CN107367542A - Portable flow field type electrode heavy metal ion detection device and electrode card - Google Patents

Abstract

The embodiment of the present invention provides a portable flow field type electrode heavy metal ion detection device assembled by an electrode card and a thin-layer flow cell. Electrode; the electrode card is pluggably and tightly inserted into the card slot of the thin-layer flow cell, the working area on the surface of the electrode card extends into the microchannel in the thin-layer flow cell, and the three electrodes are in the working area along the to-be-measured The flow field distribution of the solution. The present invention designs the shape of the distribution of three electrodes by analyzing the flow field in the microchannel, which can obtain a longer action time and relatively ideal stability in the enrichment process of ASV analysis, which helps to improve the sensitivity and reproducibility of detection sex. The embodiment of the present invention also provides an electrode card with a flow field electrode used in the detection device.

Description

Portable flow field electrode heavy metal ion detection device and electrode card

technical field

The invention relates to the technical field of environmental detection, in particular to a portable flow field type electrode heavy metal ion detection device, which can be used for rapid detection of trace heavy metal ions in a solution by anodic stripping voltammetry analysis. The invention also provides an electrode card with a flow field electrode used in the detection device.

Background technique

A large amount of electronic waste generated by the development of the global electronic and electrical industry has caused serious environmental pollution problems and posed severe challenges to the global ecological environment. In recent years, countries have taken active measures to control the pollution and damage to the ecological environment caused by electronic products. For example, the RoHS directive issued by the European Union restricts the use of certain hazardous substances in electronic and electrical equipment entering the EU market, basically covering all types of electronic and electrical equipment that may be used in daily life. The restricted hazardous substances include lead (Pb) ﹑Heavy metals such as cadmium (Cd) and mercury (Hg).

At present, although the pre-treatment technology of electrical products is very mature, for example, microwave digestion technology is used to achieve batch processing, and its equipment does not have high requirements on the environment and site, so it can be used for on-site testing; To detect and analyze the content of heavy metals, the traditional element testing methods include atomic absorption spectrophotometry and inductively coupled plasma atomic emission spectrometry, but the detection instruments of these methods require a large working space and a suitable working environment, and have high requirements for power supply , Need ventilation system, gas cylinder and other supporting devices, and some also need circulating cooling water system. Most of the above-mentioned detection devices are large-scale instruments, which are generally expensive, consume a large amount of detection samples, and consume manpower. They are not suitable for rapid on-site detection, making it difficult to improve the efficiency of on-site detection of heavy metal ions. Anodic stripping voltammetry (Anodic Stripping Voltammetry, ASV) as an electrochemical analysis method, its detection limit can reach the ppb-ppt level, which fully meets the sensitivity requirements of heavy metal ion detection. Based on ASV, the on-site rapid detection of heavy metal ions is Expected technological development direction.

The traditional ASV heavy metal ion detection device is a three-electrode system in a beaker. The three electrodes consist of a working electrode (mostly a mercury or mercury film electrode), a counter electrode (mostly a strip-shaped platinum wire electrode) and a reference electrode (mostly a rod-shaped electrode). Calomel electrode or silver-silver chloride electrode), the heavy metal ion solution to be tested is placed in the beaker; during detection, a voltage is applied between the electrodes, and pre-electrolysis is performed first, so that the heavy metal ions in the solution are reduced and precipitated into metal enriched in The surface of the working electrode; and then stripping, so that the heavy metal to be measured deposited on the surface of the working electrode is oxidized into ions and stripped out, and the concentration of the heavy metal ion to be measured can be determined by the peak current obtained on the stripping voltammetry curve; although the above-mentioned traditional device is used for ASV Analysis can also detect trace heavy metal ions in the sample solution, but the detection process has the disadvantages of large consumption of sample solution, long pre-electrolysis time, and poor reproducibility of test results.

The research of people such as Zhiwei Zou and Am Jang discloses a kind of lab-on-a-chip sensor for in situ detection of heavy metal ions. The two ends are respectively provided with straight-through inlet and outlet of the solution to be tested; each set of electrodes is a three-electrode system, in which the working electrode is a bismuth electrode, the counter electrode is a gold electrode, and the reference electrode is a silver-silver chloride electrode , the lead wires connecting the electrodes are arranged to form a contact area. The above-mentioned chip sensor detection device uses micro-electromechanical system technology, based on the concept of a chip lab, to realize the miniaturization of the ASV detection instrument, and to avoid the use of mercury electrodes from polluting the environment; Considering the relationship between the flow field distribution and the effective working surface of the electrode, it not only prolongs the enrichment operation time, but also increases the error-generating links.

In view of the shortcomings of the above-mentioned heavy metal ion detection device with thin-layer micro-regions, in order to better realize the on-site rapid detection of heavy metal ions in a large number of samples, it is necessary to improve the detection device to increase the concentration of heavy metals on the electrode surface of the detection device during the ASV analysis process. Enrichment efficiency.

Contents of the invention

The present invention aims at the technical problem of low metal enrichment efficiency on the electrode existing in the ASV analysis process of the existing heavy metal ion detection device with a microchannel, and provides a novel portable flow field type electrode heavy metal ion detection device and The electrode card can effectively improve the enrichment efficiency of metal on the electrode surface by optimizing the electrode to form a flow field electrode.

In order to solve the above technical problems, an embodiment of the present invention provides a portable flow field type electrode heavy metal ion detection device, including a microchannel and three electrodes extending into the microchannel, the three electrodes are respectively the working electrode, Counter electrode and reference electrode, where:

The microchannel is a thin-layered cavity arranged in the thin-layer flow cell; the three electrodes are planar all-solid electrodes arranged on the substrate of an electrode card; The two ends of the channel are provided with a liquid inlet pipe and a liquid outlet pipe that communicate with the outside, and the thin-layer flow cell also includes a card slot that matches the shape of the electrode card provided under the thin-layer cavity; the electrode card can be The plug-and-pull is tightly inserted into the card slot of the thin-layer flow cell, and the area where the surface of the electrode card falls into the microchannel is the working area, and the three electrodes are in the working area along the line to be tested. The flow field distribution of the solution, the contact pins of the three electrodes extend out of the slot. The pluggable design of the electrode card can realize the free replacement of the electrode card according to the needs of continuous work, avoiding cross-contamination between samples; when working, apply voltage to the three electrodes on the electrode card through the contact pins, and detect the current between the electrodes at the same time.

Preferably, the lamellar cavity of the microchannel is set in a saddle shape, and the liquid inlet pipe and the liquid outlet pipe are respectively connected to the two top ends of the laminar cavity along the tangential direction; at this time, the The flow field of the solution to be tested in the microchannel is S-shaped, and the three electrodes are distributed along the S-shaped flow field in the working area. The shape of the lamellar cavity of the microchannel can be selected according to the needs, and besides the saddle shape, other shapes such as rectangle, ellipse or circle can also be selected.

Further preferably, the three electrodes are distributed in the first half, the second half or the entire area of the S-shaped flow field in the working area; wherein, the three electrodes in the working area may be in the form of It can be set in series or in parallel.

As a preference of the aforementioned technical solution, the sharp corners of the edges of the three electrodes are rounded, and optionally, the edges of the conductive connection parts of the three electrodes are also set as smooth curves.

As a preference of the aforementioned technical solution, the width of the working electrode and the reference electrode is larger than that of the counter electrode.

As a preference of the foregoing technical solution, the liquid inlet pipe and the liquid outlet pipe have protruding pipe openings.

The embodiment of the present invention also provides an electrode card, which is used in the aforementioned technical solution and assembled with the thin-layer flow cell to form the portable flow field type electrode heavy metal ion detection device.

In the technical scheme of the above-mentioned embodiments of the present invention, the three electrodes in the detection device are transformed by analyzing the flow field in the thin-layer micro-region type microchannel, so that the electrodes are distributed along the flow field in the microchannel to form a The heavy metal ion detection device of the field electrode has the following beneficial effects:

1. In the detection device of the embodiment of the present invention, the three electrodes of the electrode card are designed in a shape distributed with the flow field, such as S-shape, which is different from traditional electrode distribution shapes such as straight lines or circles, and can be used in the enrichment of ASV analysis Longer action time and ideal stability are obtained in the process, which helps to improve the sensitivity and reproducibility of detection;

2. Since the electrode needs to work in two working states of enrichment in a flowing state and stripping in a static state, the embodiment of the present invention increases the area of the working electrode and the reference electrode, which can improve the working state in the flowing state. efficiency;

3. In the embodiment of the present invention, rounding is carried out on the sharp part of the electrode card in the detection device, which can avoid the generation of the sharp point effect; and the conductive connection part on the electrode card is modified into a smooth curve, which can be made by screen printing In the process, the amount of conductive ink is saved, and the production cost is reduced.

Description of drawings

Figure 1 is a schematic diagram of the ASV analysis principle;

2 is a schematic diagram of an ASV detection device of a traditional three-electrode system;

3 is a perspective view of a portable flow field electrode heavy metal ion detection device according to an embodiment of the present invention;

Fig. 4 is a three-dimensional structure perspective view of the detection device in Fig. 3;

5 is a schematic structural view of the thin-layer flow cell of the detection device in FIG. 3, wherein FIG. 5a is a perspective view of the three-dimensional structure of the thin-layer flow cell, and FIG. 5b is an A-A sectional view of the thin-layer flow cell in FIG. 5a;

Fig. 6 is a schematic structural view of an electrode card having three electrodes in the detection device of Fig. 3, wherein Fig. 6a is a perspective view of the electrode card, and Fig. 6b is a top view of the electrode card;

Fig. 7 is a schematic diagram of the assembled structure of the detection device in Fig. 3;

Fig. 8 is the structural representation of three electrodes of conventional shape;

Fig. 9 is a schematic diagram of the flow field distribution in the angle of view of direction A in the saddle-shaped thin-layer cavity of the detection device shown in Fig. 5a;

Fig. 10 is a schematic structural diagram of a series flow field electrode according to an embodiment of the present invention. Three electrodes are arranged in parallel and distributed along an S-shaped flow field. The shape is the lower half of an S shape, and the shape of the electrode in Figure 10c is the entire S shape;

Figure 11 is a schematic structural view of a parallel flow field electrode in an embodiment of the present invention, three electrodes are arranged in series and distributed along an S-shaped flow field, wherein the shape of the electrode in Figure 11a is the upper half of an S shape, and the electrode in Figure 11b The shape is the lower half of an S shape, and the shape of the electrode in Figure 11c is the entire S shape;

Fig. 12 is a schematic structural diagram of a flow field electrode after rounding according to an embodiment of the present invention, wherein Figs. 12a to 12c are electrodes in series, and Figs. 12d to 12f are electrodes in parallel;

Fig. 13 is a schematic diagram of the layered structure of the electrode card in screen printing according to the embodiment of the present invention.

[Description of main component symbols]

c1-beaker; c2-cover plate; c3-solution to be tested; WE-carbon steel working electrode; CE-stainless steel plate auxiliary electrode; RE-reference electrode; c4-non-woven fabric;

1-thin-layer flow cell; 11-microchannel; 12-inlet pipe; 13-outlet pipe; 14-card slot; 2-electrode card; 21-substrate; 22-working area; 23-reference electrode; 24-working electrode; 25-counter electrode; 26-contact pin; Z-S-shaped flow field; Z1-first ideal zone; Z2-second ideal zone.

detailed description

In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will describe in detail with reference to the drawings and specific embodiments.

The present invention adopts anodic stripping voltammetry to detect the concentration of heavy metal ions in the solution. The detection method belongs to a kind of voltammetry in electrochemical analysis. Stripping voltammetry is formed on the basis of voltammetry combined with controlled potential electrolysis enrichment. Its detection limit can reach ppb~ppt level, and it can be applied to the analysis and detection of more than 30 elements. The stripping voltammetry analysis process is divided into two parts: enrichment (pre-electrolysis) and stripping. According to the stripping reactions that occur on different electrodes, it is divided into anodic stripping voltammetry (ASV) and cathodic stripping voltammetry (CSV). Among them, ASV is suitable for the determination of metal ions, and has become a common method for heavy metal detection due to its extremely low cost and high sensitivity.

The usual ASV detection principle is shown in Figure 1. The voltammetric curve is shown in Figure 1. First, the working electrode is used as the cathode for pre-electrolysis, and the cathode potential is controlled within the limit diffusion current potential range of the heavy metal ion M ⁿ⁺ to be measured (generally higher than the half-wave potential E _{1/ 2} minus 0.2~0.3V, corresponding to the D position in Figure 1), so that Mn ⁺ is reduced to metal and enriched on the working electrode; after the pre-electrolysis is completed, stop stirring and let stand Afterwards, stripping begins, and the potential of the working electrode is scanned from negative to positive at a constant speed. At this time, the M metal deposited on the working electrode is re-anodized into ion Mn ^{+ and} enters the solution; the stripping current is recorded during the stripping process, and the potential According to the peak height of the voltammetry curve during dissolution, the concentration of the metal substance to be tested can be determined.

An existing ASV device is shown in Figure 2. A three-electrode system composed of a carbon steel working electrode WE, a reference electrode RE, and a stainless steel auxiliary electrode CE wrapped in non-woven fabric c4 is inserted into a container containing traces of heavy metal ions. The test is carried out in the beaker c1 of the solution c3 to be tested; during the test, a voltage is first applied between the working electrode and the reference electrode. Reduction precipitation (similar to electrolysis or electroplating process), the longer the potential is applied on the working electrode, the more metals are deposited on the surface of the reduction, and the enrichment voltammetry curve in the negative current region in Figure 1 is obtained; when there is enough When the metal is enriched, after the solution to be tested is kept for a certain period of time, the stripping process is carried out: increase the forward voltage to the working electrode, and the metal deposited on the surface of the working electrode will be oxidized and stripped out. Constitute the current in the loop and record the corresponding potential of the working electrode to obtain the stripping voltammetry curve in the forward direction of the current in Figure 1. A peak current i _p of μA level or less can be measured. If all operating conditions are controlled to be highly consistent, Then the magnitude of the peak current i _p is only linearly positively correlated with the concentration of the metal ion to be tested in the solution, and the concentration to be tested can be obtained by comparing with the standard solution under the same conditions. Trace heavy metal ions in the sample solution can be detected by using the above-mentioned traditional ASV detection device, which has high sensitivity. However, the detection usually carried out in a beaker has many defects such as a large amount of sample solution, a long pre-electrolysis time, and poor reproducibility.

With the development of microfluidic technology and the demand for miniaturization of detection devices, a microfluidic detection device for ASV detection of heavy metal ions has emerged, which can effectively overcome some of the defects in the detection of the aforementioned traditional ASV devices; the microfluidic The detection device combines the microchannel with the chip sensor, and integrates the various processes of analysis and detection on the chip sensor in the microchannel to complete; the small scale of the microchannel not only makes the analysis equipment miniaturized in overall size, but also brings many microns and The nano effect makes it significantly improved in analytical performance compared with traditional analytical systems. However, the current microfluidic detection device has a simple electrode design and does not fully consider the relationship between electrode shape and detection efficiency, which not only prolongs the enrichment operation time, but also increases the error-generating links.

The technical scheme of the present invention aims at the deficiencies of the existing ASV detection device, and transforms the three electrodes on the electrode card forming the detection device by analyzing the flow field in the thin-layer micro-area microchannel, so that the electrodes are in the microchannel distributed along the flow field.

In order to realize the above technical solution, as shown in FIGS. 3 to 7 , an embodiment of the present invention provides a portable flow field type electrode heavy metal ion detection device. The detection device is assembled from two parts, the electrode card 2 and the thin-layer flow cell 1. The assembled detection device is shown in Figure 3, and its internal structure is shown in Figure 4. The assembled detection device contains microchannels 11 and three electrodes extending into the microchannel 11, the microchannel 11 is a laminar cavity arranged in the thin layer flow cell 1; The liquid inlet pipe 12 and the liquid outlet pipe 13, the thin-layer flow cell 1 also includes a slot 14 matching the shape of the electrode card 2 arranged below the thin-layer cavity, and the shape mechanism of the thin-layer flow cell 1 is shown in Figure 5a and Figure 5b Show;

An embodiment of the electrode card 2 is shown in Figure 6a and Figure 6b. The three electrodes are planar all-solid electrodes arranged on the substrate 21 of an electrode card 2. In this embodiment, the three strip electrodes start from the left. To the right are the counter electrode 25, the working electrode 24 and the reference electrode 23; the electrode card 2 can be pluggably and tightly inserted into the slot 14 of the thin-layer flow cell 1, and after the electrode card 2 is completely inserted into the slot 14, the electrode The area where the surface of the card 2 is located in the microchannel 11 is the working area 22, and the three electrodes are distributed along the flow field of the solution to be measured in the working area 22. The contact pins 26 of the three electrodes stretch out from the microchannel 11, and the electrode card 2 The way of assembling and cooperating with the thin-layer flow cell 1 is shown in FIG. 7 .

The overall shape of the thin-layer flow cell 1 is usually designed as a cuboid, and can also be designed as other shapes, as long as the interior is convenient to accommodate structures such as microchannels 11; in order to facilitate the control of internal liquid flow during the detection process, the thin-layer flow cell Pool 1 is made of transparent material, and non-transparent material can also be selected according to actual needs.

In the present embodiment, as shown in Fig. 4 and Fig. 5, the middle section of the cavity of the microchannel 11 is rectangular, the two ends are semicircular, and the whole presents a saddle shape; the microchannel of the detection device of the present invention is not limited to the above-mentioned The saddle shape, on the basis of the thin-layer cavity structure, can also be designed into a variety of shapes such as rectangle, circle, ellipse, among which the rectangle and saddle shape are the most commonly used.

The liquid inlet pipeline 12 and the liquid outlet pipeline 13 are respectively connected at the two tops of the saddle-shaped cavity of the microchannel 11, and the connection point nozzle direction is tangent to the cavity edge at this point, and the two pipelines lead to the thin cavity by the microchannel 11. On the outside of the laminar flow pool 1, a protruding pipe mouth is formed on the outer wall, and the inner diameter of the pipe is less than or equal to the thickness of the microchannel 11; the connection position of the liquid inlet pipe and the liquid outlet pipe with the microchannel and the direction of the nozzle also have multiple options. Usually the liquid inlet pipe and the liquid outlet pipe are respectively connected to the two ends of the cavity length direction of the microchannel to facilitate the solution to flow through the entire microchannel smoothly, and the direction of the nozzle is usually designed as the normal line or Tangent direction, and other directions can also be selected according to actual needs.

When the cavity of the microchannel 11 is saddle-shaped, the liquid inlet pipeline 12 and the liquid outlet pipeline 13 are respectively connected to the two tops of the saddle-shaped cavity and the nozzle direction is tangent to the cavity edge at the connection point, the solution to be measured is in the The flow in the microchannel is smooth and the flow rate is moderate. The thickness of the diffusion layer of the heavy metal ions to be measured in the solution is large, and the reactants have sufficient time to deposit on the electrode surface, which is conducive to the reduction of heavy metal ions to metals and enrichment on the working electrode. Therefore, The structure of the above-mentioned microchannel and pipeline is a preferred embodiment of the detection device of the present invention. In the following examples, the saddle-shaped microchannel is used as the basic shape for description.

In this embodiment, there is a rectangular sheet-shaped slot 14 leading to the outer wall of the thin-layer flow cell 1 below the microchannel 11. The shape and size of the slot 14 match the electrode card 2 used in this embodiment. The electrode card 2 When inserted into the card slot 14, a tight fit can be formed, and the inserted electrode card 2 can be easily pulled out for replacement; when the electrode card 2 is inserted into the card slot 14 to the end, the working area 22 is completely located in the microchannel 11, and the area of the working area 22 It contains three electrodes, and the microchannel 11 and these three electrodes form the core working area when detecting heavy metal ions; the length of the electrode card 2 is slightly larger than the depth of the slot 14, and one end of the electrode card 2 is left outside the slot 14 after being embedded. This end has three electrode contact pins 26, which serve as an interface for electrical connection with the electrochemical workstation during detection.

In the detection device of this embodiment, the electrode card 2 and the thin-layer flow cell 1 constitute a complete microfluidic system. Using the portable flow field type electrode heavy metal ion detection device described in the above examples, the process for detecting heavy metal ions in solution by the ASV method is as follows:

1. Preparation of the solution to be tested: add bismuth ion (Bi ³⁺ ) solution and acidic bottom solution to the solution to be tested containing heavy metal ions;

2. Assembling of the detection system: Connect the liquid inlet pipe 12 and the liquid outlet pipe 13 of the thin-layer flow cell to the liquid inlet hose and the liquid outlet hose respectively, and the liquid inlet hose is stretched into the solution to be tested, and the A peristaltic pump is arranged on the liquid hose, and the contact pin 26 of the electrode card 2 is connected to the corresponding interface of the electrochemical analysis workstation;

3. Enrichment process: adjust the electrochemical analysis workstation, apply a negative voltage between the working electrode 24 and the reference electrode 23; turn on the peristaltic pump, drive the solution to be tested to flow from the inlet pipe 12 into the microchannel 11 to start pre-electrolysis, and the waste liquid will automatically The outlet pipe 13 is discharged; after the pre-electrolysis is completed, the peristaltic pump is turned off, and the solution to be tested is left standing;

4. Dissolution process: adjust the electrochemical analysis workstation so that the voltage applied between the working electrode 24 and the reference electrode 23 is scanned from negative to positive, and the heavy metal to be measured enriched on the working electrode 24 is dissolved again;

5. Detection data collection: record the current and potential of the working electrode in the circuits of the working electrode 24 and the counter electrode 25 during the dissolution process, and obtain the dissolution voltammetry curve.

The peak current ip of the solution to be tested is obtained from the stripping _{voltammetry curve} , and the concentration of the solution to be tested can be obtained by comparing ip with the peak current value detected by the standard sample of known concentration under the same conditions.

As the electrode card 2 used in combination with the thin-layer flow cell 1, its conventional structure is shown in Figure 8: three electrodes are arranged in the working area 22 on the substrate 21 of the electrode card 2, and the reference is sequentially from top to bottom. The electrode 23, the working electrode 24 and the counter electrode 25 form a series three-electrode system. During the pre-electrolysis process of ASV detection, the electrolysis current of the planar electrode with solution laminar flow motion on the surface is:

In the above formula, L is the electrode size parallel to the laminar flow direction; b is the electrode size perpendicular to the laminar flow direction; u is the flow velocity of the solution; ν is the kinematic viscosity of the solution. According to the formula, increasing the flow rate and increasing the electrode area can increase the electrolysis current, which is beneficial to improve the efficiency of pre-electrolysis, but the large electrode area will cause the current density to decrease and the background noise to increase, which is extremely unfavorable for quantitative analysis. Under the premise of not increasing the electrode area, the shape of the electrode is designed so that the effective working area is located in the area with a large solution flow rate as much as possible. Taking the electrode card 2 shown in Figure 8 as an example, if it is used in conjunction with the saddle-shaped microchannel 11, the working area 22 overlaps with the microchannel 11, and the part where the three electrodes are located in the working area 22 is the effective part of the electrode. working department.

In order to make the three electrodes have more effective working parts in the saddle-shaped microchannel 11, the conventional electrodes of the electrode card 2 shown in FIG. 8 are improved. First, the flow field distribution in the microchannel 11 is simulated according to fluid dynamics theory and software calculations, using the saddle-shaped microchannel 11 and the pipeline connection in the embodiment shown in Figure 5, under the same viewing angle as Figure 5, its The whole flow field in the microchannel 11 roughly presents an S-shaped distribution as shown in Figure 9 , as shown in Figure 9; there are two ideal regions with relatively stable flow velocities in the S-shaped flow field Z, and the area near the mouth of the liquid inlet pipeline 12 The area located in the upper half of the S-shape has the fastest flow velocity, which is the first ideal zone Z1, and the area located in the lower half of the S-shape near the mouth of the liquid outlet pipeline 13 has a slow but steady flow velocity, which is the second ideal zone Z2 ; Based on the above-mentioned flow field distribution state, the three electrodes in the working area 22 on the electrode card 2 are improved to have a shape distributed along the flow field, and the flow field type electrodes designed and manufactured are different from ordinary shape electrodes. The type of electrode is used to detect heavy metal ions, and it is expected to obtain a long action time and relatively ideal stability, which will help to improve the sensitivity and reproducibility of the detection.

In view of the consideration of the effective use of the flow field, the improved flow field electrode can be a full flow field electrode, that is, the electrodes are distributed in the entire S-shaped flow field including the first ideal zone Z1 and the second ideal zone Z2; at the same time, the improved The final flow field electrode can also be a semi-flow field electrode, that is, the electrodes are distributed in the first ideal zone Z1 (the first half of the S-shaped flow field Z, that is, the upper half of the S-shape) or the second ideal zone Z2 (S-shaped The second half of the flow field Z, that is, the lower half of the S shape); on the basis of the electrodes of the electrode card 2 shown in Figure 8, the improved block flow field electrodes are shown in Figures 10a to 10c, in which The electrodes are respectively distributed in the upper half, lower half and the entire S-shaped area of the S-shaped flow field. The three electrodes of the electrode card 2 are arranged in series in the working area 22, as shown in the figure from top to bottom as the reference electrode 23 , the working electrode 24 and the counter electrode 25.

As another preferred embodiment, the improved flow field electrodes based on the electrodes of the electrode card 2 shown in Figure 8 are strips arranged in parallel, as shown in Figures 11a to 11c, where the electrodes are distributed In the upper half, lower half and the entire S-shaped area of the flow field, the three electrodes of the electrode card 2 are arranged parallel to each other in parallel in the working area 22, as shown in the figure from left to right: the counter electrode 25, the working electrode 24 and reference electrode 23.

The use of the three electrodes with the above-mentioned improved shape can obtain better action time and ideal stability without increasing the overall area of the electrodes, which helps to improve the sensitivity and reproducibility of detection.

Both the above-mentioned block and strip electrodes have sharp corners, which will produce a sharp point effect. The sharper the sharp corners, the stronger the physical effects (such as charge density, etc.) caused. Therefore, as a better embodiment, the sharp corners of the electrodes can be The rounding treatment was carried out to avoid the generation of the tip effect; in addition, considering the production cost, the edge of the conductive connection part was also modified to a smooth curve, taking shortcuts as much as possible, and saving electrode materials to the greatest extent; the improved flow through the above rounding The field electrodes are shown in Figures 12a to 12f, which correspond to improvements of the electrodes shown in Figures 10a to 10c and Figures 11a to 11c respectively.

The three electrodes on the electrode card in the present invention have two working states during detection: under the solution flow state in the enrichment process, apply voltage between the working electrode and the reference electrode for electrolysis; the solution in the stripping process is in a static state Next, a current is detected between the working electrode and the counter electrode. In order to improve the electrolytic enrichment efficiency under the flowing state of the solution, it is necessary to increase the area of the working electrode and the reference electrode, while the solution is in a static state when the counter electrode is working, and is not sensitive to the area and shape, so it can be improved in the above electrode shape Further improvement is made on the basis of increasing the area of the working electrode and the reference electrode, as shown in Figure 12a to Figure 12c, among the three strip-shaped electrodes in the figure, the width of the working electrode 24 and the reference electrode 23 is larger than that of the counter electrode 25 .

Traditional ion-selective electrodes have limitations in the scope of use, which is rooted in the use of a liquid internally filled reference electrolyte; the electrode card described in the above-mentioned embodiments of the present invention uses a pure planar all-solid-state electrode, which has the ability to enrich The advantages of short time, fast voltage scanning, automatic compensation of iR drop, and reduction of impurity ion interference can solve the problems that traditional liquid ion selective electrodes are inconvenient to carry, cannot be inverted, and are not resistant to high temperature and high pressure;

Screen printing technology is currently the main method for preparing disposable electrochemical sensor electrodes, and the electrode card in the implementation of the present invention can be made by screen printing technology. Screen printing uses a screen printing plate as a mold, and the size and shape of the sensor electrodes produced can be changed, which is easy to realize the miniaturization and integration of sensor electrodes; using the screen printing process, it is convenient to print three electrodes on the same electrode On the base material of the card, a pure planar all-solid electrode on the surface of the electrode card of the embodiment of the present invention is fabricated.

According to the requirements of ASV for the characteristics of the three electrodes, combined with the characteristics of the screen printing electrode, the material and structure of each electrode are clarified:

For the working electrode, the resistance is required to be small and the specific surface is large, so silver with strong conductivity is selected for the bottom layer, and a layer of carbon is covered on the conductive silver layer to form the surface of the working electrode of the bare carbon layer; the reference electrode requires a large resistance , the potential is stable, and it is divided into working area and non-working area. The bottom layer chooses conductive silver, and there is a certain distance fault between the working area and the non-working area in the silver layer. The surface layer of the working area uses silver-silver chloride, and the non-working area The surface layer of the area uses carbon, the carbon layer is in direct contact with the silver-silver chloride layer and covers the underlying fault area, and the resistance of the electrode is regulated by changing the distance between the underlying faults; the electrode requires low resistance and stable surface properties, choose silver for the bottom layer, and carbon for the surface layer; Finally, choose insulating ink to cover the non-working area. Combining the materials required for each layer of the three electrodes, design the electrode printing layer, as shown in Figure 13, first print the bottom conductive silver layer on the substrate material, then print the silver-silver chloride layer, then print the carbon layer, and finally print the insulating layer .

Common knowledge such as the specific structures and characteristics known in the above-mentioned schemes are not described here; each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts of the embodiments can be referred to each other, and the technical features involved in each embodiment can be combined with each other on the premise that there is no conflict between them.

In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "upper", "lower", "front", "rear" etc. are based on the drawings and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as limiting the present invention; in addition, the terms "first" and "second" are used only are for descriptive purposes and should not be construed as indicating or implying relative importance.

The above is only a preferred embodiment of the present invention, and it should be pointed out that for those of ordinary skill in the art, some improvements and modifications can also be made without departing from the principles of the present invention. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (10)

1. A portable flow field type electrode heavy metal ion detection device, comprising a microchannel (11) and three electrodes extending into the microchannel (11), the three electrodes are respectively the working electrode (24), the pair The electrode (25) and the reference electrode (23), are characterized in that the microchannel (11) is a thin-layered cavity arranged in the thin-layer flow cell (1); the three electrodes are planar full A solid-state electrode is set on a substrate (21) of an electrode card (2); wherein: The thin-layer flow cell (1) is provided with an inlet pipe (12) and an outlet pipe (13) connected to the outside at both ends of the microchannel (11), and the thin-layer flow cell (1) also includes A card slot (14) matching the shape of the electrode card (2) provided under the laminar cavity; The electrode card (2) is pluggably and tightly inserted into the card slot (14) on the thin layer flow cell (1), and the surface of the electrode card (2) falls into the microchannel (11 ) is the working area (22); the three electrodes are distributed along the flow field of the solution to be tested in the working area (22); when the electrode card (2) is fully inserted into the card slot (14) At this time, the contact feet (26) of the three electrodes protrude out of the slot (14). 2. The detection device according to claim 1, characterized in that, the lamellar cavity of the microchannel (11) is saddle-shaped, and the liquid inlet pipe (12) and the liquid outlet pipe (13) are respectively along the The tangential direction connects the two apexes of the laminar cavity. 3. The detection device according to claim 2, characterized in that, the flow field of the solution to be tested in the microchannel (11) is S-shaped, and the three electrodes are in the working area (22) distributed along the S-shaped flow field. 4. The detection device according to claim 3, characterized in that the three electrodes are distributed in the first half, the second half or the entire area of the S-shaped flow field in the working area (22). 5. The detection device according to claim 4, characterized in that, the parts of the three electrodes in the working area (22) are arranged in series. 6. The detection device according to claim 4, characterized in that, the parts of the three electrodes in the working area (22) are arranged in parallel. 7. The detection device according to claim 3, characterized in that the sharp corners of the edges of the three electrodes are rounded. 8. The detection device according to any one of claims 1 to 7, characterized in that, the width of the working electrode (24) and the reference electrode (23) is larger than that of the counter electrode (25). 9. The detection device according to any one of claims 1 to 7, characterized in that, the liquid inlet pipe (12) and the liquid outlet pipe (13) have protruding pipe openings. 10. An electrode card (2) used in the portable flow field electrode heavy metal ion detection device according to any one of claims 1 to 9.