CN116124860A - Electrochemical method for rapidly detecting arsenic ions in food - Google Patents
Electrochemical method for rapidly detecting arsenic ions in food Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/416—Systems
- G01N27/42—Measuring deposition or liberation of materials from an electrolyte; Coulometry, i.e. measuring coulomb-equivalent of material in an electrolyte
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/416—Systems
- G01N27/48—Systems using polarography, i.e. measuring changes in current under a slowly-varying voltage
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- Molecular Biology (AREA)
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Abstract
The invention discloses an electrochemical method for rapidly detecting arsenic ions in food. The invention discloses an electrochemical method for rapidly detecting arsenic ions in food, which adopts a screen printing electrode modified by in-situ deposition of chloroauric acid and L-cysteine. And after the screen printing electrode is connected with the portable electrochemical workstation, immersing the screen printing electrode into the sample mixed solution, and detecting the sample mixed solution by adopting an anodic stripping voltammetry. The composition position of the electrolyte deposited in situ by the screen printing electrode is chloroauric acid, L-cysteine and sulfuric acid solution. The concentration of chloroauric acid is in the range of 30-80 mu M, the concentration of L-cysteine is in the range of 0.1-0.8mM, and the concentration of sulfuric acid is in the range of 20-80mM. The method has the advantages of high sensitivity, simple and convenient operation, good specificity and high detection efficiency. Can be widely used for on-site quantitative detection of arsenic ions in food samples such as water bodies, rice, wheat, corn, paddy and the like.
Description
Technical Field
The invention belongs to the technical field of food safety detection, and relates to a rapid and efficient detection method for arsenic ions in foods such as water, rice, wheat, corn, rice, grains, tea and the like.
Background
Arsenic (As) is a heavy metal element widely existing in nature, and common arsenic compounds are trivalent arsenic, pentavalent arsenic and arsine. Arsine and arsenic trioxide are compounds with stronger toxicity, the former is combined with red blood cells to seriously destroy cell membranes, hemolysis is caused when the concentration is low, and tissue organ lesions are caused when the concentration is high; the latter is easy to combine with sulfhydryl groups in human cells to form a complex, which reduces the activity of enzymes in tissue cells, thereby affecting the normal metabolism of the human body, and food and water contaminated with arsenic enter the human body through the mouth and are distributed throughout the body along with blood. Arsenic poisoning phenomena (acute poisoning and chronic poisoning) of different degrees can be caused by accumulation of arsenic content in the body. The most easily caused is damage to the skin, which is manifested as gradual dryness, severe keratinization, abnormal pigmentation; once the arsenic content in the edible water reaches 50mg/L, cancers can be caused; the lung, kidneys, liver, nervous system, circulatory system, respiratory system, urinary system and digestive system of the human body are compromised to varying degrees when arsenic is excessive. The serious cases cause the damage of digestive tracts, and symptoms such as nausea, vomiting, abdominal pain, nerve abnormality, esophageal hemorrhage, heart failure and the like appear.
Currently, anodic Stripping Voltammetry (ASV) is the most important and widely used technique for determining trace arsenic. In an Anodic Stripping Voltammetry (ASV) rapid detection technology, a modified glassy carbon or screen printing electrode is often adopted in a rapid detection method of arsenic in food to preconcentrate and enrich contained arsenic atoms, trivalent arsenic is reduced to generate zero-valent arsenic and deposited on the electrode, and then the detection of arsenic atoms is carried out by anodic stripping and detection corresponding to the maximum stripping current to realize the detection of arsenic. The existing method has the problems of low sensitivity, long enrichment time and the like caused by large chemical potential energy of arsenic ions converted from arsenic ions to zero-valent arsenic on the electrode, and also has the problem of serious interference of metal ions such as copper ions in the detection process.
In order to improve the electrode sensitivity, the prior art mostly adopts modified glassy carbon electrodes or modified screen printing electrodes, such as glassy carbon electrodes modified by nano gold and glassy carbon electrodes modified by platinum nano particles, and the electrode modification cost is high and the operation is complicated. In the prior art, an atomic absorption spectrometry or an inductively coupled plasma mass spectrometry and other instruments are adopted to detect the arsenic content in the solution, food is required to be digested first, and although the detection result is accurate, the process is complex, the consumed time is long, the efficiency is low, and the cost is high.
Therefore, it is needed to provide a rapid, highly sensitive, highly specific method for detecting arsenic ions in foods with simple operation.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the prior art described above. Therefore, the invention provides an electrochemical method for rapidly detecting arsenic ions in food, which has the advantages of high sensitivity, simple and convenient operation, good specificity and high detection efficiency.
The invention aims to provide an electrochemical method for rapidly detecting arsenic ions in food, which is characterized in that chloroauric acid and L-cysteine in-situ deposition modified Screen Printing Electrode (SPE) is adopted in the electrochemical method. And after the screen printing electrode is connected with the electrochemical workstation, immersing the screen printing electrode into the sample mixed solution, and detecting the sample mixed solution by adopting an anodic stripping voltammetry.
The beneficial effects of the invention are as follows: the invention improves the enrichment capacity of arsenic ions on the surface of a modified screen printing electrode by in-situ electrochemical deposition of gold nanoparticles of chloroauric acid and L-cysteine for signal amplification, and utilizes the enrichment advantages of a portable electrochemical workstation and an anode stripping voltammetry to construct a detection method capable of detecting total arsenic in water and food in a field, simply, quickly and highly sensitively.
In addition, the invention adopts the screen printing electrode, the electrode has low cost, is disposable, is simple and convenient to operate, and has very stable testing performance. Meanwhile, the invention utilizes the enrichment effect, and improves the detection sensitivity to a certain extent. The detection method provided by the invention has the characteristics of simplicity in operation, low cost, high sensitivity and the like; meanwhile, the construction and use processes of the electrochemical sensor do not need to depend on large-scale instruments and professional operators, and the electrochemical sensor can be widely used for on-site quantitative detection of arsenic ions in samples such as water bodies, foods and the like.
The invention provides an electrochemical method for rapidly detecting arsenic ions in food, which comprises the following steps:
s1, activating an electrode. Before electrochemical measurement, the screen-printed electrodes were alternately cleaned with absolute ethanol and ultrapure water, and then the electrodes were immersed in an activation treatment liquid and activated by voltammetry.
S2, preparing a modified screen printing electrode for in-situ deposition of chloroauric acid and L-cysteine.
S3, detecting a sample. And after the screen printing electrode is connected with the electrochemical workstation, immersing the screen printing electrode into the sample mixed solution, and detecting the sample mixed solution by adopting an anodic stripping voltammetry.
Further, in the step S1, the activating treatment liquid is one or more of sulfuric acid, hydrochloric acid, acetic acid, phosphoric acid and hypochlorous acid.
Further, in the S1, the voltammetry is preferably cyclic voltammetry, and the sweep voltage is 0.6V to 1.0V.
Further, in the step S2, the composition position of the electrolyte solution deposited in situ by the screen printing electrode is chloroauric acid, L-cysteine and sulfuric acid solution. The concentration of chloroauric acid is in the range of 30-80 mu M, the concentration of L-cysteine is in the range of 0.1-0.8mM, and the concentration of sulfuric acid is in the range of 20-80mM.
Further, in the step S3, a voltage for detecting the arsenic ions by an anodic stripping voltammetry (LSASV) is scanned from a negative voltage to a positive voltage; the negative voltage is-0.8V to-0.10V, and the positive voltage is +0.1V to +0.8V; the scanning speed is 1V/s to 5V/s, the sampling interval is 0.001V, the resting time is 5s to 20s, the depositing time is 1000s to 2000s, the depositing potential is-0.5V to-1.5V, the stirring speed in the depositing process is set to 50rpm to 300rpm, and no stirring is performed in the dissolving process.
Further, all detection methods were performed at room temperature.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 shows the effect of scan voltage and deposition time on peak current values of arsenic dissolution.
Figure 2 shows the significant differences in electrode surface before and after gold nanoparticle deposition.
Figure 3 shows the significant differences in electrode surface before and after L-cysteine deposition.
FIG. 4 shows the linear anodic stripping voltammogram of As (III).
FIG. 5 shows the peak As (III) current value versus arsenic concentration.
Detailed Description
In order to make the technical solutions of the present invention more apparent to those skilled in the art, the following examples will be presented. It should be noted that the following examples do not limit the scope of the invention.
Example 1: rapid detection of arsenic ions in tap water
(1) And (5) preparing a sample. Taking 100ml of tap water sample to be measured, filtering by a microporous membrane with the thickness of 0.22 mu m, and obtaining filtrate which is the tap water sample to be measured.
(2) And (5) activating the electrode. Before electrochemical measurements were performed, the screen printed electrodes were alternately rinsed with absolute ethanol and ultra-pure water, after which the electrodes were immersed in 0.5mol/L sulfuric acid and activated for 5 cycles by cyclic voltammetry (from 0.6V to 1.0V).
(3) And (5) detecting a sample. The cleaned and activated electrodes were immersed in a 1mL sample cell containing 800. Mu.L of electrolyte solution and 200. Mu.L of tap water sample to be tested for detection by anodic stripping voltammetry. The electrolyte composition is chloroauric acid, L-cysteine and sulfuric acid solution. Chloroauric acid has a concentration of 40. Mu.M, L-cysteine has a concentration of 0.3mM, and sulfuric acid has a concentration of 40mM. The detection parameters of the anodic stripping voltammetry are as follows: scanning voltage-0.15V-0.5V, scanning speed 2V/s, sampling interval 0.001V, resting time 10s, depositing time 1400s, depositing potential-0.8V, stirring speed in depositing process set to 100rpm, and no stirring in stripping process. All detection methods were performed at room temperature. The blank tap water sample, the 10. Mu.g/L labeled tap water sample and the 50. Mu.g/L labeled tap water sample were each examined.
As a comparative example, the effect of the scan voltage and deposition time obtained on the peak current value of the arsenic dissolution liquid was changed as shown in fig. 1.
As a comparative example, arsenic was detected without adding aqueous chloroauric acid, and the specific procedure was the same as the above, except that no aqueous chloroauric acid was added, and the surface morphology of the obtained screen-printed electrode was characterized by scanning electron microscopy as shown in FIG. 2.
As a comparative example, arsenic was detected without adding an L-cysteine aqueous solution, and the specific procedure was the same as the above, except that the L-cysteine aqueous solution was not added, and the surface morphology of the obtained screen-printed electrode was characterized by a scanning electron microscope as shown in FIGS. 4 and 5.
Example 2: rapid detection of arsenic ions in tea
(1) And (5) preparing a sample. Dissolving tea powder sample in 0.1M sulfuric acid solution, heating for 15min, cooling to room temperature, standing for 5min, and filtering supernatant with 0.22 μm microporous membrane.
(2) And (5) activating the electrode. Before electrochemical measurements were performed, the screen printed electrodes were alternately rinsed with absolute ethanol and ultra-pure water, after which the electrodes were immersed in 0.5mol/L sulfuric acid and activated for 5 cycles by cyclic voltammetry (from 0.6V to 1.0V).
(3) And (5) detecting a sample. The cleaned and activated electrodes were immersed in a 1mL sample cell containing 800. Mu.L of electrolyte solution and 200. Mu.L of the tea leaf sample to be tested for detection by anodic stripping voltammetry. The electrolyte composition is chloroauric acid, L-cysteine and sulfuric acid solution. Chloroauric acid was 50. Mu.M in concentration, L-cysteine was 0.4mM in concentration, and sulfuric acid was 50mM in concentration. The detection parameters of the anodic stripping voltammetry are as follows: scanning voltage-0.15V-0.5V, scanning speed 2V/s, sampling interval 0.001V, resting time 10s, depositing time 1400s, depositing potential-0.8V, stirring speed in depositing process set to 100rpm, and no stirring in stripping process. All detection methods were performed at room temperature. And detecting a blank tea sample, a 10 mug/L labeled tea sample and a 50 mug/L labeled tea sample respectively. The linear anodic stripping voltammetry curve of As (III) and the peak As (III) current value versus arsenic concentration are shown in FIGS. 4 and 5.
Example 3: the blank sample and the labeled sample of the above examples 1 and 2 were analyzed by inductively coupled plasma mass spectrometry (ICP-MS), respectively. Table 1 shows the results of the detection of example 1, example 2 and ICP-MS.
Table 1 determination of As (iii) in tap water and tea samples (number n=3)
As (III) in tap water and tea samples were detected by in situ deposition of chloroauric acid and L-cysteine on SPE, and tap water and tea samples with low, medium and high levels of As (III) added were assayed. As shown in Table 1, the recovery rate was between 93.8% and 105.4%, indicating that the electrochemical sensor accuracy was good. In addition, the Relative Standard Deviation (RSD) is lower than 5%, which shows that the reproducibility of gold nanoparticles and L-cysteine in-situ deposition modified Screen Printing Electrode (SPE) is better.
Example 4: rapid detection of arsenic ions in rice
1. Sample pretreatment:
(1) Pulverizing grains into powder, and sieving (40 mesh);
(2) Accurately weighing 1.00g of a sample to be tested into a 10mL centrifuge tube, adding 5mL of 0.1mol/L hydrochloric acid reagent, oscillating for 2min by a shaking table, centrifuging for 2min by a centrifuge at 3000r/min, and testing the supernatant;
2. sample measurement and result determination
(1) Selecting a detection item of 'arsenic' and a sample type of 'rice' on a portable grain heavy metal detector;
(2) Taking out the disposable screen printing electrode and inserting the disposable screen printing electrode into an electrode mounting plug of the miniature stirrer;
(3) Taking out the analysis cell, adding 800 mu L of reagent B (reagent B component: chloroauric acid, L-cysteine and sulfuric acid solution: chloroauric acid concentration is 50 mu M, L-cysteine concentration is 0.4mM, sulfuric acid concentration is 50 mM.) into the analysis cell, putting the analysis cell into a micro-stirrer, pressing an electrode down, clicking a start button of a detection interface, and activating the electrode;
(4) After the electrode activation is completed, 200 mu L of supernatant of a sample to be detected is added into an analysis pool, and a start button of a detection interface is clicked to detect the sample;
(6) After the detection is completed, clicking a report button of the detection interface to check the result and the detection report.
Example 5: working electrode shape optimization for screen printed electrodes
1. The portable electrochemical workstation adopts square wave voltammetry, and sets the parameters as follows: deposition potential-0.8V, deposition time 3 00S, scanning initial potential-0.15V, termination potential 0.35V, potential increment 0.004V, amplitude 0.025V, frequency 12.5Hz;
2. accurately transferring 800 mu L of 0.05mol/L sulfuric acid solution of 0.5% sodium tetrachloroaurate into a sample cup by using a micropipette, inserting a screen printing electrode (square, round, rectangular and oval) into an electrode plug, pressing the electrode plug to enable an electrode working area to be completely immersed in the solution, clicking a working button at the interface of a portable electrochemical workstation, and activating the electrode;
3. after the activation is finished, 200 mu L of 170 mu g/L of inorganic arsenic standard solution is accurately added, a working button of a portable electrochemical workstation interface is clicked, detection is carried out, and oxidation-reduction current signals are read and recorded. The results are shown in the following table:
the influence of different working electrode shapes in the table on the current signal can be seen from the results in the table, under the same area condition, the round working electrode has the highest current signal, the oval and square working electrodes are inferior, and the rectangular working electrode has the lowest current signal; and the circular working electrode has the highest stability, so the circular working electrode is selected.
Meanwhile, the same labeled sample is measured by adopting the most commonly used ICP-MS detection method at present. The test results are shown in Table 1, and as can be seen from Table 1, the method of the invention is consistent with the detection results of the common ICP-MS detection method, and the deviation is within 5%. The method has the advantage of good detection accuracy.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (5)
1. An electrochemical method for rapidly detecting arsenic ions in food is characterized in that an in-situ deposition modified screen printing electrode of chloroauric acid and L-cysteine is adopted in the electrochemical method, the screen printing electrode is connected with a portable electrochemical workstation, and then the screen printing electrode is immersed into a sample mixed solution, and the sample mixed solution is detected by adopting an anodic stripping voltammetry.
2. An electrochemical method for rapid detection of arsenic ions in food according to claim 1, wherein the electrolyte composition deposited in situ by screen printing electrode is chloroauric acid, L-cysteine and sulfuric acid solution, the concentration of chloroauric acid is in the range of 30-80 μm, the concentration of L-cysteine is in the range of 0.1-0.8mM, and the concentration of sulfuric acid is in the range of 20-80mM.
3. An electrochemical method for rapid detection of arsenic ions in food according to claim 1, characterized in that the voltage at which the arsenic ions are detected by anodic stripping voltammetry is scanned from negative voltage, which is-0.8V to-0.10V, to positive voltage, which is +0.1v to +0.8v; the scanning speed is 1V/s to 5V/s, the sampling interval is 0.001V, the resting time is 5s to 20s, the depositing time is 1000s to 2000s, the depositing potential is-0.5V to-1.5V, the stirring speed in the depositing process is set to 50rpm to 300rpm, no stirring is carried out in the dissolving process, and all the detection methods are carried out at room temperature.
4. An electrochemical method for rapid detection of arsenic ions in food according to claim 1, characterized in that the screen printed electrodes are alternately washed with absolute ethanol and ultra-pure water before the electrochemical measurement is performed, and then the electrodes are immersed in an activation treatment liquid for activation by voltammetry.
5. The electrochemical method for rapid detection of arsenic ions in food according to claim 4, wherein the activating treatment liquid is one or more of sulfuric acid, hydrochloric acid, acetic acid, phosphoric acid, hypochlorous acid, and the like.
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