Principle and use of pH electrode maintenance precautions

Principle and use of pH electrode maintenance precautions

 

Core prompt：

The pH electrode, also known as the pH probe, is the part of the pH meter that contacts with the measured substance and is used to measure the electrode potential device。

 

The electrodes used in the potentiometric analysis are called galvanic cells. A galvanic cell is a system that converts the energy of a chemical reaction into electrical energy. The voltage of this cell is called electromotive force (EMF). The electromotive force (EMF) consists of two and a half cells. One of the cells is called a measuring electrode, and its potential is related to a specific ion activity; The other half cell is the reference half cell, often referred to as the reference electrode, which is usually communicated with the measuring solution and connected with the measuring instrument. The most familiar and commonly used pH indicator electrode is the glass electrode. Bell T225 electrode is suitable for the measurement of pure water and high pure water in pharmaceutical pulp and paper making, electroplating, biological pharmaceutical, power plant and other industries. It is a glass tube with a pH-sensitive glass film blown at the end. The tubes were filled with 3 mol/ L KCl buffer solution saturated with AgCl and the pH value was 7. Ag/AgCl conduction system is used to reflect the pH potential difference existing on the two sides of the glass film。

 

Precautions for the use and maintenance of pH electrodes：

1．Electrodes must be calibrated (at least 2 points) with a standard buffer solution of known pH before measurement.span>

2．After each calibration and measurement, before the next operation, the electrode should be cleaned with distilled water or deionized water, and then the electrode should be cleaned with the tested solution。

3．When removing the electrode sheath, the sensitive glass bubble of the electrode should be avoided from contact with hard objects, as any breakage or brushing will make the electrode ineffective。

4．At the end of measurement, the electrode protective sleeve should be placed in time. A small amount of saturated KCl liquid should be placed in the electrode sleeve to keep the electrode bulb moist and avoid soaking in distilled water。

5．The external reference supplement solution of the composite electrode is 3mol/L potassium chloride solution. The supplement solution can be added from the hole on the top of the electrode. When the composite electrode is not in use, the rubber plug is covered to prevent the supplement from drying up。

6．The lead end of the electrode must be kept clean and dry to absolutely prevent short circuit at both ends of the output, otherwise it will lead to measurement error or failure。

7．Electrodes should be with a higher input impedance than the pH meter & GE; 3× 1011Ω Matching to make it maintain good characteristics。

8．The electrode should avoid long-term immersion in distilled water, protein solutions and acidic fluoride solutions。

9．Avoid contact with silicone oil。

10．If the slope of the electrode is slightly reduced after long-term use, the lower end of the electrode can be soaked in 4%HF hydrofluoric acid (3~5) s, washed with distilled water, and then soaked in 0.1Mo L/L hydrochloric acid solution to make it new. It is best to replace the electrode。

11．If the measured solution contains the material which is easy to pollute the sensitive bulb or block the liquid interface and makes the electrode passivated, the slope will be reduced and the reading is inaccurate. If this phenomenon occurs, it should be cleaned with appropriate solution according to the nature of the pollutant to make the electrode new。