ASTM D2427 Method for Determination of C2 through C5 Hydrocarbons in Gasolines
ASTM D2427 Standard Test Method for Determination of C2 through C5 Hydrocarbons in Gasolines by Gas Chromatography
7. Preparation of Apparatus
7.1 Column Preparation - The method used to prepare the column is not critical as long as the finished column produces the desired separation. Preparation of the packing is not difficult once the support, partitioning liquid, and loading level have been determined. Some stationary phases are susceptible to oxidation and must be protected from excessive exposure to air during the evaporation and drying steps. The following general directions have been found to produce columns of acceptable characteristics:
7.1.1 Weigh out the desired quantity of support, usually twice that required to fill the column.
7.1.2 Calculate and weigh out the required quantity of partitioning agent. Dissolve the partitioning agent in a volume of chemically inert, low-boiling solvent equal to approximately twice the volume of support.
7.1.3 Gradually add the support material to the solution with gentle stirring.
7.1.4 Slowly evaporate the solvent while gently agitating the mixture until the packing is nearly dry and no free liquid is apparent.
7.1.5 Spread the packing in thin layers on a nonabsorbent surface and air or oven dry as required to remove all traces of solvent.
7.1.6 Resieve the packing to remove fines and agglomerates produced in the impregnation step.
7.1.7 Fill the column tubing with packing by plugging one end with a wad of glass wool and pouring the packing into the other end through a small funnel. Vibrate the tubing continuously over its entire length while filling. When the packing ceases to flow, tap the column gently on the floor or bench top while vibrating is continued. Add packing as necessary until no further settling occurs during a 2-min period. Remove a small amount of packing from the open end, plug with a wad of glass wool, and shape the column to fit the chromatograph.
7.1.8 If multiple columns are joined by tubing unions, the dead volume in the union should be filled with column packing.
7.2 Chromatograph - Mount the column in the chromatograph and establish the operating conditions required to give the desired separation (see Annex A1). Allow sufficient time for the instrument to reach equilibrium as indicated by a stable recorder base line. Control the oven temperature so that it is constant to within 0.5°C without thermostat cycling which causes an uneven base line. Set the carrier gas flow rate, measured with a soap film meter, so that it is constant to within 1 mL/min of the selected value.
