What is automatic titrator?
is a common analytical instrument designed for volumetric analysis based on the principle of the potentiometric method, which uses potentiometric titration to determine the titration endpoint by measuring the change in potential during the titration process. It can be used for the titration of colored or turbid solutions, where the use of an indicator is not possible; in the absence or lack of an indicator, this method is used to solve the problem. It can also be used for dilute test solutions or where the titration reaction is not carried out completely enough; it is sensitive and accurate and can be automated and continuously determined. It is therefore very versatile.
Application of automatic titrator
Automatic potentiometric titrator
belongs to the laboratory general basic equipment, the use is very wide, can be applied in food, drug testing, disease control, commercial inspection, water treatment, petroleum, chemical, marine, environmental protection, new energy, scientific research and other fields. Used as the following applications.Pharmaceutical industry:
penicillin antibiotic content, sodium cyclamate purity, quinine sulfate purity, phenol content. Water quality analysis:
determination of hardness, determination of chloride ion content, pH measurement, acid/base reactivity, etc. Tobacco industry:
determination of acid value of flavor and fragrance, inspection of cigarette paper quality, determination of reducing sugar, determination of glycerol triacetate, determination of atmosphere content in tobacco, etc. Food industry:
acid content in food, chloride ion content in food, citric acid in beverage, sugar content in juice, monosodium glutamate content in seasoning, amino acid content in oral liquid, etc. Chemical fiber industry:
determination of the content of terminal carboxyl groups, acid value, saponification value, hydroxyl value, iodine value, epoxy value, oxygen content in epoxy resin, etc. Petroleum products:
AN/TAN (acid value/total acid), BN/TBN (alkali value/total alkali), bromine number/bromine index, determination of thiol sulfur, chloride ion content, etc.
Automatic titrator working principle
The working principle of automatic titrator is as follows,
Automatic potentiometric titrator is composed of an indicator electrode, reference electrode, and test solution, in the process of potentiometric titration, with the addition of titrant, a chemical reaction occurs in the solution, the concentration of the measured ion changes continuously, thus causing the potential between the indicator electrode and reference electrode to change. In the vicinity of the equivalence point, the potential between the two electrodes jumps, and the endpoint of the titration can be obtained by combining this sudden potential change with the internal calculation program of the instrument.
Structure of the automatic titrator
Potentiometric titrator is mainly composed of a control processor (main unit), exchange unit (exchange unit), and stirrer, which can be used for different types of analytical titrations with corresponding indicator electrodes. Depending on the type of titration reaction, it can be divided into acid-base titration, precipitation titration, complexation titration, and redox titration. The electrodes selected for different test methods are also different.
Automatic titrator connection and installation
Titration device installation
1)JB-1A stirrer 2)electrode clamp 3)solenoid valve 4)solenoid valve screw 5)rubber tube 6)burette clamp 7)burette 8)burette clamp fixing screw 9)bent burette holder(II) 10)tubular burette holder(I) 11)Nut 12)Jacket 13)Core 14)Support head screw 15)Mounting thread 16)Tight ring
The titration device is mounted on the JB-1A stirrer. The installation steps are as follows,
Screw the dropper holder (i) of serial number 10 onto the mounting threads (15) of the stirrer.
Align the holes of the core (13) and jacket (12), pass the dropper holder (I) of serial number 10, adjust it to the proper position, and tighten the nut (11) to fix it.
Insert the end of the solenoid valve (3) into the core (13), and tighten the head screw (14) to fix it.
Install the drip clamp (6) on the drip holder (2) of serial number 9, adjust it to the proper position, and fix it by tightening the drip holder fixing screw (8).
Clamp the burette (7) on the burette holder (6), and put the rubber tube above the solenoid valve into the end of the burette (7).
Attach the electrode clamp (2) to the lower end of the serial number 9 burette holder (II). Install the electrode and capillary tube, and put the rubber tube below the solenoid valve into the capillary tube. Electrode and capillary tube installation see the following figure.
1)electrode rod clamp 2) spring ring 3) dropper (glass capillary) clamp 4) glass (pH, pNa) electrode clamp 5) glymeric (reference) electrode clamp
Solenoid valve structure, adjustment and piping installation or replacement
Before use, the stub screw (4) should be adjusted so that when the solenoid valve is disconnected, no dripping liquid drips down; when the solenoid valve is opened, the dripping liquid drips down and the appropriate flow rate is adjusted.
Installation or replacement of the pipe.
First, unscrew the middle nut and pull out the base. Then unscrew the two screws on the base and loosen the compression screws. That is, the pipe can be replaced.
Types of automatic titrator
According to the different types of titration reactions, automatic titrators
can be divided into:
* Acid-base titrations
* Precipitation titration
* complexation titrations and redox titrations.
Depending on the type of burette and the circuit, there are three types of automatic titrator:
* Automatic titrator with ordinary glass buret plus analog titration endpoint control circuit.
* Automatic titrator with digital automatic burette plus analog titration endpoint control circuit.
* Automatic titrator with digital automatic burette and digital titration endpoint.
The different control systems can be divided into:
* Automatic titrator controlled by a microcontroller, there are two kinds of combined type and integral type.
* The automatic titrator is controlled by a microcomputer as the upper computer and controlled by a microcontroller, which forms the automatic titration system, also has two types combined and integral types.
Automatic titrator specification and feature
Benchtop automatic titrator
|Burette infusion or replenishment rate
1. Benchtop automatic titrator supports two titration modes: determination of gas ion content and calibration of silver nitrate solution.
2. Support automatic calculation function, which can automatically calculate the concentration of silver nitrate titrant and chloride ion concentration in the sample.
3. Support blank titration, which can automatically calculate the blank value and apply it to the determination of the sample (automatic deduction of blank).
Automatic potentiometric titrator
|Repeatability of volumetric analysis
1. Automatic potentiometric titrator allows control of the titration endpoint at a set potential.
2. Adjustable with control potential.
3. A solenoid valve is used to control the titration, which is safe and efficient.
Laboratory requirements for automatic titrator
The normal conditions of use of potentiometric titrator
are as follows:
① Ambient temperature: 5℃~35℃
② Relative humidity: not more than 80%
③ Working power supply: AC (220±11)V, frequency 50±1Hz
④ No strong corrosive gas exists in the environment
⑤ No significant electromagnetic field interference except for the earth's magnetic field.
How to use automatic titrator?
1. Take out the ph electrode from soaking in saturated KCL water solution and wash it with distilled water and wipe it clean.
2. Insert the pipette into the distilled water and the burette into the waste bottle.
3. Turn on the power of the main unit and the stirrer of the automatic potentiometric titrator, and start the working program.
4. Click "Parameters" on the working program interface to set the parameters, and arrange the settings for the titration by yourself.
5. Click the "Send" button on the operation page, enter the volume (20-50ml), and press "Send" to fill the pipeline with liquid.
6. See if there are bubbles if there is a bubble needle inserted into the quantitative tube to suck out the gas.
7. Then insert the pipette into the standard liquid; insert the burette into the liquid to be measured, and at the same time put the magnetic stirrer on the liquid to be measured and put down the stirrer. Repeat step 5 above.
8. Insert the washed ph electrode into the liquid to be measured, with the electrode head submerged in the liquid.
9. When the electrode potential is stable, start the measurement procedure on the operation interface.
10. At this time, the potentiometric titrator draws a curve on the screen while titrating, and after the titration is finished, the instrument automatically finds out the end volume, end potential, and concentration of the liquid to be measured.
11. After the measurement, take out the electrode and clean it, put it back into the KCL saturated liquid to be used, turn off the titrator and the computer to turn off the power, and end the operation.
Precautions for using automatic titrator
Preparation of the automatic titrator before use
a. Before starting the machine, first of all, the automatic titrator should do a check. See if the normal conditions of use of the titrator are fully guaranteed, see if the basic parts are installed in place, and see if the connection of each flow supply pipe joint is reliable. Check whether the various connections of the electrical circuit are matched and correct.
b. If the last test used precipitation or crystallization of the burette (such as silver nitrate AgNO3), the burette should be carefully cleaned to avoid crystallization damage to the valve.
c. Do not replace the burette before starting the machine. The buret in use on the instrument must be replaced only when the buret has completed a replenishment action and the piston is in the lower dead center position.
d. Check the volume of the titrant, which should not be less than 5 ml. If the "Redox titration" mode is selected, the solution cup should not contain less than 100 ml of solution.
e. The time interval between the last start-up and the current start-up should not be less than 1 minute.
Precautions when using the automatic potentiometric titrator
a. The input terminal (electrode socket) of the instrument must be kept dry and clean. When the instrument is not in use, insert the Q9 short-circuit plug into the socket to prevent the intrusion of dust and water vapor.
b. When calibrating the instrument with a buffer solution, make sure the reliability of the buffer solution, and does not match the wrong buffer solution, otherwise, it will lead to inaccurate measurement.
c. When measuring, the introduction wire of the electrode should be kept static, otherwise, it will cause unstable measurement.
d. The outer reference of the compound electrode (or glycolic electrode) should be often noted to have saturated potassium chloride solution, supplementary solution can be added from the small hole at the upper end of the electrode.
e. After removing the electrode sleeve, the sensitive glass bubble of the electrode should be avoided to contact with hard objects, because any breakage or rubbing hair will make the electrode fail.
f. The electrode should avoid being immersed in distilled water, protein solution, and acidic fluoride solution for a long time.
g. The electrode should avoid contact with silicone oil.
h. It is good to rinse the solenoid valve rubber tube several times with the dropping solution before titration.
i. After reaching the endpoint, you can not press the "titration start" button, otherwise, the instrument will start titration again.
j. Do not use potassium permanganate or other solutions that work with the rubber tube.
How to order automatic titrator?
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