Effect of the Hydrogen and Carrier Gas Flow Rates on the Relative Molar Response of the FID

Abstract

The dependence of ionization efficiency on the carrier gas and hydrogen flow rates can, for various substances, follow a different course. Under these circumstances, the relative molar response (RMR) would also depend on the above parameters. On these grounds, the ionization efficiency of compounds of different chemical structure (nonane, benzene, thiophene, pyridine, butyl acetate, propyl alcohol, and tetrachloromethane) has been measured, varying independently the carrier gas (N2) and H2 flow rates in the range of from 0.5 to 2.0 m1/sec. From the data obtained, the respective RMR's were evaluated using nonane as a reference substance. The effects of the flow rates were elucidated statistically using a model of factorial experiments. In case of benzene, thiophene, pyridine, and tetrachlo-romethane, no significant influence of the flow rate variations on the RMR's has been proven, whereas the RMR's of all oxygen-containing substances investigated were strongly dependent on both the N2 and H2 flow rates. Within the ranges given, the RMR's of acetone, butyl acetate, and propyl alcohol varied within 0.18–0.23, 0.72–0.86, and 0.26–0.30 respectively. The facts found point to the difficulties which might be met in carrying out quantitative analyses while referring to the FID relative molar responses listed in the literature.