Development Of 100 Mu Mol Mol(-1) Cl-2 Standard Gas Mixture For Accurate Calibration Of Ambient Cl-2 Sensors And Stack Emission Monitors

To accurately measure Cl-2 mixing ratio using stack emission monitors and leak monitoring sensors in a workplace, it is essential calibrating monitors and sensors periodically using a Cl-2 standard gas mixture. Because there is no reliable analytical technique for Cl-2, an international standard for high-pressure Cl-2 gas mixtures has not been established. A novel approach for the quantification of Cl-2 was developed using quadrupole mass spectrometry (QMS) with an expanded uncertainty of 0.7 mu mol mol(-1). A 100 mu mol mol(-1) chlorine (Cl-2)/N-2 gas mixture was produced through a two-step procedure involving dilution of Cl-2 with N-2 in high-pressure aluminum cylinders. To check the consistency between 100 mu mol mol(-1) Cl-2 gas mixtures in different cylinders, Cl-2 gas mixtures were quantified using the QMS based approach. It was found that four cylinders of 100 mu mol mol(-1) Cl-2 gas mixtures prepared in 2016 agreed within 0.7 mu mol mol(-1). The long-term stability of 100 mu mol mol(-1) Cl-2 gas mixtures was assessed through changes in the Cl(2 )mixing ratio over a one-year. It was found that the 100 mu mol mol(-1) Cl-2 gas mixture was stable within +/- 0.7 mu mol mol(-1) over one year. Finally, 100 mu mol mol(-1) Cl-2/N-2 gas mixture was successfully developed in a high pressure cylinder with an expanded uncertainty of 2.0 mu mol mol(-1) (k = 2; 95% confidence level).