CN116626122A - Sensor and method for detecting chemical oxygen demand in water body - Google Patents

Abstract

The invention discloses a water chemical oxygen demand detection sensor, which comprises a microfluidic device and a gold three electrode, wherein a gold nanoparticle layer is covered on the surface of the gold three electrode, the microfluidic device comprises a cover die fixedly connected to the surface of the gold three electrode, a strip-shaped groove is concavely arranged on the side surface of the cover die facing the gold three electrode, a reaction cavity is formed between the strip-shaped groove and the gold three electrode, and a water inlet flow channel and a water outlet flow channel which are communicated with the reaction cavity are respectively penetrated on the cover die at positions corresponding to the two ends of the reaction cavity. The invention also discloses a method for detecting the chemical oxygen demand of the water body by using the detection sensor. The invention generates the electric signal on the electrode surface through the chemical reaction between the target analyte and the gold nano particles, indirectly measures the COD value of the target analyte by measuring the electric signal, has the advantages of convenient detection, high accuracy, low cost and no secondary pollution to the surrounding environment.

Description

Sensor and method for detecting chemical oxygen demand in water body

technical field

The invention relates to the technical field of sensors, in particular to a sensor and a detection method for detecting chemical oxygen demand in water bodies.

Background technique

With the development of industry and the growth of population in big cities, a large amount of urban wastewater is produced. However, due to the lack of people's awareness of environmental protection, a large amount of domestic sewage and factory wastewater will be discharged into lakes and reservoirs, resulting in eutrophication of water bodies. Chemical Oxygen Demand (COD) is a measure of the amount of organic matter in water. The chemical oxygen demand of water is usually measured with potassium dichromate as the oxidizing agent, which is defined as the amount of oxidizing agent consumed to oxidize reducing substances in 1 liter of water sample under certain conditions, after all oxidation, it is converted into The milligrams of oxygen required by the water sample, in mg/L. This method needs to use a variety of toxic chemical reagents, which is easy to cause secondary pollution, takes a long time to detect, and requires high requirements for operators, which increases the cost of detection and leads to inaccurate detection results.

Contents of the invention

Aiming at the deficiencies of the above-mentioned prior art, the technical problem to be solved by the present invention is: how to provide a sensor for detecting the chemical oxygen demand of water body which is convenient to detect, has high accuracy, and will not cause secondary pollution to the surrounding environment.

In order to solve the above technical problems, the present invention adopts the following technical solutions:

A detection sensor for chemical oxygen demand in water, comprising a microfluidic device and a gold three-electrode, the surface of the gold three-electrode is covered with a gold nanoparticle layer, the microfluidic device includes a cover mold fixedly connected to the surface of the gold three-electrode, The side of the cover mold facing the gold three-electrode is concavely provided with a strip-shaped groove, and the reaction chamber is formed between the strip-shaped groove and the gold three-electrode. Connected water inlet flow channel and water outlet flow channel.

As an optimization, the thickness of the gold nanoparticle layer is 400±50nm.

As an optimization, the water inlet channel includes a liquid inlet groove recessed on the side of the cover mold facing the gold three electrodes and located outside one end of the bar-shaped groove, and the water outlet channel includes a liquid inlet groove recessed on the side of the cover mold facing the gold three electrodes. The cover mold faces the liquid outlet groove on the side of the gold tri-electrode and is located outside the other end of the bar-shaped groove, and the liquid inlet groove and the liquid outlet groove are respectively formed as a liquid inlet cavity and a In the liquid outlet cavity, the side of the cover mold facing the gold three electrodes and between the liquid inlet groove and the strip groove is recessed with an inlet groove, and the inlet groove is connected to the liquid inlet groove and the strip groove respectively. The strip-shaped groove is connected, and an inlet flow channel is formed between the inlet groove and the gold three-electrode. The position between them is recessed with an outlet groove, the outlet groove is respectively connected with the liquid outlet groove and the strip groove, and the outlet flow channel is formed between the outlet groove and the gold three electrodes, and the corresponding inlet and outlet channels are respectively formed on the cover mold. The position of the liquid tank and the liquid outlet tank is pierced with a liquid inlet pipe and a liquid outlet pipe. One end of the liquid inlet pipe extends into the liquid inlet chamber, and the other end is located outside the cover mold. One end of the liquid storage tank extends into the outlet. Inside the liquid chamber, the other end is located outside the cover mold.

As an optimization, the groove depth of the strip groove is 150±50 μm.

The invention also discloses a method for detecting the chemical oxygen demand of water body, comprising the following steps:

(1) obtain three gold electrodes, the surface of the three gold electrodes is covered with a gold nanoparticle layer;

(2) Configure multiple water bodies with different COD values;

(3) One part of the water body is dropped on the surface of the gold tri-electrode, and an electrochemical workstation is used to detect the current between the working electrode and the counter electrode circuit on the gold tri-electrode to obtain a current response curve;

(4) After cleaning the surface of the three gold electrodes, repeat the operation step (3) until all water bodies are detected;

(5) According to the COD value of the water body and the corresponding current size, y=0.15x-2.3 is obtained by linear fitting, wherein x represents the current size, and y represents the COD value;

(6) Drop the water body to be detected on the surface of the gold tri-electrode, after detecting the current size between the working electrode and the counter electrode circuit on the gold tri-electrode according to the electrochemical workstation, calculate by the linear fitting formula in step (5) Get the COD value of the water body.

As an optimization, the above-mentioned detection sensor for chemical oxygen demand in water is used in step (1).

Compared with the prior art, the present invention has the following beneficial effects: the present invention generates an electrical signal on the electrode surface through a chemical reaction between the target analyte and the gold nanoparticle, and indirectly measures the COD value of the target analyte by measuring the magnitude of the electrical signal , convenient detection, high accuracy, low cost, and no secondary pollution to the surrounding environment.

Description of drawings

Fig. 1 is the cyclic voltammetry graph of detection sensor and bare gold three electrodes in the present invention;

Figure 2 is the current response curve of the bare gold three electrodes in pure water and glucose solutions with concentrations of 50 mg/L and 100 mg/L;

Fig. 3 is the electric current response curve figure in the glucose solution of 200mg/L, 300mg/L and 400mg/L of bare gold three electrodes in concentration;

Figure 4 is a linear fitting diagram of the current magnitude and concentration of the bare gold three electrodes in pure water and glucose solutions with concentrations of 50mg/L, 100mg/L, 200mg/L, 300mg/L and 400mg/L;

Fig. 5 is the current response curve diagram of detection sensor in the present invention in pure water and the glucose solution that concentration is 50mg/L, 100mg/L;

Fig. 6 is the current response graph of the detection sensor in the present invention in concentrations of 200mg/L, 300mg/L and 400mg/L glucose solution;

Fig. 7 is a linear fitting diagram of the current magnitude and concentration of the detection sensor in the present invention in pure water and glucose solutions with concentrations of 50mg/L, 100mg/L, 200mg/L, 300mg/L and 400mg/L.

specific implementation

The detection sensor of water body chemical oxygen demand in this specific embodiment comprises a microfluidic device and a gold three-electrode, and the surface of the gold three-electrode is covered with a layer of gold nanoparticle layer, and the microfluidic device includes a gold three-electrode fixedly connected on the surface The cover mold, the side of the cover mold facing the gold three electrodes is concavely provided with a strip groove, and the reaction chamber is formed between the strip groove and the gold three electrodes, and the positions corresponding to the two ends of the reaction chamber are respectively pierced on the cover mold There are water inlet flow channels and water outlet flow channels connected with the reaction chamber.

In this specific embodiment, the thickness of the gold nanoparticle layer is 400 nm.

In this specific embodiment, the water inlet channel includes a liquid inlet groove recessed on the side of the cover mold facing the gold three electrodes and located outside one end of the bar-shaped groove, and the water outlet channel includes A liquid outlet groove is recessed on the side of the cover mold facing the gold three electrodes and is located outside the other end of the bar-shaped groove. The liquid inlet groove and the liquid outlet groove are formed between the gold three electrodes respectively. A liquid chamber and a liquid outlet chamber, on the side of the cover mold facing the gold three electrodes and between the liquid inlet groove and the strip groove, an inlet groove is recessed, and the inlet groove is respectively connected to the liquid inlet groove. The groove communicates with the bar-shaped groove, and an inlet flow channel is formed between the inlet groove and the gold three-electrode. The position between the shaped grooves is concavely provided with an outlet groove, the outlet groove is respectively connected with the liquid outlet groove and the strip-shaped groove, and an outlet flow channel is formed between the outlet groove and the gold three electrodes, and on the cover mold A liquid inlet pipe and a liquid outlet pipe are respectively pierced corresponding to the positions of the liquid inlet tank and the liquid outlet groove. One end of the liquid inlet pipe extends into the liquid inlet chamber, the other end is located outside the cover mold, and one end of the liquid storage tank extends into the liquid outlet cavity, and the other end is located outside the cover mold.

In this specific implementation manner, the groove depth of the strip-shaped groove is 150 μm.

A method for detecting chemical oxygen demand in water, comprising the following steps:

(1) obtain three gold electrodes, the surface of the three gold electrodes is covered with a gold nanoparticle layer;

(2) Configure multiple water bodies with different COD values;

(3) One part of the water body is dropped on the surface of the gold tri-electrode, and an electrochemical workstation is used to detect the current between the working electrode and the counter electrode circuit on the gold tri-electrode to obtain a current response curve;

(4) After cleaning the surface of the three gold electrodes, repeat the operation step (3) until all water bodies are detected;

(5) According to the COD value of the water body and the corresponding current size, y=0.15x-2.3 is obtained by linear fitting, wherein x represents the current size, and y represents the COD value;

(6) Drop the water body to be detected on the surface of the gold tri-electrode, after detecting the current size between the working electrode and the counter electrode circuit on the gold tri-electrode according to the electrochemical workstation, calculate by the linear fitting formula in step (5) Get the COD value of the water body.

In this specific embodiment, the above-mentioned sensor for detecting the chemical oxygen demand of the water body is used in step (1).

Take 20mL (0.5mol/L) NaOH solution standard solution in a 25mL beaker, and use an electrochemical workstation to measure the cyclic voltammetry curve (CV) of the detection sensor and the bare gold three electrodes, as shown in Figure 1. The current response of the detection sensor is significantly larger than that of the bare gold tri-electrode, indicating the good conductivity of the gold nanoparticle layer.

When testing the chemical oxygen demand of water quality, glucose solution is usually used as the standard solution. Dissolve glucose of known quality in 0.5mol/L NaOH solution, configure glucose stock solutions of 50mg/L, 100mg/L, 200mg/L, 300mg/L and 400mg/L as chemical oxygen demand standard solution, take Put 20mL standard solution in a 25mL beaker, insert the bare gold three-electrode into the electrode adapter, cover the electrode adapter on the beaker, so that the bare gold three-electrode part is just completely immersed in the standard solution, and use the electrochemical workstation for measurement. Measure the current response curves caused by the bare gold three-electrode in different concentrations of glucose standard solutions, and finally draw a standard curve according to the changes in current magnitude and glucose concentration, as shown in Figure 2 and Figure 3. As can be seen from the figure, the concentration of the glucose solution has a linear relationship with the magnitude of the current, and linear fitting is performed, as shown in Figure 4, the linear range is 0-200 mg/L, and the relationship between the concentration y of the glucose solution and the current x is y=0.0649x+0.21, the correlation coefficient is 0.998. This shows that the current of the bare gold three-electrode has a good correlation with the concentration of the glucose solution, so the chemical oxygen demand of the water sample can be judged by the change of the current.

Utilize the detection sensor of the water body chemical oxygen demand in this specific embodiment to measure the current response curve caused by the glucose standard solution of different concentrations, then draw a standard curve according to the variation of the current size and the glucose concentration, as shown in Figure 5 and Figure 6 . It can be seen from the figure that the concentration of the glucose solution has a linear relationship with the magnitude of the current, and the linear fitting is performed. As shown in Figure 7, the linear range is 0-400 mg/L. Compared with the bare gold three electrodes without depositing gold nanoparticles , the linear range is doubled. The relationship between the concentration y of the glucose solution and the current x is y=0.15x-2.3, and the correlation coefficient is 0.989. The current measured by the detection sensor in this embodiment has a good linearity with the concentration of the glucose solution.

Utilize the detection sensor of water body chemical oxygen demand in this specific embodiment to measure and carry out the detection of chemical oxygen demand to a plurality of samples, as shown in table 1:

Table 1

According to the comparison between the measurement results of the sample of the detection sensor and the measurement results of the national standard HJ828-2017, each sample was measured 3 times in parallel, and the relative error between the two was between 3.7% and 8%, indicating that this method can be applied to the general surface Rapid determination of COD value of water samples.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than limit the technical solutions. Those of ordinary skill in the art should understand that those who modify or replace the technical solutions of the present invention without departing from the present technology The purpose and scope of the scheme should be included in the scope of the claims of the present invention.

Claims (6)

1. A detection sensor of water body chemical oxygen demand, is characterized in that: comprise microfluidic device and gold three electrodes, the surface of gold three electrodes is covered with one deck gold nanoparticle layer, and microfluidic device includes being fixedly connected in gold three electrodes The cover mold on the surface, the side of the cover mold facing the gold three electrodes is concavely provided with a strip groove, and the reaction chamber is formed between the strip groove and the gold three electrodes, and the positions on the cover mold correspond to the two ends of the reaction chamber A water inlet channel and an outlet water channel communicated with the reaction chamber are perforated. 2 . The sensor for detecting chemical oxygen demand in water bodies according to claim 1 , characterized in that: the thickness of the gold nanoparticle layer is 400±50 nm. 3. The sensor for detecting the chemical oxygen demand of water body according to claim 1, characterized in that: the water inlet flow channel is concavely arranged on the side of the cover mold facing the gold tri-electrode and is located in a bar-shaped A liquid inlet groove outside one end of the groove, and the water outlet channel includes a liquid outlet groove recessed on the side of the cover mold facing the gold three electrodes and located outside the other end of the strip-shaped groove. The liquid tank and the liquid outlet tank are respectively formed as a liquid inlet chamber and a liquid outlet chamber with the gold three electrodes, and the cover mold is located on the side of the gold three electrodes and is located between the liquid inlet tank and the strip groove The position between them is concavely provided with an inlet groove, the inlet groove communicates with the liquid inlet groove and the strip groove respectively, an inlet flow channel is formed between the inlet groove and the gold three electrodes, and the cover mold faces the gold electrode. On one side of the three electrodes and between the liquid outlet groove and the strip-shaped groove, an outlet groove is recessed, the outlet groove is respectively connected with the liquid outlet groove and the strip-shaped groove, and the outlet groove is connected to the strip-shaped groove. An outlet flow channel is formed between the gold three electrodes, and a liquid inlet pipe and a liquid outlet pipe are pierced on the cover mold corresponding to the positions of the liquid inlet groove and the liquid outlet groove respectively, and one end of the liquid inlet pipe extends into the liquid inlet chamber , the other end is located outside the cover mold, one end of the liquid storage tank extends into the liquid outlet cavity, and the other end is located outside the cover mold. 4. The sensor for detecting the chemical oxygen demand of water body according to claim 1, characterized in that: the groove depth of the strip-shaped groove is 150±50 μm. 5. A detection method for chemical oxygen demand in water, characterized in that: comprising the following steps: (1) Obtain the gold three-electrode, the surface of the gold three-electrode is covered with a layer of gold nanoparticle layer; (2) Configure multiple water bodies with different COD values; (3) Drop one part of the water on the surface of the gold tri-electrode, use the electrochemical workstation to detect the current between the working electrode and the counter electrode circuit on the gold tri-electrode, and obtain the current response curve; (4) After cleaning the surface of the gold three electrodes, repeat the operation step (3) until all the water bodies are detected; (5) According to the COD value of the water body and the corresponding current value, y=0.15x-2.3 is obtained through linear fitting, where x represents the current value and y represents the COD value; (6) Drop the water body to be tested on the surface of the gold tri-electrode, and after detecting the current between the working electrode and the counter electrode circuit on the gold tri-electrode according to the electrochemical workstation, calculate by the linear fitting formula in step (5) Get the COD value of the water body. 6. A method for detecting chemical oxygen demand in water bodies according to claim 5, characterized in that: in step (1), the detection method for chemical oxygen demand in water bodies described in any one of claims 1 to 4 is used sensor.