An Improved Moving Wire Liquid Chromatography Detector

Authors:
  • RSR. P. W. Scott
    R. P. W. Scott
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Abstract
The Moving Wire Detector functions by wetting the surface of a wire with a thin film of the column eluant. The wire passes into an evaporator to remove the mobile phase and thence to a pyrolyser where the involatile solutes are pyrolysed. The pyrolysis products are swept by a gas stream into an argon or flame ionisation detector. Such a detector has an ultimate sensitivity of about 4 µg/ml of mobile phase (1). This paper describes modifications to the instrument whereby the solute obtained after evaporating the mobile phase is not pyrolysed but is burnt in oxygen to carbon dioxide and water. The carbon dioxide and excess oxygen are mixed with hydrogen and passed over a nickel catalyst to convert the carbon dioxide to methane which is then detected by a flame ionisation detector. The sensitivity of the system has been increased to 1.1 µg/ml of solute in the mobile phase. As opposed to the pyrolysis system, it is linear over 4 orders of concentration range and has a quantitative response to the mass of solute on the wire that can be predicted from its carbon content, providing the molecular formula is known.