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A Simple Contactless Conductivity Detector Employing a Medium Wave Radio Integrated Circuit for the Signal Treatment
Author(s) -
Opekar František,
Štulík Karel,
Fenclová Kateřina
Publication year - 2010
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.200900381
Subject(s) - conductivity , signal (programming language) , detector , materials science , thermal conductivity detector , electrode , capillary action , voltage , analytical chemistry (journal) , conductance , polyethylene , optoelectronics , chemistry , chromatography , electrical engineering , optics , composite material , physics , computer science , condensed matter physics , programming language , engineering
A new procedure has been tested for the treatment of the alternating signal coming 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 a 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 a 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 μS cm −1 , corresponding to ca. 9×10 −5 to 5×10 −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 commercial 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 μm, employed in microseparation procedures.