Abstract
Chromatographic techniques utilizing an argon ionization detector with helium carrier gas are described for measuring one ppm and less of fixed gases such as carbon monoxide, hydrogen, and methane in one-milliliter air samples. The instruments's low standing current and low noise level required to achieve this order of sensitivity are provided by in-line purification of commercial helium carrier gas and by due attention to analytical column operation to minimize residual contaminant bleedout. Slight modifications have been made in the geometry and usual manner of installation of the detector. Practical application of these techniques are demonstrated.
In summary, fixed gases may be readily detected with an argon ionization detector when helium is used as carrier gas. By use of simple helium purification techniques, and with due attention to analytical column operation and detector installation, it is possible to achieve extreme sensitivities. The order of sensitivity possible has been illustrated herein by a chromatogram showing close to full scale recorder pen deflections for fixed gases present in concentrations of 100 ppm in 0.05 milliliter of air sample. A 2.0-milliliter air sample, in practice, shows similar deflections for 2.5 ppm traces. In these studies, relatively little attempt was made to utilize the capacity of the instrument beyond each immediate need in the development of catalyst and sorbent performance data. It is certain that much greater sensitivities, if needed, could be readily achieved with more attention to helium purification, column operation, and full instrument capacity.