CN105588857B - A kind of surfactant detection means - Google Patents

Abstract

The invention discloses a surfactant detection device, which is characterized in that it comprises: a sensitive probe, an excitation signal drive circuit, a signal conditioning circuit, a signal acquisition circuit and a wireless communication circuit, the sensitive probe is arranged on one side of the excitation signal drive circuit, and the sensitive The probe is connected with the signal conditioning circuit through the excitation signal drive circuit, the signal conditioning circuit is connected with the signal acquisition circuit, and the signal acquisition circuit is connected with the wireless communication circuit. In this embodiment, the detected signal is sent to the signal conditioning circuit through the active agent sensitive module and the temperature sensitive module, and the signal conditioning circuit converts the received signal into a DC signal, and converts the DC signal into a surface The active agent concentration signal is transmitted to the user, with low power consumption, temperature compensation, high sensitivity and accuracy, and can be applied to long-term online detection of surfactants in water.

Description

A surfactant detection device

technical field

The invention relates to the field of surfactant detection, in particular to a surfactant detection device.

Background technique

Surfactant is a substance that can significantly change the interface state of its solution system, and can reduce the surface tension of the liquid. It is widely used in various fields of the national economy. It has the functions of dispersion, wetting, penetration, solubilization, emulsification, and Foaming, lubrication, sterilization, washing, anti-corrosion, anti-static and a series of characteristics. Surfactants are used in large quantities, and are directly discharged into the natural environment without treatment, causing persistent foam in the environmental water body, lowering the concentration of dissolved oxygen, making the water smelly, polluting the soil in the water, and indirectly affecting the quality of aquatic products and agricultural production. Since surfactants are the main components of detergents, and detergents are widely used in daily life, if a large amount of surfactants remain in food and beverages, or in tableware, and are accidentally ingested by the human body, if the dosage is too large, it will cause Cause poisoning. Surfactants are generally used by being dissolved in water and discharged into the environment through wastewater. Therefore, the detection of surfactants in water is very necessary and of great significance.

Existing methods for measuring surfactants mainly include liquid chromatography, potentiometric titration, spectrophotometry, fluorescence photometry, infrared methods, nuclear magnetic resonance methods, biosensor methods, and conductivity sensor methods.

Liquid chromatography uses liquid as the mobile phase, and uses a high-pressure infusion system to pump a single solvent with different polarities or a mixed solvent of different proportions, buffer solution and other mobile phases into a chromatographic column equipped with a stationary phase. After being separated, it enters the detector for detection.

The potentiometric titration method needs to dissolve the sample in a solvent, add an acid, and after a pretreatment reaction, add a titrant, and judge the concentration of the surfactant according to the titration curve.

The spectrophotometric method is to react with the analyte by means of the chromogenic agent, and then determine the concentration of the surfactant according to the absorption spectrum. For anionic surfactants, the determination method in the national standard is the methylene blue spectrophotometry, and its determination principle is Methylene blue reacts with anionic surfactant to form a blue ion association, which is then extracted with chloroform, and the absorbance is measured at a wavelength of 625nm.

Fluorescence spectrophotometry For anionic surfactant AS, the detection principle is to use the characteristic that the ion association formed by the reaction of anionic surfactant and rhodamine can be extracted, and measure its fluorescence intensity at 550nm.

Infrared method and nuclear magnetic resonance method both need pretreatment of the sample, and use infrared spectroscopy and nuclear magnetic resonance spectrum to determine the surfactant. The sensor method is the most suitable method for long-term on-line detection. The biosensor has strong specificity and cannot be applied to the measurement of different types of surfactants, and has certain requirements for the detection environment.

The conventional conductivity sensor method is to use two electrodes immersed in the solution to measure the change of conductivity between the electrodes, while the change rate of the conductivity of liquid detergent is relatively small, showing that the slope of the curve is small, which is inconvenient. Therefore, conventional conductivity sensors are only suitable for the detection of high-concentration surfactant solutions. The conductivity is affected by many factors such as the solution concentration, the type of electrolyte, and the temperature.

The prior art is generally only capable of measuring certain types of non-ionic, anionic or cationic surfactants, which has poor versatility and has the following defects:

(1) Liquid chromatography needs to sample the sample, and the operation is complicated, the instrument is expensive, and it is not suitable for online measurement;

(2) The potentiometric titration method requires sampling and sample pretreatment, which can only be used in the laboratory and cannot be used for in-situ online detection;

(3) The spectrophotometric method is very cumbersome to operate and is easily affected by various coexisting substances. Organic carboxylates, sulfonates, sulfates and inorganic sulfates, phosphates, chlorides, etc. will interfere with the method , and the extraction ability of anions is relatively weak, the sensitivity is low, the minimum detection concentration is 0.05mg/L, and the chloroform used is a toxic substance, which can act on the central nervous system and is carcinogenic; it is oxidized by air under the action of sunlight It will generate highly toxic phosgene, which will easily pollute the environment;

(4) Fluorescence photometry needs to react to form associates, and needs to be extracted with benzene, etc., and has certain requirements for pH. Therefore, like spectrophotometry, the operation is complicated and it is not easy to be used for online measurement;

(5) Both infrared method and nuclear magnetic resonance method require expensive instruments for analysis, and the process is complicated and time-consuming;

(6) The biosensor has singleness, poor versatility, and short life, so it is not suitable for long-term measurement;

(7) Conventional conductivity sensors have poor sensitivity, are easily polarized, and are easily interfered by other components in the solvent;

(8) Liquid chromatography, potentiometric titration, and spectrophotometry are time-consuming and laborious, and require the use of harmful solvents such as formaldehyde and chloroform, which are harmful to the human body.

Contents of the invention

Aiming at the defects of the above technical problems, the present invention provides a surfactant detection device.

In the first aspect, the present invention proposes a surfactant detection device, including: a sensitive probe, an excitation signal drive circuit, a signal conditioning circuit, a signal acquisition circuit and a wireless communication circuit, and the sensitive probe is arranged on the excitation signal drive circuit. On one side, the sensitive probe is connected to the signal conditioning circuit through the excitation signal drive circuit, the signal conditioning circuit is connected to the signal acquisition circuit, and the signal acquisition circuit is connected to the wireless communication circuit;

Wherein, the sensitive probe includes a temperature sensitive module and a plurality of active agent sensitive modules;

The active agent sensitive module includes: a silicon wafer, a silicon dioxide film layer grown on the silicon wafer, an electrode array formed on the silicon dioxide film layer, and an oxide layer covering the electrode array. The two adjacent pins of the electrode array form an electrode, and the two adjacent pins are used as the power excitation terminal and the signal detection terminal respectively, and are connected in parallel with two pins apart, and the electrode array shares a pair of metal positive and negative contacts. point, the electrode arrays in the plurality of active agent sensitive modules are connected in parallel through the metal male-female contacts.

Optionally, openings are provided on the oxide layer at positions corresponding to the electrode arrays.

Optionally, the device further includes: a solar cell panel and a float housing, and the solar cell panel is arranged on the first surface of the float housing.

Optionally, the signal acquisition circuit and the signal conditioning circuit are arranged on the second surface of the float housing.

Optionally, the wireless communication circuit runs through the float housing, and one end is connected to the wireless communication circuit.

Optionally, the device further includes: a power drive circuit, a power supply and a charging and discharging circuit, one end of the power driving circuit is connected to the signal conditioning circuit, the other end is connected to the power supply, and the power supply is connected to the charging and discharging circuit. circuit connected.

Optionally, the device further includes: a waterproof casing, the waterproof casing is a C-shaped frame, and the signal conditioning circuit, signal acquisition circuit, wireless communication circuit, power supply, power supply drive circuit and charging and discharging circuit are all arranged in the In the C-shaped frame, the excitation signal drive circuit and the sensitive probe are arranged at the opening of the C-shaped frame, and a filter cap is also arranged at the opening.

Optionally, the power supply is connected to the solar panel.

The invention provides a surfactant detection device, which sends the detected signal to the signal conditioning circuit through the active agent sensitive module and the temperature sensitive module, and the signal conditioning circuit converts the received signal into a DC signal, and passes the signal acquisition circuit and The wireless communication circuit converts the DC signal into a surfactant concentration signal and transmits it to the user. The surfactant detection device has low power consumption, temperature compensation, high sensitivity and accuracy, and can be applied to long-term online detection of surfactants in water. .

Description of drawings

Fig. 1 is a schematic structural diagram of a surfactant detection device provided by an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are the Some, but not all, embodiments are invented. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

A structural schematic diagram of a surfactant detection device provided by an embodiment of the present invention, as shown in Figure 1, the surfactant detection device includes: a sensitive probe 1, an excitation signal drive circuit 2, a signal conditioning circuit 3, and a signal acquisition circuit 4 and a wireless communication circuit 5, the sensitive probe 1 is arranged on one side of the excitation signal drive circuit 2, the sensitive probe 1 is connected to the signal conditioning circuit 3 through the excitation signal drive circuit 2, and the signal The conditioning circuit 3 is connected to the signal acquisition circuit 4, and the signal acquisition circuit 4 is connected to the wireless communication circuit 5;

Wherein, the sensitive probe includes a temperature sensitive module 12 and a plurality of active agent sensitive modules 11;

The active agent sensitive module 11 includes: a silicon wafer, a silicon dioxide film layer grown on the silicon wafer, an electrode array formed on the silicon dioxide film layer, and an oxide layer covering the electrode array, Two adjacent pins of the electrode array form an electrode, and the two adjacent pins are respectively used as a power supply excitation terminal and a signal detection terminal, and are connected in parallel with two pins apart, and the electrode array shares a pair of metal yin and yang contacts, the electrode arrays in the plurality of active agent sensitive modules are connected in parallel through the metal male-female contacts.

The above-mentioned surfactant detection device sends the detected signal to the signal conditioning circuit through the active agent sensitive module and the temperature sensitive module, and the signal conditioning circuit converts the received signal into a DC signal, and converts the DC signal through the signal acquisition circuit and the wireless communication circuit. It is converted into a surfactant concentration signal and transmitted to the user, so that the user can detect the surfactant according to the DC signal. The surfactant detection device has low power consumption, temperature compensation, high sensitivity and accuracy, and can be applied to long-term online Surfactants in water detected.

The sensitive probe is a group of tiny sheets fixed horizontally on the printed circuit board. There are five layers in total, each layer is 0.7mm thick, and the distance between each layer is 0.5mm. Among them, four layers are active agent sensitive modules, and the last layer is temperature sensitive. module.

The active agent sensitive module includes: a silicon chip, a silicon dioxide film layer grown on the silicon chip, an electrode formed on the silicon dioxide film layer, and an oxide layer covering the electrode. Openings are provided on the oxide layer at positions corresponding to the electrode arrays. There are multiple electrodes, and two adjacent electrodes are respectively connected to the power excitation terminal and the signal detection terminal on the excitation signal drive circuit.

Among them, the specific process of the active agent sensitive module is to cover a thin silicon dioxide layer of 2.5 μm on the surface of the silicon wafer by thermal growth, using it as a substrate, and then covering the substrate with magnetron sputtering technology. A layer of 230nm highly conductive material tantalum disilicide (TaSi2), and then use reactive ion etching technology to form a staggered 500-pin electrode array on the substrate, each electrode pin width is 3μm, and the electrode length is 1.5mm , There is a 3μm interval between the two electrodes, the total width of the entire electrode array is 3.5mm, the separated electrodes are connected in parallel, and the two adjacent electrodes arranged in a staggered manner are respectively connected to the power supply and ground, and the driving signal uses a frequency of 100Hz-1000kHz , the voltage is 25mV, two 1μm-sized aluminum points are realized by photolithography technology at both ends of each group of electrodes, and they are used as electrode detection lead contacts. Finally, 4μm thick silicon oxide is covered on the surface of the electrode array by low-pressure chemical vapor deposition technology. This material has a lower density than silicon dioxide or quartz formed by thermal growth. Photolithography technology is used to open grooves on the oxide layer of the electrode pins. A silica capillary with an upper opening is formed. The groove width is 3 μm, the height is 4 μm, and the length is 1.5 mm. The signal is passed on to subsequent circuits.

The temperature sensitive module is manufactured using MEMS technology and is a piezoresistive temperature sensor. The process method is to make a through-hole array through an anisotropic dry etching process, and then use an isotropic undercutting process to form a cavity through the through-hole array, and form epitaxial silicon on a silicon wafer by a low-pressure chemical vapor deposition method to complete the sealing. , and then form a piezoresistive module as a stress-sensitive element through a boron diffusion process, form an ohmic contact on the piezoresistor through a heavy doping process, and then form a composite film of LPEOS and LP-SiN through a deposition process. The dielectric layer is formed by etching, then the aluminum film layer is formed by electroplating, and the pads for electrical connection are formed by etching. Finally, the cantilever beam structure is released by the dry etching process on the front side.

The temperature sensitive module and the active agent sensitive module are glued side by side on the printed circuit board, and there are wires on the printed circuit board respectively connected to the two sensors through contact contacts, and transmit their signals to the subsequent conditioning circuit. The signal conditioning circuit extracts the useful signal through multiple links such as amplification, filtering, and detection, and converts it into a DC signal.

The excitation signal driving circuit is connected to the power supply excitation terminal of the electrode array of the surfactant sensitive module, and provides a driving signal with a frequency of 100Hz-1000kHz for the electrode array; the signal conditioning circuit is connected to the signal of the electrode array of the surfactant sensitive module The detection end extracts the useful signal through multiple links such as flow pressure conversion, amplification, filtering, and wave detection, and converts it into a DC signal. At the same time, the signal conditioning circuit is connected to the output end of the temperature sensitive module, and the The output signal of the temperature sensitive module is amplified and filtered, and then the two-way signal is sent to the signal acquisition circuit connected to it, and the signal acquisition circuit simultaneously collects the two-way signal, passes through the built-in algorithm model, and performs temperature compensation algorithm to calculate the corresponding surfactant concentration; the wireless communication circuit is connected to the signal acquisition circuit, and its antenna extends to the top of the floating ball and passes through the solar panel, and the signal acquisition circuit calculates The resulting surfactant concentration is sent via the wireless communication circuit.

After the signal is conditioned by two signal conditioning circuits, it is sent to the signal acquisition circuit and the wireless communication circuit, and converted into a digital signal. Since the impedance detected by the surfactant sensitive module is not only related to the concentration of the surfactant, but also affected by the temperature Influence, the temperature has a great influence on the conductivity of the detergent solution, especially the high temperature above 50 ℃, especially the powder detergent. Therefore, after the impedance signal and temperature signal are collected, the temperature will be induced according to the built-in preset algorithm The error is compensated, and finally the accurate concentration value of the surfactant is calculated, and then the signal can be transmitted through wireless communication power.

The device also includes: a solar panel 6 and a float housing 7, the solar panel is arranged on the first surface of the float housing; the signal acquisition circuit 4 and the signal conditioning circuit 3 are arranged On the second surface of the floating ball housing 7 ; the wireless communication circuit 5 runs through the floating ball housing 7 , and one end is connected to the wireless communication circuit 5 . The device also includes: a power drive circuit 8, a power source 9 and a charging and discharging circuit 10, one end of the power drive circuit 8 is connected to the signal conditioning circuit 3, and the other end is connected to the power source 9, and the power source 9 is connected to the The charging and discharging circuit 10 is connected. The power source 9 is connected to the solar panel 6 .

The device also includes: a waterproof casing 13, the waterproof casing is a C-shaped frame, and the signal conditioning circuit, signal acquisition circuit, wireless communication circuit, power supply, power supply drive circuit and charging and discharging circuit are all arranged in the C-shaped frame Inside, the excitation signal driving circuit and the sensitive probe are arranged at the opening of the C-shaped frame, and a filter cap 14 is also arranged at the opening. The probe protection filter cap can be disassembled as a whole. When the water body to be tested is turbid, it needs to be installed to prevent suspended matter in the water from clogging the grooves and gaps on the tiny sensitive components and damaging the detection performance. The top of the filter cap is covered with a A 400-mesh stainless steel filter screen with corrosion resistance and oxidation resistance, which can be disassembled and replaced, needs to be replaced every once in a while to ensure a better filtering effect.

The power supply of this device can be powered by a lithium-ion battery, and the battery and the charging and discharging circuit are sealed at the bottom of the device, and at the same time play the role of a counterweight, so that the device will not easily fall over.

The upper part of the floating ball housing with solar panels is always exposed above the water surface. The top of the floating ball is a solar panel, which converts light into electrical energy to charge the lithium-ion battery. At the same time, the floating ball provides an upward buoyancy for the entire device. The battery at the lower end as a counterweight and the charging and discharging circuit jointly maintain the balance of the device.

The active agent sensitive module in the above embodiment adopts CMOS technology, and the temperature sensitive module adopts MEMS technology and the application of material processing technology. The sensitive probe manufactured by the application has extremely high sensitivity, which makes the detection limit of this device ten times lower than the conventional conductivity detection method Above; the output linearity is good, and the measurement results are hardly affected by the stains in the water; because the AC power supply is used in the conductometric measurement, the electrode polarization phenomenon is relatively weak; this device is very power-saving, and can independently replenish energy through sunlight, There is basically no need for artificial charging; this device can realize wireless communication.

The invention is applied to the quantitative measurement of extremely low content surfactants in water bodies, without sampling, and can realize fast online monitoring, timely, accurate, and pollution-free; simple in structure, easy to move, suitable for water quality monitoring, environmental evaluation, aquaculture, Various applications such as water source monitoring. Compared with the original technology, it has extremely low detection limit and sensitivity, is not easily disturbed, has lower requirements on the measurement environment, and has strong adaptability.

Furthermore, those skilled in the art will understand that although some embodiments described herein include some features included in other embodiments but not others, combinations of features from different embodiments are meant to be within the scope of the invention. and form different embodiments.

Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention. within the bounds of the requirements.

Claims (8)

1. A surfactant detection device, characterized in that, comprises: a sensitive probe, an excitation signal drive circuit, a signal conditioning circuit, a signal acquisition circuit and a wireless communication circuit, and the sensitive probe is arranged on one of the excitation signal drive circuits On the side, the sensitive probe is connected to the signal conditioning circuit through the excitation signal drive circuit, the signal conditioning circuit is connected to the signal acquisition circuit, and the signal acquisition circuit is connected to the wireless communication circuit; Wherein, the sensitive probe includes a temperature sensitive module and a plurality of active agent sensitive modules; The active agent sensitive module includes: a silicon wafer, a silicon dioxide film layer grown on the silicon wafer, an electrode array formed on the silicon dioxide film layer, and an oxide layer covering the electrode array. The two adjacent pins of the electrode array form an electrode, and the two adjacent pins are used as the power excitation terminal and the signal detection terminal respectively, and are connected in parallel with two pins apart, and the electrode array shares a pair of metal positive and negative contacts. point, the electrode arrays in the plurality of active agent sensitive modules are connected in parallel through metal positive and negative contacts; Among them, the specific process of the active agent sensitive module is to cover a thin silicon dioxide layer of 2.5 μm on the surface of the silicon wafer by thermal growth, using it as a substrate, and then covering the substrate with magnetron sputtering technology. A layer of 230nm high-conductivity material tantalum disilicide, and then use reactive ion etching technology to form a staggered electrode array of 500 pins on the substrate, each electrode pin width is 3μm, and the electrode length is 1.5mm. There is a 3μm interval between the electrodes, and the total width of the entire electrode array is 3.5mm. The separated electrodes are connected in parallel, and two adjacent electrodes arranged in a staggered manner are respectively connected to the power supply and ground. Photolithography technology is used at both ends of each group of electrodes. Two aluminum dots with a size of 1 μm are used as electrode detection lead contacts, and finally, 4 μm thick silicon oxide is covered on the surface of the electrode array by low-pressure chemical vapor deposition technology. 2 . The device according to claim 1 , wherein an opening is provided on the oxide layer at a position corresponding to the electrode array. 3 . 3 . The device according to claim 1 , further comprising: a solar cell panel and a float housing, the solar cell panel being disposed on a first surface of the float housing. 4 . 4. The device according to claim 3, wherein the signal acquisition circuit and the signal conditioning circuit are arranged on the second surface of the float housing. 5. The device according to claim 3, wherein the wireless communication circuit runs through the float housing, and one end is connected to the wireless communication circuit. 6. The device according to claim 3, further comprising: a power drive circuit, a power supply and a charging and discharging circuit, one end of the power drive circuit is connected to the signal conditioning circuit, and the other end is connected to the The power supply is connected, and the power supply is connected with the charging and discharging circuit. 7. The device according to claim 6, characterized in that, the device further comprises: a waterproof casing, the waterproof casing is a C-shaped frame, the signal conditioning circuit, signal acquisition circuit, wireless communication circuit, power supply, power supply Both the driving circuit and the charging and discharging circuit are arranged in the C-shaped frame, the excitation signal driving circuit and the sensitive probe are arranged at the opening of the C-shaped frame, and a filter cap is also arranged at the opening. 8. The device of claim 6, wherein the power source is connected to the solar panel.