阅读说明：本技术 一种水中重金属的检测方法 (Method for detecting heavy metals in water ) 是由 周庆 董思宇 石杰 于 2019-10-17 设计创作，主要内容包括：本发明涉及一种水中重金属的检测方法,涉及分析检测的技术领域,其包括以下检测步骤：S1：水样采集：采用取样器对所需测定的水体进行取样,得到水体样本；S2：在得到的水体样品中加入pH调节剂,调节pH值至2-4,并搅拌加热至40℃后,对水体样本进行过滤；S3：对S2中水体样本进行前处理；S4：测定待分析样品中的重金属铬的种类和含量。通过在S3中用以对水体样品进行前处理,使得水体中的六价铬和三价铬可以进行预分离和富集,从而便于检测出痕量存在在水体中的六价铬和三价铬含量。(The invention relates to a detection method of heavy metals in water, relating to the technical field of analysis and detection, and comprising the following detection steps: s1: water sample collection: sampling a water body to be measured by using a sampler to obtain a water body sample; s2: adding a pH regulator into the obtained water body sample, regulating the pH value to 2-4, stirring and heating to 40 ℃, and filtering the water body sample; s3: preprocessing the water sample in S2; s4: and (4) determining the type and content of heavy metal chromium in the sample to be analyzed. By pretreating the water body sample in S3, the hexavalent chromium and the trivalent chromium in the water body can be pre-separated and enriched, so that the content of the hexavalent chromium and the trivalent chromium existing in trace amount in the water body can be detected conveniently.)

1. A method for detecting heavy metals in water is characterized by comprising the following steps: the method comprises the following detection steps:

s1: water sample collection: sampling a water body to be measured by using a sampler to obtain a water body sample;

s2: adding a pH regulator into the obtained water body sample, regulating the pH value to 2-4, stirring and heating to 40 ℃, and filtering the water body sample;

s3: preprocessing the water sample in S2;

s4: and (4) determining the type and content of heavy metal chromium in the sample to be analyzed.

2. The method for detecting the heavy metal in the water according to claim 1, wherein the method comprises the following steps: the pretreatment comprises the following detection steps: measuring 1-5ml of filtered water body sample, adding 2-4 ml of complexing agent, uniformly stirring for 10-20min, heating in 40 ℃ constant temperature water bath for 15-20min, cooling to room temperature, rapidly adding 1-3ml of extracting agent and 1-3ml of dispersing agent into the sample solution, uniformly stirring, centrifuging the mixed solution at the rotation speed of 4000rpm for 2min, and taking supernatant to obtain the sample to be analyzed.

3. The method for detecting the heavy metal in the water according to claim 2, wherein the method comprises the following steps: the complexing agent comprises the following raw materials in percentage by weight: 40-60% of ethylenediamine tetraacetic acid and 40-60% of pyrrolidine ammonium dithiocarbamate.

4. The method for detecting the heavy metal in the water according to claim 2, wherein the method comprises the following steps: the pH regulator comprises the following raw materials in percentage by weight: 10-20% of nitric acid, 6-10% of sodium citrate, 6-10% of sodium dihydrogen phosphate, 10-20% of hydrochloric acid, 6-10% of hypochlorous acid and the balance of deionized water.

5. The method for detecting the heavy metal in the water according to claim 2, wherein the method comprises the following steps: the extractant comprises the following raw materials in percentage by weight: 24-26% of 1-hexyl-3-methylimidazole hexafluorophosphate, 24-26% of disodium hydrogen phosphate, 6-10% of ammonium chloride and the balance of deionized water.

6. The method for detecting the heavy metal in the water according to claim 2, wherein the method comprises the following steps: the dispersant comprises one or more of acetone, methanol and ethanol, preferably 40-60% of ethanol and 40-60% of methanol.

7. The method for detecting the heavy metal in the water according to claim 1, wherein the method comprises the following steps: adopt the PP cotton to filter among the S2 to observe the PP cotton after filtering, can tentatively judge the pollution concentration condition of water sample according to the depth degree of PP cotton colour.

8. The method for detecting the heavy metal in the water according to claim 1, wherein the method comprises the following steps: the S4 includes the following detecting steps:

1) preparing a series of standard solutions with different concentrations by taking a plurality of different heavy metals, and performing pretreatment in S3 on the prepared standard solutions to prepare standard solutions to be detected;

2) performing flame atomic absorption spectrophotometer measurement on the standard solution to be measured to obtain absorbances of different heavy metals and different concentrations, and drawing a concentration-absorbance standard curve of the heavy metals according to the concentration, wherein each element corresponds to one standard curve;

3) carrying out flame atomic absorption spectrophotometer determination on a sample to be analyzed;

4) and comparing the absorbance of the sample to be analyzed with the absorbance of the standard solution to obtain the type and concentration of the heavy metal chromium in the sample to be analyzed.

9. The method for detecting the heavy metal in the water according to claim 8, wherein the method comprises the following steps: the flame atomic absorption spectrophotometer uses a chromium cathode lamp, and the parameters of the flame atomic absorption spectrophotometer are set as follows: lamp current 5mA, wavelength 357.9nm, spectrum 0.7nm, air pressure 0.1MPa, air flow 15L/min, acetylene pressure 0.13MPa, acetylene flow 2.8L/min, burner height 10 mm.

10. The method for detecting the heavy metal in the water according to claim 1, wherein the method comprises the following steps: the pretreatment comprises the following detection steps: measuring 1-5ml of filtered water body sample, adding 2-4 ml of complexing agent, uniformly stirring for 10-20min, adding ammonia water, adjusting the pH value to 6-7, heating in 80 ℃ constant-temperature water bath for 15-20min, cooling to room temperature, rapidly adding 1-3ml of extracting agent and 1-3ml of dispersing agent into the sample solution, uniformly stirring, centrifuging the mixed solution for 2min at the rotation speed of 4000rpm, and taking supernatant to obtain the sample to be analyzed.

Technical Field

The invention relates to the technical field of analysis and detection, in particular to a method for detecting heavy metals in water.

Background

Chromium is a VIB group element, has an average content of 0.010-0.011 percent in the earth crust and mainly exists in the forms of trivalent chromium and hexavalent chromium. Studies have shown that chromium behaves as an essential element or as a harmful element, the valence state of which plays a decisive role. Trivalent chromium is a necessary trace element for human body, is indispensable for normal glycolipid metabolism, and chromium deficiency can cause arteriosclerosis and other diseases. But high concentrations of trivalent chromium still exhibit cytotoxic reactions. Hexavalent chromium has a strong toxicity, can damage DNA of human and animals, and is one of the identified carcinogens. Chromium has a wide range of applications and is commonly used in leather, printing and dyeing, electroplating, steel and other industries. Due to the discharge of a large amount of waste water, the content of chromium in water is increasing day by day, and the water environment is seriously polluted. Therefore, the analysis of toxic forms of chromium becomes important.

At present, methods related to detecting metal ions include methods such as Flame Atomic Absorption (FAAS), inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma emission spectroscopy (ICP-OES), electrothermal atomic absorption spectroscopy (ETAAS) and the like.

However, the direct detection of the water body by using the detection means has many problems, because the metal chromium in the water body exists in trace amount, the direct detection of the water body is easy to cause that the content of the heavy metal chromium cannot reach the detection limit, and the content of the metal chromium cannot be determined.

Disclosure of Invention

The invention aims to provide a method for detecting heavy metals in water, which is convenient for detecting the content of trace metal chromium in water.

The above object of the present invention is achieved by the following technical solutions:

a method for detecting heavy metals in water comprises the following detection steps:

s1: water sample collection: sampling a water body to be measured by using a sampler to obtain a water body sample;

s2: adding a pH regulator into the obtained water body sample, regulating the pH value to 2-4, stirring and heating to 40 ℃, and filtering the water body sample;

s3: preprocessing the water sample in S2;

s4: and (4) determining the type and content of heavy metal chromium in the sample to be analyzed.

By adopting the technical scheme, the trivalent chromium is easily adsorbed in suspended matters and particles in the water body, and the trivalent chromium can generate certain precipitation when the pH value is about 4.6. The pH regulator is added into the water body to regulate the pH value to 2-4 so as to dissolve out trivalent chromium in suspended matters and particles adsorbed in the water body, prevent the trivalent chromium from precipitating and improve the accuracy of data detection. And when the pH value of the complex of the trivalent chromium is 2-4, the state is stable, and the complex is not easy to be extracted by an extracting agent, so that the data detection of the hexavalent chromium can not be influenced by the trivalent chromium. The temperature is heated to 40 ℃ to accelerate the dissolution speed of the trivalent chromium and improve the detection efficiency. Meanwhile, the influence on the stability between the trivalent chromium and the hexavalent chromium and the conversion between the hexavalent chromium and the trivalent chromium caused by the overhigh temperature is prevented, and the accuracy of data detection is influenced. And can get rid of water suspended solid, particulate matter, reduce the turbidity, avoid the accuracy that the suspended solid in the water influences data detection. And S3, the method is used for pre-treating a water body sample, so that hexavalent chromium and trivalent chromium in the water body can be pre-separated and enriched, and the content of trace hexavalent chromium and trace trivalent chromium in the water body can be conveniently detected.

The invention is further configured to: the pretreatment comprises the following detection steps: measuring 1-5ml of filtered water body sample, adding 2-4 ml of complexing agent, uniformly stirring for 10-20min, heating in 40 ℃ constant temperature water bath for 15-20min, cooling to room temperature, rapidly adding 1-3ml of extracting agent and 1-3ml of dispersing agent into the sample solution, uniformly stirring, centrifuging the mixed solution at the rotation speed of 4000rpm for 2min, and taking supernatant to obtain the sample to be analyzed.

By adopting the technical scheme, the complexing agent is added firstly for pre-separating and enriching the hexavalent chromium and the trivalent chromium in the water body, so that the content of the hexavalent chromium and the trivalent chromium existing in trace in the water body can be conveniently detected. The dispersing agent is added, so that the extracting agent is uniformly dispersed in the solution in a microdroplet form to form emulsion, the contact area of the extracting agent and the sample solution is increased, the target analyte is quickly extracted into the microdroplet of the extracting agent, and then the extracting agent dispersed in the solution is deposited to the bottom of a test tube through centrifugation. The ionic liquid aqueous two-phase extraction is adopted, so that hexavalent chromium in the sample can be further separated and enriched, the detection limit of the method is reduced, and the sensitivity of the method is improved.

The invention is further configured to: the complexing agent comprises the following raw materials in percentage by weight: 40-60% of ethylenediamine tetraacetic acid and 40-60% of pyrrolidine ammonium dithiocarbamate.

By adopting the technical scheme, the ethylene diamine tetraacetic acid can be complexed with trivalent chromium to form a stable complex. And the pyrrolidine ammonium dithiocarbamate can be complexed with hexavalent chromium to form a stable complex. The hexavalent chromium and the trivalent chromium in the water body are pre-separated and enriched by the compound use of the hexavalent chromium and the trivalent chromium, so that the content of trace hexavalent chromium and trace trivalent chromium in the water body can be conveniently detected. The concentration of the ethylene diamine tetraacetic acid is 100mg/L, and the concentration of the ammonium pyrrolidine dithiocarbamate is 10 g/L.

The invention is further configured to: the pH regulator comprises the following raw materials in percentage by weight: 10-20% of nitric acid, 6-10% of sodium citrate, 6-10% of sodium dihydrogen phosphate, 10-20% of hydrochloric acid, 6-10% of hypochlorous acid and the balance of deionized water.

By adopting the technical scheme, hexavalent chromium is easily reduced into trivalent chromium under an acidic condition, and the reduction of the hexavalent chromium is prevented by adding hypochlorous acid, so that the detection accuracy of the trivalent chromium and the hexavalent chromium in water is improved. Sodium citrate is added to prevent the trivalent chromium from being oxidized, thereby improving the detection accuracy of the trivalent chromium and the hexavalent chromium in the water. Nitric acid and hydrochloric acid are both strong acids, which facilitates adjustment of the pH of the solution. The disodium hydrogen phosphate can improve the migration speed and the migration quantity of the trivalent chromium from the suspended matters, thereby improving the detection accuracy of the trivalent chromium and the hexavalent chromium in the water. Meanwhile, sodium citrate and disodium hydrogen phosphate can be complexed with trivalent chromium and hexavalent chromium to a certain extent, so that the trivalent chromium and the hexavalent chromium are prevented from being oxidized or reduced, and the detection accuracy of the trivalent chromium and the hexavalent chromium in the water is further improved. And the preseparation and enrichment of hexavalent chromium and trivalent chromium in the water body can be realized, so that the content of trace hexavalent chromium and trivalent chromium in the water body can be conveniently detected. The sodium citrate and the disodium hydrogen phosphate can be compounded to form a buffer solution for stabilizing the pH value of a water body sample.

The invention is further configured to: the extractant comprises the following raw materials in percentage by weight: 24-26% of 1-hexyl-3-methylimidazole hexafluorophosphate, 24-26% of disodium hydrogen phosphate, 6-10% of ammonium chloride and the balance of deionized water.

By adopting the technical scheme, the 1-hexyl-3-methylimidazolium hexafluorophosphate is ionic liquid, the disodium hydrogen phosphate is inorganic salt, the trace metal chromium in the water is enriched by adopting ionic liquid-inorganic salt aqueous two-phase extraction, the emulsification phenomenon is avoided, the phase separation can be completed within 2min, and the detection efficiency and accuracy are improved. And the used disodium hydrogen phosphate can be recycled and reused, and has the advantages of simple and convenient operation and low analysis cost. And the disodium hydrogen phosphate can be complexed with trivalent chromium, so that the trivalent chromium is prevented from entering supernatant liquid during layering, and the detection accuracy of hexavalent chromium is further influenced. The ammonium chloride can be used as a cosolvent to improve the solubility of hexavalent chromium in the ionic liquid, can be used as an inhibitor of coexisting elements, and can also inhibit the interference of CO, Fe, Ni, V, Pb and Mg.

The invention is further configured to: the dispersant comprises one or more of acetone, methanol and ethanol, preferably 40-60% of ethanol and 40-60% of methanol.

By adopting the technical scheme, the ionic liquid is more thoroughly dispersed in the methanol, and the extraction is more facilitated. However, methanol has certain toxicity, and the toxicity of the dispersing agent is reduced while the dispersing effect of the ionic liquid is improved by compounding ethanol and methanol, so that the subsequent waste liquid treatment is facilitated.

The invention is further configured to: adopt the PP cotton to filter among the S2 to observe the PP cotton after filtering, can tentatively judge the pollution concentration condition of water sample according to the depth degree of PP cotton colour.

Through adopting above-mentioned technical scheme, can tentatively judge the pollution concentration condition of water sample, the judgement of the later detection data accuracy of being convenient for, the experimenter of being convenient for operates.

The invention is further configured to: the S4 includes the following detecting steps:

1) preparing a series of standard solutions with different concentrations by taking a plurality of different heavy metals, and performing pretreatment in S3 on the prepared standard solutions to prepare standard solutions to be detected;

2) performing flame atomic absorption spectrophotometer measurement on the standard solution to be measured to obtain absorbances of different heavy metals and different concentrations, and drawing a concentration-absorbance standard curve of the heavy metals according to the concentration, wherein each element corresponds to one standard curve;

3) carrying out flame atomic absorption spectrophotometer determination on a sample to be analyzed;

4) and comparing the absorbance of the sample to be analyzed with the absorbance of the standard solution to obtain the type and the content of the heavy metal in the sample to be analyzed.

The invention is further configured to: the flame atomic absorption spectrophotometer uses a chromium cathode lamp, and the parameters of the flame atomic absorption spectrophotometer are set as follows: lamp current 5mA, wavelength 357.9nm, spectrum 0.7nm, air pressure 0.1MPa, air flow 15L/min, acetylene pressure 0.13MPa, acetylene flow 2.8L/min, burner height 10 mm.

By adopting the technical scheme, the method is used for carrying out quantitative and qualitative analysis on the hexavalent chromium of the water body sample. And the parameters of the flame atomic absorption spectrophotometer are set as shown above, so that the detection sensitivity and accuracy of the flame atomic absorption spectrophotometer can be improved.

The invention is further configured to: the pretreatment comprises the following detection steps: measuring 1-5ml of filtered water body sample, adding 2-4 ml of complexing agent, stirring uniformly for 10-20min, dropwise adding ammonia water, adjusting the pH value to 6-7, heating in 80 ℃ constant-temperature water bath for 15-20min, cooling to room temperature, quickly adding 1-3ml of extracting agent and 1-3ml of dispersing agent into the sample solution, stirring uniformly, centrifuging the mixed solution at the rotation speed of 4000rpm for 2min, and taking supernatant to obtain the sample to be analyzed.

By adopting the technical scheme, when the pH value is 6-7 and the heating temperature is 80 ℃, the complex of trivalent chromium and hexavalent chromium can be completely extracted, and the amount of the trivalent chromium can be detected by subtracting the amount of the hexavalent chromium from the amount of the total metal chromium, so that the operation of detection personnel is facilitated, and the detection efficiency is improved. The mass concentration of the ammonia water is 20%.

In conclusion, the beneficial technical effects of the invention are as follows:

1. the pH regulator is added into the water body to regulate the pH value to 2-4 so as to dissolve out trivalent chromium in suspended matters and particles adsorbed in the water body, prevent the trivalent chromium from precipitating and improve the accuracy of data detection;

2. by pretreating the water body sample in S3, the hexavalent chromium and the trivalent chromium in the water body can be pre-separated and enriched, so that the content of trace hexavalent chromium and trace trivalent chromium in the water body can be conveniently detected;

3. the nitric acid, the sodium citrate, the sodium dihydrogen phosphate, the hydrochloric acid and the hypochlorous acid are used in a compounding manner to adjust the pH value of a water body sample and prevent hexavalent chromium reduction and trivalent chromium oxidation, so that the detection accuracy of the trivalent chromium and the hexavalent chromium in water is improved, and the pre-separation and enrichment of the hexavalent chromium and the trivalent chromium in the water body can be realized, so that the content of trace hexavalent chromium and trivalent chromium in the water body can be conveniently detected.

Detailed Description