科研之友
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摘要
A new procedure has been tested for the treatment of the alternating signal coining from a contactless conductivity detection cell. The cell consists of a polyethylene (2 mm o.d., 1.5 mm i.d.) or polytetrafluoroethylene (1.6 mm o.d.. 0.8 mm i.d) tubing, with 5 mm wide tubular electrodes placed over the tubing and separated by it 5 mm gap. An unmodulated or an amplitude-modulated AC voltage is applied to the cell and the AC Current passing through the cell is treated by it TDA 1072A integrated circuit, obtaining a signal depending on the conductivity of the quiescent or flowing solution inside the cell. Under optimized conditions, the solution conductance can be measured within a range from ca. 10 to 700 mu S cm(-1), corresponding to ca. 9 x 10(-5) to 5 x 10(-3) M KCl. The detector was used to measure the conductivities of various drinking waters and the Values obtained were in a good agreement with those provided by a commerical contact conductometer. It has been found that the use of unmodulated input voltage is advantageous both experimentally. and from the point of view of the quality of the analytical characteristics. The integrated circuit tested is not, however, sufficiently sensitive for application to capillary detection cells with diameters of a few tens of mu m, employed in microseparation procedures.
- 出版日期2010-1
