Modified Diatomaceous Earth as a Principal Stationary Phase Component in TLC

Abstract

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 60GF<inf>254</inf> (Si-60GF<inf>254</inf>). Modification is carried out by flux calcination and refluxing with acid. Natural DE, modified DEs flux calcinated (FC)DE and FCDE-I), and Si-60GF<inf>254</inf> are characterized by scanning electron microscopy and Fouriertransform-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-60GF<inf>254</inf> 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-60GF<inf>254</inf> and FCDE-I individually, and on various FCDE-I and Si-60GF<inf>254</inf> 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 (R<inf>f</inf>) 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-60GF<inf>254</inf>. 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, α<inf>OH(s)</inf>] and those of the mobile phase (e.g., polarity and acidity) on R<inf>f</inf> values and the separability of components.