Improved system for detecting compounds in a gaseous sample using induced photoionizations and electron capture detection

An electron capture detector comprising:

• (a) a closed chamber having a helium flow inlet and spaced helium flow outlet to enable helium flow therethrough;
• (b) spaced electrodes cooperating with a DC current source thereby permitting an electrical arc to be formed between said spaced electrodes defining a spark thereacross, said spaced electrodes being positioned in said chamber to form a spark gap across said helium flow through said chamber;
• (c) a dopant gas source connected to said chamber to provide a controlled dopant flow at continuously adjustable locations within said chamber thereby forming a base current within said chamber where said base current is initiated by said spark across said spark gap;
• (d) a sample gas source connected to said chamber to provide sample gas containing eluted compounds of unknown concentration;
• (e) current detector electrode means spaced along the axis of said chamber for collection of current formed as a result of said spark across said spark gap wherein said helium flow moves toward said current detector electrodes to enable currents to be formed and measured indicative of one or more said eluted sample compound concentrations in said chamber and dependent on the dopant gas in said helium;
• and
• (f) wherein said current detector electrode means measures the eluted sample concentrations in said chamber by changes in said current flow.