Open tubular columns classification

There are two general classifications of gas chromatographic columns, packed and capillary or open tubular columns. 

The retention index system has the advantage of being based on readily available reference materials that cover a wide boiling range. In addition, the temperature dependence of retention indexes is relatively small. In 1984 Sadtier Research Laboratories introduced a library of retention indexes measured on four types of fused-silica open tubular columns. The computerized format of the database allows retention index searching and possible identity recall with a desktop computer. Measurement of retention indexes is the basis of the Rohrschneider-McReynolds scheme for classification of stationary phases in GC (see Section 27C-4),... 

This chapter discusses the types of stationary phases, their classification, their applications, and the criteria used in selecting an appropriate liquid phase for a given separation. With packed columns, the choice of the stationary phase is critical, but it is less so for open tubular columns because of their higher efficiency. Individual chapters are devoted to each of the two column types, and this chapter is more relevant for packed columns (Chapter 5). 

Two types of gas chromatography exist gas-liquid chromatography (GLC) and gas-solid chromatography (GSC). Other classification schemes such as GSC. GLC plus capillary gas chromatography (CGC) are outdated because nowadays GLC and GSC can be performed both in packed columns and in capillary or open tubular columns,... 

A complete classification scheme is shown in Figure 1.2. Note especially the names used to describe the open tubular (OT) GC columns and the LC columns they do not conform to the guidelines just presented. However,... 

As follows from the classification of open tubular capillary columns, capillary gas chromatography includes one more type of adsorption column, viz., an open capillary column with a nonporous (unextended) inner wall surface. This type of columns is distinguished by the following features 1) low sorption capacity, which can be described, for example, by the as = S/L value, where S is the total surface area of inner column walls and L is the column length 2) high phase ratio P/ =Wg/S, where Vtg is the gas-phase volume in the column and S is the total surface area of the inner column walls 3) high rates of mass exchange between gas phase and inner column wall surface. 

---