ASTM D7059 Standard Test Method for Determination of Methanol in Crude Oils by Multidimensional Gas Chromatography
4. Summary of Test Method
4.1 An internal standard, 1-propanol, is added to the sample, which is then introduced into a gas chromatograph equipped with two columns and a flow switching system between the two columns. The sample first passes through the polydimethylsiloxane WCOT column that performs a pre-separation of the methanol and 1-propanol and eliminates unwanted hydrocarbons. The methanol and 1-propanol are transferred to the analytical PLOT column for oxygenates. While the methanol and 1-propanol are eluting from the analytical PLOT column for oxygenates, auxiliary carrier gas is used to elute higher boiling crude oil hydrocarbons from the pre-column, either in the forward or backflush mode, to yield a stable baseline for the next analysis.
5. Significance and Use
5.1 Methanol is used in production of crude oil to prevent formation of gas hydrates. The presence of residual methanol in crude oils can lead to costly problems in refinery operations.
