CN221765378U - Automatic titration device with back titration function - Google Patents

Abstract

The utility model belongs to the technical field of chemical analysis, and specifically relates to an automatic titration device with a back titration function. The utility model connects a sample bottle, a standard liquid bottle, a back-drip liquid bottle, a buffer bottle and a color indicator bottle to a titration cell through independent pipelines, thereby ensuring that there is no cross contamination of liquids and improving the accuracy of titration. By arranging a quantitative dosing device on each independent pipeline, the quantitative dosing device is used to control the single addition amount of liquid in the sample bottle, the standard liquid bottle, the back-drip liquid bottle, the buffer bottle and the color indicator bottle, so that the speed during titration and the accuracy of back titration can be controlled, thereby achieving the purpose of reducing the titration error on the basis of shortening the total titration time.

Description

An automatic titration device with back titration function

Technical Field

The utility model belongs to the technical field of chemical analysis, and in particular relates to an automatic titration device with a back titration function.

Background Art

Titration is a means of quantitative analysis and a chemical experimental operation. It determines the content of a certain solute through the quantitative reaction of two solutions. It indicates the titration endpoint based on the color change of the indicator, and then calculates the analysis result based on the volume consumed by the standard solution.

At present, there are many types of automatic titrators that can realize the full automation of the titration process, and use color sensors instead of manual naked eyes to determine the color change at the titration endpoint, eliminating the human judgment error in the manual titration process and reducing the error of the titration result.

However, in the control program of the automatic titrator, the volume of the titration standard liquid for each titration is fixed. Since the concentration of the solvent to be tested cannot be predicted, in order to prevent the "over-titration" phenomenon, that is, to prevent the volume of the titration standard liquid added once from exceeding the theoretical titration volume required for the titration endpoint when the titration endpoint is reached, the volume of the standard liquid added each time by the automatic titrator is required to be as small as possible. Although this reduces the error, it results in too long a time from the start of adding the standard liquid to the titration endpoint.

If the titration efficiency is to be improved, the volume of the standard solution for each titration must be increased, which will result in a large error in the endpoint titration. Therefore, the above-mentioned method of reducing the volume of the standard solution for each titration is usually the only option.

However, some types of titration analysis require the shortest possible titration analysis time. For example, when using chrome black T as an indicator to measure the hardness of water, chrome black T as an indicator is prone to oxidation and deterioration, so the titration time needs to be shortened as much as possible. If the titration time exceeds 3 minutes, the indicator may oxidize and deteriorate, and a more accurate titration analysis result may not be obtained.

Utility Model Content

The purpose of the utility model is to solve the above problems and provide an automatic titration device with back titration function. Based on the back titration method, the speed of titration analysis is improved without reducing the accuracy of titration analysis. The single addition amount of liquid in the standard liquid bottle and the back titration liquid bottle is controlled by the quantitative dosing device, which can reduce the titration error and shorten the time of titration analysis.

The technical problem to be solved by the utility model is achieved by the following technical scheme: an automatic titration device with back titration function, comprising a sample bottle, a standard liquid bottle, a back titration liquid bottle, a buffer bottle, a color indicator bottle, a titration cell, a quantitative dosing device and a controller;

The sample bottle, standard solution bottle, dripping solution bottle, buffer bottle and color indicator bottle are connected to the titration cell through independent pipelines, and each pipeline is provided with a quantitative dosing device;

The quantitative dosing device is used to control the single addition amount of liquid in the sample bottle, standard liquid bottle, dripping liquid bottle, buffer bottle and color indicator bottle;

The controller is connected to the quantitative dosing device signal, and is used to control the start and stop of the quantitative dosing device and to set and record the number of additions of the quantitative dosing device. By setting and recording the number of additions of the quantitative dosing device by the controller, the total amount of liquid added can be set and calculated.

Preferably, the utility model further comprises a color sensor connected to the controller signal, wherein the color sensor is used to detect the color change of the sample in the titration cell;

The controller controls the start and stop of the quantitative dosing device according to the color change signal of the sample in the titration cell. In order to improve the accurate identification of the titration end point and reduce the titration error, the color sensor is used to monitor the color change of the sample in the titration cell in real time, so as to automatically stop the quantitative dosing device and avoid over-titration.

In the preferred embodiment of the present invention, the quantitative dosing device is a metering pump, which can realize quantitative delivery of liquid.

In the utility model, the single addition amount of liquid in the quantitative dosing device connected to the standard liquid bottle is greater than the single addition amount of liquid in the quantitative dosing device connected to the back-drip liquid bottle. In order to shorten the titration time and improve the accuracy of back titration, the single addition amount of liquid in the quantitative dosing device connected to the standard liquid bottle needs to be greater than the single addition amount of liquid in the quantitative dosing device connected to the back-drip liquid bottle.

In the utility model, the ratio of the single addition amount of the liquid of the quantitative dosing device connected to the return dripping liquid bottle to the single addition amount of the liquid of the quantitative dosing device connected to the standard liquid bottle is preferably 1/50 to 1/10. In order to ensure the titration accuracy and shorten the titration time, the ratio of the single addition amount of the liquid of the quantitative dosing device connected to the return dripping liquid bottle to the single addition amount of the liquid of the quantitative dosing device connected to the standard liquid bottle is controlled between 1/50 and 1/10.

The utility model preferably has a single addition amount of liquid in the quantitative dosing device connected to the standard liquid bottle of 0.1 to 0.5 ml. In order to increase the titration speed of the titration standard liquid and shorten the back titration time, the single addition amount of liquid in the quantitative dosing device connected to the standard liquid bottle is controlled to be 0.1 to 0.5 ml to ensure that the back titration time is controllable.

In the preferred embodiment of the present invention, a stirring device is provided in the titration cell. In order to speed up the reaction speed in the titration cell, a stirring device is provided in the titration cell to speed up the reaction between the reagents by stirring and mixing.

The automatic titration device of the utility model is used for titration, the standard liquid bottle is used to hold the titration standard liquid, the return drip liquid bottle is used to hold the return titration standard liquid, the single addition amount of the liquid of the quantitative dosing device connected to the standard liquid bottle and the single addition amount of the liquid of the quantitative dosing device connected to the return drip liquid bottle are V1 and V2 respectively, and the unit is mL.

The formula for calculating the concentration of the corresponding solute in the solution to be titrated is:

c = ( _{V1 total} * _{aV2 total} * b) / V (1)

_V1total ＝V1·n1(2)

_V2total ＝V2·n2(3)

Wherein, V is the volume of the solution to be tested, mL; _{V1total is} the total volume of the titration standard solution, mL; _{V2total is} the total volume of the back-titration standard solution, mL; n1 is the number of titrations of the titration standard solution; n2 is the number of titrations of the back-titration standard solution; c is the concentration of the corresponding solute in the solution to be titrated, mol/L; a is the concentration of the standard liquid, mol/L; b is the concentration of the back-titration standard liquid, mol/L.

Compared with the prior art, the utility model has the beneficial effect that the utility model connects the sample bottle, standard liquid bottle, back-drip liquid bottle, buffer bottle and color indicator bottle to the titration cell through independent pipelines respectively, thereby ensuring that there is no cross contamination of liquids and improving the accuracy of titration.

By arranging a quantitative dosing device on each independent pipeline and using the quantitative dosing device to control the single addition amount of liquid in the sample bottle, standard liquid bottle, back-drip liquid bottle, buffer bottle and color indicator bottle, the speed of titration and the accuracy of back-titration can be controlled, thereby achieving the purpose of reducing the titration error on the basis of shortening the total titration time.

By using the controller to set and record the number of additions of the quantitative dosing device, the total amount of liquid added can be set and calculated, so as to calculate the concentration of the solvent to be tested.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of an automatic titration device with a back titration function in an embodiment of the present utility model;

In the figure, 1 is a sample bottle, 2 is a standard solution bottle, 3 is a back-drip solution bottle, 4 is a buffer bottle, 5 is a color indicator bottle, 6 is a titration cell, and 7 is a quantitative dosing device.

DETAILED DESCRIPTION

In order to clearly illustrate the technical features of the utility model patent, the utility model patent is explained below through a specific implementation method.

As shown in Fig. 1, an automatic titration device with back titration function includes a sample bottle 1, a standard solution bottle 2, a back titration bottle 3, a buffer bottle 4, a color indicator bottle 5, a titration cell 6, a quantitative dosing device 7 and a controller. The sample bottle 1 is used to store the solution to be tested, the standard solution bottle 2 is used to store the titration standard solution, the back titration bottle 3 is used to store the back titration standard solution, the buffer bottle 4 is used to store the buffer, and the buffer is used to stabilize the pH value of the solution to be tested, and the color indicator bottle 5 is used to store the color indicator.

The sample bottle 1, standard solution bottle 2, dripping solution bottle 3, buffer bottle 4 and color indicator bottle 5 are connected to the titration cell 6 through independent pipelines, and each pipeline is provided with a quantitative dosing device 7. The titration cell 6 is provided with a stirring device.

The quantitative dosing device 7 is used to control the single addition amount of liquid in the sample bottle 1 , the standard liquid bottle 2 , the dripping liquid bottle 3 , the buffer bottle 4 and the color indicator bottle 5 .

The controller is connected to the quantitative dosing device 7 by signal, and is used to control the start and stop of the quantitative dosing device 7 and to set and record the number of times the quantitative dosing device 7 adds medicine.

The automatic titration device with back titration function further comprises a color sensor connected to the controller signal, and the color sensor is used to detect the color change of the sample in the titration cell 6.

The controller controls the start and stop of the quantitative dosing device 7 according to the color change signal of the sample in the titration cell 6 measured by the color sensor.

The quantitative dosing device 7 is a metering pump.

The single addition amount of liquid in the quantitative dosing device 7 connected to the standard liquid bottle 2 is greater than the single addition amount of liquid in the quantitative dosing device 7 connected to the dripping liquid bottle 3 .

The ratio of the single addition amount of liquid of the quantitative dosing device 7 connected to the dripping liquid bottle 3 to the single addition amount of liquid of the quantitative dosing device 7 connected to the standard liquid bottle 2 is 1/50 to 1/10.

The single addition amount of liquid in the quantitative dosing device 7 connected to the standard liquid bottle 2 is 0.1-0.5 ml.

Taking the determination of water hardness as an example, the specific implementation plan is: determination of water hardness (in accordance with the chrome black T method in GB/T 6909).

The water hardness automatic titrator with back titration function mainly includes: a human-machine interface system, a control system, a titration tank 6, a color sensor, a reagent adding system, a stirring system, etc. The reagent adding system includes a quantitative dosing device 7, and the specific quantitative dosing device 7 is a metering pump.

The sample bottle 1 stores the water sample to be tested;

The standard liquid bottle 2 contains EDTA standard liquid with a concentration of amol/L;

The back-titration standard liquid with a hardness of bmol/L (with 1/2Ca ²⁺ as the basic unit) is stored in the back-titration liquid bottle 3;

The buffer bottle 4 stores an ammonia-ammonium chloride buffer solution;

The color indicator bottle 5 stores chrome black T indicator solution with a concentration of 5 g/L.

The sample bottle 1 , the standard solution bottle 2 , the back-drip solution bottle 3 , the buffer bottle 4 and the color indicator bottle 5 are connected to the titration cell 6 through the quantitative dosing device 7 respectively.

The key steps of the entire automatic titration are as follows:

Step 1: The quantitative dosing device 7 connected to the sample bottle 1 adds the water sample with a volume of V mL to be tested into the titration cell 6.

Step 2: The quantitative dosing device 7 connected to the buffer bottle 4 adds a certain volume of ammonia-ammonium chloride buffer solution into the titration cell 6.

Step 3: The quantitative dosing device 7 connected to the color indicator bottle 5 adds a certain volume of chrome black T indicator solution into the titration cell 6.

Step 4: Stir the liquid in the titration cell 6 using a stirring system.

Step 5: The color sensor samples the color of the liquid in the titration cell 6 and determines whether the titration endpoint has been reached (in this embodiment, the color of the liquid is blue at the titration endpoint).

If the titration endpoint is reached, proceed to step seven; if the titration endpoint is not reached, repeat "step six, step four, step five".

Step 6: The quantitative dosing device 7 connected to the standard liquid bottle 2 adds a preset volume of EDTA standard liquid into the titration cell 6.

Step 7: The quantitative dosing device 7 connected to the back-titration liquid bottle 3 adds a preset volume of back-titration standard liquid into the titration cell 6 .

Step 8: Stir the liquid in the titration cell 6 using a stirring system.

Step nine: The color sensor samples the color of the liquid in the titration cell 6 and determines whether the color of the liquid has returned to the color before the titration endpoint (red in this embodiment).

If the color of the liquid changes back to the color before the titration endpoint, the entire titration analysis process is completed; if the color of the liquid does not change back to the color before the titration endpoint, repeat "step seven, step eight, step nine".

Assuming that during the entire analysis process, the total volume of the EDTA standard liquid added is V3mL, and the total volume of the back titration standard liquid added is V4mL, the hardness calculation formula for the analyzed water sample is as follows:

Hardness of water sample c = (V3*a-V4*b)/V;

In the above formula: V3 refers to the total volume of the added EDTA standard liquid, mL;

V4 refers to the total volume of the back titration standard liquid added, mL;

a refers to the concentration of EDTA standard liquid, mol/L;

b refers to the concentration of the back titration standard liquid, mol/L.

By controlling the preset volume of each titration of the EDTA standard liquid in step 6, it is ensured that the titration end point is reached quickly; and by controlling the preset volume of each titration of the back-titration standard liquid in step 7, the error of the back-titration is reduced. Since the back-titration is only performed on the last titration of the EDTA standard liquid, the number of titrations can be estimated, the time of the back-titration can be shortened, and the accuracy of the back-titration can be controlled.

Claims (7)

1. An automatic titration apparatus with back titration function, characterized in that: the device comprises a sample bottle (1), a standard liquid bottle (2), a back drop bottle (3), a buffer bottle (4), a color indicator bottle (5), a titration cell (6), a quantitative dosing device (7) and a controller;

The sample bottle (1), the standard liquid bottle (2), the back drop bottle (3), the buffer bottle (4) and the color indicator bottle (5) are respectively connected with the titration cell (6) through independent pipelines, and each pipeline is provided with a quantitative dosing device (7);

The quantitative dosing device (7) is used for controlling the single addition amount of liquid in the sample bottle (1), the standard liquid bottle (2), the drip return bottle (3), the buffer bottle (4) and the color indicator bottle (5);

The controller is in signal connection with the quantitative dosing device (7) and is used for controlling the starting and stopping of the quantitative dosing device (7) and setting and recording the adding times of the quantitative dosing device (7).

2. The automatic titration apparatus with back titration function according to claim 1, wherein: the color sensor is in signal connection with the controller and is used for detecting the color change of the sample in the titration cell (6);

the controller controls the start and stop of the quantitative dosing device (7) according to the color change signal of the sample in the titration cell (6).

3. The automatic titration apparatus with back titration function according to claim 1, wherein: the quantitative dosing device (7) is a metering pump.

4. The automatic titration apparatus with back titration function according to claim 1, wherein: the single adding amount of the liquid of the quantitative dosing device (7) connected with the standard liquid bottle (2) is larger than that of the liquid of the quantitative dosing device (7) connected with the drip return bottle (3).

5. The automatic titration apparatus with back titration function according to claim 1, wherein: the ratio of the single adding amount of the liquid of the quantitative dosing device (7) connected with the drip return bottle (3) to the single adding amount of the liquid of the quantitative dosing device (7) connected with the standard liquid bottle (2) is 1/50-1/10.

6. The automatic titration apparatus with back titration function according to claim 1, wherein: the single adding amount of the liquid of the quantitative dosing device (7) connected with the standard liquid bottle (2) is 0.1-0.5 ml.

7. The automatic titration apparatus with back titration function according to claim 1, wherein: a stirring device is arranged in the titration tank (6).