Continuous Monitoring of pH and Blood Gases Using Ion-Sensitive and Gas-Sensitive Field Effect Transistors Operating in the Amperometric Mode in Presence of Drift (CAT#: STEM-PPA-0005-LJX)

Introduction

Accurate and cost-effective integrated sensor systems for continuous monitoring of pH and blood gases continue to be in high demand. The capacity of ion-selective and Gas-sensitive field effect transistors (FETs) to serve as low-power sensors for accurate continuous monitoring of pH and blood gases is evaluated in the amperometric or current mode of operation. A stand-alone current-mode topology is employed in which a constant bias is applied to the gate with the drain current serving as the measuring signal. Compared with voltage-mode operation (e.g., in the feedback mode in ion-selective FETs), current-mode topologies offer the advantages of small size and low power consumption.

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Principle Applications Procedure Materials Notes Related Products

Principle

The ion-sensitive field-effect transistor method (ISEFT) uses voltage source and drain (source and channel) transistors separated by insulators. Insulators (gates) are made of metal oxides. Hydrogen ions in the medium can accumulate on it, as on a glass electrode, and the positive charge generated by its outer layer will form a "mirror symmetry" in the inner layer of the gate, resulting in a negative charge, so that the gate has electrical conductivity. The lower the pH of the solution, the more hydrogen ions are concentrated on the gate, and the more current flowing between the source and drain can be measured.

Applications

For determining the approximate PH value of solutions in food production, wastewater treatment, pharmaceutical and chemical industries

Procedure

1. Select the "pH" file of the instrument, immerse the cleaned electrode into the standard pH buffer solution to be measured, press the measurement button, turn the positioning adjustment knob, so that the pH value displayed by the instrument is stable at the pH value of the standard buffer solution
2. Release the measuring button, take out the electrode, rinse with distilled water several times, and carefully blot the solution on the electrode with filter paper
3. Place the electrode in the liquid to be tested, press the measurement button, read the stable pH value, and record
4. Release the measurement button, remove the electrode, clean according to step 2, and continue to measure the next sample solution
5. After measuring, clean the electrode and soak the glass electrode in distilled water

Materials

• Sample Type:
Mammalian cells

Notes

1. If you need to measure pH with high accuracy, in order to avoid the effect of CO2 in the air, especially the pH of alkaline solutions, the exposure time to the air should be as short as possible, and the reading should be as fast as possible.
2. In order to ensure the accuracy of the results, the electrodes need to be cleaned in time before and after each measurement.

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