On-body pH measurement by the ion sensitive field effect transistor array (CAT#: STEM-PPA-0010-LJX)

Introduction

Recent advances in electronics and electrochemical sensors have led to an emerging class of next generation wearables, detecting analytes in biofluids such as perspiration. Most of these devices utilize ion-selective electrodes (ISEs) as a detection method; however, ion-sensitive field-effect transistors (ISFETs) offer a solution with improved integration and a low power consumption.

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Principle Applications Procedure Materials Notes

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:
Biofluids, such as perspiration

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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