CN114216948B - Electrochemical method for detecting arsenic ions in solution - Google Patents
Electrochemical method for detecting arsenic ions in solution Download PDFInfo
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- CN114216948B CN114216948B CN202111285676.6A CN202111285676A CN114216948B CN 114216948 B CN114216948 B CN 114216948B CN 202111285676 A CN202111285676 A CN 202111285676A CN 114216948 B CN114216948 B CN 114216948B
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- G—PHYSICS
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- 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
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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
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/333—Ion-selective electrodes or membranes
Abstract
The invention belongs to the technical field of electrochemical analysis and detection, and particularly relates to an electrochemical method for detecting arsenic ions in a solution. An electrochemical method for detecting arsenic ions in a solution, wherein the solution to be detected contains 0.005-0.05 mol/L buffer substance, the pH value of the solution to be detected is 1-2.8, and the graphene screen printing electrode and an electrochemical workstation are adopted to detect the arsenic ions in the solution to be detected through an anodic stripping voltammetry. The method has sensitive response to arsenic, can complete enrichment in extremely short time, even has no need of setting enrichment time, has low detection limit and has the lowest Detection Limit (DL) of 0.28 mug/L. Each voltammogram can be obtained in less than 2-3 minutes without the enrichment stage of conventional methods. The graphene screen-printed electrode using this method does not need to be modified and the measurement can be performed without applying an activation potential.
Description
Technical Field
The invention relates to the technical field of electrochemical analysis and detection, in particular to an electrochemical method for detecting arsenic ions in a solution.
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 nano-gold modified glassy carbon electrodes, platinum nano-particle modified glassy carbon electrodes and gold nano-particle modified Indium Tin Oxide (ITO) electrode working electrodes, the electrode modification cost is high, and the electrode modification method is mostly used for measuring pure water and is not suitable for detecting arsenic in foods. 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 desirable to provide a method for detecting arsenic, which has high detection sensitivity and high detection efficiency.
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 detecting arsenic ions in solution, which has high sensitivity, short enrichment time and high detection efficiency, and even the enrichment time is not required to be set.
The invention is characterized in that: according to the invention, the unmodified graphene screen printing electrode is adopted, and the arsenic ions can be rapidly enriched on the unmodified graphene screen printing electrode even without reserving specific enrichment time by selecting specific buffer substances and specific concentration thereof and selecting specific pH of a solution to be tested. When the electrode potential is changed from the enrichment potential to the dissolution potential, the maximum dissolution current of the zero-valent arsenic converted into trivalent arsenic ions, also called arsenic oxidation peak current, is detected, and the aim of electrochemically detecting arsenic by adopting the unmodified graphene screen printing electrode is fulfilled.
In a first aspect the invention provides an electrochemical method for detecting arsenic ions in a solution.
Specifically, an electrochemical method for detecting arsenic ions in a solution is provided, wherein a solution to be detected contains 0.005-0.05 mol/L buffer substance, the pH value of the solution to be detected is 1-2.8, and the arsenic ions in the solution to be detected are measured by adopting a graphene screen printing electrode and an electrochemical workstation through an anodic stripping voltammetry.
Compared with the prior art, the invention has the following beneficial effects: according to the method, by selecting a specific buffer substance and a specific concentration thereof and selecting a specific pH value of a solution to be detected, arsenic ions can be rapidly enriched on an unmodified graphene screen printing electrode even without reserving a specific enrichment time, so that the aim of rapidly and accurately detecting arsenic is fulfilled. The Detection Limit (DL) is 0.28 mug/L, and each voltammogram can be obtained in less than 2-3 minutes without the enrichment stage in the conventional method.
Preferably, an electrochemical method for detecting arsenic ions in a solution, wherein the parameter for detecting the arsenic ions comprises a pulse amplitude of 10mV to 200mV. By limiting the pulse amplitude, the signal of zero-valent arsenic oxidation can be narrowed, the maximum oxidation current becomes clearer, and the detection accuracy is improved.
Preferably, an electrochemical method for detecting arsenic ions in solution comprises the steps of:
(1) Preparing a series of trivalent arsenic solutions with known concentration, wherein the series of trivalent arsenic solutions with known concentration contain 0.005mol/L to 0.05mol/L of buffer substances, and the pH value of the series of trivalent arsenic solutions with known concentration is=1 to 2.8;
(2) Determining arsenic ions in the series of trivalent arsenic solutions with known concentrations through an anodic stripping voltammetry by adopting a graphene screen printing electrode and an electrochemical workstation, detecting the arsenic ions with a parameter pulse amplitude of 10 mV-200 mV, obtaining a series of stripping voltammetry diagrams of the arsenic in the trivalent arsenic solutions with known concentrations, recording the maximum stripping current intensity of the arsenic ions in the trivalent arsenic solutions with known concentrations, and drawing an arsenic ion concentration-current calibration curve;
(3) The solution to be measured contains 0.005 mol/L-0.05 mol/L buffer substance, the pH=1-2.8 of the solution to be measured, the stripping voltammogram of arsenic of the solution to be measured is obtained under the same condition as that of the step 2), the maximum stripping current intensity of arsenic ions of the solution to be measured is recorded, and the arsenic ion concentration in the solution to be measured is calculated according to the arsenic ion concentration-current calibration curve.
Preferably, the buffer substance concentration in the step (1) is 0.005mol/L to 0.01mol/L.
Preferably, the buffer substance in the step (1) is one of phosphoric acid and its salt, hypochlorous acid and its salt, acetic acid and its salt, chlorous acid and its salt, silicic acid and its salt, metaaluminate and its salt.
Preferably, the buffer substance in step (1) is phosphoric acid or a salt thereof.
Preferably, the pH of the solution to be tested in the step (1) is 1.8-2.8.
Preferably, the voltage at which the arsenic ions are detected in step (2) is scanned from a negative voltage to a positive voltage; the negative voltage is-0.20V to-0.1V, and the positive voltage is +0.20V to +0.1V.
Preferably, the voltage at which the arsenic ions are detected in step (2) is scanned from-0.80V to +0.80V.
Preferably, the parameter pulse amplitude for detecting the arsenic ions in the step (2) is 100 mV-200 mV.
Preferably, the parameter scan increment for detecting the arsenic ions in the step (2) is 2 mV-10 mV.
Preferably, the parameter pulse width for detecting the arsenic ions in the step (2) is 20ms to 200ms.
Preferably, the parameter pulse period for detecting the arsenic ions in the step (2) is 0.2s to 1s.
Preferably, in the step (3), a reducing substance is added to the solution to be measured before the arsenic ion detection, and the reducing substance reduces pentavalent arsenic to trivalent arsenic. The step can ensure that the solution only contains trivalent arsenic during detection, and improves the accuracy of detecting total arsenic.
Preferably, the reduced substance in the step (3) is one of sodium sulfate, sodium sulfite, ferrous chloride, potassium iodide and oxalic acid.
Preferably, the reduced material in step (3) is sodium sulfate.
In a second aspect the invention provides the use of an electrochemical method for detecting arsenic ions in solution.
The method for measuring arsenic in the solution is applied to a standard addition method.
The method for measuring arsenic in the solution is applied to the detection of the arsenic ion content of food.
Preferably, the food is a liquid food or a solution of the food after extraction.
Preferably, the food comprises milk products, edible oil, alcoholic beverages, honey and fruit and vegetable drinks.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the electrochemical method, the concentration of a specific buffer substance (0.005 mol/L-0.05 mol/L) and the pH value of a specific solution to be detected (pH=1-2.8) are selected, so that arsenic ions can be rapidly enriched on a graphene screen printing electrode (which is a non-modified graphene screen printing electrode), even specific enrichment time is not required to be reserved, and the aim of rapidly and accurately detecting arsenic is fulfilled. So that the accuracy is raised and the Detection Limit (DL) is at least 0.28. Mu.g/L. Because no specific enrichment time is required to be reserved, each voltammogram can be obtained in less than 2-3 minutes.
(2) The method reduces or even does not set enrichment time, can effectively reduce the working time of the electrode, and further prolongs the service life of the electrode.
(3) By limiting the pulse amplitude, the signal of zero-valent arsenic oxidation can be narrowed, the maximum oxidation current becomes clearer, and the effect of improving the detection precision is achieved.
(4) The signal of zero-valent arsenic oxidation can be narrowed by limiting the pulse amplitude, which is favorable for distinguishing the signal of zero-valent arsenic oxidation from the oxidation signal peaks of other metal ions, so that the method has strong metal ion interference resistance. Even when the interfering ion is copper ion, the relative error RE of the method data is only 1.3 percent.
(5) The reducing substance reduces pentavalent arsenic into trivalent arsenic, so that the solution can be ensured to contain only trivalent arsenic during detection, and the accuracy of detecting total arsenic is improved.
Drawings
FIG. 1 is a graph showing arsenic ion concentration versus current calibration in example 1 of the present invention;
FIG. 2 shows the maximum elution current of arsenic ions at different pH values in example 3 of the present invention;
FIG. 3 shows the maximum elution current of arsenic ions in buffer solutions of phosphoric acid and salts thereof with different concentrations in example 4 of the present invention;
FIG. 4 is a graph showing the relationship between the peak current of arsenic oxidation and the pulse amplitude in the range of 10mV to 500mV in example 5 of the present invention;
FIG. 5 is data of 20 measurements repeated for 5.0. Mu.g/L of trivalent arsenic solution according to example 6 of the invention;
FIG. 6 is a graph showing the effect of different enrichment potentials on the maximum dissolution current in example 7 of the present invention;
FIG. 7 is a graph showing the effect of different enrichment times on the maximum dissolution current in example 7 of the present invention;
FIG. 8 is the oxidation peak current of arsenic with different kinds of metal ion concentrations of 50. Mu.g/L, 100.0. Mu.g/L and 1000.0. Mu.g/L, respectively, in example 8 of the present invention;
FIG. 9 shows the peak currents of the trivalent arsenic solution according to example 8 of the invention without interfering ions and the peak currents of arsenic oxidation at a concentration of 700.0. Mu.g/L of interfering ions of different species;
FIG. 10 is a graph showing the concentration-current calibration of standard arsenic addition to tap water measured by standard addition in example 8 of the invention.
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.
The starting materials, reagents or apparatus used in the following examples are all available from conventional commercial sources or may be obtained by methods known in the art unless otherwise specified.
The specific types of the graphene screen printing electrode and the electrochemical workstation in the embodiment of the invention are as follows:
graphene screen-printed electrodes (DRP-110 gph, dropsens), electrochemical analyzers (electrochemical workstation, chiinstrument 600E).
Example 1
An electrochemical method for detecting arsenic ions in a solution, comprising the steps of:
(1) Preparing a series of trivalent arsenic solutions with known concentration, wherein the series of trivalent arsenic solutions with known concentration contains 0.01mol/L phosphoric acid and salt buffer substances thereof, and the pH value of the solutions is=2.8;
(2) Determining arsenic ions in a series of arsenic solutions with known concentrations by adopting a graphene screen printing electrode (DRP-110 GPH, dropSens) and an electrochemical analyzer (CHInstrument 600E) through an anodic stripping voltammetry, scanning from-0.80V to +0.80V without setting enrichment time, obtaining a series of stripping voltammetry diagrams of arsenic in a trivalent arsenic solution with known concentrations, recording the maximum stripping current intensity of the arsenic ions in the trivalent arsenic solution with known concentrations, and drawing an arsenic ion concentration-current calibration curve, wherein the pulse amplitude is 200mV, the scanning increment is 4mV, the pulse width is 80ms and the pulse period is 0.5 s;
(3) Mixing 5.0mL of a sample to be tested with 0.02mol/L sodium sulfate in an acidic medium to reduce the content of pentavalent arsenic, mixing 10.0mL of phosphoric acid and a salt buffer solution thereof with 0.01mol/L, pH =2.8 and 150 mu L of the sample to be tested to obtain a solution to be tested, wherein the solution to be tested contains 0.01mol/L phosphoric acid and a salt buffer substance thereof, the pH value of the solution to be tested is=2.8, obtaining a stripping voltammogram of arsenic of the solution to be tested under the same conditions as in the step 2), recording the maximum stripping current intensity of arsenic ions of the solution to be tested, and calculating the arsenic ion concentration in the solution to be tested according to the arsenic ion concentration-current calibration curve.
FIG. 1 is a graph showing arsenic ion concentration-current calibration in example 1 of the present invention, wherein the abscissa represents trivalent arsenic ion concentration (As (III)), and the ordinate represents current intensity (Ip), and the specific equation of the graph is: y= 4.523X-0.332; r= 0.9983. The Detection Limit (DL) was 0.28. Mu.g/L, the Quantitative Limit (QL) was 0.92. Mu.g/L, and the Standard Deviation (SD) was 0.418. Mu.g/L.
The concentration of trivalent arsenic was studied in the range of 0.10. Mu.g/L to 50.0. Mu.g/L. Under this condition, the oxidation peak is proportional to the concentration of trivalent arsenic in the range of 0.0. Mu.g/L to 5.0. Mu.g/L.
Example 2
Example 2 two apple juice samples (sample 1, sample 2) were tested for arsenic ions using the test method as in example 1, each sample being assayed in parallel 3 times. Meanwhile, the same sample was measured by an atomic absorption spectrometer-gas atomization apparatus (AAS-HG), and the measurement results were compared. The measurement results are shown in the following table 1:
TABLE 1
| Sample of | The method is used for measuring the arsenic content (mug/L) | AAS-HG(μg/L) |
| 1 | 20.0±0.03 | 19 |
| 2 | ＜0.06 | ＜5 |
As can be seen from Table 1, the results of the arsenic content determined by the present method are very close to those of the atomic absorption spectrometer-gaseous atomization apparatus (AAS-HG).
Example 3: influence of pH on the sensitivity of the detection method
To illustrate the effect of pH on the sensitivity of the detection method, the pH was measured in 0.01mol/L phosphoric acid (H 3 PO 4 ) In the presence of sodium hydroxide (NaOH) solution with the concentration of 4.0mol/L, the pH value of the solution is changed between 1.8 and 5.5, 10.0 mug/L of trivalent arsenic solution is measured by using a graphene screen printing electrode (DRP-110 GPH, dropSens) and an electrochemical analyzer (CHInstrument 600E), and the anode voltammogram curve is measured to obtain the maximum elution current of arsenic ions under different pH values.
As a result, as shown in FIG. 2, FIG. 2 shows the maximum elution current of arsenic ions at different pH values in example 3 of the present invention, the abscissa shows the pH value, the left ordinate shows the current intensity (Ip), and the right ordinate shows the voltage (Ep), and the solid circles in FIG. 2 show the relationship between the concentration of phosphoric acid and its salt buffer solution and the current intensity (Ip), and the hollow circles show the relationship between the concentration of phosphoric acid and its salt buffer solution and the voltage (Ep). At ph=1.8-2.8, the maximum elution current of arsenic ions is between 20.0 μΑ and 17.6 μΑ. When the pH was increased from 2.8 to 3.3, the peak current dropped rapidly from 17.6 μa to 8.1 μa, with a very small current of 1.3 μa at ph=4.0 Shi Feng. It can be stated that the sensitivity of the method assay is best when ph=1.8-2.8.
Example 4: influence of phosphate and its salt buffer concentration on sensitivity of detection method
To illustrate the effect of phosphate and its salt buffer concentration on the sensitivity of the detection method, 10 μg/L of trivalent arsenic solution was measured with a graphene screen printing electrode (DRP-110 gph, dropsens) and an electrochemical analyzer (chnument 600E) in the presence of phosphate and its salt buffer at a ph=2.8 and a concentration in the range of 0.005mol/L to 0.200mol/L, and the anodic voltammogram was measured to obtain the maximum elution current of arsenic ions in phosphate and its salt buffer at different concentrations.
As a result, as shown in FIG. 3, FIG. 3 shows the maximum elution current of arsenic ions in the buffer solutions of phosphoric acid and its salts at different concentrations in example 4 of the present invention, and the abscissa shows the concentration of the buffer solutions of phosphoric acid and its salts and the ordinate shows the current intensity (Ip). The results showed that the peak current for zero valent arsenic oxidation decreased from 12.0. Mu.A to 2.0. Mu.A as the phosphate and its salt buffer concentration increased from 0.01mol/L to 0.10 mol/L.
Example 5: influence of pulse amplitude on sensitivity of detection method
To illustrate the effect of pulse amplitude on the sensitivity of the detection method, the pulse amplitude was varied from 10mV to 500mV, 10. Mu.g/L of trivalent arsenic solution was measured using a graphene screen-printed electrode (DRP-110 GPH, dropSens) and an electrochemical analyzer (CHInstrument 600E), and the anodic voltammogram was measured to obtain the maximum elution current of arsenic ions at different pulse amplitudes.
As a result, FIG. 4 shows the relationship between the peak current of arsenic oxidation and the pulse amplitude in the range of 10mV to 500mV in example 5 of the present invention, and the abscissa shows the pulse amplitude and the ordinate shows the current intensity (Ip). The results show that the oxidation peak current of arsenic is in a linear relation with the pulse amplitude within the range of 10 mV-500 mV. However, when the pulse amplitude is greater than 200mV, the peak potential moves in a more negative direction and the signal of zero-valent arsenic oxidation becomes very broad.
Example 6: stability of graphene screen-printed electrodes
To demonstrate the stability of the graphene screen-printed electrode under the present method, 20 replicates of 5.0 μg/L trivalent arsenic solution were tested with a graphene screen-printed electrode (DRP-110 gph, dropsens) and electrochemical analyzer (chnument 600E) under the same conditions as in example 1.
The results obtained are shown in FIG. 5, and FIG. 5 is data of 20 measurements repeated for 5.0. Mu.g/L of the trivalent arsenic solution in example 6 of the present invention, the abscissa is the number of times of detection and the ordinate is current. As a result, the average current was 30.6. Mu.A, the standard deviation was 1.5, and the relative standard deviation was 5%.
Example 7
To illustrate the short enrichment time of the present method, even without setting the enrichment time, the following experiment was performed in example 7.
The enrichment time is set to be 10s, a graphene screen printing electrode (DRP-110 GPH, dropSens) and an electrochemical analyzer (CHInstrument 600E) are used for carrying out anodic stripping voltammetry, different enrichment potentials are set for a trivalent arsenic solution containing 0.01mol/L, pH =2.8 phosphoric acid and salt buffer solution thereof and 10.0 mug/L, and the influence of the different enrichment potentials on the maximum stripping current is recorded.
As a result, FIG. 6 shows the relationship between the maximum elution current and the different enrichment potentials in example 7 of the present invention, and the abscissa shows the concentration potential (E acc ) The ordinate is amperage (Ip). The results show that at different enrichment potentials, the peak current for zero-valent arsenic oxidation stabilizes around 5 μA.
Setting the enrichment potential to 0.3V the trivalent arsenic solution containing 0.01mol/L, pH =2.8 phosphoric acid and its salt buffer, 10.0 μg/L was analyzed by anodic stripping voltammetry using graphene screen printing electrodes (DRP-110 gph, dropsens) and electrochemical analyzer (chnsement 600E), and the effect of different enrichment times on the maximum stripping current was recorded.
ResultsAs shown in FIG. 7, FIG. 7 is a graph showing the relationship of the effect of different enrichment times on the maximum dissolution current in example 7 of the present invention, and the abscissa is the enrichment time (t acc ) The ordinate is amperage (Ip). The results show that the maximum dissolution current is almost constant at enrichment times between 0s and 300 s. Thus, to avoid unnecessarily increasing the analysis time, the measurement is performed directly without applying enrichment time. The reduction of the enrichment time, namely the reduction of the working time of the electrode, is beneficial to improving the durability of the graphene screen printing electrode.
Example 8
In order to demonstrate the strong anti-interference capability of the method, the following experiment was performed in this example.
Determination of the Metal ion to Cu 2+ 、Pb 2+ 、Hg 2+ 、Cd 2+ 、Mn 2+ 、Mg 2+ 、Fe 3+ 、Bi 3+ 、Se 4+ And Cr (V) 6+ The peak currents at 50. Mu.g/L, 100.0. Mu.g/L and 1000.0. Mu.g/L, respectively, are shown in FIG. 8, and FIG. 8 shows the oxidation peak currents of arsenic at 50. Mu.g/L, 100.0. Mu.g/L and 1000.0. Mu.g/L, respectively, for the different kinds of metal ions in example 8 of the present invention, the abscissa shows the kind of metal ion (M n+ ) The ordinate is amperage (Ip).
Determination of peak current of 2.0. Mu.g/L trivalent arsenic solution without interfering ions, and interfering ions (Cu 2+ 、Pb 2+ 、Hg 2+ 、Cd 2 + 、Mn 2+ 、Mg 2+ 、Fe 3+ 、Bi 3+ 、Se 4+ And Cr (V) 6+ ) As a result of the trivalent arsenic peak current of the trivalent arsenic solution of 2.0. Mu.g/L at a concentration of 700.0. Mu.g/L, as shown in FIG. 9, FIG. 9 shows the peak current of the trivalent arsenic solution of example 8 of the present invention without interfering ions, and the peak current of arsenic oxidation at a concentration of 700.0. Mu.g/L of different kinds of interfering ions, the abscissa shows the metal ion species (M n+ ) The ordinate is amperage (Ip). As can be seen from the results of FIG. 9, however, cu 2+ The presence of (2) increases the arsenic current and moves it to a more negative potential (-0.04V). Cu (Cu) 2+ Is the main interfering ion of arsenic, because in Cu 2+ Trivalent arsenic and Cu in the presence of 2+ Will react to generate intermetallic compound, and extractHigh peak current sensitivity of arsenic.
The following is a method for detecting that the method is applied to a standard addition method and contains 50.0 mug/L trivalent arsenic ion and 1.3mg/L Cu 2+ Tap water solution of interfering ions:
(1) 10.0mL, 0.01mol/L, pH =2.8 phosphoric acid and salt buffer solution thereof and 200 mu L of a sample to be tested are mixed to obtain a solution to be tested, the solution to be tested is multiple and each volume of the solution to be tested is 10.0mL, the solution to be tested contains 0.01mol/L phosphoric acid buffer substance, and the pH value of the solution to be tested is=2.8.
(2) And (3) adding a certain amount of standard trivalent arsenic solution with known concentration into the solution to be detected in the step (1) to prepare the solution to be detected with different known standard trivalent arsenic ion concentrations.
(3) And (3) measuring arsenic ions in the solution to be measured with different known standard trivalent arsenic ion concentrations by adopting a graphene screen printing electrode (DRP-110 GPH, dropSens) and an electrochemical analyzer (CHInstrument 600E) through an anodic stripping voltammetry, scanning from-0.80V to +0.80V without setting enrichment time, wherein the pulse amplitude in arsenic ion detection parameters is 200mV, the scanning increment is 4mV, the pulse width is 80ms and the pulse period is 0.5s, obtaining the stripping voltammogram of the arsenic of the solution to be measured with different known standard trivalent arsenic ion concentrations, and recording the maximum stripping current intensity of the arsenic ions.
As a result, as shown in FIG. 10, FIG. 10 is a graph showing a concentration-current calibration curve of a standard trivalent arsenic ion concentration (As) added to tap water measured by the standard addition method in example 8 of the present invention, and the abscissa is the standard trivalent arsenic ion concentration (As 3+ ) The ordinate is amperage (Ip). The standard curve is y=3.160+3.120 x, r:0.9985. The measured result shows that the concentration of the unknown arsenic solution in the solution to be measured is 1.01282 mug/L, and the concentration of arsenic ions in the corresponding tap water is 50.6+/-0.1 mug/L, and the relative error RE=1.3% (50.6 mug/L= 1.01282 mug/L, 10mL/200 mug). It can be seen that the interfering ion Cu 2+ The arsenic detection of the method is not interfered.
Claims (8)
1. An electrochemical method for detecting arsenic ions in a solution is characterized in that the electrochemical method uses a solution to be detected, the solution to be detected contains 0.005-0.05 mol/L buffer substance, the pH value of the solution to be detected is 1-2.8, and an unmodified graphene screen printing electrode and an electrochemical workstation are adopted to detect the arsenic ions in the solution to be detected through an anodic stripping voltammetry;
the parameter pulse amplitude for detecting the arsenic ions is 10 mV-200 mV;
the buffer substance is one of phosphoric acid and its salt, hypochlorous acid and its salt, acetic acid and its salt, chlorous acid and its salt, silicic acid and its salt, metaaluminate and its salt.
2. The electrochemical method for detecting arsenic ions in solution according to claim 1, comprising the steps of:
(1) Preparing a series of trivalent arsenic solutions with known concentration, wherein the series of trivalent arsenic solutions with known concentration contain buffer substances with 0.005-0.05 mol/L, and the pH=1-2.8 of the series of trivalent arsenic solutions with known concentration;
(2) Measuring arsenic ions in the series of trivalent arsenic solutions with known concentrations by adopting an unmodified graphene screen printing electrode and an electrochemical workstation through an anodic stripping voltammetry, detecting the arsenic ions with a parameter pulse amplitude of 10 mV-200 mV, obtaining a series of stripping voltammograms of the arsenic in the trivalent arsenic solutions with known concentrations, recording the maximum stripping current intensity of the arsenic ions in the trivalent arsenic solutions with known concentrations, and drawing an arsenic ion concentration-current calibration curve;
(3) The solution to be measured contains 0.005 mol/L-0.05 mol/L buffer substance, the pH value of the solution to be measured is=1-2.8, the stripping voltammogram of arsenic in the solution to be measured is obtained under the same condition as that of the step 2), the maximum stripping current intensity of arsenic ions in the solution to be measured is recorded, and the arsenic ion concentration in the solution to be measured is calculated according to the arsenic ion concentration-current calibration curve.
3. The electrochemical method for detecting arsenic ions in a solution according to claim 2, wherein in the step (1), the buffer substance concentration is 0.005mol/L to 0.01mol/L.
4. The electrochemical method for detecting arsenic ions in a solution according to claim 2, wherein in step (1), the pH of the solution to be detected is 1.8 to 2.8.
5. The electrochemical method for detecting arsenic ions in solution according to claim 2, wherein in step (2), the voltage at which the arsenic ions are detected is scanned from a negative voltage to a positive voltage; the negative voltage is-0.20V to-0.1V and the positive voltage is +0.20V to +0.1V.
6. The electrochemical method for detecting arsenic ions in a solution according to claim 2, wherein in step (3), a reducing substance is added to the solution to be detected before the detection of arsenic ions, the reducing substance reduces pentavalent arsenic to trivalent arsenic, and the reducing substance is one of sodium sulfate, sodium sulfite, ferrous chloride, potassium iodide and oxalic acid.
7. Use of an electrochemical method for detecting arsenic ions in a solution according to any one of claims 1 to 6 in a standard addition method.
8. Use of an electrochemical method for detecting arsenic ions in a solution according to any one of claims 1 to 6 for detecting arsenic ion content in a food product.
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