Gas Phase Titrimetry of Acetylene Based on Image Processing of Glow Discharge Plasma During Ionization of Hydrogen as Titrant: Standardization of Hydrogen Standard Solution at Parts Per Billion Levels

摘要

A novel gas phase titrimetry is introduced for acetylene (C2H2) determination at parts per million (ppm) levels based on the non-thermal glow discharge plasma-based ionization of hydrogen (H-2) standard solution. For this purpose, a constant flow of H-2 solution is introduced to an ionization chamber containing a fixed volume of C2H2 solution. The end point (EP) of the titration is indicated by the image processing of the plasma generated between a two-electrode system including Al rod as anode and multi-walled carbon nanotubes (MWCNTs) as cathode using a charged coupled device (CCD) camera during applying a fixed breakdown voltage (832 +/- 1 V). According to the results, the ratio of C-H2/[C2H2] is evaluated to 2.34 +/- 0.01. No interference is observed during introduction of at most 1000 folds (Weight ratio) excess of various foreign gas species to a fixed solution of acetylene (similar to 5.0 ppm). Only a constant negative error to similar to -8% is evaluated due to the multi-step reaction of hydride (H-) as the ionization form of H-2 with C2H2. This method is also considered as an analytical technique that is adopted for standardization of H-2 standard solution at parts per billion levels. Finally the reliability of the method is validated via analyses of two real samples.