Method for determining nitrogen or carbon isotope ratio of N2 or CO2 gas on basis of elemental analyzer-stable isotope mass spectrometer combined device

Abstract

The invention provides a method for determining nitrogen or carbon isotope ratio of N2 or CO2 gas on the basis of an elemental analyzer-stable isotope mass spectrometer combined device. The method comprises the following steps of: continuously introducing inert gas from a gas inlet of an oxidation tube of an elemental analyzer; injecting the to-be-detected gas sample N2 or CO2 through a sampling port of a gas sampling device; causing the to-be-detected gas sample N2 or CO2 together with the inert gas enter into a stable isotope mass spectrometer through a reduction tube of the elemental analyzer; and determining the nitrogen or carbon isotope ratio by the stable isotope mass spectrometer. According to the method provided by the invention, working standard gas N2 and CO2 can be determined and meanwhile the pure natural abundant N2 and CO2 gas sample also can be determined; the required external device is saved when the stable isotope mass spectrometer is used for determining the gas sample; the method provided by the invention is simple, convenient and high in result accuracy.

Description

technical field [0001] The invention relates to a detection method of gas isotope ratio, in particular to a method for determining N 2 or CO 2 Method for nitrogen or carbon isotope ratios of gases. Background technique [0002] At present, the commonly used N in the laboratory 2 , CO 2 There are three methods for calibrating the isotope ratio of the working standard gas: the first method is to use the dual-channel sampling system for dual-channel comparative measurement calibration, using the certified stable isotope standard gas as the standard, and the stable isotope mass spectrometer. Multiple double-sample comparison measurements are used to calibrate the working standard gas, but the dual-channel sampling system is expensive, and some laboratories are not equipped with this system, so the dual-channel sampling system cannot be used to calibrate the working standard gas; the second One method is to use an elemental analyzer and an isotope mass spectrometer (EA-IRMS) ...

AI Technical Summary

Problems solved by technology

[0002] At present, the commonly used N in the laboratory 2 , CO 2 There are three methods for calibrating the isotope ratio of the working standard gas: the first method is to use the dual-channel sampling system to perform dual-channel comparative measurement calibration, using the certified stable isotope standard gas as the standard, and test it on the stable isotope mass spectrometer. Multiple double-sample comparison measurements are used to calibrate the working standard gas, but the dual-channel sampling system is expensive, and some laboratories are not equipped with this system, so the dual-channel sampling system cannot be used to calibrate the working standard gas; the second The first method is to use elemental analyzer and isotope mass spectrometry (EA-IRMS) to calibrate the standard working gas, that is, to use certified isotopic solid standard substances to calibrate the cylinder gas as the working standard gas, including N 2 and CO 2 etc., but this method cannot be carried out in the absence of isotope solid standard substances; the third method is to use a trace gas pre-concentration device and an isotope mass spectrometer to concentrate the required calibration gas through a cold trap, and finally enter the stable isotope Mass spectrometer for measurement, but there are certain difficulties for laboratories lacking trace gas pre-concentration devices

Images