What is polarographic analyzer?
is an electrochemical analytical instrument for qualitative and quantitative analysis of the content of different ions in an electrolyte solution based on the current-voltage curve obtained when the substance is electrolyzed. The result of the test is a polarographic curve or a polarogram. The half-wave potential of each substance on the polar graph is the basis for qualitative analysis, while the wave height represents the limit diffusion current for quantitative analysis.
Application of polarographic analyzer
Polarographic analysis machine
has a wide range of applications and can be used for the analysis of inorganic ions and organic substances. Many national standards, and industry standards, especially in geology, metallurgy, soil, health and epidemic prevention, and physical and chemical testing. Although the use of mercury drop electrodes as working electrodes in the polarimetric analysis is somewhat anachronistic in today's environment, properly handled, the mercury operates in a closed environment and has no impact on the environment, just like sphygmomanometers, although various methods are available, many doctors are used to using mercury sphygmomanometers, and the mercury in these sphygmomanometers does not leak out and is used in a closed system. In addition, the advantages of polarimetry are obvious: the analysis range is from inorganic to organic, from trace to macronutrients, and the price is moderate, which makes it especially suitable for analytical work in basic laboratories.
Polarographic analyzer working principle
DC polarimetry also referred to as polarimetry, is a polarimetric method based on the electrolysis process with controlled potential. The experimental setup is similar to the general electrolysis setup and has three main parts: the first part is a device that provides a variable applied voltage; the second part is a device that indicates the change in the current flowing through the electrolytic cell during the electrolysis with a voltage change, and the third part is the electrolytic cell. The difference between a polarographic analysis and an electrolytic analysis device is the two electrodes. The two electrodes used in the polarographic analysis are generally mercury electrodes, one of which is a drop mercury electrode with a small electrode area, the working electrode, and the other is a mercury electrode with a large area, or a saturated glycerol electrode with a constant potential, the reference electrode. Polar spectroscopy is performed using the obtained current-voltage curve, i.e., the polar wave or polar plot.
Polarographic analyzer advantages
Polarographic analyzers have some advantages due to the special working electrodes and analytical testing methods used, as follows.
Wide range of application
The overpotential of hydrogen at the mercury electrode is so high that even in acidic media, the potential of the mercury drop electrode becomes negative to -1.0 V without interference from the reduction of oxygen ions. When the mercury drop electrode is used as an anode, the potential change can not exceed +0.4 V because the mercury itself will be oxidized. within the above suitable potential range, substances that can be reduced or oxidized on the electrode, including inorganic and organic substances, can be measured by polarographic method, which is also a means to determine the equilibrium constants of chemical reactions and study the mechanism of electrode reactions.
Wide range of components to be measured
Generally, the concentration range of the measured components in the electrolyte is from 10-5 to 10-2 mol/L, which is suitable for the determination of trace components. In recent years, it has also been used to determine constant components. If some recent polarographic methods are used, the concentration of the measurable components in the electrolyte can be as low as 10-10~10-7 mol/L, which is suitable for the determination of ultra-trace components.
High accuracy and reproducibility
Since the mercury droplets are constantly updated and the working electrodes are always clean, the experimental data obtained are more accurate and reproducible. The relative error is about 1% in general, and it can be reduced to 0.5% using a very precise polarographic analysis machine.
Good selectivity, continuous measurement can be realized
Since the potential of the working electrode is fully controllable, various metal ions with a potential difference of about 50mV or more can be reduced to metal at different electrodes of the working electrode without overlapping polar spectral waves. It does not interfere with each other and can realize the continuous determination of certain coexisting metal ions in the same electrolyte.
Types of polarographic analyzer
DC polarimetry is also known as constant potential polarimetry. It is an electrochemical analysis method that determines the concentration of the measured component in a solution by measuring the current-potential curve obtained during the electrolysis process.
Single-scan polarographic method
In the electrolytic cell containing the measured substance, two electrodes are inserted, one is a drop mercury electrode and the other is a reference electrode (such as a glycerol electrode), and a DC voltage that varies linearly with time is added. The polarographic current through the electrolytic cell produces a voltage drop iR across the resistor R, which is amplified and added to the vertically biased plate of the oscilloscope. The current-potential curve is then observed on a fluorescent screen. Here, the mercury drop electrode is used as a constant area electrode.
Catalytic polar spectrometry
Polarographic analysis. Usually, a combination of electrode reactions and chemical reactions, results in a large increase in electrolytic current, which increases the sensitivity of the analysis up to 10 --- dagger 1 DinggM, sometimes even up to 10 ---" M.
Polarographic analyzer specifications
Oscillometric polarographic analyzer
|Sensitivity ||＜5×10-8mol/l(Cd++, linear scanning polarimetry)
|Resistance to pre-reduced substances ||>10000:1
|Repeatability error ||＜0.5%
|Range conversion error ||＜0.5%
1. Oscillometric polarographic analyzer
adopts a new type of suspended mercury electrode, no mercury plugging, maintenance-free, automatic double electric valve intelligent control of suspended mercury circuit
2. Double conductive sampling technology, strong anti-interference ability, and good reproducibility.
Benchtop polarographic analyzer
|Polarization current range ||400uA～15nA (F.S.)
|Polarization potential range ||+3904～-3904mV, good small adjustment amount 32mV
|Scanning voltage rate ||50～1000mV/S
|Scanning voltage amplitude ||50～1000mV
Benchtop polarographic analyzer can be connected with computer software to form a polarimetric processing system and complete software control, setup, operation, measurement, analysis, and printing of the instrument. It can be used alone or in conjunction with a computer and is a flexible and easy-to-use automatic measurement instrument.
Selection guide for polarographic analyzer
a. When using polarographic analysis machine, if two or more substances are mixed together in the measured substance, they may or may not be separated. Select an appropriate supporting electrolyte so that the various substances do not interfere with each other and are measured separately.
b. If one is a reversibly reducing substance and the others are irreversibly reducing substances, when measured by anodization, only the polarization wave of the reversibly reducing substance appears and its concentration can be measured.
c. Measuring the first reduced substance by cathodic polarization and the first oxidized substance by anodic polarization can avoid interference and measure accurate results.
d. Using the primary derivative polarization wave, or using the second derivative polarization wave, the amount of both substances in solution can also be accurately measured.
e. An appropriate supporting electrolyte should be chosen to prepare the substrate so that the measured substances are not interfered in this substrate.
f. For a three-electrode system, a very low concentration of supporting electrolyte can be used as the substrate.
g. For the measurement of low content substances, if there is oxygen wave interference that cannot be measured, oxygen must be removed.
h. Sometimes great aberration peaks appear on the polar spectrum curve, the lower the concentration of supporting electrolyte, the higher the concentration of ions to be measured and the lower the temperature, the more likely to produce aberration peaks, which are often not reproducible.
i. A small amount of extremely large inhibitor such as animal glue can be added, and its content generally does not exceed 0.005%, otherwise the wave peak of the measured substance will be greatly reduced.
Precautions for using polarographic analyzer
1. Polarographic analyzers should avoid vibration, during the measurement process, if the mercury is accidentally scattered outside, should immediately do a good job of mercury removal, to avoid the vapor of scattered mercury causing chronic poisoning of the analyst.
2. When using "high current compensation", must be light and slow, so as not to damage the flow detector.
3. Damping mediation with the first to close the main switch, damping selected, and then open the main switch, each damping adjustment is required to operate to avoid excessive swing due to capacitor charging and discharging the detector.
How to maintain polarographic analyzer?
1. nsert the electrolytic cell plug and electrode plug once and tighten them.
2. The platinum electrode and glycol electrode connecting wires must not be short-circuited (touching each other) to the electrode clamping rod and the machine case (ground).
3. The electrode, electrode cap, and rubber plug for fixing the electrode must be kept clean and dry to avoid rusting and pollution.
4. If the solution is not saturated or too little, add the appropriate amount of analytically pure potassium chloride crystals and saturated potassium chloride solution.
5. After checking the polarographic analyzer, insert the cable plug of the electrode holder into the "electrolytic cell" socket of the rear panel of the instrument, the cable plug of the mercury electrode into the "reference electrode" socket, and the cable plug of the platinum electrode into the "auxiliary electrode" socket. "socket.
6. The electrode chuck is clamped on the upper end of the capillary electrode, and the capillary mercury drip electrode, the glycerol electrode, and the platinum electrode are fixed on the rubber plug, and the three electrodes are not allowed to touch each other.
7. If the polarographic analyzer uses three electrodes to measure the solution, just turn the electrode switch on the panel to "three electrodes".
8. If the polarographic analyzer measures the solution with two electrodes, turn the electrode switch on the panel to "two electrodes", then insert the platinum electrode into the large mercury layer at the bottom of the electrolytic cell (the platinum electrode is not allowed to touch the bottom of the electrolytic cell) without removing the glycol electrode.
9. If you use a solid electrode as a working electrode, just clamp the solid electrode on the electrode chuck and let the solid electrode lead connect to the chuck screw.
10. The electrode is not allowed to vibrate when polarographic analyzer is working.
How to buy polarographic analyzer?
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