Abstract: The present invention relates to apparatus for and a method of instrumental detection. The apparatus comprises in combination (a) an instrumental detector such as a chromatographic, spectrophotometric, fluorimetric, electrometric determination detector, and the like for analyzing an analyte and (b) a hollow dialysis fiber for eliminating such materials as insoluble and soluble polymeric materials and polymer bonded portions from the sample to be detected that would foul the instrumental detector so that the material delivered to the eluent stream flowing to the instrumental detection means is essentially free of such contaminating materials.