The effect of gaseous additives on the response of the helium ionization detector

Characteristic negative response of the helium ionization detector

“…Neon has an ionization potential of 21.5 eV which is higher than the metastable energy of helium (19.8 eV), and accordingly it is not ionized by He*. Some investigators (5)(6)(7)(8)(9), however, have found that when the purest commercially available helium is used as a carrier gas (where impurities are in the range of parts per billion), the detector responds negatively not only to neon but to some other gases as well. It was found that the detector response can be made positive for all gases except neon upon the addition of small concentrations (5-35 ppm) of gaseous additives (5)(6)(7)(8)(9).…”

“…Some investigators (5)(6)(7)(8)(9), however, have found that when the purest commercially available helium is used as a carrier gas (where impurities are in the range of parts per billion), the detector responds negatively not only to neon but to some other gases as well. It was found that the detector response can be made positive for all gases except neon upon the addition of small concentrations (5-35 ppm) of gaseous additives (5)(6)(7)(8)(9). Adding higher concentrations of gaseous additives produces a positive response for neon as well (8).…”

“…It was found that the detector response can be made positive for all gases except neon upon the addition of small concentrations (5-35 ppm) of gaseous additives (5)(6)(7)(8)(9). Adding higher concentrations of gaseous additives produces a positive response for neon as well (8). Addition of large concentrations of gaseous additives to the helium carrier gas increases the detector response but it also increases the noise level, and it also makes the analysis of small concentrations of the added gas difficult (8).…”

Standardization of helium carrier gas for helium detector applications

“…In such grades of helium, impurities are in the range of a few parts per billion (1,2). Using this grade of helium in a leak-free chromatographic system, the detector will characteristically respond negatively to a small concentration of selected gases (Ne, H2, Ar, 02, and N2) and positively to other gases (3)(4)(5). Addition of a small concentration of gaseous additive will provide a positive response to all gases and compounds tested (3)(4)(5).…”

“…Using this grade of helium in a leak-free chromatographic system, the detector will characteristically respond negatively to a small concentration of selected gases (Ne, H2, Ar, 02, and N2) and positively to other gases (3)(4)(5). Addition of a small concentration of gaseous additive will provide a positive response to all gases and compounds tested (3)(4)(5). Recently the HID was operated in the saturation region of the detector field intensity to provide a sensitive and reliable response (6, 7).…”