Method and apparatus for electrochemical analysis of small samples of blood

Claim 2

The electrode system of claim 1 wherein the electrolyte contained in the reference electrode is a 0.16M NaCl solution.

Claim 3

The electrode system of claim 1 wherein the common measuring chamber has two end portions and terminates at one end as a cavity having an inlet passageway and an outlet passageway, the inlet passageway being continuous with and defining a portion of the common measuring chamber.

Claim 4

The electrode system of claim 4 wherein the measuring chamber is less than about 2 1/2 inches in length.

Claim 5

The electrode system of claim 4 wherein the cavity is cylindrical.

Claim 6

The electrode system of claim 6 wherein the sensing portions of the PCO2 and PO2 electrodes define portions of the cylindrical cavity at opposite ends of the cavity.

Claim 7

The electrode system of claim 6 wherein the inlet passageway feeds into the cylindrical cavity substantially tangentially.

Claim 8

The electrode system of claim 1 wherein the flow-through pH electrode has a ratio of fused electrolyte cladding length to glass capillary length of less than 1:1.2.

Claim 9

In an electrode system for the electrochemical analysis of a single stationary sample of blood which comprises means defining a measuring chamber for the blood sample, a PCO2 electrode, a PO2 electrode, a pH electrode, and a pH reference electrode, each of the electrodes having sensitive portions exposed to the measuring chamber, tHereby making the measuring chamber common to all the electrodes, the improvements comprising in combination: a. the pH electrode being a flow-through pH electrode having a hydrogen ion sensitive surface defining a portion of the common measuring chamber; b. the pH reference electrode having a liquid junction portion exposed to the common measuring chamber through a semi-permeable membrane between an electrolyte contained in the reference electrode and the common measuring chamber, the surface area of the electrolyte which contacts the membrane being less than the surface area of the membrane exposed to the common measuring chamber, said common measuring chamber having an entrance passageway and an exit passageway; c. a peristaltically activated micro-sampling pump communicating with the exit passageway of the common measuring chamber; d. vacuum means communicating with the exit passageway beyond the pump; e. a liquid flushing system communicating with the entrance passageway of the common measuring chamber, the flush system being activatable with and by the vacuum means; f. circuitry electrically associated with the electrodes to determine and display pH, PCO2, and PO2 values of a sample in the chamber; g. calculators adapted to receive and apply values from the pH and PCO2 electrodes to calculate values for HCO3 , total CO2, and base excess; and h. circuitry electrically associated with the calculators of (g) to display the HCO3 , total CO2, and base excess values.