Preparation Of Xerogel Monolithic Material

As a novel chromatographic material, monolithic material has been widely applied in μ-HPLC、capillary electrochromatography、preparative HPLC etc. Because of its unique double holes structure, monoliths have good separation performance and can be modified easily. In addition, the advantages of stable chemical properties, function diversity, good permeability as well as easy preparation make monolithic material attract increasing interest.In general, monolithic material can be classified into three categories: organic polymer-based monolith, inorganic monolith (silica-based monolith) and organic-inorganic hybrid monolith. Different types of monolith has different preparation methods. Sol-gel and xerogel are the main preparation methods of silica-based monolith. Because of its unmanageable reaction condition, the silica-based monolith using sol-gel is easy to fall off from tube wall and it often suffers from rupturing, collapsing etc. In comparison, xerogel monolith is easier to prepare, and those structure defects mentioned above do not appear.In the process of xerogel method, potassium silicate was utilized as silicon source, formamide was utilized as catalyst. We have prepared the silica monolithic materials in polypropylene centrifugal tube, quartz capillary and glass tube. The different preparation condition have been investigated. The main work includes the following three aspects:1. Silica monolithic material was fabricated in polypropylene centrifugal tube (i.d.=2.8 cm) by xerogel method. The sources of potassium silicate, the reaction temperature, the heating mode and the modulus of potassium silicate were investigated in our experiment. The structure of silica monolithic material was characterized by SEM, and the BET surface area was determined by nitrogen adsorption method.2. Silica monolithic material was fabricated in quartz capillary by xerogel method. The capillary pretreatment method, the reaction temperature, the capillary inner diameter and the modulus of potassium silicate were investigated in this part. The structure of the different monolith was observed by microscope.3. Silica monolithic material was fabricated in glass tube (i.d.=1.0 cm) by xerogel method. The glass surface treatment method, the reaction temperature, the heating mode and the modulus of potassium silicate were investigated in this experiment. The properties of silica monolithic material were characterized by pigment chromatography mainly.