CN112946048B - Method for directly detecting heavy metals in food through membrane electrochemical sensor - Google Patents
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Abstract
The invention discloses a method for directly detecting heavy metals in food by a membrane electrochemical sensor, which comprises the following steps: by passing through
Solution growth method, depositing silicon dioxide nano channel on the surface of indium tin oxide conductive substrate, and removing residual by adopting ethanol solution containing hydrochloric acid
The solution is used for preparing a mesoporous silica-nano channel film/indium tin oxide composite material; modifying polydimethylsiloxane on the surface of the mesoporous silica-nano channel film/indium tin oxide composite material by adopting a plasma deposition method to prepare a plasma-triggered polydimethylsiloxane modified mesoporous silica nano channel@indium tin oxide electrochemical sensor; the sensor is then inserted directly into a complex matrix and the concentration of heavy metals in the sample is detected by differential pulse stripping voltammetry. The modified electrode disclosed by the invention has high selectivity and high sensitivity for measuring heavy metals, and is short in detection time, and the heavy metals are directly detected in complex samples, so that the operation is convenient.
Description
Technical Field
The invention belongs to the field of food detection, and particularly relates to a method for directly detecting heavy metals in food through a membrane electrochemical sensor.
Background
With the development of industry and agriculture, various fertilizers, micronutrients, pesticides and the like are widely used in order to ensure good growth and quality of agricultural products. However, the increasing use of these agrochemicals contaminates the ecosystem and may also be detected in food samples. Heavy metal pollution of agricultural products is serious, and the quality and the human health of the products are affected. Among them, lead (Pb) and cadmium (Cd) are two important representatives, which cause serious food contamination and serious risks to human health. Pb has the characteristics of non-biodegradability, long half-life period, serious harm to human health and the like. Cd2+ has a variety of toxic effects on the kidney, liver, nerves and cardiovascular system. Although their concentration in the natural environment is low, they accumulate in the human body through the food chain and long-term exposure can lead to fatal diseases, including cancer.
Accumulation of Pb and Cd is found in various foods such as rice, apple, strawberry, grape, pomegranate, kiwi, and tomato. While Pb and Cd levels in fruits, berries and vegetables are generally low, consuming such foods or juices and beverages in large quantities results in increased exposure to these heavy metals. The fruit juice mainly comprises carbohydrates, proteins, fat, vitamins, salt and other minerals in water, and in the processes of raw material collection, processing and packaging, the quality control measures are not strict due to the unscientific production process, and the fruit juice can face greater risks of heavy metal pollution, and is still a serious food safety problem worldwide. In addition, fruit and vegetable juices and beverages are becoming increasingly popular among young people due to their ready availability, processing and convenient drinking characteristics. Therefore, there is an urgent need to develop a sensitive, rapid, low-cost, and accurate detection and analysis method for detecting Pb and Cd in these samples.
Conventional methods for detecting heavy metals in food samples include x-ray fluorescence spectroscopy (XRF), inductively coupled plasma optical emission spectroscopy (ICP-OES), atomic absorption spectroscopy (FAAS), and inductively coupled plasma spectroscopy mass spectrometry (ICP-MS). However, these methods have disadvantages of high cost, complicated operation, long pretreatment steps, limited industrial or market use, and the like. Thus, these techniques have difficulty meeting the increasing demands for on-site monitoring and on-line analysis. In contrast, electrochemical methods, in particular Anodic Stripping Voltammetry (ASV), are widely used for their quantification due to the possible enrichment of metals at the electrode surface, with significant sensitivity even at trace/ultra trace levels. The method can reduce cost, has high sensitivity, is compact and simple, and can be used for on-site rapid detection and trace analysis. In recent years, mesoporous silica-nanochannel membrane sensors have attracted increasing attention for their ability to selectively analyze small analytes in complex samples. Such nanochannels exhibit permeation selective pass effects in size, charge and sensitivity to positively charged analytes due to enrichment effects resulting from electrostatic attraction and spatial confinement within the channel. Steric hindrance has been widely used for nonspecific adsorption of macromolecules on electrodes, such as an antifouling effect, and has attracted great attention. The application of mesoporous silica materials in the fields of molecular separation, molecular detection, nanofluidic, drug delivery, simulated biological membranes and the like has been reported.
Despite good steric hindrance properties, direct electrochemical detection is still challenging in real food samples due to interference from large amounts of interfering substances. Small electroactive molecules (e.g., antioxidants, vitamins) in the food product can enter traditional nanochannels and create interfering electrochemical signals. At present, no nano sensor with high sensitivity, convenient treatment and low cost is developed for detecting Pb and Cd heavy metals in food samples.
Disclosure of Invention
The invention provides a method for directly detecting heavy metals in food by a membrane electrochemical sensor, which has the characteristics of high sensitivity, low detection limit, wide dynamic range, strong anti-interference capability, short detection time and the like, and can directly detect heavy metals in complex samples.
A method for directly detecting heavy metals in food by a membrane electrochemical sensor, comprising:
(1) By passing through
Solution growth method, depositing silicon dioxide nano channel on the surface of indium tin oxide conductive substrate, removing residual +.>
The solution is used for preparing a mesoporous silica-nano channel film/indium tin oxide composite material;
(2) And modifying polydimethylsiloxane on the surface of the mesoporous silica-nano channel film/indium tin oxide composite material by adopting a plasma deposition method to prepare the plasma-triggered polydimethylsiloxane modified mesoporous silica nano channel@indium tin oxide electrochemical sensor, and then detecting heavy metals in the sample by a differential pulse stripping voltammetry.
The electrochemical sensor is prepared by depositing polydimethylsiloxane on a silicon dioxide nano channel @ indium tin oxide electrode, wherein the nano channel of the electrochemical sensor is filled with dense polydimethylsiloxane, so that most molecules can be inhibited from passing, only small heavy metal ions can pass, heavy metal ions can be directly detected in a complex environment, hydrophilic substances, hydrophobic substances and macromolecular substances in a sample cannot be adsorbed on the surface of the indium tin oxide electrode, and only small heavy metal ions can be adsorbed on the electrode, thereby improving the sensitivity and selectivity of heavy metal compound detection.
In step (1), the following
The solution is prepared by dissolving cetyl trimethyl ammonium bromide in a mixed solution of water and ethanol and adding ammonia solution and tetraethyl orthosilicate, wherein the mass ratio of the cetyl trimethyl ammonium bromide to the ammonia solution to the tetraethyl orthosilicate is 15-24:0.91-1.12:7.45.
In the step (1), further, the ethanol solution containing hydrochloric acid is used for removing the residual
Cetyl trimethylammonium bromide in solution.
The concentration of hydrochloric acid in the ethanol solution containing hydrochloric acid is not lower than 0.1mol/L.
And adding ethanol solution containing hydrochloric acid to remove residual cetyltrimethylammonium bromide in the silica nanochannel, so that the silica nanochannel has hydrophilicity, the residual cetyltrimethylammonium bromide cannot be completely removed due to the fact that the concentration of hydrochloric acid in the ethanol solution of hydrochloric acid is too low, the residual cetyltrimethylammonium bromide can remain in the silica nanochannel, the hydrophilicity of the silica nanochannel is affected, and the selectivity of detection of the small molecular compound is reduced.
In the step (2), the plasma deposition method is to place the indium tin oxide/silicon dioxide composite material on a glass plate, surround the polydimethylsiloxane monomer on the periphery of the glass plate, and place the glass plate into a plasma cleaner for plasma deposition for 10-35s.
The length of the polydimethylsiloxane is 1.8-2.3cm, and the width is 0.2-0.4cm.
In the step (3), the sample solution is filtered by adding the sample solution to a filter membrane with a pore size of 0.40-0.45 μm (Millipore) before heavy metal detection by using the differential pulse stripping voltammetry.
Compared with the method for detecting heavy metals in inductively coupled plasma mass spectrometry (ICP-MS) measurement, the method for detecting heavy metals provided by the invention has the advantages that the sample does not need further pretreatment, and the developed on-site electrochemical sensor is simple, quick and convenient.
In the step (3), the differential pulse stripping voltammetry adopts a three-electrode system, wherein a silver chloride/silver electrode is used as a reference electrode, a platinum wire electrode is used as a counter electrode, and a plasma-triggered polydimethylsiloxane modified silica nano-channel@indium tin oxide electrode is used as a working electrode.
In the step (3), the differential pulse stripping voltammetry mainly comprises electrochemical deposition and stripping, and comprises the following steps:
(1) Adopting a method for reducing heavy metal, and depositing heavy metal ions on the plasma-triggered polydimethylsiloxane modified mesoporous silica nano-channel@indium tin oxide electrochemical sensor under the voltage of-0.95 to-0.2V;
(2) Anodic stripping is carried out on Pb and Cd electrodeposited by adopting differential pulse voltammetry under the voltage of-0.95 to-0.2V;
(3) The deposited residual species are removed from the surface by applying a potential of +0.3 to +0.6V for 60-90s, and the used electrode is recovered for the next detection.
In the step (3), the experimental conditions of the differential pulse stripping voltammetry are as follows: the scanning potential range is-0.95 to-0.2V, the incremental potential is 0.01V, the amplitude is 0.05V, the pulse width is 0.05s, and the balance period is 30s.
In the step (3), the electrolyte solution adopted in the differential pulse stripping voltammetry is potassium chloride-hydrochloric acid solution, acetic acid-sodium acetate is buffer solution, and the pH value of the electrolyte solution is adjusted to be 5-6.
Under the condition of proper pH, the inner wall of the pore canal can be deprotonated and negatively charged, so that the mass transfer process of heavy metal ion signals can be quickened, the sensitivity of detection of the micromolecular compound is enhanced, the influence of potassium sulfate-sulfuric acid or potassium chloride-hydrochloric acid solution on the heavy metal ion signals is smaller, and the interference on the heavy metal ion signal transmission is reduced.
The invention provides a plasma-triggered polydimethylsiloxane modified silicon dioxide nano channel@indium tin oxide electrode prepared by a method for detecting heavy metals by using an electrochemical modified electrode, wherein the modified electrode has higher selectivity and sensitivity, and the minimum detection limit of lead ions and cadmium ions is 4 mug/L and 2 mug/L.
The beneficial effects of the invention are mainly as follows:
(1) The invention provides a plasma-triggered polydimethylsiloxane modified silicon dioxide nano channel @ indium tin oxide electrode, wherein the nano channel is filled with dense polymerInhibiting most molecules including hydrophilic and hydrophobic molecules, only small heavy metal ions can pass through, so that the method has higher selective permeability to small-size compounds in the process of detecting the small-size compounds in complex samples, and can detect the small-size compounds with the concentration of 4-1500 mu g L -1 Lead ions of (2) and 30-900 mu g L -1 Therefore, has higher sensitivity and selectivity.
(2) The method for detecting heavy metals in the sample by adopting the method provided by the invention only needs 8-15min, and the detection time is far lower than that of the prior art.
Drawings
FIG. 1 is a schematic diagram of a polydimethylsiloxane-modified mesoporous silica nanochannel/indium tin oxide electrode placed prior to plasma deposition (PDMS- - -polydimethylsiloxane, MSF- - -mesoporous silica nanochannel, ITO- - -indium tin oxide);
FIG. 2 is a Cyclic Voltammogram (CVs) of indium tin oxide, mesoporous silica nanochannel/indium tin oxide, plasma triggered polydimethylsiloxane modified mesoporous silica nanochannel/indium tin oxide electrode containing (a) Ru (NH 3) 63+, (b) Fe (CN) 63-, - (c) Fc-MeOH, (d) ascorbic acid, (e) retinol, (f) melatonin scan rate of 50mV s-1 in 0.5M KCl;
FIG. 3 is a graph of electrochemical signal contrast over a plasma triggered polydimethylsiloxane modified mesoporous silica nanochannel/indium tin oxide electrode and indium tin oxide electrode in a lead ion solution of the same concentration;
FIG. 4 is a graph showing the linear relationship between the current signal change and the heavy metal ion concentration of the ionophore-triggered polydimethylsiloxane modified mesoporous silica nanochannel/indium tin oxide electrode prepared in example 1 in standard solutions with different lead ion and cadmium ion concentrations;
FIG. 5 plasma triggered polydimethylsiloxane modified mesoporous silica nanoparticlesDetection pb of meter channel/indium tin oxide electrode 2+ And Cd 2+ Is an anti-interference evaluation effect graph;
FIG. 6 is a photograph of (a) direct electrochemical detection of grape juice, grape beverage, apple juice, rice fermented beverage with a plasma-triggered polydimethylsiloxane-modified mesoporous silica nanochannel/indium tin oxide electrode (b) plasma-triggered polydimethylsiloxane-modified mesoporous silica nanochannel/indium tin oxide electrode for detecting Cd in grape juice, grape beverage, apple juice, rice fermented beverage samples 2+ Is a graph of the operation of (1). (c) Plasma-triggered polydimethylsiloxane-modified mesoporous silica nano-channel/indium tin oxide electrode for measuring Pb in grape juice, grape beverage, apple juice and rice fermented beverage samples 2+ Is a graph of the operation of (1).
Detailed Description
The invention is further illustrated by the following examples:
(1) Cleaning an electrode: firstly, immersing an indium tin oxide electrode in an ethanol solution containing 1mol/L sodium hydroxide, carrying out ultrasonic treatment for 1 hour, then sequentially immersing the electrode in acetone and ethanol, respectively carrying out ultrasonic treatment for 15 minutes, then washing the electrode with deionized water for 15 minutes, repeating the steps for two times, and finally, drying the electrode with nitrogen for standby.
(2) Depositing a silicon dioxide nano channel film on the surface of an indium tin oxide electrode:
1. configuration of
Solution: 0.16g of cetyltrimethylammonium bromide was dissolved in 100mL of a water/ethanol mixed solution (70 mL/30 mL), and after cetyltrimethylammonium bromide was completely dissolved, an ammonia solution (100. Mu.L, 2.5 wt%) and tetraethyl orthosilicate (80. Mu.L) were slowly added to the cetyltrimethylammonium bromide solution, respectively, with stirring;
2. soaking indium tin oxide electrode in the above-mentioned
Heating in water bath at 60deg.C, avoiding the whole process as much as possibleVibration-free, after 24 hours, the electrode was taken out and rinsed with a large amount of water and dried with nitrogen, then the electrode was placed in a dry box and left at 100 ℃ for 12 hours for aging, at which time the nanochannels of the obtained electrode were filled with surfactant;
3. the surface active agent cetyl trimethyl ammonium bromide in the nano channel is removed by soaking in ethanol solution containing 0.1mol/L hydrochloric acid, and the indium tin oxide/silicon dioxide nano channel composite material of the silicon dioxide nano channel array with the pore channel perpendicular to the substrate is obtained on the surface of the indium tin oxide conductive substrate.
(3) Plasma scrubber deposition: placing the indium tin oxide/silicon dioxide nano channel composite material at 12.5cm 2 And the glass plate is surrounded by 1g of polydimethylsiloxane monomer at the three sides, and the glass frame is put into a plasma cleaner, and is treated for 30 seconds with low power, so as to prepare the plasma-triggered polydimethylsiloxane modified mesoporous silica nano channel/indium tin oxide electrode.
(4) The electrochemical detection adopts a classical three-electrode system: the standard silver chloride/silver electrode is used as a reference electrode, the platinum wire electrode is used as a counter electrode, and the modified indium tin oxide electrode is used as a working electrode. The electrolyte background of the detection system is 0.5mol/L potassium chloride solution, the buffer solution is acetic acid-sodium acetate solution, the pH value of the solution is 5.5, the probe molecule/ion concentration is 200 mu mol/L, the electrochemical sensing characteristics (cyclic voltammetry) of indium tin oxide, mesoporous silica nano channel/indium tin oxide and plasma triggered polydimethylsiloxane modified mesoporous silica nano channel/indium tin oxide electrodes are compared, and the three electrodes contain (a) Ru (NH) 3 ) 6 3+ ，(b)Fe(CN) 6 3- (c) Fc-MeOH, (d) ascorbic acid, (e) retinol, (f) melatonin scan rate of 50mVs -1 Cyclic Voltammograms (CVs) in 0.5M KCl, see FIG. 2.
In the lead ion solution with the same concentration, plasma triggers an electrochemical signal comparison graph on the polydimethylsiloxane modified mesoporous silica nano channel/indium tin oxide electrode and the indium tin oxide electrode, and is shown in fig. 3.
As can be seen from FIG. 2, to study the electrochemical behavior of the plasma-triggered polydimethylsiloxane-modified mesoporous silica nanochannel/indium tin oxide electrode, cyclic Voltammetry (CVs) was used on typical Ru (NH) 3 ) 6 3+ ，Fe(CN) 6 3- The Fc-MeOH probe was studied electrochemically. As shown in fig. 2, on the bare indium tin oxide electrode, a clear current wave was observed for all three redox probes. The nanochannel electrode also exhibited a distinct current peak when the indium tin oxide was modified with a mesoporous silica nanochannel, however, no molecules were able to penetrate the nanochannel filled with plasma-triggered polydimethylsiloxane, as all redox peaks on the plasma-triggered polydimethylsiloxane-modified mesoporous silica nanochannel/indium tin oxide electrode disappeared. Similar phenomena are seen with the usual electroactive molecules in foods (i.e. ascorbic acid, retinol and melatonin), which can also enter the mesoporous silica modified indium tin oxide nanochannel and generate a significant peak signal, whereas no signal can be observed on the plasma-triggered polydimethylsiloxane modified nanochannel electrode, which shielding performance is much better than before using the heating method (heating 12h to deposit polydimethylsiloxane, which still allows small neutral or hydrophobic molecules to pass through nanochannels these results clearly show that the plasma-triggered polydimethylsiloxane modified mesoporous silica nanochannel can significantly inhibit the passage of most molecules including hydrophilic, hydrophobic molecules while allowing smaller heavy metal ions to pass through, as shown in fig. 3, in which case the plasma-triggered polydimethylsiloxane modified mesoporous silica nanochannel/indium tin oxide electrode shows resistance to surface contamination and contamination, allowing electrochemical analysis of heavy metal ions in real or complex media.
(5) Drawing a working curve:
20mL of acetic acid buffer (0.1M,Pb2+pH 6.0,Cd2+pH5.5) is used as a medium for detecting heavy metal ions. The effective area of the working electrode immersed in the electrolyte was 1cm×1cm. Preparation of 1000. Mu.g of Pb of mL-1 2+ And Cd 2+ Gradually diluting the standard stock solution to obtain different concentrations, and depositing heavy metal ions on the p-PDMS@MSF/ITO electrode for 300s under the voltage of-0.9V; subsequently, the electrodeposited Pb and Cd were anodically leached using Differential Pulse Voltammetry (DPV) under the following conditions: the scanning potential range is-0.1V, the incremental potential is 0.01V, the amplitude is 0.05V, the pulse width is 0.05s, and the balance period is 30s. Peak current signal and Pb 2+ And Cd 2+ The concentration data were linearly fitted, and a standard curve was drawn as shown in FIG. 4, cd 2+ 30-900 mug/L and Pb 2+ A better linear relationship appears between 4 μg/L and 1500 μg/L, with linear correlation coefficients of R= 0.9991 and 0.9883, respectively. Then adding a set volume of to-be-detected liquid into the acetic acid-sodium acetate+potassium chloride solution, and according to the response current of the plasma triggered polydimethylsiloxane modified mesoporous silica nano channel/indium tin oxide electrode and the polydimethylsiloxane modified indium tin oxide electrode to heavy metal lead and cadmium ions, combining the linear relation curve of the current and the concentration, and calculating to obtain the concentration of heavy metal ions in the to-be-detected liquid so as to realize the determination of the concentration of the heavy metal in the to-be-detected liquid; during electrodeposition and pretreatment, the test solution was stirred with a magnetic stirrer. Furthermore, after each measurement, the deposited residual species were purged from the surface by applying a pre-step at a potential of +0.3V for 60s, and the used electrode could be recovered for the next detection.
The anti-interference properties are critical for practical applications of electrochemical sensors, especially for complex food samples. The presence of common interferents such as food additives, amino acids, starches, antioxidants and minerals can have a serious impact on the detection of heavy metal ions. The anti-interference characteristic is critical to the practical application of the electrochemical sensor. Mesoporous silica nanochannel/tin oxide electrochemical sensor modified by detecting plasma-triggered polydimethylsiloxane modification and other possible Pb 2+ And Cd 2+ Co-existing interferents (Fe 3+ The responses of glycine (Gly), glucose, fructose, sucrose, vitamin C (Vc), glutamic acid (Glu), citric acid and starch were determinedInterference of the sensor. Pb 2+ And Cd 2+ The results of the interference resistance evaluation of (a) are shown in FIG. 5, which shows that the interference resistance evaluation is performed on the interference-free substrate (I) or the interference-free substrate (I 0 ) When the peak current is used, the relative signal change (I/I 0 ). With Pb 2+ And Cd 2+ Observed I/I 0 The resulting response change in the addition of other disturbances is negligible compared to the significant response of the values. Even when Pb is contained 2+ (100. Mu.g/L) and Cd 2+ Adding large amount of each interfering substance (1000. Mu.g/L) and Pb to the solution (100. Mu.g/L) 2+ And Cd 2+ Has little significant change in peak current. The result shows that the plasma-triggered polydimethylsiloxane modified mesoporous silica nano channel/tin oxide electrochemical sensor has quite anti-interference performance on food additives, amino acids, starch and minerals and Pb 2+ And Cd 2+ Has higher selectivity.
The plasma-triggered polydimethylsiloxane-modified mesoporous silica nanochannel/indium tin oxide electrode prepared in the embodiment detects heavy metal ions in a real sample, and the comparative analysis of the obtained working curves is shown in fig. 6 and table 1.
TABLE 1 Pb in juice and beverage samples 2+ And Cd 2+ Calibration curve and statistical contrast analysis for detection
Grape juice, grape beverage, apple juice and rice fermented beverage samples purchased from the market were used as heavy metal ion analysis samples. Commercial juice and beverage samples were filtered through a filter membrane having a pore size of 0.45 μm (Millipore), and then adjusted to pH and electrolyte concentration by adding an acetic acid buffer solution, and analyzed. The prepared sample is directly detected without other complicated pretreatment. Since no P is found in the collected sampleb 2+ And Cd 2+ The final concentration was thus found to be 35. Mu. g L -1 And 40 mu g L -1 Pb of (2) 2+ And final concentrations of 40 μ g L, respectively -1 And 55 mu g L -1 Cd of (2) 2+ Respectively adding into actual food samples, and measuring pb in grape juice, grape beverage, apple juice and rice fermented beverage by adopting plasma-triggered polydimethylsiloxane-modified mesoporous silica nano channel/tin oxide electrochemical sensor differential pulse digestion voltammetry and inductively coupled plasma mass spectrometry (ICP-MS) method 2+ And Cd 2+ The content comparison is shown in Table 2.
TABLE 2 Pb in fruit juices and beverages 2+ And Cd 2+ Is of direct electrochemical detection of (a)
As can be seen from Table 2, pb in four actual food samples (commercial fruit juice and beverage) 2+ And Cd 2+ Is a result of electrochemical detection of (a). Determination of 35. Mu.g/L Pb 2+ The relative recovery rate of (C) is 98.98% -103.43%, and 40 mug/L Pb is measured 2+ The Relative Standard Deviation (RSD), n=3) is 0.96-5.72, and 40 μg/L Pb is measured 2+ The relative recovery rate of (C) is 95.40-102.93%, and 55 mug/L Cd is measured 2+ The relative recovery rate of (2) is 95.27-101.98%, wherein Cd 2+ The relative recovery rate of (2) is 95.40-102.93%, and Cd 2+ The relative recovery rate of the catalyst is 95.27-101.98 percent, and the detection is 40 mug/L Cd 2+ Is 0.91-6.54, and 55 μg/L Cd is detected 2+ The relative standard deviation of (2) is 1.93-9.08. The heavy metal in the sample is detected for 8-15min, and in the inductively coupled plasma mass spectrometry (ICP-MS) detection, the final detection is carried out after the sample is subjected to filtration, extraction, enrichment and microwave digestion treatment, but in the method established by the invention, the sample does not need to be subjected to the next stepAnd (5) preprocessing. The method is remarkable in that the recovery rate of the heavy metal ions detected in the fruit juice and beverage samples is high, and the plasma-triggered polydimethylsiloxane-modified mesoporous silica nano channel/tin oxide electrode can enrich the heavy metal ions and has excellent removal performance on the interfering substances such as starch, food additives and organic matters in actual foods. The results show that the method is applicable to pb in actual food samples 2+ And Cd 2+ The detection of the method has higher accuracy and has higher application prospect in food industry, environmental protection and clinical research. In addition, the developed on-site electrochemical sensor is simple, quick, convenient and low in cost, and is a feasible solution. In contrast, existing inductively coupled plasma mass spectrometry (ICP-MS) for detecting heavy metals is entirely laboratory-based equipment, which is expensive, time consuming, requires training and high running costs.
Claims (10)
1. A method for directly detecting heavy metals in food by a membrane electrochemical sensor, comprising:
(1) By passing through
Solution growth method, depositing silicon dioxide nano channel on the surface of indium tin oxide conductive substrate, removing residual +.>
The solution is used for preparing a mesoporous silica-nano channel film/indium tin oxide composite material;
(2) And modifying polydimethylsiloxane on the surface of the mesoporous silica-nano channel film/indium tin oxide composite material by adopting a plasma deposition method to prepare a plasma-triggered polydimethylsiloxane modified mesoporous silica nano channel@indium tin oxide electrochemical sensor, and detecting heavy metals in a sample by a differential pulse stripping voltammetry, wherein the heavy metals are lead ions or cadmium ions.
2. According to the weightsThe method for directly detecting heavy metals in food by membrane electrochemical sensor according to claim 1, wherein in step (1), said method comprises the steps of
The solution is prepared by dissolving cetyl trimethyl ammonium bromide in a mixed solution of water and ethanol and adding ammonia solution and tetraethyl orthosilicate, wherein the mass ratio of the cetyl trimethyl ammonium bromide to the ammonia solution to the tetraethyl orthosilicate is 15-24:0.91-1.12:7.45.
3. The method for directly detecting heavy metals in food by membrane electrochemical sensor according to claim 2, characterized in that in step (1), residual is removed by using ethanol solution containing hydrochloric acid
Cetyl trimethylammonium bromide in solution.
4. A method for direct detection of heavy metals in food by membrane electrochemical sensor according to any of claims 1-3 characterized in that the concentration of hydrochloric acid in said ethanol solution containing hydrochloric acid is not lower than 0.1mol/L.
5. The method for directly detecting heavy metals in food by membrane electrochemical sensor according to claim 1, wherein in step (2), said plasma deposition method is to place indium tin oxide/silicon dioxide composite material on a glass plate, and around its periphery, polydimethylsiloxane monomer, and place the glass plate into a plasma cleaner to deposit plasma for 10-35s.
6. The method for directly detecting heavy metals in food by membrane electrochemical sensor according to claim 5, wherein said polydimethylsiloxane has a length of 1.8-2.3cm and a width of 0.2-0.4cm.
7. The method for directly detecting heavy metals in food by membrane electrochemical sensor according to claim 1, characterized in that in step (2), before detecting heavy metals by differential pulse stripping voltammetry, sample solution is added into a filter membrane with pore diameter of 0.40-0.45 μm for filtration.
8. The method for directly detecting heavy metals in food by a membrane electrochemical sensor according to claim 1, wherein in the step (2), the differential pulse stripping voltammetry adopts a three-electrode system, wherein a silver chloride/silver electrode is used as a reference electrode, a platinum wire electrode is used as a counter electrode, and a plasma-triggered polydimethylsiloxane modified silica nanochannel@indium tin oxide electrode is used as a working electrode.
9. The method for directly detecting heavy metals in food by membrane electrochemical sensor according to claim 1, wherein in step (2), said differential pulse stripping voltammetry method for detecting heavy metals comprises:
(1) Adopting a method for reducing heavy metal, and depositing heavy metal ions on the plasma-triggered polydimethylsiloxane modified mesoporous silica nano-channel@indium tin oxide electrochemical sensor under the voltage of-0.95 to-0.2V;
(2) Anodic stripping is carried out on Pb and Cd electrodeposited by adopting differential pulse voltammetry under the voltage of-0.95 to-0.2V;
(3) The deposited residual species are removed from the surface by applying a potential of +0.3 to +0.6V for 60-90s, and the used electrode is recovered for the next detection.
10. The method for directly detecting heavy metals in food by membrane electrochemical sensor according to claim 1, wherein in step (2), electrolyte solution adopted in said differential pulse stripping voltammetry is potassium chloride-hydrochloric acid solution, acetic acid-sodium acetate is buffer solution, and pH of said electrolyte solution is adjusted to 5-6.
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| US7825037B2 (en) * | 2005-10-17 | 2010-11-02 | Stc.Unm | Fabrication of enclosed nanochannels using silica nanoparticles |
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| CN109580744A (en) * | 2018-11-19 | 2019-04-05 | 浙江理工大学 | A kind of improved silica nano pore film modified electrode and preparation method and application |
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