[Determination of natural gas by gas chromatography with external standard-area normalization method]

A GC method for determination of natural gas by external standard-normalization has been established. O2, N2, CH4, CO2, and C2H4 were separated by 13X molecular sieves (1 m x 3 mm i.d., 50 degrees C) connected with PORAPAK T columns (2 m x 3 mm i.d.) in series and detected by TCD and the hydrocarbons of C3 and higher were separated by an SE-30 column (50 m x 0.32 mm i.d.) at 50 degrees C and detected by FID at first. Then O2 + N2 + CH4, CO2 and C2-C5 hydrocarbons were separated on a column (6 m x 3 mm i.d.) with mixed phases of beta, beta'-oxydipropionitrile and dibutyl phthalate at ambient temperature, and detected by TCD. Peak areas from SE-30 column and mixed phase column were correlated with C5, and area normalization was used for quantitative analysis; then normalization correction factors of each component in sample on 13X molecular sieves, PORAPAK T and SE-30 columns were calculated. In analysis, only the first step, area normalization was used for quantitative analysis. The method achieved calibration by SP-6000 Natural Gas Analyzer itself. It is economic, convenient, rapid and accurate.