Apparatus and methods for sensing fluid components

• US 4,946,562 A
• Filed: 08/04/1988
• Issued: 08/07/1990
• Est. Priority Date: 01/29/1987
• Status: Expired due to Fees

• Current Assignee: Medtest Systems Incorporated
• Original Assignee: Medtest Systems Incorporated
• Inventors: Guruswamy, Vinodhini
• Primary Examiner(s): Niebling, John F.
• Assistant Examiner(s): MARQUIS, STEVEN
• Application Number:
  US07/228,020
• Time in Patent Office: 733 Days
• Field of Search: 204/1 T, 204/416, 204/417, 204/418, 204/419
• US Class Current: 205/792
• CPC Class Codes: G01N 27/27 Association of two or more measuring systems or cells, each measuring a different parameter, where the measurement results may be either used independently, the systems or cells being physically associated, or combined to produce a value for a further parameter
• CPC Class Codes: G01N 27/4165 for pH meters
• CPC Class Codes: G01N 27/4166 measuring a particular property of an electrolyte

Abstract

Provided herein is a method for accurate, reproducible analytical solution evaluation eliminating the need for a reference sensor by determining the activity of selected species employing species specific sensors and species combination sensors in conjunction with Nernst-type equations. Also provided are sensor structures for elimination of edge effects to signals thereby yielding accurate, reproducible measurements, and a cartridge structure adapted to incorporate an array of the new sensors for employment of the new method where the cartridge is particularly adapted for miniaturization, maintaining a fixed volume of solution for analysis and providing an anaerobic testing environment. Lastly, a compact instrument embodying miniaturization especially adapted for field use and use of the cartridge is provided herein.

Claims

1. A method that is capable of single point calibration measurement of at least first and second dissimilar species in solution employing only ion specific sensors, the ion specific sensors being equal to the number of species plus one where in a multi-component solution containing at least two species to be measured a first sensor is sensitive to the first and second species, a second sensor is sensitive to the first species and a third sensor is sensitive to the second species, the method comprising the steps of:

(a) contacting the sensors with a solution containing the first and second species,

(b) obtaining first and second signals, said first signal being the difference between said first and second sensors and said second signal being the difference between said first and third sensors,

(c) conveying the first and second signals to a signal processor,

(d) contacting the sensors with a second solution containing known quantities of the first and second species and obtaining third and fourth signals from the first and second sensors and said first and third sensors, respectively,

(e) conveying the third and fourth signals to a signal processor,

(f) establishing algebraic constants from said third and fourth signals,

(g) inputting the constants into a calculating device to determine the concentration of said first and second species.

2. A method according to claim 1 where the signals represent electrode voltages.

3. A method according to claim 2 where the concentration of the first species is determined by calculations using the half cell voltage produced by the second sensor and the half cell voltage produced by the third sensor.

4. A method according to claim 3 where the voltages from the sensors are multiplexed and passed to a differential amplifier.

5. A method according to claim 1 including the steps of providing the sensors with a substantially uniform geometry at the solution interface and minimizing flux density.

6. A method according to claim 1, further comprising the step of minimizing flux density variations caused by edge effects.

7. A method according to claim 1, further including the steps of arraying the sensors along a surface of a chamber isolated from the ambient environment and introducing a precise volume of solution into the chamber.

8. A method according to claim 1 where the sensors are arrayed in a cartridge and the cartridge is electrically connectable to a signal processor further including the step of establishing electrical contact between the cartridge and the processor.

9. A method according to claim 1 where the number of species to be measured is N and the number of sensors is N+1 where N is greater than 2.

10. The method of determining the quantities of materials in a solution comprising the steps of the developing a plurality of ion selective electrode potentials in a system having only ion specific electrodes, said potentials being a function at each electrode of the material of the electrode and of material in a solution in which the electrodes are immersed, and

developing signals such that the deference in the signals represent the differences in the EMFs of the reactions taking place only at the ion specific electrodes.