Preparation of the solid support from diatomite in Thailand for Chromatographic columns

Abstract

The microstructure of Thai diatomite from Lampang was found as diatoms named Melosira granulata which was the same as that of Gas Chrom Q. The diatomite from the Mae deposit contained 71.09% Sio₂, 11.83% AI₂O₃, 2.86% Fe₂O₃, 0.44% MgO, 0.20% CaO, 1.16% Na₂O, 1.55% K₂O, 4.52% other oxides and 6.35% loss on ignition. The method of benefication of Lampang diatomite by mechanical means was 4-stage washing with H₂O (at a solid:liquid ratio of 1:5 w/v), isolating coarse minerals and clay by decantation. The clean diatomite was l-stage extracted with 10% v/v HCI (at a solid:liquid ratio of 1:5 w/v). The acid treated diatomite was flux-calcined with 8.55% Na₂CO₃ at 1000℃ for 3 hours. The flux-calcined product was crushed into the required particles and silanized with 5% v/v DMCS (dimethyl dichlorosilane) in toluene solution. The prepared support showed more surface area and more adsorptive effect on the coating of 5% OV-101 than those of Gas Chrom Q. The chromatographic characteristics for separation of non-polar compounds were the same. However, for the separation of intermediately polar and polar compounds, it provided better column efficiency than Gas Chrom Q. The sensitivity for analysis of hydrocarbons, esters and alcohols from the prepared support column was the same as that from the Gas Chrom Q column. Therefore, this prepared support was proposed as an excellent solid support for gas chromatography and it was named as “Diatochrom L”.