A COD detection method and a detection disk chip

Abstract

This invention proposes a COD detection method and a detection disk chip. The COD detection method includes: firstly, selecting no fewer than five detection zones in the detection cell of a horizontally arranged disk chip, and detecting the absorbance of the solution to be tested in each zone along the vertical direction; then, from the acquired absorbance detection results, removing peak values, valley values, second-highest values, and second-lowest values ​​respectively, calculating the arithmetic mean of the remaining absorbance detection results, and calculating the COD value of the solution to be tested based on a calibration dataset of absorbance and COD values. This invention also provides a detection disk chip, which includes a cubic cavity serving as the detection cell, the cubic cavity being interconnected with the disk chip body surface through at least one inlet channel and at least one outlet channel. The detection method of this invention can obtain relatively accurate COD detection values ​​even in the presence of sediment in the detection cell, and has good application prospects.

Description

Technical Field

[0001] This invention relates to the field of COD detection equipment technology, and in particular to a COD detection method and a detection disk chip. Background Technology

[0002] The current method for COD detection uses a method where the light source and sensor are irradiated from above and below each other. The light source emitter and the sensor receiver are fixed at the upper and lower ends of the detection cell, respectively. The absorbance of the solution to be tested is detected by a single irradiation, and then the COD is obtained according to the corresponding relationship between absorbance and concentration in the corresponding detection instrument.

[0003] In specific COD detection methods, to avoid the influence of chloride ions in the solution on the COD detection results, chloride ions need to be masked. Mercuric sulfate is usually added as a masking agent. However, the addition of mercuric sulfate easily leads to significant precipitation in the test solution. Under the influence of gravity, the precipitation settles at the bottom of the detection cell, greatly affecting the intensity of light received by the sensor receiver, thus affecting the absorbance of the test solution. When the detection cell has a disk-chip structure, it is impossible to change the illumination path from vertical to horizontal. Therefore, it is necessary to optimize the detection method to solve the impact of precipitation on the detection results. Summary of the Invention

[0004] In view of this, the present invention proposes a COD detection method and a detection disk chip that can be applied to COD with precipitates.

[0005] The technical solution of this invention is implemented as follows: This invention provides a COD detection method, comprising:

[0006] Step 1: In the detection cell of the horizontally set disk chip, take no less than 5 detection areas and detect the absorbance of the solution to be tested in the detection area along the vertical direction;

[0007] Step 2: From the multiple absorbance detection results obtained, remove the peak, valley, second peak and second valley values ​​respectively, calculate the arithmetic mean of the remaining absorbance detection results, and calculate the COD value of the test solution based on the calibration dataset of absorbance and COD value.

[0008] Based on the above technical solutions, the preferred option is that different detection zones have the same area.

[0009] Based on the above technical solutions, preferably, the method for determining the location of the detection area includes: taking no less than 5 detection areas at equal intervals along a straight line in the detection pool, with the edge of each detection area being inside the detection pool.

[0010] Based on the above technical solutions, preferably, each detection zone has the same shape.

[0011] Based on the above technical solutions, preferably, the detection area is circular, and the centers of multiple detection areas are arranged at equal intervals along a straight line.

[0012] Based on the above technical solutions, preferably, the detection pool is rectangular, and multiple detection zones are arranged at equal intervals along the length of the detection pool.

[0013] More preferably, the number of detection zones is 10.

[0014] Based on the above technical solutions, the preferred method for obtaining the calibration dataset of absorbance and COD value includes: preparing calibration solutions of various concentrations, irradiating the calibration solutions of different concentrations with detection light in the detection cell of the disk chip, and collecting absorbance values ​​to obtain the calibration dataset of absorbance and COD value.

[0015] The present invention also provides a detection disk chip, including a disk chip body, the disk chip body being made of transparent material, a cubic cavity being formed inside the disk chip body, the cubic cavity serving as a detection pool, and the cubic cavity communicating with the surface of the disk chip body through at least one liquid inlet channel and at least one liquid outlet channel.

[0016] Based on the above technical solutions, preferably, the disk chip body includes an incident surface and an exit surface that are parallel to each other, and the incident surface and the exit surface are parallel to two opposite sides of the cubic cavity.

[0017] The present invention has the following advantages over the prior art:

[0018] (1) The COD detection method of the present invention can be used in online COD monitoring equipment. In the process of COD detection of microfluidic equipment, in order to prevent the precipitation in the test liquid from affecting the normal propagation of the optical path and ultimately affecting the detection of absorbance, the present invention obtains multiple sets of detection data by changing the detection position point without changing the direction of the absorbance detection optical path. After deleting the lowest, highest, next lowest and second highest interference values ​​of absorbance, the obtained absorbance detection values ​​are calculated by arithmetic average. Then, the COD value is obtained according to the average absorbance value. This detection method does not require changing the COD detection optical path of the microfluidic equipment. By moving the detection position point to obtain multiple sets of absorbance value data, a more accurate COD value that can eliminate precipitation interference is obtained.

[0019] (2) At the same time, the present invention also provides a detection disk chip structure that can be used in the above COD detection method. Specifically, a cubic cavity detection pool is set inside the disk chip body to contain the liquid to be tested. The detection light source and the sensor are respectively set on opposite sides of the disk chip body. After the light enters the liquid inside the cavity, it exits into the sensor and finally obtains the detection value. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram showing the movement direction of the light source and sensor along the detection pool of the disk chip in the COD detection method of the present invention.

[0022] Figure 2 This is a perspective view of the disk chip used for testing in this invention;

[0023] Figure 3 This is an isometric view of the disk chip used for testing in this invention;

[0024] Figure 4 This is an isometric view of the disk chip used for testing in this invention.

[0025] In the diagram: 1-Chip body, 11-Cube cavity, 12-Liquid inlet channel, 13-Liquid outlet channel, 14-Inlet surface, 15-Outlet surface. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] like Figure 1 As shown, combined with Figure 2-4 The detection disk chip of the present invention includes: a disk chip body 1, the disk chip body 1 being made of transparent material, a cubic cavity 11 being formed on the inner side of the disk chip body 1, the cubic cavity 11 serving as a detection pool, and the cubic cavity 11 being interconnected with the surface of the disk chip body 1 through at least one liquid inlet channel 12 and at least one liquid outlet channel 13 respectively.

[0028] In the above embodiments, the disk chip is used to perform COD detection on the liquid to be tested. Specifically, the liquid to be tested enters the cubic cavity 11 through the inlet channel 12. The light source illuminates the cubic cavity 11 from one side of the disk chip body 1, and then the emitted light exits from the other side of the disk chip body 1 and enters the corresponding sensor. After the detection is completed, the absorbance value is obtained according to the light intensity detected by the sensor. According to the pre-obtained calibration dataset of absorbance and COD value, the corresponding COD value is calculated. In the COD detection method of the present invention, after the sensor acquires an absorbance value at one position, it will move synchronously with the light source to the next position and perform the next irradiation and absorbance value acquisition. Figure 1 As shown, after moving 6 times in the direction of the arrow, six absorbance values ​​are obtained. Then, the maximum, minimum, second largest, and second smallest values ​​are removed. The arithmetic mean of the remaining two sets of absorbance data is calculated. The resulting absorbance data is substituted into the calibration dataset of absorbance and COD value to obtain the corresponding COD value. This COD value is the target detection value of the liquid to be tested.

[0029] In a specific embodiment, the disk chip body 1 includes an incident surface 14 and an exit surface 15 that are parallel to each other, and the incident surface 14 and the exit surface 15 are parallel to two opposite sides of the cubic cavity 11.

[0030] In the above embodiments, in order to avoid refraction or other unnecessary losses when light is incident, the detection disk chip of the present invention includes a parallel incident surface 14 and an exit surface 15, and the incident surface 14 and the exit surface 15 are parallel to the two opposite sides of the cubic cavity 11, respectively. At this time, when the incident light is perpendicular to the incident surface 14, the light will not be refracted, effectively avoiding unnecessary loss of light.

[0031] To verify the accuracy of the COD detection method of the present invention, the following embodiments are used for experimental illustration.

[0032] First, obtain the calibration dataset of absorbance and COD values:

[0033] Ten sets of calibration solutions with different concentrations were prepared and added sequentially to the detection cell of the disk chip. The disk chip was irradiated with incident light of fixed intensity and wavelength perpendicular to its incident surface. The transmitted light was then collected by a PD sensor at the exit surface to obtain the absorbance. Based on the numerical relationship between different COD concentrations and absorbance, and according to Beer-Lambert's Law: A = lg(I0 / I) = kbc (where A is absorbance, I0 is incident light intensity, I is transmitted light intensity, k is the absorption coefficient (a constant), b is the liquid layer thickness, and c is the solution concentration), ten sets of k values ​​can be calculated. An average k value can be calculated using the arithmetic mean. Based on this k value and the subsequently measured absorbance A, and given the liquid layer thickness b, the solution concentration c can be obtained.

[0034] Example 1

[0035] A COD concentration of 100 mg / L solution was prepared, and a small amount of inert inorganic insoluble powder was added. This powder was then placed into a detection disk chip with a length of 18 mm, a width of 7 mm, and a height of 1 mm. Six detection zones were formed, each a circle with a diameter of 7 mm. The distance between the centers of two adjacent detection zones was 1.5 mm. After detection, the peak, trough, second-peak, and second-trough values ​​were removed, resulting in two absorbance values. The average value was calculated and substituted into the formula A = kbc. The obtained COD concentration value was 103.2 mg / L, with an error of 3.2%.

[0036] Example 2

[0037] A COD concentration of 200 mg / L solution was prepared, and a small amount of inert inorganic insoluble powder was added. This powder was then placed into a detection disk chip. The cube cavity had a length of 18 mm, a width of 7 mm, and a height of 1 mm. Seven detection zones were selected, each a circle with a diameter of 7 mm. The distance between the centers of two adjacent detection zones was 1.1 mm. After detection, the peak, trough, second-peak, and second-trough values ​​were removed, resulting in three absorbance values. The average value was calculated and substituted into the formula A = kbc. The obtained COD concentration was 205.8 mg / L, with an error of 2.9%.

[0038] Example 3

[0039] A COD concentration of 300 mg / L solution was prepared, and a small amount of inert inorganic insoluble powder was added. This powder was then placed into a detection disk chip with a length of 18 mm, a width of 7 mm, and a height of 1 mm. Eight detection zones were selected, each a circle with a diameter of 7 mm. The distance between the centers of two adjacent detection zones was 1 mm. After detection, the peak, trough, second-peak, and second-trough values ​​were removed, resulting in four absorbance values. The average value was calculated and substituted into the formula A = kbc. The obtained COD concentration value was 309.0 mg / L, with an error of 3%.

[0040] Example 4

[0041] A COD concentration of 400 mg / L solution was prepared, and a small amount of inert inorganic insoluble powder was added. This powder was then placed into a detection disk chip with a length of 18 mm, a width of 7 mm, and a height of 1 mm. Ten detection zones were selected, each a circle with a diameter of 7 mm. The distance between the centers of two adjacent detection zones was 1.1 mm. After detection, the peak, trough, second-peak, and second-trough values ​​were removed, resulting in six absorbance values. The average value was calculated and substituted into the formula A = kbc. The obtained COD concentration value was 412.4 mg / L, with an error of 3.1%.

[0042] Comparative Example 1

[0043] A solution with a COD concentration of 400 mg / L was prepared, and a small amount of inert inorganic insoluble powder was added. This powder was then placed into a detection disk chip. The cube cavity had a length of 18 mm, a width of 7 mm, and a height of 1 mm. Ten detection zones were selected, each a circle with a diameter of 7 mm. The distance between the centers of two adjacent detection zones was 1.1 mm. After detection, ten absorbance values ​​were obtained. The average value was calculated and substituted into the formula A = kbc. The resulting COD concentration was 526.8 mg / L, with an error of 31.7%.

[0044] Comparative Example 2

[0045] A COD concentration of 400 mg / L solution was prepared, and a small amount of inert inorganic insoluble powder was added. This powder was then placed into a detection disk chip. The cube cavity had a length of 18 mm, a width of 7 mm, and a height of 1 mm. Ten detection zones were selected, each a circle with a diameter of 7 mm. The distance between the centers of two adjacent detection zones was 1.1 mm. After detection, peak and trough values ​​were removed, resulting in eight absorbance values. The average value was calculated and substituted into the formula A = kbc. The obtained COD concentration was 466.3 mg / L, with an error of 16.6%.

[0046] As can be seen from the data in the above embodiments, the COD detection method of the present invention can obtain a highly accurate COD detection value even when there is precipitation in the test liquid, and has good application prospects.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A detection disk chip, characterized in that, For implementing a COD detection method, the detection disk chip includes a disk chip body (1), which is made of transparent material. A cubic cavity (11) is opened on the inner side of the disk chip body (1). The cubic cavity (11) serves as a detection pool. The cubic cavity (11) is connected to the surface of the disk chip body (1) through at least one liquid inlet channel (12) and at least one liquid outlet channel (13). The disk chip body (1) includes a parallel incident surface (14) and an exit surface (15). The incident surface (14) and the exit surface (15) are both closed surfaces. The incident surface (14) and the exit surface (15) are parallel to two opposite sides of the cubic cavity (11). Multiple light sources are set on the incident surface, and multiple sensors are set on the exit surface in a corresponding manner, so that the sensors can receive the light beam emitted by the light source. The COD detection method includes: Step 1: In the detection cell of the horizontally set disk chip, take no less than 5 detection areas and detect the absorbance of the solution to be tested in the detection area along the vertical direction. The detection areas are arranged at equal intervals in the detection cell, and the edge of each detection area is inside the detection cell. Step 2: From the multiple absorbance detection results obtained, remove the peak value, valley value, second peak value and second valley value respectively, calculate the arithmetic mean of the remaining absorbance detection results, and calculate the COD value of the test solution based on the calibration dataset of absorbance and COD value. The method for obtaining the calibration dataset of absorbance and COD values ​​includes: preparing calibration solutions of various concentrations, irradiating the calibration solutions of different concentrations with detection light in the detection cell of the disk chip, and collecting the absorbance values ​​to obtain the calibration dataset of absorbance and COD values.

2. The detection disk chip as described in claim 1, characterized in that, The detection area is circular, and the centers of multiple detection areas are arranged at equal intervals along a straight line.

3. The detection disk chip as described in claim 1, characterized in that, The detection pool is rectangular, and multiple detection zones are arranged at equal intervals along the length of the detection pool.

4. The detection disk chip as described in claim 1, characterized in that, The number of detection zones is 10.

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