PROCEDURE FOR DETERMINING THE CONCENTRATION OF A SUBSTANCE IN A TEST AND APPARATUS FOR USE IN EXERCISING THE PROCEDURE

摘要

Apparatus for measuring carbon dioxide and chloride in blood. A blood sample is reacted with acid in a sample container to release carbon dioxide, a portion of which diffuses through a gas-permeable membrane and reacts with an electrolyte to change the pH thereof. A pair of pH measuring electrodes monitor the electrolyte pH at respective locations adjacent to and remote from the region of reaction within the electrolyte. The pH electrodes are coupled to respective input terminals of a differential amplifier to derive a differential pH signal. The differential pH signal is differentiated to derive a rate of change of pH output signal which is measured to indicate the concentration of carbon dioxide. The pH measuring electrodes are in electrolytic communication and means is provided to renew the electrolyte between measurements. Coulometric measurement of chloride in the sample is performed simultaneously with the carbon dioxide measurement.