... quantitative tube 1, after sweeping clean, switch V1 from OFF to ON, carrier gas 1 takes sample into analytical ... column DC200, before components flowing out, switch valve 1 from OFF to ON, C6+ was flow back to TCD, ... by gas carrier 2 and be detected, switch the valve V2 from ON to OFF. Before CO2 and C2 ... will be detected by TCD in sequence. Switch the valve V3 from ON to OFF, components O2, N2, CH4 ...