Nitrogen isotope separation with displacement chromatography using cryptand polymer

Chromatographic nitrogen isotope separation was experimentally studied in a break through manner. A solution of 0.4 mol·dm-3 NH4Cl in methanol was continuously fed at 0.12, 0.25 and 0.50 cm3·min-1 into a glass tube packed with cryptand (2B,2,1) polymer. The temperature of column was kept constant at 293 K by passing temperature-controlled water through a jacket. Nitrogen gas was generated from the effluent reacted with Ca(ClO)2 solution after removing methanol by vacuum distillation, and the ratio of 14N15N to 14N14N was measured with a mass spectrometer (Finnigan MAT252). NH4Cl concentrations in the samples were gravimetrically determined. An enrichment factor, which is defined as an equilibrium separation factor minus unity was determined to be 0.0025±0.0013. A HETP (height equivalent to a theoretical plate) was evaluated 0.5±0.2 cm at 14 cm·h-1. This is the first report on nitrogen isotope separation with cryptand polymer. (author)