Gas-liquid equilibrium experiments and gas chromatography analysis, urgent! ! !

　Gas-liquid equilibrium. 　　A closed system composed of a mixture of n components, with gas and liquid phases coexisting, reaches equilibrium at a certain temperature and pressure; at this point, the chemical potentials of each component in the gas and liquid phases tend to be equal. It is more convenient to use fugacity: when the fugacity of component i in the gas phase and the liquid phase of a mixture is equal, it is called gas-liquid equilibrium. For the fugacity of the component ； i represents the component ； The superscripts L and V denote the liquid phase and gas phase, respectively. Thus, the calculation of vapor-liquid equilibrium can be reduced to the calculation of the fugacity of components in the gas phase. Data on gas-liquid equilibrium is needed to solve many problems. 　　Under different temperature, pressure, and composition conditions, a vapor-liquid system composed of a volatile liquid mixture (or a single-component substance) and its vapor reaches a critical state. At this point, the mass transfer rates of each component between the vapor and liquid phases are equal, both from the vapor phase to the liquid phase and from the liquid phase to the vapor phase; thus, the net mass transfer rate is zero ； At the macroscopic level, this is manifested as a constant concentration of each component in the liquid or vapor phase of a mixture (or single-component substance), thereby achieving vapor-liquid equilibrium. By changing the temperature, pressure, or composition of the system, it will reach a new vapor-liquid equilibrium. 　　When the gas and liquid phases come into contact, the gas dissolves in the liquid, resulting in a certain solubility ； A gas dissolved in a liquid, as a solute, necessarily generates a certain partial pressure. Gas-liquid equilibrium is reached when the partial pressure generated by the solute equals the partial pressure of that gas in the gas phase. The establishment of phase equilibrium indicates that mass transfer has reached its limit, and the absorption process then ceases. It is an important factor in controlling the operation of the absorption system. For dilute solutions of most gases, the equilibrium relationship between gas and liquid can be expressed by Henry’s law. Based on the theory above, I think you should use the sample from above, rather than the point at the layer boundary. Both substance A and B have a density lower than that of water; they are located above and are also soluble in water

Well, I understand what you mean, but what I want to measure is the total amount of both components in the liquid phase. The gas phase also separates into layers after condensation; so how can we determine the total amount in the gas phase?

It is recommended that you measure the ratio of the contents of methane and ethane to water in the gaseous portion above. Experimental online high-temperature and high-pressure sampling can be employed. The gas-liquid mixture is directly taken into the chromatograph for analysis. This method can be implemented by using a six-way valve for sampling, with all sampling lines being insulated. If there is high pressure, it can be relieved using a high-temperature backpressure valve.

But the project specifies that it should be low pressure, around ten-odd PA...

Lower pressure is better! It saved a lot of trouble.