Basic principles of electrochemistry instruments Main categories and practical application points

The electrochemical instrument takes electrochemical analysis as the core technology, and realizes the accurate determination of the composition and content of the solution by detecting the electrochemical properties such as potential, conductance, and electricity of the analyzed solution. According to the difference in analysis principles, it is mainly divided into potential analysis, conductivity analysis, coulombic analysis and polar spectrum analysis, and the corresponding instruments are potentiometers, Conductivity Analyzers, coulombs and polar spectrometers, which together constitute the basic equipment system in the field of electrochemical analysis.

Potentiometers are one of the most widely used categories of electrochemical instruments, which can be divided into potentiometers and ion-selective electrodes. The potentiometric titrator is used to determine the end point of the titration by inserting the indicator electrode and the reference electrode into the solution to be tested, and the potentiometric potentialm is used to determine the end point of the titration by using the potential jump near the isocurrent point, especially suitable for solutions that cannot be judged by conventional indicators such as colored and turbid, and can also be used to measure chemical constants such as acid-base dissociation constant and electrode potential, and the equipment is usually composed of burette, titration cell, electrode, stirrer and millivolt meter.

As an important part of the potentiometer, the ion-selective electrode is an indicator electrode with a selective response to a specific ion, and its electrode potential has a linear relationship with the activity logarithm of the target ion in solution. At present, dozens of commercial electrodes can analyze nearly 30 kinds of ions, and some gas-sensitive electrodes can also directly detect gases. Common types include pM response glass film electrodes (such as Na⁺ electrodes, which are widely used), solid-state film electrodes (such as fluoride ion electrodes with LaF₃ single crystals as the film), liquid film electrodes (such as calcium ion electrodes), potential selectivity coefficient, response time are the core indicators to measure its performance, detection limit, electrode resistance, service life, etc. also need to be paid attention to.

The application advantages of ion-selective electrodes are outstanding: the measurement process is fast and efficient, and the selectivity of the target ion eliminates the need for complex interfering ion separation steps; It can directly analyze opaque and viscous solutions without pretreatment; The amount of sample required is very small, and the special electrode only needs a few microliters of test solution; The supporting instrument is simple and the cost is low. our country has successfully developed selective electrodes for Na⁺, K⁺, F⁻, Cl⁻ and other ions, which can not only directly measure ion activity, but also expand the application scope of potential titration as an indicator electrode, but there is still room for improvement in its theoretical system, manufacturing process and interference elimination method.

In summary, electrochemical instruments occupy an irreplaceable position in the field of chemical analysis based on the unique analytical logic based on the electrochemical properties of solutions. Among them, the potentiometer has become the core tool for industrial production control (such as raw material composition detection, product quality control), environmental monitoring (such as water ion concentration analysis), scientific research experiments (such as chemical constant determination) and other scenarios by virtue of the accurate endpoint determination ability of the potentiometric titrator and the convenient and efficient characteristics of ion-selective electrodes. Although technologies such as ion-selective electrodes are still in the continuous optimization stage, with the deepening of theoretical research, the upgrading of manufacturing processes and the breakthrough of interference cancellation technology, the scope of application of electrochemical instruments will be further expanded, and the analytical accuracy and efficiency will also continue to improve.