Conductimetric_sensors Part1

Conductimetric_sensors Part1 - Conductimetric Sensors...

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Conductimetric Sensors
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Conductance-Based Sensors Conductance-Based Sensors Nanowire sensors are potentiometric sensors Although a change in nanowire (channel) conductance is measured , the analyte influences the surface potential of the nanowire. Conductimetric sensors In conductimetric sensors the conductance is influenced directly by the analyte itself and not via an electronic transduction mechanism. Micro- and Nanopore Sensors Conductimetric sensors are used for particle (cell) counting and sizing. The particles reduce the cross-section area of a micro- or nanopore through which an ionic current is passing. Conductimetric sensors are often nonspecific.
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Coulter Counter Coulter Counter R.R. Henriquez et al., Analyst , 129 , 478-482, 2004 (a) The general experimental approach for electric field-driven Coulter counting . A membrane containing a single channel divides two chambers containing an electrolyte solution. If particles of an appropriate size and charge are present, they will enter the channel and reduce the ion current . (b) Coulter counter data consist of a series of current pulses associated with the presence of particles within the channel. The height of the pulse , Δ i c , is related to particle size and the width, Δt , corresponds to the particle transit time .
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Coulter Counter Coulter Counter M. D. Graham, JALA Vol. 8, Iss. 6, 72-81 (2003). Functional schematic of the Coulter sample stand, coinvented by the Coulter brothers. •When stopcock F is opened, the mercury in the manometer reservoir R is drawn upward by a small vacuum pump connected to P . •After the stopcock is closed, the sample suspension E is drawn from the sample vessel through the hole in aperture wafer A into sample tube B . Via connections H and I , electrodes C and D couple an electrical current through the aperture, and the resultant signal pulses to an amplifier and pulse counter. •The volume of sample to be analyzed is determined by three control electrodes ( K , L , M ) penetrating the wall of the manometer tubing; when the flowing mercury causes electrical contact between K and L , the pulse counter starts, while mercury contact with M at a calibrated distance from L terminates it.
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Coulter Counter Coulter Counter W. H. Coulter, Proceedings of the National Electronics Conference 12, 1034-1042 (1956).
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Coulter Counter Coulter Counter M. D. Graham, JALA Vol. 8, Iss. 6, 72-81 (2003). The latest descendant of the Model A Coulter Counter, the LH 750 analyzer, is a fully automated instrument that determines 26 reportable hematological parameters . Coulter Counters are able to
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Conductimetric_sensors Part1 - Conductimetric Sensors...

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