Analysis of Hydrocarbon Composition in Gasoline with Direct Heating Packed Capillary Column
直热式毛细管柱对直馏汽油组成的分析

A packed glass capillary column with an electric resistance wire inside is a new type of column. It can be directly used for temperature programming without GC oven. Satisfactory results have been obtained with this new column type for gas analysis. In this paper, straight run gasoline is analyzed by using this column type. Stationary phase is made by coating 13X molecular sieve on 102 Packing. Put the stationary phase into a glass tubing with an electric resistance wire inside and draw them into packed capillary column with a metal core. Two metal unions are specially designed on each end of the column. The union links up the glass capillary column and a quartz capillary. Electric power is applied through outside of the metal union which is in close contact with the inside heating wire. Graphite ferrules are used for their endurance of high temperature. The temperature of the column is programmed by gradual increase of electric voltage applied. Baseline compensation is used in analyzing straight run gasoline by the direct heating column. The apparent temperature can be observed through the thermocouple bound to the column. The apparent and actual temperature can be correlated by the retention time of components. The actual temperature of direct heating column is usually above the apparent value. The repeatability of retention time for most component of six runs is less than 3%. The relative deviation of quantitative results for each component in straight run gasoline is less than 5%. The analysis time is shorter by direct heating mode than that by oven heating. Increasing the coat thickness of 13X molecular sieve will increase the column efficiency, but the elution temperature is increased when the thickness of molecular sieve coat increased. Thirty percent 13X molecular sieve loaded on 102 is used for the above analysis.