CN114216948A - Electrochemical method for detecting arsenic ions in solution - Google Patents
Electrochemical method for detecting arsenic ions in solution Download PDFInfo
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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 comprises the steps that the solution to be detected contains 0.005-0.05 mol/L of buffer substances, the pH value of the solution to be detected is 1-2.8, and the arsenic ions in the solution to be detected are detected through an anodic stripping voltammetry method by adopting a graphene screen printing electrode and an electrochemical workstation. The method has sensitive response to arsenic, can finish enrichment in extremely short time, even does not need to set the enrichment time, and has low Detection Limit (DL) which is 0.28 mu g/L at least. Each voltammogram can be obtained in less than 2-3 minutes without the enrichment stage of conventional methods. The graphene screen-printed electrode using the method does not need to be modified, and can be measured 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 present in nature, and common arsenic compounds are trivalent arsenic, pentavalent arsenic and arsine. The arsenic hydride and arsenic trioxide are compounds with strong toxicity, the former is combined with erythrocytes to cause severe damage to cell membranes, so that the hemolysis phenomenon is caused when the concentration is low, and the pathological changes of tissues and organs are caused when the concentration is high; the latter is easy to combine with sulfhydryl group in human body cell to produce complex, and can reduce activity of enzyme in tissue cell, so that it can affect normal metabolism of human body, and the food and water polluted by arsenic can be fed into human body by mouth, and can be distributed in every part of the whole body along with blood. As arsenic accumulates in the body, arsenic poisoning phenomena (acute poisoning and chronic poisoning) occur to varying degrees. The most easily caused are skin lesions, which are indicated by gradual dryness, severe keratinization, abnormal pigmentation; cancer can be caused once the arsenic content in the edible water reaches 50 mg/L; when the arsenic content is excessive, the lung, kidney, liver, nervous system, circulatory system, respiratory system, urinary system and digestive system of the human body are all harmed to different degrees. Severe patients may have damaged digestive tract, nausea, emesis, abdominal pain, nerve abnormality, esophageal hemorrhage, and heart failure.
Currently, Anodic Stripping Voltammetry (ASV) is the most important and most widely used technique for determining trace arsenic. In the fast detection technology of Anodic Stripping Voltammetry (ASV), the fast determination method of arsenic in food usually adopts modified glassy carbon or silk-screen printing electrode to pre-concentrate and enrich contained arsenic atoms, zero-valent arsenic is generated by reducing trivalent arsenic and is deposited on the electrode, and then the detection of arsenic detection is realized by anode stripping arsenic atom detection corresponding to maximum stripping current. At present, the method has the problems of low sensitivity, long enrichment time and the like caused by large chemical potential energy of converting arsenic ions from arsenic ions to zero-valent arsenic on an electrode, and the problem of serious interference of metal ions such as copper ions in the detection process. In order to improve electrode sensitivity in the prior art, modified glassy carbon electrodes or modified screen-printed electrodes are mostly adopted, 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, so that electrode modification cost is high, most of electrodes are used for pure water determination, and are not suitable for detection of arsenic in food. In the prior art, instruments such as an atomic absorption spectrometry or an inductively coupled plasma mass spectrometry are adopted to detect the arsenic content in a solution, food needs to be digested firstly, 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 is directed to solving at least one of the problems of the prior art described above. Therefore, the invention provides an electrochemical method for detecting arsenic ions in a solution, which has the advantages of high sensitivity, short enrichment time, no need of setting the enrichment time and high detection efficiency.
The invention conception of the invention is as follows: according to the invention, the unmodified graphene screen printing electrode is adopted, and 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 the unmodified graphene screen printing electrode even without reserving a specific enrichment time. When the electrode potential is changed from the enrichment potential to the dissolution potential, the maximum dissolution current of the trivalent arsenic ion converted from the zero-valent arsenic is detected, which is also called as the oxidation peak current of arsenic, so that the aim of electrochemically detecting arsenic by adopting the unmodified graphene screen printing electrode is fulfilled.
In a first aspect of the invention, an electrochemical method for detecting arsenic ions in a solution is provided.
Specifically, an electrochemical method for detecting arsenic ions in a solution comprises the steps that the solution to be detected contains 0.005-0.05 mol/L of buffer substances, the pH value of the solution to be detected is 1-2.8, and the arsenic ions in the solution to be detected are detected through an anodic stripping voltammetry by adopting a graphene screen printing electrode and an electrochemical workstation.
Compared with the prior art, the invention has the following beneficial effects: according to the method, the arsenic ions can be rapidly enriched on the unmodified graphene screen printing electrode even without reserving specific enrichment time by selecting a specific buffer substance and specific concentration thereof and selecting specific pH of a solution to be detected, so that the aim of rapidly and accurately detecting the arsenic is fulfilled. The Detection Limit (DL) is 0.28. mu.g/L, and each voltammogram can be obtained in less than 2-3 minutes without an enrichment stage in the conventional method.
Preferably, the parameters for detecting the arsenic ions in the electrochemical method for detecting the arsenic ions in the solution comprise the pulse amplitude of 10 mV-200 mV. The signal of zero-valent arsenic oxidation can be narrowed by limiting the pulse amplitude, the maximum oxidation current becomes clearer, and the detection precision is improved.
Preferably, the electrochemical method for detecting arsenic ions in a solution comprises the following steps:
(1) preparing a series of trivalent arsenic solutions with known concentration, wherein the series of trivalent arsenic solutions with known concentration contain 0.005-0.05 mol/L of buffer substances, and the pH value of the series of trivalent arsenic solutions with known concentration is 1-2.8;
(2) measuring arsenic ions in the series of trivalent arsenic solutions with known concentrations by adopting a graphene screen printing electrode and an electrochemical workstation through an anodic stripping voltammetry, obtaining a series of stripping voltammograms of arsenic in the trivalent arsenic solutions with known concentrations, recording the maximum stripping current intensity of the arsenic ions in the series of trivalent arsenic solutions with known concentrations, and drawing an arsenic ion concentration-current calibration curve, wherein the parameter pulse amplitude for detecting the arsenic ions is 10 mV-200 mV;
(3) and (3) the solution to be detected contains 0.005-0.05 mol/L of buffer substances, the pH value of the solution to be detected is 1-2.8, a dissolution voltammogram of arsenic in the solution to be detected is obtained under the same condition as the step 2), the maximum dissolution current intensity of arsenic ions in the solution to be detected is recorded, and the concentration of the arsenic ions in the solution to be detected is calculated according to the arsenic ion concentration-current calibration curve.
Preferably, the concentration of the buffer substance in the step (1) is 0.005mol/L to 0.01 mol/L.
Preferably, the buffer substance in step (1) is one of phosphoric acid and salts thereof, hypochlorous acid and salts thereof, acetic acid and salts thereof, chlorous acid and salts thereof, silicic acid and salts thereof, and meta-aluminate acid and salts thereof.
Preferably, the buffer substance in step (1) is phosphoric acid and its salt.
Preferably, the pH value of the solution to be detected in the step (1) is 1.8-2.8.
Preferably, the voltage for detecting the arsenic ions in the 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 for detecting the arsenic ions in the step (2) is scanned from-0.80V to + 0.80V.
Preferably, the pulse amplitude of the parameter for detecting the arsenic ions in the step (2) is 100 mV-200 mV.
Preferably, the increment of parameter scanning 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 200 ms.
Preferably, the parameter pulse period for detecting the arsenic ions in the step (2) is 0.2s to 1 s.
Preferably, in the step (3), a reducing substance is added to the solution to be detected before the arsenic ion detection, and the reducing substance reduces pentavalent arsenic into trivalent arsenic. The step can ensure that only trivalent arsenic is contained in the solution during detection, and the accuracy of detecting the total arsenic is improved.
Preferably, the reducing substance in 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 a 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 content of arsenic ions in food.
Preferably, the food is a liquid food or a solution of extracted food.
Preferably, the food comprises dairy 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 specific buffer substance concentration (0.005-0.05 mol/L) and the specific pH (1-2.8) of the solution to be detected are selected, so that arsenic ions can be rapidly enriched on the graphene screen printing electrode (which is a graphene screen printing electrode without modification) even without reserving specific enrichment time, and the purpose of rapidly and accurately detecting arsenic is achieved. The accuracy is improved, and the Detection Limit (DL) is 0.28 mug/L at the minimum. As specific enrichment time is not required to be reserved, each voltammogram can be obtained within 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) The signal of zero-valent arsenic oxidation can be narrowed by limiting the pulse amplitude, 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 beneficial to distinguishing the signal of zero-valent arsenic oxidation and the oxidation signal peak of other metal ions, so that the method has strong metal ion interference resistance. Even if the interfering ions are copper ions, the relative error RE of the data of the method is only 1.3 percent.
(5) The reduction substance reduces pentavalent arsenic into trivalent arsenic, which can ensure that the solution only contains trivalent arsenic during detection and improve the accuracy of total arsenic detection.
Drawings
FIG. 1 is a calibration curve of arsenic ion concentration-current in example 1 of the present invention;
FIG. 2 is a graph showing the maximum arsenic ion elution current at different pH values in example 3 of the present invention;
FIG. 3 is the maximum stripping current of arsenic ions in buffer solutions of phosphoric acid and its salts with different concentrations in example 4 of the present invention;
FIG. 4 is a graph showing the relationship between the oxidation peak current of arsenic in the range of 10mV to 500mV versus the pulse amplitude in example 5 of the present invention;
FIG. 5 is data of 20 repeated measurements on a 5.0. mu.g/L trivalent arsenic solution in example 6 of the present invention;
FIG. 6 is a graph showing the relationship between 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 shows the oxidation peak currents of arsenic with different concentrations of metal ions of 50. mu.g/L, 100.0. mu.g/L and 1000.0. mu.g/L in example 8 of the present invention;
FIG. 9 shows the peak current of non-interfering ions in the trivalent arsenic solution and the oxidation peak current of arsenic at a concentration of 700.0 μ g/L for different types of interfering ions in example 8 of this invention;
FIG. 10 is a calibration curve of concentration-current for a standard arsenic solution in tap water, as measured by the standard addition method in example 8 of the present 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 are given for illustration. It should be noted that the following examples are not intended to limit the scope of the claimed invention.
The starting materials, reagents or apparatuses used in the following examples are conventionally commercially available or can be obtained by conventionally known methods, unless otherwise specified.
The specific models of the graphene screen printing electrode and the electrochemical workstation in the embodiment of the invention are as follows:
graphene screen-printed electrodes (DRP-110GPH, DropSens), electrochemical analyzer (electrochemical workstation, heat cell 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 contain 0.01mol/L of phosphoric acid and salt buffer substances thereof, and the pH value of the solutions is 2.8;
(2) measuring arsenic ions in a series of arsenic solutions with known concentrations by adopting a graphene screen printing electrode (DRP-110GPH, DropSens) and an electrochemical analyzer (CHInsTrent 600E) through an anodic stripping voltammetry method, detecting scanning from-0.80V to +0.80V without setting enrichment time, obtaining a series of stripping voltammograms of the arsenic solutions with known concentrations, recording the maximum stripping current intensity of the arsenic ions in the series of trivalent arsenic solutions with known concentrations, and drawing an arsenic ion concentration-current calibration curve, 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 0.5 s;
(3) mixing 5.0mL of a sample to be detected with 0.02mol/L of sodium sulfate in an acidic medium to reduce the content of pentavalent arsenic, mixing 10.0mL of the sample to be detected, 0.01mol/L, pH ═ 2.8 phosphoric acid and salt buffer solution thereof with 150 μ L of the sample to be detected to obtain a solution to be detected, wherein the solution to be detected contains 0.01mol/L of phosphoric acid and salt buffer substance thereof, the pH value of the solution to be detected is 2.8, obtaining a dissolution voltammogram of arsenic ions in the solution to be detected under the same conditions as those in the step 2), recording the maximum dissolution current intensity of arsenic ions in the solution to be detected, and calculating the concentration of arsenic ions in the solution to be detected according to the arsenic ion concentration-current calibration curve.
Fig. 1 is a calibration curve of arsenic ion concentration-current in example 1 of the present invention, in which the abscissa is trivalent arsenic ion concentration (As (iii)) and the ordinate is current intensity (Ip), and the specific curve equation is As follows: Y-4.523X-0.332; r-0.9983. The Detection Limit (DL) was 0.28. mu.g/L, the Quantification 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 ion using the test method as in example 1, with 3 replicates per sample. Meanwhile, the same samples were measured with an atomic absorption spectrometer-gaseous atomization device (AAS-HG), and the measurement results were compared. The measurement results are shown in table 1 below:
TABLE 1
| Sample (I) | The method determines arsenic content (mu g/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 determination of arsenic content by the method are very close to those of the determination by an atomic absorption spectrometer-gaseous atomization device (AAS-HG).
Example 3: effect 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 at 0.01mol/L phosphoric acid (H)3PO4) In the presence of the arsenic ions, a sodium hydroxide (NaOH) solution with the concentration of 4.0mol/L is added to change the pH value of the solution between 1.8 and 5.5, a 10.0 mu g/L trivalent arsenic solution is measured by a graphene screen printing electrode (DRP-110GPH, DropSens) and an electrochemical analyzer (CHInsmetric 600E), and an anodic voltammetry curve is measured to obtain the maximum stripping current of the arsenic ions under different pH values.
As shown in FIG. 2, FIG. 2 shows the maximum arsenic ion elution current at different pH values in example 3 of the present invention, with the abscissa representing the pH value, the left ordinate representing the current intensity (Ip), and the right ordinate representing the voltage (Ep), and the solid circles in FIG. 2 show the relationship between the concentrations of the elution solutions of phosphoric acid and its salts and the current intensity (Ip), and the hollow circles show the relationship between the concentrations of the buffer solutions of phosphoric acid and its salts and the voltage (Ep). The maximum arsenic ion elution current is between 20.0 and 17.6 mua at pH 1.8-2.8. The peak current rapidly dropped from 17.6 μ a to 8.1 μ a as the pH increased from 2.8 to 3.3, with a peak current of very little 1.3 μ a at pH 4.0. It can be shown that the sensitivity of the method is best when the pH is 1.8-2.8.
Example 4: effect of phosphoric acid and its salt buffer concentration on the sensitivity of the detection method
To illustrate the effect of the concentration of phosphoric acid and its salt buffer on the sensitivity of the detection method, a 10 μ g/L trivalent arsenic solution was measured with a graphene screen-printed electrode (DRP-110GPH, DropSens) and an electrochemical analyzer (CHInstrument600E) in the presence of a phosphoric acid and its salt buffer having a pH of 2.8 and a concentration in the range of 0.005mol/L to 0.200mol/L, and the anodic voltammetry was measured to obtain the maximum elution current of arsenic ions in phosphoric acid and its salt buffer solutions of different concentrations.
As shown in FIG. 3, FIG. 3 shows the maximum elution current of arsenic ions in the buffer solutions of phosphoric acid and its salt at different concentrations in example 4 of the present invention, with the abscissa representing the concentration of the buffer solution of phosphoric acid and its salt and the ordinate representing the current intensity (Ip). The results show that when the concentration of the phosphate and the salt buffer solution thereof is increased from 0.01mol/L to 0.10mol/L, the peak current of zero-valent arsenic oxidation is reduced from 12.0 muA to 2.0 muA.
Example 5: influence of pulse amplitude on sensitivity of detection method
In order to illustrate the influence of the pulse amplitude on the sensitivity of the detection method, the pulse amplitude is changed from 10mV to 500mV, a 10 mu g/L trivalent arsenic solution is measured by a graphene screen printing electrode (DRP-110GPH, DropSens) and an electrochemical analyzer (CHInsmeasuring 600E), and an anodic voltammetry curve is measured to obtain the maximum stripping current of arsenic ions under different pulse amplitudes.
As shown in FIG. 4, FIG. 4 shows the relationship between the oxidation peak current of arsenic in example 5 of the present invention and the pulse width in the range of 10mV to 500mV, with the pulse width on the abscissa and the current intensity (Ip) on the ordinate. The result shows that the oxidation peak current of arsenic is in a linear relation with the pulse amplitude in the range of 10 mV-500 mV. However, when the pulse amplitude is greater than 200mV, the peak potential shifts in the more negative direction and the signal for zero-valent arsenic oxidation becomes very broad.
Example 6: stability of graphene screen-printed electrode
To illustrate the stability of the graphene screen-printed electrode under this method, a 5.0 μ g/L trivalent arsenic solution was repeatedly tested under the same conditions as in example 1 using a graphene screen-printed electrode (DRP-110GPH, DropSens) and an electrochemical analyzer (CHInsparent 600E) for 20 times.
The results are shown in FIG. 5, and FIG. 5 is data of 20 times of repeated measurement of 5.0 μ g/L trivalent arsenic solution in example 6 of the present invention, with the abscissa representing the number of times of detection and the ordinate representing the current. 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, and even the absence of the need to set the enrichment time, example 7 performs the following experiment.
The enrichment time was set to 10s, anodic stripping voltammetry was performed with a graphene screen-printed electrode (DRP-110GPH, DropSens) and an electrochemical analyzer (electrochemical 600E) to set different enrichment potentials for a solution containing 0.01mol/L, pH ═ 2.8 phosphoric acid and its salt buffer, and 10.0 μ g/L of trivalent arsenic, and the effect of the different enrichment potentials on the maximum stripping current was recorded.
The results are shown in FIG. 6, in which FIG. 6 shows the influence of different enrichment potentials on the maximum dissolution current in example 7 of the present invention, and the abscissa shows the enrichment potential (E)acc) And the ordinate represents the current intensity (Ip). The results show that the peak current of zero-valent arsenic oxidation is stabilized around 5 muA under different enrichment potentials.
An anodic stripping voltammetry was performed with a graphene screen-printed electrode (DRP-110GPH, DropSens) and an electrochemical analyzer (chinstrum 600E) set at an enrichment potential of 0.3V to analyze a trivalent arsenic solution containing 0.01mol/L, pH ═ 2.8 phosphoric acid and its salt buffer and 10.0 μ g/L, and the influence of different enrichment times on the maximum stripping current was recorded.
The results are shown in FIG. 7, which is a graph of the different enrichment times versus the maximum in example 7 of the present inventionThe influence relationship of the dissolution current, the abscissa is the enrichment time (t)acc) And the ordinate represents the current intensity (Ip). The results show that the maximum dissolution current is almost constant between the enrichment time 0s and 300 s. Thus, to avoid unnecessarily increasing the analysis time, the measurement is performed directly without applying an enrichment time. The enrichment time is reduced, namely the working time of the electrode is reduced, and the durability of the graphene screen printing electrode is improved.
Example 8
To illustrate the strong anti-interference capability of the method, the following experiment is performed in this embodiment.
Determination of the Metal ion being Cu2+、Pb2+、Hg2+、Cd2+、Mn2+、Mg2+、Fe3+、Bi3+、Se4+And Cr6+The peak currents at concentrations of 50. mu.g/L, 100.0. mu.g/L and 1000.0. mu.g/L, respectively, are shown in FIG. 8, where FIG. 8 is the oxidation peak currents of arsenic at concentrations of 50. mu.g/L, 100.0. mu.g/L and 1000.0. mu.g/L, respectively, for different kinds of metal ions in example 8 of the present invention, and the abscissa is the kind of metal ion (M.sub.g/L)n+) And the ordinate represents the current intensity (Ip).
Determination of Peak Current of non-interfering ions, and interfering ions (Cu) in a 2.0. mu.g/L trivalent arsenic solution2+、Pb2+、Hg2+、Cd2 +、Mn2+、Mg2+、Fe3+、Bi3+、Se4+And Cr6+) The results of the peak current of trivalent arsenic of 2.0. mu.g/L trivalent arsenic solution with a concentration of 700.0. mu.g/L are shown in FIG. 9, where FIG. 9 shows the peak current of non-interfering ions of trivalent arsenic solution in example 8 of the present invention, and the oxidation peak current of arsenic with a concentration of 700.0. mu.g/L of interfering ions of different species, and the abscissa shows the type of metal ion (M)n+) And the ordinate represents the current intensity (Ip). As can be seen from the results of FIG. 9, however, Cu2+The presence of arsenic increases the arsenic current and moves it to a more negative potential (-0.04V). Cu2+Is the main interfering ion for arsenic, since in Cu2+In the presence of trivalent arsenic and Cu2+Can react to generate intermetallic compounds, and improves the peak current sensitivity of arsenic.
The followingThe method is applied to a standard addition method for detecting the arsenic ions containing 50.0 mu g/L of trivalent arsenic ions and 1.3mg/L of Cu2+Tap water solution of interfering ions:
(1) 10.0mL, 0.01mol/L, pH ═ 2.8 phosphoric acid and its salt buffer solution and 200 μ L of test sample were mixed to obtain a test solution, the test solution was in multiple portions and 10.0mL in volume, the test solution contained 0.01mol/L phosphoric acid buffer substance, and the pH of the test solution was 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 to obtain solutions to be detected with different known standard trivalent arsenic ion concentrations.
(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-110GPH, DropSens) and an electrochemical analyzer (electrochemical analyzer 600E) through an anodic stripping voltammetry method, detecting that no enrichment time is needed to be set in scanning from-0.80V to +0.80V, obtaining stripping voltammograms of the arsenic in the solution to be measured with different known standard trivalent arsenic ion concentrations when the pulse amplitude is 200mV, the scanning increment is 4mV, the pulse width is 80ms and the pulse period is 0.5s in arsenic ion detection parameters, and recording the maximum stripping current intensity of the arsenic ions.
The results are shown in FIG. 10, in which FIG. 10 is a calibration curve of concentration-current of standard trivalent arsenic solution 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+) And the ordinate represents the current intensity (Ip). The standard curve is Y-3.160 +3.120X, R: 0.9985. The result is that the unknown arsenic solution concentration of the solution to be tested is 1.01282 mug/L, corresponding to the arsenic ion concentration in tap water being 50.6 +/-0.1 mug/L, and the relative error RE is 1.3% (50.6 mug/L-1.01282 mug/L10 mL/200 mug). It is known that the interfering ion Cu2+There is no interference with the detection of arsenic in the present method.
Claims (10)
1. The electrochemical method for detecting the arsenic ions in the solution is characterized in that a solution to be detected is used in the electrochemical method, the solution to be detected contains 0.005-0.05 mol/L of buffer substances, the pH value of the solution to be detected is 1-2.8, and the arsenic ions in the solution to be detected are detected through an anodic stripping voltammetry method by adopting a graphene screen printing electrode and an electrochemical workstation.
2. The electrochemical method according to claim 1, wherein the amplitude of the pulse of the parameter for detecting the arsenic ion is 10mV to 200 mV.
3. Electrochemical process according to claim 2, characterized in that it comprises the following steps:
(1) preparing a series of trivalent arsenic solutions with known concentration, wherein the series of trivalent arsenic solutions with known concentration contain 0.005-0.05 mol/L of buffer substances, and the pH value of the series of trivalent arsenic solutions with known concentration is 1-2.8;
(2) measuring arsenic ions in the series of trivalent arsenic solutions with known concentrations by adopting a graphene screen printing electrode and an electrochemical workstation through an anodic stripping voltammetry, obtaining a series of stripping voltammograms of arsenic in the trivalent arsenic solutions with known concentrations, recording the maximum stripping current intensity of the arsenic ions in the series of trivalent arsenic solutions with known concentrations, and drawing an arsenic ion concentration-current calibration curve, wherein the parameter pulse amplitude for detecting the arsenic ions is 10 mV-200 mV;
(3) and (3) the solution to be detected contains 0.005-0.05 mol/L of buffer substances, the pH value of the solution to be detected is 1-2.8, a dissolution voltammogram of arsenic in the solution to be detected is obtained under the same condition as the step 2), the maximum dissolution current intensity of arsenic ions in the solution to be detected is recorded, and the concentration of the arsenic ions in the solution to be detected is calculated according to the arsenic ion concentration-current calibration curve.
4. The electrochemical method according to claim 3, wherein in the step (1), the concentration of the buffer substance is 0.005mol/L to 0.01 mol/L.
5. The electrochemical process according to claim 3, wherein in the step (1), the buffer substance is one of phosphoric acid and a salt thereof, hypochlorous acid and a salt thereof, acetic acid and a salt thereof, chlorous acid and a salt thereof, silicic acid and a salt thereof, and meta-aluminate and a salt thereof.
6. The electrochemical method according to claim 3, wherein in the step (1), the pH of the solution to be measured is 1.8 to 2.8.
7. The electrochemical method according to claim 3, wherein in the step (2), the voltage for detecting the arsenic ions 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.
8. The electrochemical method according to claim 3, wherein in the step (3), a reducing substance is added to the solution to be tested before detecting the arsenic ions, the reducing substance reduces pentavalent arsenic into trivalent arsenic, and the reducing substance is one of sodium sulfate, sodium sulfite, ferrous chloride, potassium iodide and oxalic acid.
9. Use of the electrochemical process of any one of claims 1 to 8 in a standard addition process.
10. Use of the electrochemical method according to any one of claims 1 to 8 for detecting the arsenic ion content of a food product.
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