ZDDN-II automatic Kjeldahl analyzer

user's Guide

ZHEJIANG TOP INSTRUMENT Co., Ltd.

Head      record

First , the working principle of ZDDN-II Kjeldahl nitrogen analyzer..............................3

1. Overview...............................................................3

2. Working principle (Kjeldahl principle) .............................................3

3. Operation steps ......................................................4

4. Instrument composition ......................................................4

Second, technical parameters ...................................................5

Third, the function and use of the introduction (the part of the distiller) ........................6

1. Front view and function introduction.......................................6

2. Left side schematic and function introduction.......................................9

3. Introduction to the right side diagram and function introduction .......................................10

Fourth, reagent preparation......................................................11

1. Instruments and Tools ......................................................11

2. Reagents..................................................................11

V. Sample digestion .............................................12

Sixth, the operation method (the part of the distiller) .................................12

1. Description of each parameter setting ................................................12

1.1 LCD operating instructions................................................12

1.2 Calculating the pump flow value ...................................................14

2. Distillation operation process......................................................15

2.1 Preparations......................................................15

2.2 Ventilation check......................................................15

2.3 Sample Distillation......................................................16

3. Titration............................................................16

4. Shutdown............................................................17

Seven, common troubleshooting methods (still part)........................18

Eight, matters needing attention ...................................................18

Nine, complete list .............................................20

one. ZDDN-II Kjeldahl instrument working principle

1. Overview:

ZDDN-II Kjeldahl is an automatic nitrogen distillation system designed according to the classical (Kjeldahl) method. (Distillation part) can realize automatic acid addition, automatic alkali addition and automatic distillation process, and can set parameter values ​​according to different industries. The instrument is easy to install and operate; safe, reliable, time-saving and labor-saving; high degree of automation, suitable for analysis, teaching and research in grain and oil testing, feed analysis, plant nutrient testing, soil and fat testing, medicine, chemical industry, etc. The ideal tool for operating the user.

2. Working principle (Kjeldahl principle):

Proteins are organic compounds containing nitrogen. The food is heated and digested together with sulfuric acid and a catalyst to decompose the protein, and the decomposed ammonia combines with sulfuric acid to form ammonium sulfate. The ammonia is then freed by alkalization distillation, and the released ammonia gas and water vapor are condensed together through a condenser and then introduced into an Erlenmeyer flask containing boric acid. After being absorbed by boric acid, it is titrated with a standard solution of sulfuric acid or hydrochloric acid, and the protein content is obtained by multiplying the consumption of the acid by the conversion factor.

2.1. Ammonium (digestion furnace section) in the organic matter under intense heat and catalyst and concentrated H ₂ SO _4, nitrification generating (NH _{4) 2} SO ₄

The reaction formula is:

2NH ₂ —+H ₂ S0 ₄ +2H+=(NH ₄ ) ₂ S0 ₄

2.2. (distiller part) The digestive tube containing the sample after digestion reacts with alkali under the action of high temperature steam, releases NH ₃ and water vapor, and collects in H ₃ BO ₃ solution.

The reaction formula is:

(NH ₄ ) ₂ SO ₄ +2 NaOH high temperature steam = 2NH ₃ ↑ + 2H ₂ O + Na ₂ SO ₄

2NH ₃ +4H ₃ BO ₃ =(NH ₄ ) ₂ B ₄ O ₇ +5H ₂ O

2.3. (Titration) Titrate with a known concentration of H ₂ SO ₄ (or HCI) standard solution, calculate the nitrogen content based on the HCI consumption, and then multiply by the corresponding conversion factor to obtain the protein content.

The reaction formula is:

(NH ₄ ) ₂ B ₄ O ₇ +H ₂ SO ₄ +5H ₂ O=(NH ₄ ) ₂ SO ₄ +4H ₃ BO ₃

(NH ₄ ) ₂ B ₄ O ₇ +2HCl+5H ₂ O=2NH ₄ Cl+4H ₃ BO ₃

3. Operation steps:

Sampling → Digestion → Distillation → Titration → Calculation

4. Instrument composition:

It consists of a digestion furnace (the company is equipped with 04C, 08C, 12C, 20C and other digesting furnace models) and a fully automatic nitrogen analyzer distiller.

The digestion furnace (exponential display type) is controlled by a temperature control table, which is heated by infrared radiation, has a good temperature control effect, uniform heating, and convenient operation. The harmful gas such as S0 ₂ escaping in the digestive tract is carried into the sewer through the suction pump on the digestive pipe through the suction pump, effectively suppressing the escape of harmful gases, and omitting the installation of the fume hood in the laboratory. It takes about 40-90 minutes to digest a batch of samples (depending on the amount of nitrogen). For specific instructions, please refer to the instruction manual of the digestion furnace in the attached file.

1. Determination of varieties: food, feed, food, dairy products, beverages, soil, water, drugs, sediments and chemicals.

2. Working mode: automatic (without titration), or manual mode.

3. Determination of the number: can digest 4-20 at the same time (according to the number of digesting furnace holes), using a single distillation.

4. Measuring range: nitrogen content in 0.1 ~ 200mgN (mg nitrogen)

(nitrogen content 0.02% to 99%)

5. Recovery rate: 100±1% (relative error, including digestion process)

6. Repeat rate: relative standard deviation <±1%

7. Working time: digestion time 40-90 minutes, distillation time 5-15 minutes.

According to different samples, the user can set it by himself.

8. Working voltage: AC 220V/50HZ.

9. Cooling water consumption: 5L/min of digestion

Distillation section 3L/min

(water temperature is less than 20 degrees)

10. Power consumption: Digestion part of the four holes 800W, eight holes 1200W, twelve holes 1600W,

20 holes 2000W.

The distillation section was 1000W.

The structure of the whole machine is as follows:

1. Front view and function introduction:

1. ABS panel: It adopts gray ABS material, which is resistant to acid and alkali, effectively protects the instrument and prolongs the service life.

. â‘¡ digestive tube: 300 × Φ45 using the digestive tract, digestive tract contents was digested samples, it may be equipped with an automatic good (NH _{4) 2} SO ₄ samples.

Hard PTFE tube â‘¢: the distillation process, the heated steam produced from heating cup tube into the digestive tract, the digestive tract so that the sample reacts with a base.

â‘£ Organic glass: a closed state during operation, upper end attracted by the magnet. In the event of an accident, when the alkali runs out, it plays a role in protecting life.

5. Digestive Tray: The digestive tract can be installed by manually pressing the tray.

6. Conical bottle tray: Sweep the conical flask in the direction of the lower end of the conical flask, and move the tray up and down. When it is in the proper position, let go and then move it up and down, then it can be clamped and kept stable. Bayonet).

7. Conical flask: generally use a 250mL conical flask.

8. Ammonia gas reflux glass nozzle: The ammonia gas generated in the digestive pipe 2 and the water vapor pass through the glass nozzle into the conical flask 7, and the working time must ensure that the glass nozzle enters below the liquid level of the conical flask 7 to prevent ammonia gas. The escape has affected the measurement results.

9. Acidizing glass nozzle: Boric acid enters the conical flask 7 through the glass nozzle, and the glass nozzle is not allowed to spray the solution in the conical flask 7 during operation.

10. Control display area:

The function of each button in the button area:

Adding acid: Pressing this button will automatically add acid. Pressing this button during acid addition will suspend the acid addition. Press this button again to continue adding acid. In the time setting state (press the function enter key first), select this button to enter the change acid time mode.

Add alkali: press this button will automatically add alkali, press this button in the process of adding alkali will suspend the addition of alkali, press this button again to continue adding alkali. In the time setting state (press the function enter key first), select this button to enter the change alkali time mode.

Distillation: Press this button to start distillation. Pressing this button during distillation will suspend distillation. Press this button again to continue distillation. In the time adjustment state (press the function entry key first), select this button to enter the change distillation time mode.

OK: Determine the current setting or change operation; press this button to enter the automatic working mode after all parameter settings are completed.

Function: When the language status appears after power on, you can press this key to switch the language (Chinese and English); after entering the main interface, you can press this key to enter the working time mode of each function.

Increase: (In the time adjustment state) Increase the current time setting value; long press and hold this button to speed up the change.

Decrease: (In time adjustment state) Decrease the current time setting value; long press and hold this button to speed up the change.

Cancel: Stop the current operation.

Note: When adding acid, alkali and distillation, you must first press the cancel button, otherwise you will not be able to operate.

2. Left side schematic and function introduction:

  1. Distilled water inlet: Cut into the required length with the rubber tube in the fitting, insert one end into the interface, and put it into the container bottle containing distilled water.

2. Distilled water outlet: Cut the required length with the rubber tube in the fitting, insert one end into the interface, and put it into the waste recovery container bottle (or directly into the sewer). Since it is discharged as hot water, be careful with hot hands. There is a water dragon switch here, and the switch must be turned off when working.

3. Cooling water inlet: Cut the required length with the rubber tube in the fitting, insert one end into the interface, and connect the tap water switch at one end. (common tap water instead of cooling water)

4. Cooling water outlet: Cut the required length with the rubber tube in the fitting, insert one end into the interface, and put it into the waste recovery container bottle (or directly into the sewer).

5. Alkali import: Cut the required length with the rubber tube in the fitting, insert one end into the interface, and put it into the plastic bottle containing the lye.

6. Acid inlet: Cut the required length with the rubber tube in the fitting, insert one end into the interface, and put it into the solution bottle containing the acid.

7. Heating cup water level observation port: used to observe the water level in the internal heating cup of the instrument.

Note: The first six nozzles must be tightened to prevent operation due to air leaks. At the same time, the lye cannot be contained in a glass bottle, and other liquids are not particularly required.

3. The right side schematic and function introduction:

1. Power switch: also called the ship type switch. Used to control the total power of the whole machine. When the instrument has an alarm or other abnormal fault, the main switch is checked again.

â‘¡ Block Power: the power supply line accessories. (AC 220V)

For details on the structure and function of the digestion furnace, please refer to the instructions of the nearby digestion furnace.

1. Instruments and tools

a. Analytical balance: Sensitivity 0.0001g

b. Acid burette: 25ml or 10ml

c. Conical flask: volume 250ml

2. Reagent

a. Concentrated sulfuric acid (H ₂ SO ₄ ): chemically pure, 95% to 98%, no nitrogen

b. Copper sulfate (CuSO ₄ .5H ₂ O), potassium sulfate (K ₂ SO ₄ ): analytical grade

c. NaOH solution: chemically pure, 400 g dissolved in 1000 ml of distilled water to prepare a 40% aqueous solution (m/v).

d. Boric acid (H ₃ BO ₃ ): analytically pure, 2 g dissolved in 100 mL of distilled water to prepare a 2% aqueous solution (m/v).

e. Hydrochloric acid (HCL): Analytically pure, 0.05 mol/L standard solution, (4.2 ml hydrochloric acid was injected into 1000 ml of distilled water) and the sodium carbonate method was used to calibrate hydrochloric acid.

f. Mixing indicator: methyl red (G ₅ H ₅ N ₃ O ₂ ) is dissolved in ethanol to form a 0.1% ethanol solution, bromocresol green is dissolved in ethanol to form a 0.5% ethanol solution, and the two solutions are kept in an equal volume and kept in a cool place. (The retention period is three months).

Weigh 0.20g ~ 2.00g solid sample or 2.00g ~ 5.00g semi-solid sample or draw 10.00ml ~ 25.00ml liquid sample (about 30mg ~ 40mg), transfer to dry digestive tube, add 0.2g sulfuric acid Copper, 6g potassium sulfate and 20ml concentrated sulfuric acid, placed on the digestion furnace and carefully heated. After the contents are all carbonized, the foam completely disappears, increase the firepower, and keep the liquid in the tube slightly boiling until the liquid is blue-green clear and transparent. Continue for another 0.5h to 1h. Remove and let cool to be used for distillation. (For details of the operation of the digestion process, please refer to the operating instructions of the digestion furnace in the attached file.)

1. Description of each parameter setting

1.1 LCD operating instructions :

Press the “Function” button to switch between Chinese and English. After selecting the language, press the “OK” button. (The retention time in Figure 1 is relatively short, pay attention to it, otherwise it will only be restarted.)

2 work mode selection : When the language selection is over, the system will automatically add water. The LCD displays “Add water... Please wait”. The water level can be seen through the water level observation port on the left side of the instrument (need to flow over the heating wire). When the water is added, it will enter as shown in Figure 2.

To use the manual mode, press the “Add Acid”, “Alkaline” or “Distillate” buttons directly; if the automatic mode is selected, press the “OK” button.

3 time adjustment : When the instrument interface enters the mode of Figure 2, press the “Function” button, the LCD screen will display as shown in Figure 3:

To adjust the acid addition time, press the “Add Acid” button. The interface appears as shown in Figure 4:

Press the “Add” button to increase the acid addition time. Press the “Reduce” button to decrease the acid addition time. Then press the "OK" button to return to the interface of Figure 3. The method of adjusting alkali and distillation time is the same as above. After all the time is set, press the “OK” button to return to the interface of Figure 2, and the setting is completed.

1.2 Calculate the pump flow value (this item needs to be operated in the automatic mode) :

Purpose of the work: Determine the flow rate of the pump per unit time so that the amount of acid or base required can be determined according to the required time.

Specific operation: First, connect the distilled water inlet, acid inlet and alkali inlet to the rubber tube, and insert the other end of the tube into the surface of the distilled water. Then turn on the power switch, the instrument enters the state of adding water. At this time, the distilled water is automatically added to the heating cup. After the water is added, the state of Figure 2 appears on the display interface. Next, place an empty conical flask on the Erlenmeyer Tray and place an empty digestion oven on the Digestion Tray. Then press the "add acid" button, until the acid glass nozzle in the conical flask has liquid flowing out, and after the flow rate is stable, press the "cancel" button again. At this time, the acid pump stops adding acid, and the cone is removed. liquid. (The main purpose is to: pass the pipeline to prevent the air in the pipeline from being miscalculated.) Then put the conical flask back and continue to press the “add acid” button. After a while, press the “add acid” button again. After stopping the acid addition, observe the acid addition time on the display screen, and then take off the value of the cone flask to calculate the flow rate of the acid pump (acid pump flow per second). The alkali pump flow test method is the same as the acid pump. After measuring the flow rate of the pump, in the automatic working mode, the required time can be input according to the conversion between time and flow (depending on the amount of the experiment). Set the time for adding acid and alkali to be in seconds. (Generally, the amount of alkali is more than twice the amount of sulfuric acid in digestion, and about 50m1 of boric acid, depending on the actual situation.)

The distillation time is generally set at 5-15 minutes.

After the time is set, press the “OK” button, the system will automatically save the current parameters and restore the interface of Figure 2.

2. Distillation process

2.1 Preparation:

Use the rubber tube in the accessory to cut into different lengths according to actual needs. Connect the rubber tube according to the left side diagram described above (be careful to prevent leakage, especially several inlets). The other end of the rubber tube must be immersed below the corresponding liquid level. Place an empty digestive tube in the digestive tract tray and place an empty conical flask on the conical flask.

2.2 ventilation check:

(1). Turn on the faucet switch (cooling water) and pay attention to the flow rate, generally 2-3L/min. Connect the power cord and turn on the main power switch. The company name appears first on the display, then the language selection (the default is Chinese status, you can press the “Function” button to switch). Then the instrument starts to add water automatically. From the side beaker water level observation port, you can see that the water level in the beaker is rising. After a period of time, the water will be automatically stopped (automatically controlled by the water level probe in the system. The water level at this time has no effect on the instrument). After the water is added, the mode selection state appears on the display (Figure 2 above).

(2). Then according to the flow determination method of the pump described above, first determine the flow rate of the pump (at this time, distilled water can be used instead of acid and alkali to determine the flow rate of the pump. After the value is determined, the corresponding rubber tube is placed into the acid and alkali. In the liquid). After the determination is made, the acid, alkali and distillation time are calculated according to the actual needs. Then set the time of each content according to the display operation method described above. After the setting is completed, return to the interface of Figure 2.

(3). Then press the “Add Acid” button and wait for about 10 seconds and then press the “Cancel” button to pour off the liquid in the Erlenmeyer flask. In the same way, press the “Add Alkali” button and wait for about 10 seconds and then press the “Cancel” button to pour off the liquid in the digestive tract. Replace the conical flask and the digestive tract. Then directly select the "distillation" button, and the bubble in the hard PTFE tube in the digestive tube is sprayed from it and continue to be distilled for about 5 minutes. Press the "Cancel" button first, then directly turn off the power. The whole machine is ventilated and water is completed.

2.3 Sample distillation:

Replace the digested and cooled sample on the digestive tube tray. Replace the 250ml conical flask on the conical flask tray, adjust the height of the tray and return the ammonia gas to the bottom of the glass.

Turn the power back on. When the display interface is in the state of Figure 2, press the “OK” button directly. The sample can be distilled. (In the distillation process, the cone can adjust the height of the tray according to the amount of the solution, so as to ensure that the ammonia gas is immersed in the glass nozzle under the liquid surface, and the acid glass nozzle cannot be sprayed to the liquid surface.) If the manual mode is selected, Directly press "Add Acid", "Add Alkali" and "Distillate".

After the distillation is completed, the volumetric flask is moved down, the ammonia gas is returned to the glass nozzle to leave the liquid surface, the outer wall of the glass nozzle is rinsed with distilled water, and the distillation is continued by the "distillation" key for half a minute, and then the conical flask is taken for titration. The second sample is the same as above.

Note: There is no need to turn off the power when changing the sample. When the first sample is tested, the distillation time can be extended slightly.

3 . Titration (The following data is for reference only, based on this industry standard)

The solution in the receiving bottle was titrated with 0.05 mol/L HCL, titrated to (dark) gray, and the number of milliliters of HCL consumed was recorded, and the protein content was calculated according to the following formula:

Protein%=

Where: X—the amount of protein in the sample, %

V ₁ — volume of sample consumption sulfuric acid or hydrochloric acid standard solution, ml;

V ₂ — the volume of the reagent blank consumed sulfuric acid or hydrochloric acid standard solution, ml;

N-sulfuric acid or hydrochloric acid standard solution equivalent concentration;

0.014—1N sulfuric acid or hydrochloric acid standard solution 1ml is equivalent to the number of grams of nitrogen;

M—the mass (volume) of the sample, g (ml);

F - protein coefficient, calculated by 16% multiplied by 6.25 is the protein.

(Blank determination: 0.1 g of sugar instead of sample or no sample for blank determination)

4. Shutdown

First change the empty digestive tube and conical flask, put the other end of the rubber tube imported with alkali into the distilled water container, press the “alkali” button in manual mode, and wash the alkali pump with distilled water, usually about 15 seconds. The same method of acid pump is washed with distilled water.

Then turn off the cooling water (tap tap), unplug the acid inlet, the alkali inlet, the distilled water inlet, the cooling water inlet and the outlet rubber tube, leave the distilled water outlet rubber tube, open the distilled water drain switch, and drain the distilled water. Press the “Add Acid” button and the “Add Base” button again to drain the remaining liquid in the tube (need to receive the remaining liquid with an empty digestive tube and conical flask). Finally turn off the main power and unplug the power cord.

Seven. Common troubleshooting methods (distiller part)

1. Because the NaOH solution is not used for a long time, the tube is prone to sticking. After switching to manual mode every day, the external PBS solution is transferred into the distilled water bottle. The front part is packed with the digestive tube for several times. When it is used next time, it is distilled. 100 ml of NaOH must be drained in case the first sample has insufficient NaOH concentration. After a while, wash the evaporating furnace with dilute acid and wash it several times with water.

2. In order to avoid interference, ensure the normal operation of the instrument and personal safety, the grounding wire must be strictly in operation.

3. If the operation is not correct, after the 10A fuse is blown, please unplug the power plug, replace it with a new one, turn off the water tap, open the drain faucet and drain the boiler water, and restart the operation according to the startup debugging procedure.

4. During the operation of the instrument, the plexiglass cover outside the digestive tract must be closed.

5. Every day after the instrument is used, it must be cleaned with water to keep the instrument clean and tidy (both inside and outside the instrument).

6. Under the conditions of the user's transportation, storage, installation and use procedures, if the instrument fails to work properly due to manufacturing problems, it will be found that the package is defective and damaged during the one year from the date of receipt of the goods, or the accessories are If the packing list does not match or the parts are small, please contact the quality inspection department of the company.
Letters indicate: product model number, serial number, factory year, month.

The warranty period of this instrument is guaranteed (except glassware), users can directly contact our quality inspection department.

1. Nitrogen analyzer 1

2. Power cord 1

3. Rubber tube 5 meters

4. Instruction manual 1 copy

5. Certificate and Warranty Card 1 set