Precautions and working principle of PH analyzers during use
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Precautions for PH analyzers: 1. When installing the instrument, it is necessary to be able to select the appropriate testing reagent. 2. Bubbles must not be drawn in by the instrument during sample aspiration, as this will lead to unreliable results. 3. The 220V voltage inside the back compartment of the instrument poses a risk to personal safety; do not open the back cover of the instrument until the power plug has been removed. 4. When the instrument is operating in online mode, do not use it during thunderstorms to avoid accidents. Working principle: Online pH analyzers primarily use the ion-selective electrode method to achieve accurate measurements. Electrodes on the instrument: pH and reference electrode. The pH electrode has an ion-selective membrane that reacts with corresponding ions in the sample being tested. The membrane acts as an ion exchanger; its potential changes in response to the charge of the ions, thereby allowing the measurement of the potential between the liquid, the sample, and the membrane. The difference in potential between the two sides of the membrane generates an electric current; the sample, the reference electrode, and the reference electrode solution form one side of the \"circuit\", while the membrane, the internal electrode solution, and the internal electrode constitute the other side. The difference in ion concentration between the internal electrode solution and the sample generates an electrochemical voltage on both sides of the membrane at the working electrode; this voltage is conducted to the amplifier via the highly conductive internal electrode, and the reference electrode is also connected to the amplifier. A calibration curve is obtained by testing a standard solution with a precise, known ion concentration, thereby allowing the detection of the ion concentration in the sample. When the ion to be measured in the solution comes into contact with the electrode, ion migration occurs within the aqueous layer of the ion-selective electrode matrix. The change in the charge of the migrating ions creates a potential, which in turn causes a change in the potential across the membrane surface, resulting in a potential difference between the measuring electrode and the reference electrode. An ion-selective electrode contains an electrolyte solution with a known ion concentration; through diffusion of ions from the sample across the ion-selective membrane, a membrane potential is generated on either side of the membrane. The ion concentration in the sample determines the magnitude of the resulting potential signal, and by measuring this potential signal, it is possible to determine the ion concentration in the sample.
Although the electrode used for pH measurement has a certain ion-selective property, it is not classified as an ion-selective electrode in the industry; it belongs to its own category, known as glass electrodes, which are special types of glass membranes. Additionally, the sodium electrode is similar to the pH electrode, except that it has a higher selectivity for sodium; essentially, it is also a glass electrode. This type of electrode is a high-impedance electrode; it differs from conventional ion-selective electrodes—such as silver sulfide electrodes, fluoride electrodes, liquid-membrane calcium and magnesium electrodes, ammonium ion electrodes, potassium ion electrodes, etc.—whose membrane impedance is not particularly high. Your description of the pH electrode is too amateurish. You explained the principle of ion-selective electrodes in relation to pH electrodes, which is unprofessional.