nbsp; Figure 31. The Heated IR Flow-through Cell   The trap was connected to the IR cell and could be electrically heated by appropriate heater coils to 250ûC. The trap was packed with 15% w/w of Apiezon Grease on 60-80 BS. mesh brick. Around the outside of the trap were a series of cooling coils that could carry cold water, the flow through which was controlled by a programmed solenoid valve. The column was all glass 60 ft long, 4.0 mm I.D., and packed with 60-80 BS mesh brick dust carrying 15% w/w of Apiezon Grease   The column consisted of a series of glass U tubes and each U section was packed individually. After packing all the individual U sections, they were sealed together

of capillary columns and their operating conditions were determined, almost exclusively, using these home made columns. The first columns were made from copper capillary 1/16 in. O.D. and 0.010 I.D. which was readily available commercially and relatively inexpensive. The standard length then was 100 ft and the stationary phase was coated on the walls of the column from a solution in a volatile solvent. It was soon found that only dispersive stationary phases (see book 7 of this series) such as Apiezon Grease or squalane could be made to form a stable film on the copper surface particularly at higher temperatures. Polar stationary phases such as dinonyl phthalate or polyethylene glycol would not form a stable film and degenerated into tiny drops on the column wall particularly as the column temperature was raised. These drops dramatically increased the high resistance to mass transfer in the stationary phase and greatly reduced the efficiency. The next type of column material to be

remove metal oxides or other corrosion products that may remain adhering to the walls, washed with water and the again washed with methanol and methylene dichloride. Finally the column is dried in a stream of hot nitrogen. Metal columns provide the high efficiencies expected from open tubular columns and were used for the analysis of petroleum and fuel oils, etc. Metal columns, however, have some disadvantages as although easily coated with dispersive stationary phases (e.g., squalane, Apiezon grease etc.) they are not so easily coated with the more polar stationary phases such as CARBOWAX®. In addition, hot metal surfaces can cause decomposition or molecular rearrangement of many thermally labile materials such as the terpenes contained in essential oils. Metal can also react directly with some materials by chelation and adsorb polar material which results in asymmetric and tailing peaks. Nevertheless, metal columns are rugged, easy to handle and easy to remove and

Trimethylpentane 8.3-Ethylpentane 21.4-Methylheptane 9.2,3,4-Trimethylpentane 22.3-Methylheptane 10.n-Heptane 23.3-Ethylheptane 11.2,2-Dimethylhexane 24. 2,4-Dimethylhexane 12.2,5-Dimethylhexane 25.#-Methyl-2-ethylpentane 13.2,4-Dimethylhexane 26.n-Octane The column temperature was 78.6˚C, and the column packing 2.5w/w Apiezon Oil on C22 firebrick 100-120 mesh. The column diameter was 2 mm, the inlet pressure 200 p.s.i., and the column efficiency 30,000 theoretical plates. The argon detector was used and the sample weight was 20 mg. Figure 12. Chromatogram from a 50 ft Column Showing the Separation of the Isomeric Heptanes and Octanes