Abstract: Apparatus is disclosed for measuring the electrochemical activity of a liquid, for example, the hydrogen ion activity or pH value of blood. A disposable cartridge includes spaced indicating and reference electrodes which develop electrical properties as a function of the electrochemical activity. The cartridge carries a capsule containing an electrolyte solution. A machine for measuring the electrochemical activity includes a socket in a pivoting door for receiving the cartridge. When the door is pivoted into a closed position, the capsule is automatically crushed thereby covering the electrodes with the solution. The breaking of the capsule triggers an electronic measurement of the resultant electrical properties that develop between the two electrodes. This calibration factor is stored and used to compute the electrochemical characteristics of the sample when it is introduced into the cartridge to cover the indicating electrode.

Abstract: A blood collecting device (10) includes a lancet (40) and a capillary tube (30) carried together by an elongated member (14). The tube (30) is simultaneously positioned adjacent the skin when the lancet (40) is advanced by the member (14) to puncture the skin. The lancet (40) is automatically retracted by a retraction spring (54) but the tube (30) is maintained in close proximity with the puncture for collecting blood issuing therefrom without further manipulation by the user.

Abstract: A method and apparatus for measuring a chemical characteristic of a liquid such as its hydrogen ion activity or pH value. A disposable cassette having a reference and indicating electrode therein utilizes the same solution to first calibrate the device and then as an electrolytic bridge from the liquid sample to the reference electrode. The solution has the properties of a buffered pH and also provides a stable electrochemical environment around the reference electrode. In one embodiment, a volume of a liquid sample is placed into a capillary tube and the open end of the tube is then placed over the indicating electrode immersed in the solution. The electrical potential between the indicating electrode and the spaced reference electrode in the electrolyte solution provides a measurement of the pH value of the liquid when compared to the calibration potential previously measured without the liquid sample contacting the indicating electrode.