CH4, CO2, N2O detection dedicated gas chromatograph

Wuhan Tetworth, providing CH4, CO2, N2O detection gas chromatograph. The same chromatograph can simultaneously detect CH4, CO2 and N20 in air samples by retrofitting the gas chromatograph, analyzing the gas path and valve drive system. The test results show that the sensitivity, resolution and precision of the instrument are very high, and the linear range meets the requirements. The instrument system can be stably operated in the field laboratory for a long time, and can be conveniently used to determine the emissions of the terrestrial ecosystems C02, CH4 and N20. Obtain observational data quickly, accurately, and reliably.

The determination of CO2 and N2O emissions from terrestrial ecosystems is generally performed by static chamber/gas chromatography (GC); the determination of CO2 can be performed by vorticity correlation (a method of micrometeorology), and for low vegetation, boxing can also be used. The vorticity correlation method calculates the net exchange flux of CO2 between the vegetation canopy and the atmosphere by measuring the vertical wind speed pulsation and the co2 concentration pulsation in the normal flux layer above the canopy, and there is almost no artificial disturbance to the underlying surface. Although in principle, the vorticity correlation method is an ideal method for determining the net exchange flux of CO2 between the terrestrial ecosystem interface and the atmosphere, it requires a high precision, fast response turbulence and gas concentration change measuring instrument, and requires There are sufficiently flat, open underlying surfaces, and effective observations are only readily available during periods of no rain during periods of neutral atmospheric conditions. Compared with this, the box method, especially the static box method, has the advantages of simple principle, low cost, easy operation, convenient movement, high sensitivity, etc., but has different degrees of disturbance to the observed object. There is currently no better way to arbitrate the CO2 flux values ​​obtained from the atmospheric and surface CO2 exchange fluxes of terrestrial ecosystems. According to the new literature reported by Zui, in the better state, the results of the two methods for observing CO2 flux differ by 5% to 30%, indicating that the methods are comparable if properly operated. However, the price of a box/gas chromatography observation system is only 1/3 to 1/5 of the micro-meteorological method, and multiple points and multiple components can be observed simultaneously. Obviously, the surface gas emission observations, especially for the different conditions of the process mechanism research, the box method is more practical.

In general, when gas chromatography is used to detect CO2, CH4 and N20, a hydrogen flame ion detector and an electron capture detector are used. FID only signals to carbon-containing organic matter and does not respond to CO2. CO2 is first converted to CH4 by the action of hydrogen under the action of hydrogen, and then detected by FID. Therefore, it is generally impossible to measure CO2 and CH4 at the same time. ECD is used to detect N2O. For experiments, especially large-scale field observation experiments, experimenters often want to use less sample analysis time to obtain more data information. After many years of practical exploration, the author has modified the gas chromatograph injection, analysis gas path and valve drive system, and realized the simultaneous analysis of three kinds of greenhouse gases, CH4, CO2 and N2O, which fully improved the utilization efficiency of the instrument. It saves sample analysis time and makes the system suitable for large-scale terrestrial ecosystem greenhouse gas emission observation experiments.