Rapid analysis using short capillary columns in gas chromatography

Abstract

The EHI can be used to collect a sample by simple attachment to any sparging cell; then after the sample is collected the EHI is connected to the gas chromatographic inlet. Priorto desorption, a flow controller is used to establish a flow of 30 mllmin through the EHI and into the injector. A split flow greater than the EHI flow is required if the column head pressure is to remain constant, although short splitless periods can be tolerated. The temperature of the EHI is then rapidly increased to the desired desorption temperature. This fast heating rate causes rapid vaporization and transfer of sample into the capillary (comparable to that of a syringe injection). For most solutes it is not necessary to thermally contain the compound at the head of the capillary column; however, for less volatile compounds it is necessary to inject at a column temperature which will ensure that the solute is contained at the column head. This effect is shown in Figure 2 which demonstrates that there is no observable loss of column efficiency for the injection of a mixture of dodecane, tridecane, tetradecane, and hexadecane (n-Cln, n-Cj3, n-C14 and n-C16 hydrocarbons, respectively) by either syringe or EHI. Chromatogram A was run isothermally at 150OC while chromatogram B was held at 50°C during desorption; then the oven was heated at the maximum rate of 32°C/min. to 15OOC. The thermal conditions of chromatogram B were necessary only to sharpen the elution profile of n-Cq6 (6. P. 287OC). It was observed that no such thermal focusing was necessary to obtain sharp peaks for n-Cj4 (B. P. 248OC).In conclusion, we have developed a simple apparatus which can be used to collect samples external to the chromatographic system and then inject these samples directly on to a capillary column without serious loss of chromatographic efficiency.

Determination of polycyclic aromatic hydrocarbons in a coal tar standard reference material

“…This SRM will serve as a reference among analytical laboratories involved in the determination of polycyclic aromatic compounds in complex mixtures. Since coal tar samples have already found use in a number of laboratories for the evaluation of gas chromatographic performance (e.g., column efficiency and/or selectivity) (19)(20)(21)(22)(23)(24)(25)(26)(27), SRM 1597 will also serve as a common reference sample for such comparisons among various laboratories.…”

Potentials of capillary gas chromatography in toxicology today

“…The lenght of capillaries does not require much discussion; usually, two lenghts are used (24-30 m or 50-60 m), which are chosen according to particular needs. For rapid analysis some authors [21] advocate the use of short (5-10 m) capillaries. It should be noted, however, that such columns lose the most important feature of capillaries, i.e.…”

Aspects of High-Resolution Gas Chromatography as Applied to the Analysis of Hydrocarbon Fuels and Other Complex Organic Mixtures. Volume 1

“…The same jet fuel sample analyzed in Figure 7 was chromatographed with a longer column, and the corresponding chromatogram is presented in Figure 8. Other workers [43,44] have performed very rapid separations of high-moleeular-weight materials by using hydrogen carrier gas at mean axial velocities of 0.5 to 1.5 meters per second. Thus, the use of hydrogen as the carrier gas is another option.…”