Investigation of adsorption characteristics of four toxic gases (NO, NO 2 , SO 2 , and HCl) on the inner surface of nickel coated manganese steel and aluminum cylinders.

To develop standard toxic gas mixtures, it is essential to identify adsorption characteristics of each toxic gas on the inner surface of a gas cylinder. Thus, this study quantified adsorbed amounts of the four toxic gases (NO, NO2 , SO2 , and HCl) on the inner surface of aluminum and nickel coated manganese steel cylinders. After eluting adsorbed gases on the inside of cylinders with ultrapure water, a quantitative analysis was performed by an ion-chromatograph. To evaluate the reaction characteristics of the toxic gases with cylinder materials, quantitative analyses of Ni, Fe, and Al were also performed by an inductively coupled plasma-optical emission spectrometry (ICP-OES). It was found that amounts of NO, NO2 , and SO2 adsorbed on the inner surface of aluminum cylinders were less than 1.0 % at the level of 100 μmol/mol mixing ratios whereas the signal for most heavy metal elements were below their respective detection limits. This study found that amounts of HCl adsorbed on the inner surface of nickel coated manganese steel cylinders were less than 5 % at the level of 100 μmol/mol mixing ratio, while amounts of Ni (86 μmol) and Fe (28 μmol) were detected in the same cylinders. It was revealed that the adsorption mainly took place via the reaction of HCl with inner surface material of nickel coated manganese steel cylinders. On the other hand, in the case of aluminum cylinders, amounts of the adsorption were determined to be less than 1 % at the level of HCl 100 μmol/mol mixing ratios whereas most of Ni, Fe, and Al were detected levels similar to their limits of detection. As a result, this study found that aluminum cylinders are more suitable for preparing HCl gas mixtures than nickel coated manganese steel cylinders. Implications To develop a standard toxic gas mixture, it is essential to understand adsorption characteristics of each toxic gas inside a gas cylinder. It was found that amounts of NO, NO2 , and SO2 adsorbed inside aluminum cylinders were less than 1.0 % at the level of 100 μmol/mol mixing ratios. The amounts of HCl adsorbed inside nickel coated manganese steel cylinders were less than 5 % at the level of 100 μmol/mol mixing ratio whereas that inside aluminum cylinders was less than 1 %, indicating that aluminum cylinder is more suitable for preparing HCl gas mixtures.