Long-term Stability Assessment of Dimethyl Sulfide Primary Reference Gas Mixtures in Varying Aluminum Cylinder Treatments (at nmol mol(-l) Levels)

Dimethyl sulfide (DMS) plays an important role in atmospheric chemistry and climate change ranging from several hundred pmol mol(-1) to several nmol mol(-1) levels in the atmosphere. DMS is one of the essential reactive gases that are monitored to track its long-term trend in the World Meteorological Organization Global Atmospheric Watch program for better understanding of its role in the atmospheric processes. It is thus required to use accurate and stable standard gas mixtures for precise atmospheric DMS measurement. It is crucial to evaluate the long-term stability of DMS at nmol mol(-1) levels in aluminum cylinders for developing its standard gas mixtures. In this study, DMS primary reference gas mixtures (PRMs) at both 2 nmol mol(-1) and 7 nmol mol(-1) levels were prepared in aluminum cylinders with different inner surface treatments. The stabilities of DMS PRMs were evaluated by tracking DMS-to-benzene ratio since benzene was known as stable in aluminum cylinders at nmol mol(-1) levels. Results from linear regression analysis show that stabilities are different depending on cylinder inner surface treatment and mole fractions. For 2 nmol mol(-1), DMS PRM in aluminum cylinder with Performax (inner surface treatment) is projected to be stable at least for 10 years with a target uncertainty of 3% whereas, with Aculife and Experis surface treatment, DMS PRM is predicted to be stable for about 4 years and 3 years, respectively. For 7 nmol mol(-1), DMS PRMs are projected to be stable for 9 similar to 12 years in aluminum cylinders with all three special surface treatments (Performax, Aculife, and Experis) while, without the special surface treatments, the stability varies from 1.5 years to 3.5 years.