the elongated glass filament used in the filament concentrator of a micro cleanup and concentration apparatus for trace residue analysis by gas liquid chromatography includes a jacket with an elongated filament freely suspended from a feed tube and terminating with a distal end situated adjacent the reduced drip tip of the jacket and being centralized thereby due to the inner wall of the flow tip being concentric with but slightly spaced from the outer surface of the distal end of the filament . a hypodermic needle assembly extends between the chromatographic column and the feed tube to meter the eluant through the hypodermic needle , which is readily changed depending upon the flow rate required .