Measurement of the C_H/C_D Ratio by Quadrupole Mass Spectrometer

Using a ELITE SXP 50 quadrupole mass spectrometer(QMS) with lower resolution, a method of accurately measuring the C H/ C D ratio in H 2 D 2 mixture without preparing the HD standard sample is proposed. A good linear relation between QMS response to H 2 and D 2 and component partial pressure is verified and the relation of two straight line slopes is K (H 2)= 2K (D 2). According to this fact, the relation K (HD) =1.5 K (D 2) is deduced. Various H 2 D 2 mixtures are used to verify the method and the relative deviation between C H/ C D measured and given values is less than 4.0%. The H 2 D 2 standard mixture ( C D/ C H=1.05) is measured to verify the reliability of the method. The measured C D/ C H average value is 1.07 and relative deviation between measured average value and standard value is 1.9%. It is found that the deduced relation K (HD)=1.5 K (D 2) is reliable and the C H/ C D ratio of various H 2 D 2 mixtures could be accurately measured by using this type QMS.