Apparatus, systems and methods are described for preconcentrators, chemical sensing systems and gas chromatographs. A preconcentrator is described that comprises a hollow enclosure containing a sorbent material. The enclosure may be a capillary tube that can be formed in to a desired shape and that may be heated. Heating may be accomplished by passing an electrical current through the capillary or other hollow enclosure form. The sorbent material can be a liquid, a solid, a porous ceramic material and/or a chemiselective polymer. The sorbent material can be coated to the inner wall of the enclosure. The hollow enclosure may be maintained in an insulated chamber. The preconcentrator acts to concentrate a vapor passed through the preconcentrator to a chemical sensing array that can detect chemicals present in the vapor. A gas passed through the hollow enclosure can provide a chemically concentrated input to a chromatographic column.