Si-60GF254 mixtures. Butanol-ethanol-2M ammonia (3:1:1, v/v) and butanol-acetic acid-water (12:3:5, v/v) mixtures are used as mobile phases. The polarities of stationary phases decrease, and the retention factor (Rf) values of ink components increase when the FCDE-I content of the stationary phase increases. The properties of the stationary phase can be optimized by adding FCDE-I to Si-60GF254. This study may be useful in understanding both the systematic effects of stationary phase properties [e.g., specific surface area and surface hydroxyl group density, aOH(s)] and those of the mobile phase (e.g., polarity and acidity) on Rf values and the separability of components.
YM 2 M' 3 S 6-y , (M= Ca, Sr, Ba, Mg and M′= Cu, Fe) type of compounds were synthesized and the effect of rare earth elements on these type of compounds was investigated. By replacing Y with La, LaBa 2 Cu 3 S 6-y compound was synthesized based on solid-gas reaction and the obtained samples were characterized by XRD, IR and EDX methods. Crystal structure of LaBa 2 Cu 3 S 6-y was orthorhombic and refined unit cell parameters were a =10.16(1), b=12.72(2) and c=13.54(0)Å. This compound showed a semiconducting behavior in the range 78-300 °K. After the replacement of La element with Gd and Dy, as result of the sulfidizing process for both rare earths, GdO 2 S and DyO 2 S compounds were observed in the X-ray pattern of the products. When Ba is replaced with Sr and Ca, the La 2 SrS 4 and La 2 CaS 4 products were obtained. These two compounds were synthesized first time by solid-gas sulfidizing reaction method. The La 2 CaS 4 ceramic has become a novel optical window material lately for 8-14 µm IR range.
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