Dimethyl ether (DME), abbreviated as methyl ether, molecular formula: CH OCH3。 Dimethyl ether is composed of two methyl molecules and one oxygen atom. Its chemical structure is not very stable and has a certain degree of oxidation. It can react chemically with the valve sealing ring material (commonly made of butadiene rubber) in liquefied petroleum gas cylinders, causing valve leakage. At the same time, the addition of dimethyl ether to liquefied petroleum gas cylinders may cause problems such as a decrease in calorific value. The General Administration of Quality Supervision, Inspection and Quarantine has explicitly stated in the "Quality Inspection Special Letter [2008] No. 17" that it is prohibited to add dimethyl ether to civilian liquefied petroleum gas and then fill it into liquefied petroleum gas cylinders. However, adding dimethyl ether to liquefied petroleum gas has a great profit margin, which is important for monitoring the quality of liquefied petroleum gas. Liquefied petroleum gas is mainly composed of C5 and below components such as propane, propylene, butane, and butene. If the content of C5 and above components is too high, it will reduce volatility and cause residual gas in the tank
The increase in surplus affects the interests of customers. So it is necessary to determine the content of dimethyl ether, Cs, and C5 and above components in liquefied petroleum gas.

1、 Analysis method of dimethyl ether:

Liquefied gas analysis includes component analysis of liquefied gas and analysis of dimethyl ether and methanol in liquefied gas, excluding alkynes. A gas chromatograph with a thermal conductivity detector is used to separate the components in the sample using a chromatographic column. The area normalization method or corrected area normalization method is used to quantify the percentage content of each component using an external standard method

IIGC-2010 gas chromatograph (equipped with TCD thermal conductivity detector), data processing is completed using N2000 chromatography workstation, and liquefied petroleum gas samples are all extracted from the market. Invert the liquefied gas cylinder and evenly vaporize it in a 60 ℃ constant temperature water bath. Then, pour the sample into the injection quantitative tube and repeatedly blow it, controlling the flow rate to 45ml/L and maintaining it for 1.0 minute. Then switch the six way sampler to introduce the sample into the chromatographic column. The chromatographic column is a liquefied petroleum gas column with specifications (6mx3 (OD) optional capillary column) (provided by Tengzhou Zhongke Spectral Analysis Instrument), carrier gas H2: purity>99.99%, carrier gas flow rate 45 ml/L, gas six way sampler injection, gasification temperature 90 ℃, column box temperature 45 ℃, TCD detector temperature 90 ℃, column pressure 0.12 Mpa.

After gasification in a constant temperature water bath connected to a liquefied gas cylinder, it was introduced into a chromatography column through a six way valve. The thermal conductivity detector simultaneously detected dimethyl ether and components C and above in liquefied petroleum gas, achieving good separation. The precision and accuracy of this method can meet the needs of routine analysis. It is a simple and practical chromatographic analysis method.