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Apparatus and method for determining the quanity of an analyte in a biological sample by means of transmission photometry

  • US 5,770,389 A
  • Filed: 02/14/1996
  • Issued: 06/23/1998
  • Est. Priority Date: 09/27/1993
  • Status: Expired due to Term
First Claim
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1. An apparatus for making a quantitative determination of the amount of an analyte in a biological sample comprising:

  • a. a support medium for receiving a biological sample and retaining a labeled reaction product thereon, the medium including a read window capable of receiving a source light signal and transmitting therethrough a response light signal that has been altered from the source light signal by the presence of a labeled reaction product, wherein said medium is highly light-scattering, the amount of said alteration of said response light signal by said labeled reaction product being an indication of the amount of said analyte in said biological sample;

    b. a source of light positioned to transmit a source light signal to the read window of the medium and to the labeled reaction product at the read window, whereby the response light signal is produced;

    c. a collector positioned to receive the response light signal transmitted from the read window of the medium, said collector capable of developing a variable output signal in direct correspondence to the intensity of the response light signal, said collector being a photosensitive element; and

    d. means for measuring the variable output signal and correlating the measured signal to the amount of analyte in the sample, said means for measuring the variable output signal comprising;

    (1) a capacitor network connected in series with the photosensitive element, said capacitor network comprising a capacitor, said capacitor network having a discharge cycle over a time cycled duration;

    (2) a power source coupled to the capacitor network and the photosensitive element and capable of charging the capacitor network; and

    (3) means for measuring the duration of the discharge cycle of the capacitor network through the resistance developed by the photosensitive element in response to the intensity of the response light signal, wherein the light intensity of the response light signal is related to the duration of the discharge cycle.

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