Differential probe with low-slope component

A device for measuring an analyte of a sample, comprising:

• a measurement electrode and a ground electrode contacting the sample;
• a low-slope reference electrode, in a reference electrode assembly, having a sensitivity to an analyte of less than about 55 mV/decade, wherein the electrolyte solution is in contact with the low-slope reference electrode, wherein the electrolyte solution is electrically coupled to the sample via at least one junction, wherein the low-slope reference electrode comprises an ion selective electrode for a particular ion in a solution comprising the particular ion;
• a processor;
• a memory device that stores instructions executable by the processor to:
• measure a first potential between the measurement electrode and the ground electrode;
• measure a second potential between the low-slope reference electrode and the ground electrode;
• determine the analyte in the sample by comparing the first potential and the second potential, wherein the comparing represents a hydrogen ion activity in the sample.

A method for measuring the pH of a sample, comprising:

• introducing a sample to a sample region of a measurement device;
• the measurement device comprising:
• a pH measurement electrode and a ground electrode contacting the sample;
• a low-slope reference electrode, in a reference electrode assembly, having a sensitivity to an analyte of less than about 55 mV/decade, wherein the electrolyte solution is in contact with the low-slope reference electrode, wherein the electrolyte solution is electrically coupled to the sample via at least one salt bridge, wherein the low-slope reference electrode comprises an ion selective electrode for a particular ion in a solution comprising the particular ion;
• measuring a first potential between the pH measurement electrode and the ground electrode;
• measuring a second potential between the low-slope reference electrode and the ground electrode;
• and
• determining a pH based on hydrogen ion concentration in the sample by comparing the first potential and the second potential.