Deactivation of glass capillary columns by silylation. Part 1: Principles and basic technique

A deactivation procedure is described based on a published method using hexamethyldisilazane in the gas phase. In addition to unusually high inertia and thermostability, the method produces truly neutral columns which allow simultaneous analysis of moderately strong free acids and bases. The silylated columns show their full potential only with on-column injection. Preliminary experimental directions are given; more elaborate directions will become available after extended optimization work.     

Preparation of glass capillary columns

Summary Glass capillary column chromatography is the most rapidly growing part of gas chromatography. There are many complex new analytical tasks and they require special capillary columns. Fortunately there is a wide range of column preparation methods available, and they make the preparation of glass capillary columns a more varied job than that of packed columns. In this paper these methods are reviewed and suggestions are given for making task-oriented columns.     

Separation of 28 to 114°C hydrocarbons with glass capillary columns

Techniques have been developed for the rapid separation (about 20 minutes) of the 39 compounds in crude petroleums, or petroleum distillates, which boil between 28 and 114°C. A 300 meter glass column (0.25 mm i.d.) which is etched, coated with a mixture of normal hexadecane and Kel-F10157 is utilized to perform this separation at room temperature. The separations obtained with this non–polar liquid mixture and the «inert» glass surface are much more rapid than those previously obtained with stainless steel capillary columns.     

Evaluation of graphitized glass capillary columns

The performance of graphitized glass capillary columns obtained by precoating the inner glass walls with graphitized carbon black has been evaluated. It has been shown that according to the amount of stationary phase coated such columns can operate in gas–liquid-solid chromatography and in gas–liquid chromatography so that tailor-made columns for specific separations can be prepared. The versatility of these columns is shown in the separation of various mixtures (terpenes, pesticides, isomeric species and others) of analytical importance.     

High-temperature silylation in the production of inert glass capillary columns. From the first experiments to the chemical mechanism

This retrospective article describes the beginnings and the development of silylation methods with diverse silazanes and siloxanes at high temperatures, and stresses their role in producing modern capillary columns characterized by a high degree of thermostability and adsorptive and catalytic inertness. Particular emphasis is placed on the outstanding contributions to this field of Kurt Grob, whose persilylation techniques provided the basis for the expansion of high resolution capillary gas chromatography.     

High temperature gas chromatography on narrow bore capillary columns

The use of high-temperature-stable, medium polarity glass capillary columns coated with immobilized PS-090 (a 20 % diphenyl-substituted, CH₃O-terminated polydimethylsiloxane) has made it possible to analyze routinely, and with good separation efficiency, high molecular weight compounds such as triglycerides and free base porphyrins. Cold on-column injection was used throughout this work to avoid discrimination against involatile compounds, and disposable (fused silica) retention gaps were used to protect the column against contamination with involatile material. On-column injection into narrow bore glass columns was achieved by using glass-to-silica connections to attach wider bore (0.2 mm i.d.) deactivated fused silica tubing to the columns.     

Odour evaluation,fraction collection and preparative scale separations with glass capillary columns

A simple but effective GC approach to odour evaluation and fraction collection with capillary columns is described. An allglass device splits the column effluent, with one splitter arm going to an FID. For odour evaluation, the other splitter arm is led via teflon tubing to the nose. Off-line heart-cutting is carried out by collecting the split effluent on a glass capillary microtrap, the inner walls of which are coated with OV-101. This allows recovery of nanogram amounts of material. Multipass operation or repeated collection leads to preparative capillary GC for further spectroscopic investigation. These techniques do not involve sophisticated equipment or valves. Applications of this type of smell analysis, heart-cutting and enrichment in the analysis of Rhododendron fragrantissimum essential oil, black pepper essential oil and hop essential oil, illustrating the versatility of the systems, are presented.     

Thermostable persilylated polar glass capillary columns by the ammonia-etching method

Static ammonia etching has been used to effect regular surface roughening of glass capillaries. Following such treatment, polar phases could be coated after persilylation with varioussilylation agents such as hexamethyl-, tetramethyldiphenyl-, and tetra- phenyldimethyldisilazane, respectively. This method produces columns of high thermostability, which is limited only by the maximum applicable temperature for the phase itself.     

Persilylation of glass capillary columns. Part 4: Discussion of parameters

Persilylated glass capillary columns are the most universal GC columns available. They are relatively easy to prepare, but there is nevertheless a great need for helpful practical instructions. In the recent literature, methods and conditions for the preparation of persilylated columns have been recommended, but these might confuse the individual column maker, since they seem to originate from limited observations rather than from comprehensive investigation. They will hardly help to make column preparation safer. This paper attempts a summarized view of the present experience with persilylation and provides basic information for column makers.