Method for enriching and detecting trace mercury ions in water body

Abstract

The invention provides a method for enriching and detecting trace mercury ions in a water body, and belongs to the technical field of mercury ion detection. The enrichment and detection method comprises the following steps: pretreating a water sample to be detected; mixing the pretreated water sample to be detected with a complexing agent and a surfactant to obtain a first mixed solution; adding a buffer solution into the first mixed solution, and mixing to obtain a second mixed solution; performing water bath on the second mixed solution, and centrifuging after water bath; after centrifugation is finished, carrying out ice bath, and dividing the water sample to be detected into a water phase and a surfactant phase; adding a defoaming agent into the surfactant phase to obtain an enriched water sample to be detected; the enriched water sample to be detected is prepared into a standard solution, the atomic fluorescence spectrometry is adopted for detection, the water sample to be detected is pretreated, the influence of impurities is reduced, release of mercury ions is promoted, the detection accuracy is improved, and the method is convenient to operate and implement and has high timeliness.

Description

Technical Field

[0001] The invention relates to the technical field of mercury ion detection, and in particular to a method for enriching and detecting trace mercury ions in water. Background Art

[0002] Mercury is a highly toxic heavy metal element that poses a serious threat to both the human body and the environment. 2+ ) accumulates in the human body and can cause damage to multiple systems, including the central nervous system, cardiovascular system, and immune system, and may even lead to serious health problems, such as neurological diseases and kidney damage. In addition, mercury ions can easily accumulate through the food chain, causing harm to aquatic and terrestrial organisms, and then damage the entire ecosystem. Given the high toxicity and easy accumulation of mercury ions, accurate and rapid detection of mercury ions is of great significance for environmental protection and human health. By detecting the concentration of mercury ions in the environment, the extent of mercury pollution can be assessed, and timely control measures can be taken to prevent mercury pollution from causing further harm to the ecosystem and human health. At the same time, mercury ion detection is also an important part of food safety testing, which can ensure that the content of mercury ions in food is within a safe range and protect the health of consumers.

[0003] Trace substances generally refer to substances with a content of less than 0.01% in the sample. If its content is lower than the lower limit of the analytical method, it is necessary to use a pre-enrichment method to collect the trace elements to be measured from a large amount of parent substances to a smaller volume, thereby increasing its content to above the lower limit of determination. This analytical method is called trace enrichment. When the concentration of mercury ions in water is lower than 0.01%, it is impossible to accurately measure its concentration using general detection methods. It needs to be enriched and then detected. In the prior art, extraction is generally used to enrich it, but there are technical problems in the enrichment process such as insufficient mercury ion enrichment and unstable mercury ion state, which makes it difficult to accurately detect. Therefore, it is of great practical significance to provide an enrichment and detection method with high detection accuracy. Summary of the invention

[0004] The purpose of the present invention is to provide a method for enriching and detecting trace mercury ions in water. In the method for enriching and detecting trace mercury ions in water, a water sample to be tested is pretreated to reduce the influence of impurities and improve the accuracy of detection; a complexing agent, a surfactant and other reagents are used to enrich the mercury ions in the water, the mercury ions are enriched to a greater extent, and the accuracy of detecting trace mercury ions in the water is improved.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for enriching and detecting trace mercury ions in water, comprising the following steps:

[0007] (1) pre-treating the water sample to be tested, wherein the pre-treatment comprises filtering with a filter membrane, and then acid washing with nitric acid to obtain the pre-treated water sample to be tested;

[0008] (2) mixing the pretreated water sample to be tested with a complexing agent and a surfactant to obtain a first mixed solution;

[0009] (3) adding a buffer solution to the first mixed solution and mixing the mixture to obtain a second mixed solution;

[0010] (4) placing the second mixed solution in a water bath, and then centrifuging it;

[0011] (5) After centrifugation, place the sample in an ice bath and separate it into an aqueous phase and a surfactant phase;

[0012] (6) adding a defoaming agent to the surfactant phase to obtain an enriched water sample to be tested;

[0013] (7) preparing the enriched water sample to be tested into a standard solution and detecting it by atomic fluorescence spectrometry;

[0014] The ratio of the water sample to be tested to the surfactant and the complexing agent is 10-20:1-2:1-2;

[0015] The preparation of the standard solution is to add a reducing agent to the enriched water sample to be tested, and then add dilute hydrochloric acid to make up the volume, so as to obtain a water sample to be tested that can be introduced into an atomic fluorescence spectrometer;

[0016] The reducing agent is stannous chloride, and the concentration of the stannous chloride is 5-10 g / L; the ratio of the reducing agent to the enriched water sample to be tested is 0.5-1:1.

[0017] Furthermore, the buffer is tris(hydroxymethyl)aminomethane.

[0018] Furthermore, the surfactant is Triton X-100.

[0019] Furthermore, the pH of the second mixed solution is 5-9.

[0020] Furthermore, the complexing agent is dithizone or ammonium pyrrolidine dithiocarbamate (APDC).

[0021] Furthermore, the temperature of the water bath is 30-40°C and the time is 10-20 minutes.

[0022] Furthermore, the centrifugal speed is 2500-3000 r / min, and the time is 15-20 min.

[0023] Furthermore, the ice bath time is 15 to 20 minutes.

[0024] Furthermore, the defoaming agent is tributyl phosphate, and the dosage ratio of the water sample to be tested to the defoaming agent is 100:0.5-1.

[0025] Furthermore, the pore size of the filter membrane is 0.2-0.4 μm, and the concentration of the nitric acid is 1-1.5 g / mL.

[0026] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0027] (1) The present invention filters the sample to be tested before enriching mercury ions to remove possible impurities to avoid affecting the test results; in addition, organic substances that may exist in the sample to be tested may form complexes with mercury ions, which will affect the subsequent determination of mercury ions. By using nitric acid for pretreatment, these organic substances can be destroyed to prevent them from forming complexes with metal impurity ions, and mercury ions can be converted from compound form to ionic form, which is convenient for subsequent detection, thereby improving the accuracy and precision of the determination;

[0028] (2) The present invention uses complexing agents such as dithizone or ammonium pyrrolidine dithiocarbamate (APDC), surfactant Triton X-100 and other reagents to enrich mercury ions in water to a greater extent, thereby improving the accuracy of detection;

[0029] (3) The present invention also stipulates that when preparing the standard solution, a reducing agent is used to reduce the mercury ions, so that the mercury ions are converted into a state that is easy to detect, thereby improving the accuracy of the detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The figure is a schematic diagram of the process of enrichment and detection of trace mercury ions in water according to the present invention. DETAILED DESCRIPTION

[0031] The present invention provides a method for enriching and detecting trace mercury ions in water, comprising the following steps:

[0032] (1) pre-treating the water sample to be tested, wherein the pre-treatment comprises filtering with a filter membrane, and then acid washing with nitric acid to obtain the pre-treated water sample to be tested;

[0033] (2) mixing the pretreated water sample to be tested with a complexing agent and a surfactant to obtain a first mixed solution;

[0034] (3) adding a buffer solution to the first mixed solution and mixing the mixture to obtain a second mixed solution;

[0035] (4) placing the second mixed solution in a water bath, and then centrifuging it;

[0036] (5) After centrifugation, place the sample in an ice bath and separate it into an aqueous phase and a surfactant phase;

[0037] (6) adding a defoaming agent to the surfactant phase to obtain an enriched water sample to be tested;

[0038] (7) preparing the enriched water sample to be tested into a standard solution and detecting it by atomic fluorescence spectrometry;

[0039] The ratio of the water sample to be tested to the surfactant and the complexing agent is 10-20:1-2:1-2;

[0040] The preparation of the standard solution is to add a reducing agent to the enriched water sample to be tested, and then add dilute hydrochloric acid to make up the volume, so as to obtain a water sample to be tested that can be introduced into an atomic fluorescence spectrometer;

[0041] The reducing agent is stannous chloride, and the concentration of the stannous chloride is 5-10 g / L; the ratio of the reducing agent to the enriched water sample to be tested is 0.5-1:1.

[0042] The water sample to be tested is pretreated, and the pretreatment includes filtering with a filter membrane, and then acid washing with nitric acid to obtain the pretreated water sample to be tested.

[0043] The present invention pre-treats the water sample to be tested by filtering and acid washing, wherein the filtering can remove possible impurities to avoid affecting the test results; in addition, organic substances that may exist in the sample to be tested may form complexes with mercury ions, which will affect the subsequent determination of mercury ions. By using nitric acid for pre-treatment, these organic substances can be destroyed to prevent them from forming complexes with metal impurity ions, and mercury ions can be converted from compound form to ionic form, which is convenient for subsequent detection, thereby improving the accuracy and precision of the determination.

[0044] In the present invention, the pore size of the filter membrane is preferably 0.2 to 0.4 μm, more preferably 0.2 to 0.3 μm; the concentration of the nitric acid is preferably 1 to 1.5 g / mL, more preferably 1 to 1.2 g / mL.

[0045] The pretreated water sample to be tested is mixed with a complexing agent and a surfactant to obtain a first mixed solution.

[0046] The present invention sequentially adds a complexing agent and a surfactant to the pretreated water sample to be tested, and stirs evenly to obtain a first mixed solution;

[0047] In the present invention, the complexing agent is preferably dithizone or ammonium pyrrolidine dithiocarbamate (APDC), and more preferably dithizone.

[0048] In the present invention, the surfactant is preferably Triton X-100.

[0049] In the present invention, the ratio of the water sample to be tested to the surfactant and the complexing agent is preferably 10-20:1-2:1-2, and more preferably 15-20:1:1.

[0050] When the dosage of the complexing agent is too low or too high, it will directly affect the existence state of mercury ions in the surfactant. If the mercury ions exist in the surfactant in an unstable form, they may partially remain in the water phase, thereby affecting the enrichment degree of mercury ions and ultimately affecting the detection results of trace mercury ions in the water body. The dosage of the complexing agent described in the present invention can ensure the enrichment of mercury ions to the greatest extent while avoiding waste.

[0051] A buffer solution is added to the first mixed solution, and the mixture is mixed to obtain a second mixed solution.

[0052] The present invention adds a buffer to the first mixed solution to adjust the acid-base system of the solution. The acid-base system of the solution has a direct impact on the chelation of mercury ions and the complexing agent. Excessive acidity or alkalinity will affect the stability of the chelate formed by the chelation of mercury ions and the complexing agent. The present invention uses a buffer to adjust the acid-base of the first mixed solution, so that the acid-base system is in a state most conducive to the chelation of mercury ions and the complexing agent, further improving the accuracy of detection.

[0053] In the present invention, the buffer is preferably tris(hydroxymethyl)aminomethane.

[0054] In the present invention, the pH of the second mixed solution is preferably 5-9, and more preferably 6-8.

[0055] The second mixed solution is placed in a water bath and then centrifuged.

[0056] In the present invention, the temperature of the water bath is preferably 30 to 40°C, more preferably 35 to 40°C; the time is preferably 10 to 20 minutes, more preferably 10 to 15 minutes;

[0057] The invention promotes the chelation of mercury ions and a complexing agent under water bath conditions, the water sample to be tested gradually becomes turbid, centrifuges after becoming turbid, and layers the turbid solution.

[0058] After centrifugation, an ice bath was placed, and the water sample to be tested was separated into an aqueous phase and a surfactant phase.

[0059] The present invention adopts an ice bath to make the separation of the surfactant phase and the water phase more obvious, so that the surfactant phase state is more stable, which is convenient for the subsequent separation of the water phase and the surfactant phase, thereby ensuring the stability of mercury ion detection.

[0060] In the present invention, the centrifugal rotation speed is preferably 2500-3000 r / min, more preferably 2700-3000 r / min, and the time is preferably 15-20 min, more preferably 15-18 min.

[0061] In the present invention, the ice bath time is preferably 15 to 20 minutes, more preferably 15 to 18 minutes.

[0062] After separating the water phase from the surfactant phase, a defoaming agent is added to the surfactant phase to obtain an enriched water sample to be tested.

[0063] Bubbles will be generated during the above operation. Defoaming agent is used to reduce the amount of bubbles generated and reduce the influence of surfactant on mercury ion determination.

[0064] In the present invention, the defoaming agent is preferably tributyl phosphate, and the dosage ratio of the water sample to be tested to the defoaming agent is preferably 100:0.5-1, and more preferably 100:1.

[0065] The enriched water sample to be tested is prepared into a standard solution and detected by atomic fluorescence spectrometry.

[0066] The preparation of the standard solution of the present invention is preferably to add a reducing agent to the enriched water sample to be tested, so that the mercury ions are converted into a reduced state that is easier to detect, and then dilute hydrochloric acid is added to make up the volume to obtain a water sample to be tested that can be introduced into an atomic fluorescence spectrometer;

[0067] In the present invention, the reducing agent is preferably stannous chloride, and the concentration of the stannous chloride is preferably 5-10 g / L, more preferably 5-7 g / L; the ratio of the reducing agent to the enriched water sample to be tested is preferably 0.5-1:1, more preferably 0.7-1:1.

[0068] In the present invention, unless otherwise specified, the required raw materials for preparation are all commercially available products well known to those skilled in the art.

[0069] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0070] Example 1

[0071] (1) 50 mL of the water sample to be tested is placed in a centrifuge tube, filtered using a 0.2 μm filter membrane to remove impurities, the filtered water sample to be tested is collected, and then 5 mL of nitric acid with a concentration of 1 g / mL is used to acid-wash the water sample to be tested;

[0072] (2) Mix the acid-washed water sample with 5 mL of dithizone and 5 mL of Triton X-100, stir evenly, and then add buffer solution tris(hydroxymethylaminomethane) to adjust the pH of the solution to 7;

[0073] (3) Then, the above solution was placed in a water bath at 30°C for 10 minutes to make the solution turbid;

[0074] (4) The turbid solution was centrifuged at a speed of 2500 r / min for 15 min, and then placed in an ice bath for 15 min to obtain a stratified water sample to be tested, wherein the upper layer is an aqueous phase and the lower layer is a surfactant phase. The aqueous phase and the surfactant phase were separated to obtain a water sample to be tested consisting of only the surfactant phase;

[0075] (5) adding 250 μL of tributyl phosphate to the surfactant phase to eliminate the existing bubbles and obtain an enriched water sample to be tested;

[0076] (6) Add 5 g / L of stannous chloride to the enriched water sample at a ratio of 0.5:1 to reduce the mercury ions in the solution, then use 5% dilute hydrochloric acid to make the volume 5 mL, and finally introduce it into an atomic fluorescence spectrometer for detection. The fluorescence intensity obtained is compared with the standard series of known concentrations to obtain the detection result of mercury ions in the water sample.

[0077] Example 2

[0078] (1) 50 mL of the water sample to be tested is placed in a centrifuge tube, filtered using a 0.3 μm filter membrane to remove impurities, the filtered water sample to be tested is collected, and then 5 mL of nitric acid with a concentration of 1.2 g / mL is used to acid-wash the water sample to be tested;

[0079] (2) Mix the acid-washed water sample with 10 mL of ammonium pyrrolidine dithiocarbamate and 10 mL of Triton X-100, stir evenly, and then add tris(hydroxymethyl)aminomethane buffer to adjust the pH of the solution to 8;

[0080] (3) Then, the above solution was placed in a water bath at 35°C for 15 minutes to make the solution turbid;

[0081] (4) The turbid solution was centrifuged at a speed of 2700 r / min for 18 min, and then placed in an ice bath for 18 min to obtain a layered water sample to be tested, wherein the upper layer is an aqueous phase and the lower layer is a surfactant phase. The aqueous phase and the surfactant phase were separated to obtain a water sample to be tested consisting of only the surfactant phase;

[0082] (5) adding 500 μL of tributyl phosphate to the surfactant phase to eliminate the existing bubbles and obtain an enriched water sample to be tested;

[0083] (6) Add 7 g / L stannous chloride to the enriched water sample in a ratio of 1:1 to reduce the mercury ions in the solution, then use 5% dilute hydrochloric acid to make the volume 5 mL, and finally introduce it into an atomic fluorescence spectrometer for detection. The fluorescence intensity obtained is compared with the standard series of known concentrations to obtain the mercury ion detection result in the water sample.

[0084] Example 3

[0085] (1) 50 mL of the water sample to be tested is placed in a centrifuge tube, filtered using a 0.4 μm filter membrane to remove impurities, the filtered water sample to be tested is collected, and then 5 mL of nitric acid with a concentration of 1.5 g / mL is used to acid-wash the water sample to be tested;

[0086] (2) Mix the acid-washed water sample with 5 mL of dithizone and 5 mL of Triton X-100, stir evenly, and then add buffer solution tris(hydroxymethylaminomethane) to adjust the pH of the solution to 9;

[0087] (3) Then, the above solution was placed in a water bath at 40°C for 10 minutes to make the solution turbid;

[0088] (4) The turbid solution was centrifuged at a speed of 3000 r / min for 20 min, and then placed in an ice bath for 20 min to obtain a layered water sample to be tested, wherein the upper layer is an aqueous phase and the lower layer is a surfactant phase. The aqueous phase and the surfactant phase were separated to obtain a water sample to be tested consisting of only the surfactant phase;

[0089] (5) adding 250 μL of tributyl phosphate to the surfactant phase to eliminate the existing bubbles and obtain an enriched water sample to be tested;

[0090] (6) Add 10 g / L stannous chloride to the enriched water sample at a ratio of 0.7:1 to reduce the mercury ions in the solution, then use 5% dilute hydrochloric acid to make the volume 5 mL, and finally introduce it into an atomic fluorescence spectrometer for detection. The fluorescence intensity obtained is compared with the standard series of known concentrations to obtain the mercury ion detection result in the water sample.

[0091] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for enriching and detecting trace mercury ions in water, characterized in that: The following steps are involved: (1) pre-treating the water sample to be tested, wherein the pre-treatment comprises filtering with a filter membrane, and then acid washing with nitric acid to obtain the pre-treated water sample to be tested; (2) mixing the pretreated water sample to be tested with a complexing agent and a surfactant to obtain a first mixed solution; (3) adding a buffer solution to the first mixed solution and mixing the mixture to obtain a second mixed solution; (4) placing the second mixed solution in a water bath, and then centrifuging it; (5) After centrifugation, place the sample in an ice bath and separate it into an aqueous phase and a surfactant phase; (6) adding a defoaming agent to the surfactant phase to obtain an enriched water sample to be tested; (7) preparing the enriched water sample to be tested into a standard solution and detecting it by atomic fluorescence spectrometry; The ratio of the water sample to be tested to the surfactant and the complexing agent is 10-20:1-2:1-2; The preparation of the standard solution is to add a reducing agent to the enriched water sample to be tested, and then add dilute hydrochloric acid to make up the volume, so as to obtain a water sample to be tested that can be introduced into an atomic fluorescence spectrometer; The reducing agent is stannous chloride, and the concentration of the stannous chloride is 5-10 g / L; the ratio of the reducing agent to the enriched water sample to be tested is 0.5-1:

1.

2. The method for enriching and detecting trace mercury ions in water according to claim 1, characterized in that: The buffer is tris(hydroxymethyl)aminomethane.

3. The method for enriching and detecting trace mercury ions in water according to claim 1, characterized in that: The surfactant is TritonX-100.

4. The method for enriching and detecting trace mercury ions in water according to claim 1, characterized in that: The pH of the second mixed solution is 5-9.

5. The method for enriching and detecting trace mercury ions in water according to claim 1, characterized in that: The complexing agent is dithizone or ammonium pyrrolidine dithiocarbamate (APDC).

6. The method for enriching and detecting trace mercury ions in water according to claim 1, characterized in that: The temperature of the water bath is 30-40° C., and the time is 10-20 minutes.

7. The method for enriching and detecting trace mercury ions in water according to claim 1, characterized in that: The centrifugal speed is 2500-3000 r / min, and the time is 15-20 min.

8. The method for enriching and detecting trace mercury ions in water according to claim 1, characterized in that: The ice bath time is 15 to 20 minutes.

9. The method for enriching and detecting trace mercury ions in water according to claim 1, characterized in that: The defoaming agent is tributyl phosphate, and the dosage ratio of the water sample to be tested to the defoaming agent is 100:0.5-1.

10. The method for enriching and detecting trace mercury ions in water according to claim 1, characterized in that: The pore size of the filter membrane is 0.2-0.4 μm, and the concentration of the nitric acid is 1-1.5 g / mL.

Images