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      Article Position:Home > article > Documentation > Detailed
      Karl Fischer coulometric
      Date:2016-01-18   Hit:1129

      1 The Safe Use of Unit

      1.1  Personal Safety and Safeguards

          Make sure that the power source has dependable ground wire! If it is not connected to the ground, the casualty accident may be caused.

          Please do not use the instrument in dangerous environment! The shell is not complete airtight, it is possible that the ingress of sparkle and gas can cause explosion.

          When using chemicals or solvent, you should follow the instruction manual of manufacturer and safety specifications of laboratory!

      All of the Karl Fischer reagents are flammable and toxic. If skin is inadvertently in touch with Karl Fischer reagents, you should immediately wash skin with plenty of water. If eyes are inadvertently in touch with Karl Fischer reagents, you should immediately wash skin with plenty of water and consult doctors.

      1.2 The Safeguards for Operation

      1.2.1 Do not open the shell of instrument, please send the instrument to the appointed maintenance section, which is authorized by our company.

      1.2.2 It is forbidden that the instrument is installed in a room where there are caustic gases.  The caustic gases can cause circuit corrosion so as to shorten the life of instrument.

      1.2.3 It is forbidden that the instrument is installed in a room with a room temperature lowering than 5 or higher than 40.

      1.2.4 The instrument should not be installed at a place directly irradiated by sunlight.

      1.2.5 The instrument should not be installed close to the frequently operated and high-power electrical equipment.

      1.2.6 The instrument should not be installed at a humid place or close to the flow pipe of tap water.

      1.2.7 The instrument should not be installed at a place where the power source fluctuates out of the range of stipulated value.


      2. Application Scope and Principle of Measurement

      2.1 Measurement of Moisture 

      The Karl Fischer method, a classical and the most dependable method, is used to measure the trace moisture of different substance. Karl Fischer coulometric method is more suitable for measuring the substance, the absolute water content of which is less than 100μg. The Karl Fischer coulometric method is applied in this unit. This unit is especially suitable for measuring the trace moisture in the sampling, the trace moisture in sampling can even be precisely measured if adopting the proper operation.

      2.2 The Brief Characteristics of Unit

        Taking the singlechip control as the hardware basis, which is developed through integrating with comprehension of physical and chemical phenomena in the measurement process, The analysis speed is swift, the precision is high, and the measurement results are directly displayed on the LCD, many analysis methods can be chosen freely to set , the record can be printed, the operation time can be set, in conclusion, this unit is a high-efficient, fully automatic delicate analysis instrument.

      2.3 Application Domain

      For the fields, such as petroleum, the petrochemical industry, electric power, pharmaceutical, pesticide, environmental protection, geology, and foodstuff, you may use this unit if there is a need of analyzing the water content in raw material, intermediate and product. For example, some state standards, such as GB/T 3727-2003 “Measurement of Moisture in Industry-used ethene and Propene” and GB/T 7600-1987 “Measurement Method of Water Content of Moisture in Transformer Oil (Coulometric Method)” have definitely specified that the Karl Fischer coulometric method instrument must be used.


      3     Technique Parameters

      3.1  The adopted method: Karl Fischer coulometric method

      3.2  Display: LCD with English character

      3.3  The control of electroanalysis: automatically controlled by electroanalysis electric current(the maximum electric current: 400mA);

      3.4  Measurement range: 3ug ~ 200mg water.

      3.5  Titration mode and speed: coulometric titration, 2.4mg/min(the maximum)

      3.6  Sensitivity valve: 0.1μg H2O

      3.7  Accuracy degree: postulating the absolute water content of sampling is X, the relative error is .

      3.8  Print: heat sensitivity line printer

      3.9  Power source: AC 220V, 50Hz;

      3.10           Power: 35W

      3.11          Temperature of use environment: 540;

      3.12 Humidity of use environment: 80;

      3.13 Weight: about 3.5kg;

      3.14 Outside dimension: length---33.5cm; width---33.5cm; height---18cm;


      4     Structure Characteristics and Instructions for Keys

      4.1  Total line-up

      Figure 1 Total Line-up of unit

      1.    main unit;  2.stirrer and titration cell;

      4.2  Keyboard and key function













      [AUTOSTART Key]: Measure the water content i when use together with the sampling and sample injection instrument of liquid hydrocarbon flash distillation and gasification;

      [START Key]: pressing this key, the feeding will begin after the delay time.

      [ENTER Key]: Use it to end the data input and execute the chosen order.

      [MENU Key]: Use it to return to the previous menu.

      [DATA Key]: Use it to inquire the historical measurement data.

      [HELP Key]:

      [RESET Key]: Use it to restart the instrument program, generally it can be used when the instrument exceptional.

      4.3  Brief introduction of display window

      1.    Main menu; 2. Main interface; 3. Information prompting column; 4. time display space

      Water content: the water content of sampling, unit: µg or mg;

      State: the digital display of balance point. The balance point of unit is 40;

      Speed: it is the electrolytic speed, unit: µg/s;

      Delay time: it is the time after pressing START key until turn on the electrolytic current;

      Concentration: the sampling’s concentration of water,

      4.4 Rear panel of main unit


      Figure 2 Rear Panel of Main Unit

      1.  Stirrer cable connector;

      2.  Single connector (the single cable for the sampling and sample injection instrument of liquid hydrocarbon flash distillation and gasification (model LG-5) is connected here. The automatic control of feeding is finished by it).

      3.  232 string interface, the single cable for computer is connected here.

      4.  Reserve.

      5.  Fan.

      6.  Power cable connection port.

      7.  1A fuse.

      4.5.The Introduction for Stirrer

      Figure 3 the Installation Drawing for Stirrer

      1.  Stirrer;

      2.  Plug for main unit;

      3.  Detector electrode connector;

      4.  Electroanalysis electrode connector;

      5.  Generator solution cell,

      6.  the Base of generator solution cell,

      7.  Stirrer speed adjuster (the speed is adjusted to the value that can cause vortex, please do not adjust the stirring speed during the measurement process). the minimum stirring speed or the stop of stirring; this speed is suitable when the electrolytic solution is less than 150mL; this speed is suitable when the electrolytic solution is more than 150mL; the maximum speed, generally this speed is not chosen.

      4.6  The Structure Introduction for Generator Solution Cell

      Figure 4 the Structure of Generator solution cell

      1.  Generator solution cell; 2.Detector electrode; 3. Versatile hole and sealing plug;

      4. Electrolysis electrode or cathode solution cell; 5.drying tube;

      6. Injection port of cathode solution and plug for cathode solution cell;

      7. Sample injection port and plug;

      8. The upper layer is platinum net of cathode, the middle layer is porous ceramic panel, the lower layer is platinum net of anode;

      9. Stirrer bar;

      10. Cathode solution cell connector;

      11. Detector electrode connector

      4.7 Printer and set-up of printer roll paper


      1. Printer cover;  2. Roll paper,  3. Paper entry,  4. Paper change handspike

      4.7.1 Take off the printer cover.

      4.7.2 Take off the platen from the printer. If the roll paper exists on the printer, this step can be skipped.

      4.7.3 Press the new roll paper in the groove of the printer.

      4.7.4 Push the paper change handspike in the opposite direction to the figured.

      4.7.5 Turn the nose with your hands. Put the paper in the entrance under the nose, the paper will enter in the nose slowly until appearing on the directly ahead of the nose and exposing proper length.

      4.7.6 Push the paper change handspike in the direction to the figured.

      4.7.7 Put the printer cover on, put on the printer roll paper from the exit of the printer cover.

      5. The operational instruction of the unit

      5.1 main menu instructions

        Main menu contains: ‘set’‘method’‘func.’‘super’ and ‘help’ . First of all , press the [left] key or [right] key while operating, select the main menu, then press the [enter] key to enter the corresponding submenu ,  press the [up] key or [down] key ,select the corresponding submenu , then press the [enter] key , the instrument will begin to run the function that corresponding to the submenu , if you want to return to the previous menu ,please press the [enter] key.

      5.2 The setting direction of the ‘method ‘menu

      Method menu contains :‘method No.1No.5’. The instrument contains five methods, and the parameters of them can be setted by the operators according to the analysis demands, the setting method will become the analysis method used later.

        Select the ‘method’ in main menu and press the [enter] key , select the method that you want to set , then press the [enter] key , entering the method you want to set , select the option that you want to set , press the [enter ] key, the setting items are ‘sample ID’‘sample type’‘sample unit ’‘conc.  unit’‘delay’ ‘Precision’ ‘max. current’ ‘mass method’.

      5.2.1 If you select the ‘sample ID’, the setting range you can input is between 0 and 9999 (including 0 and 9999), after inputting, you should press the [enter] key.

      5.2.2 If you select the ‘sample type’, you can input the item from the ‘gas’‘liquid’ and ‘solid’, then press the [enter] key and select the items ‘Vol.’‘Dens. ‘mass ’,inputting the data you want , then press the [enter] key.

      5.2.3 If you select ‘sample unit’, you can select the unit you want, then press the [enter] key.

      5.2.4 If you select the ‘conc.  unit’, select one of the methods you want to express the concentration ( mg/kg, mg/L, mg/m3, mL/m3,(m), (v)volume, (v)( density)) , then press the [enter] key. If the sample you select is gas , the concentration unit is mL/m3, the interface that you should input the gas molecular weight will appear, input the gas molecular weight you want , then press the [enter] key.

        (v)volumeis the volume ratio, be sure to input the volume of the sample previous to the analysis. (v)( density ) is the density ratio, be sure to input the density previous to the analysis, if you input the mass previous to the analysis , the mass must be inputted firstly.

      5.2.5 If you select the ‘delay’, the setting range of delay time is 09999 seconds ( including 0 and 9999 ), after the inputting please press the [enter] key .

      5.2.6 If you select ‘Precision’, select the accuracy request you want to set, then press the [enter] key.

      5.2.7 If you select the ‘max. current’  , the setting range is 0360 ( including 0 and 360 ), after inputting , press the [enter] key.

      5.2.8 If you select the ‘mass method’ , select ‘Input before analyzing’ or ‘Input after analyzing’ , then press the [enter] key.

      5.2.9 If you want to return the previous menu , please press the [menu] key.

      5.3 the setting direction of the ‘set’ menu :

        ‘set’ menu contains: ‘time’‘method’‘print mode’‘printer’. Select the ‘set’ key , press the [enter] key, then select the corresponding item , press the [enter] key.

      5.3.1 If you select the ‘time’ key, select the date or time you want to change , then input the data you want to set and ensure that they are correct ( if the data is one figure , please add ‘0’ in front ), after inputting , press the [enter] key.

      5.3.2 If you select the ‘method’ key , select the analysis method from the ‘ method1method1’ , then press the [enter] key.

      5.3.3 If you select the ‘print mode’ key, you can select ‘manual’ or ‘automatic’ , then press the [enter] key.

      5.3.4 If you select the ‘printer’ key, you can select the ‘RONGDA’ printer or the ‘BRIGHTEK’ printer, then press the [enter] key.

      5.3.5 If you want to return to the previous menu , please press the [menu] key.

      5.4 The setting direction of the ‘func.’ menu:

        ‘function’ menu contains : ‘analyse’‘automatic’‘print’‘reagent’. Select ‘func.’, press the [enter] key, then select the corresponding item, press the [enter] key.

      5.4.1 If you select the ‘analyse’ key, the instrument goes into delay state, press the [enter] key, you can inject the sample and analyze it.

      5.4.2 If you select the ‘automatic’ key, the instrument goes into the analysis state with our company’s “sampling and sample injection instrument of liquid hydrocarbon flash distillation and gasification”, press the [menu] key, after the sample introduction of the injector, if you press the key when you shouldn’t connect with the injector or the injector couldn’t work, please press the [RESET] key to rerun the programme.

      5.4.3 If you select the ‘print’ key , and you have setted ‘the manual printing’ in the ‘print’ option in the setting menu , the instrument goes into the print state and print the latest data , then press the [menu] key to return to the main work interface .

      5.4.4 If you select the ‘reagent’ key , select the item you want to set , if the reagent has been replaced newly , please select ‘instead now’, press the [enter] key. If you do not want to renew, please select ‘instead later’, press the [enter] key. If you select ‘capability’, please input the milligram number of the analytical water of the reagent you want.

      5.4.5 If you want to return to the previous menu, press the [menu] key.

      5.5 The setting direction of the [super] menu:

        ‘Super’ menu is our company’s debugging menu; we suggest users not to use it. ‘super’ menu contains : ‘debug’‘Balanced’. Select the ‘super’ key, press the [enter] key, then select the corresponding item, press the [enter] key.

      5.5.1 If you select the ‘debug’, display interface will remind you of inputting the code that our company provided, then press the [enter] key, select the ‘electrolyse’ or ‘detector’, press the [enter] key.

        If you select the ‘electrolyse’ , the inputting data range is 0360( including 0 and 360) , press the [enter] key , display interface will show the corresponding data you set , generally input 0 and 360 .

        If you select the ‘detector’, entering the detector debug interface, you can carry on the detector debug work, make the detector electrode short-circuit or increase a resistance of the fixed value, display interface will show the corresponding data.

      5.5.2 If you select the ‘Balanced ’, display interface will remind you of inputting the code provided by our company, then press the [enter] key, entering the inputting interface of the balanced point, you can input the corresponding data, press the [enter] key.

      5.5.3 If you want to return to the previous menu, please press the [menu] key.

      5.6 The setting direction of the ‘help’ menu:                                                                     

        Select the [help] key , press the [enter] key , then select ‘aboult’ or ‘ver.’ , then press the [enter] key , the interface will show the information of our companys name network stationfirmware version and so on . Return to the previous menu, please press the [menu] key.

      5.7 Attention

      5.7.1 Make sure to select the demand you want to use, the parameters of the method must be setted before using.

      5.7.2 When ending the analysis , that the state is lower than the balanced point arises repeatedly, and the destination parameters is of high accuracy, we should lower the balanced point, when the time of analysis approaching the balance point is too long ,we should increase the balanced point (make a reference to 5.5.2).

      5.7.3 If printing the latest analysis result, the printer couldn’t act, please examine the printing state is manual printing or not (make a reference to 5.3.3).

      6 Principles of Measurement and Method of Application

      6.1 Principles of Measurement

         The reaction of Karl Fischer reagent and water:


      The used reagent solution is composed of certainty concentration iodine, - and carbinol dissolved with sulfur dioxide and so on. The measurement principle is that conductive capability in the balanced system of certainty concentration iodine and -, after switching on electric current to two electrodes, the following reactions will begin:



      There is superfluous I- in the solution, but concentration of iodine will not cause great influence on the conductivity of solution, while the change of iodine’s concentration can cause the change of solution’s conductivity. The more the concentration of iodine is, the more the change of solution’s conductivity, we take this scope as the effective range of measurement, through measuring the current strength generated by the voltage of platinum electrodes, this current strength can reflect the conductivity of solution. This instrument converts the measured value of current strength into the digital quantity of inverse proportion, which reflects the status of solution, the more the digital quantity is, the less the conductivity is. Generally, the balanced point of iodine concentration is corresponding to 40(the digital quantity)

      The water concentration of the point is lower also, if it is lower than water concentration of sample, it can be ignored. When a certain mass of water enters into the balanced system, balance constant of main reaction is big especially, reaction progresses thoroughly, so concentration of iodine is reduced, conductivity of solution is reduced, state number of solution is increased, the above is measurement principle.

      6.2 Basis of Working and Metrology 

      According to the above-mentioned principle, we know that the preparing state of instrument is to maintain a certain concentration of iodine. Environment’s moisture is uninterrupted going into the balanced system, which causes the reduce of concentration of iodine. To maintain the concentration of iodine, we make that I- in the solution lose electron to change into iodine by adding positive electricity of electrolyte electrode, when speed of consuming electrolyte electrode is equal to speed of electrolyte generating electrolyte electrode, there is balance state in the system solution. Current, which keeps the balanced state, is called blank current, the current consumes the inbreak moisture, after conversion, the blank current is expressed by the speed of consuming inbreak moisture, namely, μgs.

      When beginning measurement, adding water is made to reduce concentration of iodine, iodine is generated in anode by electrolysis, Based on Faraday's law, all generated iodine are direct proportion to consuming electric quantity:


      amount of iodine joining in reaction is equal to amount of water. Injecting sample into electrolytic solution, water in sample joins in reaction, measuring iodine change in reaction course by instrument, consume of iodine is calculated according to electrolyzing iodine, while the amount of iodine can be calculated by the instrument, the mass of water is showed directly in LCD. Automatic control system of electrolysis current is used in the instrument, size of electrolysis current is automatic controlled according to water content of sample, the maximum is 400 milliampere. In the course of electrolysis, water content is reduced step by step, electrolysis speed is reduced with proportion till balance point, corresponding titration end point control unlock of circuit. This system insures a high precision, high delicacy and high speed in analysis process. In addition, in the course of measuring, some factors are hard to avoid, such as inbreak moisture of atmosphere, which cause blank electric current of generating in titration cell. Because there are function of recording and deduction blank electric current in the instrument, the mass showed in LCD is real mass of water in sample.

      6.3 Switch on

      After the preparation of generator solution cell, switch on 220V power source. Turn on switch of unit, the instrument will enter the initial interface, the buzzer will sound at the same time. There is the electrolysis current after 2 seconds, the instrument will automatically search balanced point, the status display will be close to 40.

      6.4 The Automatic Deduction of Blank Electric Current

          The blank electric current influences the precision of measurement greatly. This instrument has the functions of automatic-measuring and automatic deduction of blank electric current. The instrument can finish the automatic deduction of blank electric current after the 2mins running.

      When measuring the water content in sample, we wish the lowest blank electric current in order to get a high precision. But the electrolytic current still shows that it is larger than 0 and steady, now, press “SAMPLE INTRODUCTION” key, after a moment, the buzzer will sound, the display of water content is still zero or smaller than a numerical value(this numerical value should be smaller than or equal to the 10% of water content of sample. Now, the measurement can be implemented.

      When measuring the trace moisture(less than 10 ug), the generator solution cell should be desiccated thoroughly, when the status value is smaller than 45, the measurement can start.

      6.5 The Cleaning, Drying and Assembling of Titration Cell

         These processes should be operated outside the stirrer apparatus. The following are the concrete steps:

      6.5.1 Open all of the glass ports of titration cell, the titration cell, drying tube and sealing plug can be cleaned with water. After cleaning, put it into the desiccator(80) for drying, then natural cooling. The cathode solution cell and detector electrode can not be cleaned by water, it can be cleaned by carbinol or methenyl chloride, it cannot clean with acetone. After cleaning, drying it with air blower(cathode solution cell and detector electrode absolutely cannot be put into the desiccator). When cleaning, pay attention that do not clean down-lead of electrode, otherwise, this will cause measurement error.

      6.5.2 Firstly, put some absorbent cotton into drying tube to prevent the clogging of aeration port by silica gel, then, put silica gel into drying tube, be careful that do not put silica gel powder into drying tube. At last, screw the plug for the sample injection port.

      6.5.3 After finishing the above procedures, put the stirrer bar through sample injection port carefully. Then smear thin vacuum grease on the abrasive mouth of detector electrode, cathode solution cell, drying tube and sealing plug respectively, besides do not set sealing plug of cathode solution cell, the others should set on the corresponding position, rotate them slightly to seal.

      6.5.4 Pour 130~150mL electrolytic solution, with filter, through sealing port into anode cell, then pour electrolytic solution into cathode solution cell through port for drying tube, the liquid level of cathode solution should be lower than that of anode cell. Then assemble the drying tube and sealing plug, rotate them slightly to get a good sealing(the loading of electrolytic solution should be operated in the aerator). Put titration cell onto the stirring apparatus, insert the plug for detector electrode, plug for electrolysis electrode into the “measuring” and “electrolysis” sockets.

      6.6 How to Reduce Blank Electric Current

         If the status display is larger than 70, speed is larger than 0.5μg/, these indicate that the generator solution cell is not desiccated thoroughly. The reason is that there is moisture on the inner wall of titration cell. You should switch off the power, take off the titration cell, lean it slowly and sway it, to make the moisture into electrolytic solution, then set titration cell again, switch on, continue titration, this step can be repeated several times. Through the above operations, blank electric current will lower to the minimum value. If the blank electric current still does not lower, this may be caused by the intake moisture from atmosphere or the ceramic filter panel absorbs moisture. Now, do the following inspections:

      (1)   whether the sealing of titration cell’s abrasive mouth is good, whether the smearing of grease is even;

      (2)   whether the silica gel is effective, whether there is reagent in drying tube; if the silica gel has become to light blue or red, replace it immediately;

      (3)   whether the cleaning and drying of cathode solution is good;

      (4)   whether the sample injection port is hermetic, whether the pinhole of silica gel packing is leak;

      (5)   whether the liquid level of cathode is parellel or higher than the liquid level of anode;

      (6)   whether the compounds contain aldehyde or carbonyl group is poured;

      6.7 The Common Standardization of Instrument

      When the instrument reached the balanced point and is steady, you can standardize it with pure water. The standardization mode is as follows:

      (1)   Ingest 0.1 microlitre distilled water with 0.5 microlitre sample introduction instrument, prepare for the sample injection;

      (2)   Press “SAMPLE INTRODUCTION” key to start delay time;

      (3)    Before the end of delay time, pour the distilled water into the anode cell through plug for sample injection port, the pinpoint should be inserted into the electrolytic solution, and avoid contacting with inner wall of titration cell or electrode, after the end of delay time, the titration will automatically start;

      (4)   When the buzzer sounds, the instrument reaches the end point, the display result should be 100±10microgramme water(including sample introduction error), generally standardize it 2~3 times, when the result is within the error range, the measurement can begin.

      6.8 The Special Standardization Method

      When the instrument is used for a long time or there is a need of high precision, you can implement the special standardization. The special standardization should be in accordance with the state standards, the method is benzene—saturated water standardization.

      6.8.1 The Requirements for Inspection Instrument

      In order to inspect the coulometric moisture meter, you need to make the saturated solution of benzene, get water content through accurate measurement of liquid temperature. The standard sample of benzene is known, you can inspect the inspection limit, repeat error and basic error of instrument through the control of sample injection quantity.

      a)   the coulometric moisture meter to be inspected

      b)   analytical balance(precision is 0.1mg, it must has certificate for inspection of metrology);

      c)   small syringe(0.1mL,1mL,5mL);

      d)   wide-mouth bottle(250mL) with 2 holes in the plug, one is sample injection hole, the other is the hole of thermometer;

      e)   thermometer(0~50, it must has certificate for inspection of metrology);

      f)    Karl Fischer reagents(made by Daqing Rshang Instrument Co. Ltd);

      g)   Benzene(analytically pure)

      6.8.2 Standardization Method

      a)  the forming of standard sample of benzene: pour 120mL distilled water into the wide-mouth bottle, then pour 60mL~70mL benzene into it, wait 1 hour to arrive the saturation status, wait for measurement;

      b) Run the instrument, implement the measurement after the instrument stabilizes;

      c)  Clean the small syringe, that is, take in the standard sample of benzene, repeat it several times, the first cleaning should be more than 5 times, the cleaning times in analysis should exceed 3 times, the used liquid should be put back to reclaiming bottle, cleaning it until there is no water in the syringe;

      d) Take 5μL standard sample of benzene, at the same time, record the temperature of benzene’s saturated solution(the precision is 0.1), insert the pinpoint of syringe into the silica gel packing, put it onto the analytical balance to weigh, discharge the standard sample of benzene into the titration cell to measure the water content; then weigh the mass of syringe plus silica gel packing, the distraction of two weights is the mass of standard sample of benzene;

      e) According to above method, take 0.15mL, 1mL standard sample of benzene respectively to measure, you also use different volume according to the concrete cases.

      6.8.3 Inspection Results

      a)  Read the numerical value of trace moisture from display screen, the precision is 0.1μg.

      b) Search the saturation water solubility of benzene relevant to the experiment temperature from Table 1 “the Data Table for Saturated Water Solubility of Benzene”, calculate the water content of benzene, namely, it is the theoretical value, the precision is 0.1μg. The record format is listed in Table 2 “the Inspection Results of Saturated Water in Benzene for Different Sample Introduction Quantity”.

      Table 1 the Solubility Data for Saturated Water in Benzene



      water content




      water content




      water content































































      Table 2 Inspection Results of Saturated Water in Benzene for Different Sample Introduction Quantity

      Serial Number










      mass before sample injection (mg)










      mass after sample injection (mg)










      mass of sample injection (mg)










      temperature of sample injection ()










      theoretical concentration of water (μg/mg)










      average value of theoretical concentration of water(μg/mg)




      actual measured mass of water in benzene(μg)










      actual measured concentration of water in benzene (μg/mg)




      actual measured average value of water concentration (μg/mg)




      actual measured average value of water concentration(μg/mg)-theoretical concentration of water(μg/mg




      basic error(%)





      6.8.4 Check of Eligibility

       Postulating the absolute water content of sampling is X, the relative error is



      7. Measurement Method of Water Content in Sample

      71 Reference Table for Sample Injection Quantity

      Water Content

      Sample Injection quantity




      20 mg10 mg


      100 mg10 mg


               1 g10 mg


               10g10 mg


               20g100 mg





      72 Measurement of Moisture in the Liquid Sample

      721 Firstly, prepare intensive drying sample injection instrument with a pinhead(you can choose other sample injection instrument of different volume according to different determined sample), flush it 4~5 times with sample, then intake a certain volume of sample, prepared for sample injection.

      722 Press ” SAMPLE INDUCTION” key.

      723 Sample is injected to anode solution cell through sample injection instrument, be careful that needlepoint can not insert into the liquid(especially the sample that contains more water), after injecting sample, needlepoint can instantaneously contact liquid level to scour off residual sample of needlepoint, and avoid to contact the inner wall of titration cell or electrode, after injecting, the electroanalysis will automatically start when delay time ends, the ring of buzzer means the electroanalysis is finished.

      724 The unit of measurement result is “microgramme water” the calculation formula of concentration is as follows:


      measurement result (ug)   meassured result (ug)               meassured result (ug)

      water contentppm   =  ————————      =  ——————————————————

                                mass of sample (g)        sample density (g/mL)×sample volume (mL)

      73 Measurement of Moisture in the Solid Sample

      The shape of solid sample can be powdergranulelump(big lump should be shattered), when sample is difficulty to dissolve in electrolytic solution, we should choose a appropriate water evaporator, and connect it  to the main unit, and choose appropriate connector and sampling method according to species of sample.


      Figure 4

      731  In Figure 4, it is solid sample injection instrument, it is cleaned up with water,  and drying it.

      732  Taking out the cover of solid sample injection instrumentafter sample is loaded closing immediatelythen accurate weighing the solid sample injection instrument with sample, recording numerical value.

      733  Taking out plug of titration cell and cover of sample injection instrumentsample injection instrument is inserted into the entrance of sample according Figure 5.

      734  After instrument is stabilizedpress “SAMPLE INDUCTION” key delay time beginsit is assured that solid sample can dissolve sufficiently during delay time.

      735  Delay time begins, sample injection instrument is rotated 180 degree(as shown by broken line in Figure 5)sample is dropped into electrolytic solution, (when solid sample is dropped into electrolytic solution, solid sample can not contact wall of titration cell and cathode cellmeasuring electrode). After delay ends, measurement begins.

      Figure 5

      736 After the unit is balanced, and reading number accurately, sample injection instrument is taken out carefully, and covering injection plug of sample, and accurate weighing solid sample injection instrument, reading number, the subtraction between this numerical value and weighing value in Step 2 is the mass of sample injection.

      737 The measurement method of water content in solid is the same as the method of liquid.

      74 Measurement method of water content in gas sample

      When measuring water content in gas sample, 150mL electrolytic solution should be injected into the anode cell to make sure that the moisture in gas is sufficiently ingested. Simultaneity, flow speed of gas is controlled to 1-3L/min, if electrolytic solution in anode cell is reducing obviously in the course of measurement, appropriate volume of electrolytic solution is injected to replenishing in time.

      When measuring trace moisture in liquid hydrocarbon, it is suggested that you should use our company’s “sampling and sample injection instrument of liquid hydrocarbon flash distillation and gasification” simultaneously.


      8 Attention

      81 Attention for Electrolytic Solution

      811 In the course of natural measurement, every 100mL electrolytic solution should be reacted with more than 1g water, if the measurement time is long, the sensitivity of electrolytic solution will drop, you should replace with new electrolytic solution.

      812 For the electrolytic solution in cathode cellif it is found that strong air bubble or polluted and light mahogany electrolyte is released in the course of titration, blank electric current will be increased, measurement reappearance is reduced, time of reaching end point is lengthened, electrolytic should be replaced in the instance.

      813 If titration time exceeds half of an hour, the unit can not be steady, agitating is stopped by rotating agitating buttonobserve if brown iodine is generated on anode platinum net, if there is no iodine or few, electrolytic solution should be replaced.

      814 Be careful that do not inhaling electrolytic solution or contact it by hand, if contacting it with skin, it is flushed thoroughly by water, because there is poisonous component in the reagent, the laboratory should be well draughty.

      82 Attention for Measurement

      821 When sample is injected into titration cell, needlepoint of sample injection instrument can not be inserted to liquid level(especially sample in which water content is bigger), After sample is injected, needlepoint can contact liquid level momentary, residual sample on the needlepoint is flushed. When liquid, solid and gas are injected, sample should be contacted to inner wall of titration cell and electrode.

      822 The typical measurement range of the unit is 3ug-100mg, In order to obtain accurate measurement result, you should control injection volume of sample according to water content of sample.

      823 Cleaning out residual liquid on the silica gel pad of sample injection port in time.


      9 Maintenance and Inspection

      91 Maintenance of Electrolytic Solution

      The electrolyte is located in the draughty place, the temperature should under 35, temperature has no lower limit, relative humidity does not excess 75 in the place.

      92 Replacement of Silica-gel Pad

      The silica-gel pad of sample injection port is used for a long time, the pinhole of it will lose contractibility, thus, the moisture in atmosphere will go into titration cell, which can lead to measurement error, the pad should be replaced

      93 Replacement of Silica-gel

      When color of silica gel in drying pipe changes from blue to light blue or red, the silica-gel should be replaced

      94 Maintenance for the Abrasive Mouth of Titration Cell

      Turning the connect of abrasive mouth of titration cell in a week, when it can not be turned easily, it is disassembled carefully, clean the abrasive mouth and faucet, and thin vacuum grease is smeared again(attention: you should not smear too much vacuum grease, otherwise it enters into titration cell and causes measurement error), if you do not check in time, vacuum grease becomes rigidity after a long time, the components connected by abrasive mouth will agglutinate each other and can not be disassembled. So it should be maintained well, and it is easy to be disassembled and be cleaned.

      95 Treatment of Agglutination of Titration Cell’s Abrasive Mouth

      If the abrasive mouths of titration cell agglutinates firmly, it can not be disassembled, you can follow the following procedures to solve this problem:

      951 Draining off electrolytic of titration cell, and cleaning up it.

      952 Injecting a few acetone around abrasive mouth, then turning it lightly by hand, thus, it can be disassembled.

      953 If it can not be disassembled, you put titration cell into a 2L beaker, slowly pouring potassium chloride(concentration is 5%) to dip itpay attention to its liquid level, you should not put detector electrode, the end of down-lead of cathode cell electrode, dip it for more than 10 hours or 24 hours, then it can be disassembled(this method can be used repeatedly).

      96 Maintenance of Detector electrode



      short circuit

      short circuit

      easily broken


      961 When magnetic force stirrer rotates in high speed, you should pay attention that mixing propeller can be bounced to damage electrode.

      962 When detector electrode is entered into or taken out, power source should be turned off, and pay attention that not contacting detector electrode to inner wall of titration cell.

      963 When detector electrode is bent but not short circuit, it can be used or repaired. When repairing, gripping root of platinum electrode with forceps, slowly collating top end of platinum electrode.

      964 When detector electrode is polluted, wiping detector electrode with acetone, if dirt on platinum thread can not be removed, burning end of platinum thread with flame of alcohol burner. (attention: flame is approach to end of platinum thread slowly, to avoid breaking of electrode glass because of heating up rapidly).

      97 Maintenance of Cathode Cell

      871 Disassembling cathode cell

      When disassembling cathode cell, you should be slowly and should not touch the top end and inner wall of titration, because platinum thread and platinum net are stretched from the interface of cathode cell’s abrasive mouth.

      972 Cleaning of Cathode Cell

      When cathode cell is polluted, including the following cases

      1reducing efficiency of electrolysis, delaying measurement time.

      2blank electric current is increased because polluted part adsorbs moisture,.

      3titration speed is not steady, and not arriving end point.

      If above-mentioned cases occurs, cleaning dirt of glass part’s surface and platinum net with chloroform(attention: do not bump platinum thread and platinum net), pouring chloroform into cathode cell, sealing interface of drying pump with rubber plug or similarity stuff, swaying sufficiently to remove inner dirt(this can be repeatedly). Then pouring chloroform onto the whole surface of glass part to clean, but not cleaning to down-lead of electrode. When it still cannot be cleaned, you can immerge cathode cell into beaker with diluted sulfuric acid (pay attention not to contacting platinum thread and platinum net).


      position difficult

      to be dried

      easily broken








      pore wall


      973 Drying of Cathode Cell

      Drying cathode with hot wind of air blower, the moisture in sand core is difficulty to dry, so it should be dried thoroughly. When there is residual moisture, put cathode cell into vaccum desiccator to desiccate 12 hours.

      98 Maintenance of Electrode Plug and Socket

      The plug and socket of detector electrode and cathode cell electrode is used frequently, this causes the loosening of plug gradually. The dust will adhere to the plug and socket after a long time use, it makes that plug and socket of electrode is bad contact, so it should be cleaned.

      981 Loosening of Plug

      When connection of plug and socket is loose, you can press outer sheet metal of plug inwardly with vice.

      982 Cleaning of Plug and Socket

      Wiping metal part with ethanol or acetone, which can make a good contact.


      sheet metal

      10 Troubleshooting

      101 Open Circuit of Measurement and Titration

      When open circuit of measurement and titration beginsstate shows it will increase rapidly to maximum“electrode open circuit” is showed in display window.

      1011 For this case, you should check whether the contact between plug of detector electrode and cathode cell are normal.

      1012 Checking that down-lead of detector electrode and electrode of cathode cell are good contact or bad contact.

      102 Measurement of Short Circuit

      When measuring short circuit, short circuit of electrode is showed in the unit.

      1021 Checking whether detector electrode of plug and socket is short circuit.

      1022 Checking whether electrode is short circuit.

      1023 Checking whether electrode is leak which causes that the unit can not arrive end point. If detector electrode is leak, despite titration time excess half an hour, the unit can not arrive end point too(this case does not belong to reagent problem).

      1024 When new electrolyte is injected, short circuit of electrode may appear, for this problem, you can slowly drop a little distilled water until show normally.

      103 Electroanalysis of Open Circuit

      When electrolyzing open circuit, open circuit of electrolyzing is showed in the unit.

      1031 Checking whether Electrolysis electrode of plug and socket is connected.

      1032 Checking that down-lead of Electrolysis electrode and electrode of anode cell are good contact or bad contact.

      104 For other malfunctions, contact our company.



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