阅读说明：本技术 一种含铅水样的测定方法 (Determination method of lead-containing water sample ) 是由 严百平 张伟政 刘展鹏 邓配 于 2020-07-22 设计创作，主要内容包括：本发明涉及铅离子检测技术领域,具体涉及一种含铅水样的测定方法；包括以下操作步骤：S1：获取待测水样,并加入硝酸和过氧化氢进行消解前处理；S2：加入混合液和八羟基喹啉去除离子干扰,所述混合液包括中和剂和混合掩蔽剂,所述中和剂为氢氧化钠,调节待测水样PH为12,所述混合掩蔽剂由亚硫酸钠、柠檬酸三钠和焦磷酸钠的组成；S3：加入显色剂TPPS<Sub>4</Sub>于水浴锅中进行显色处理；S4：对水样中铅进行吸光度检测,检测波长为470nm。本发明的目的在于提供一种含铅水样的测定方法,针对TPPS<Sub>4</Sub>测试铅选择性差的缺陷,建立TPPS<Sub>4</Sub>光度法测试铅的实验室方法以提升其选择性。(The invention relates to the technical field of lead ion detection, in particular to a method for determining a lead-containing water sample; the method comprises the following operation steps: s1: acquiring a water sample to be detected, and adding nitric acid and hydrogen peroxide for digestion pretreatment; s2: adding a mixed solution and octohydroxyquinoline to remove ionic interference, wherein the mixed solution comprises a neutralizer and a mixed masking agent, the neutralizer is sodium hydroxide, the PH of a water sample to be detected is adjusted to be 12, and the mixed masking agent is composed of sodium sulfite, trisodium citrate and sodium pyrophosphate; s3: adding color developing agent TPPS 4 Carrying out color development treatment in a water bath; s4: and (3) carrying out absorbance detection on the lead in the water sample, wherein the detection wavelength is 470 nm. The invention aims to provide a method for determining a lead-containing water sample, which aims at TPPS 4 Testing the defect of poor lead selectivity and establishing TPPS 4 Laboratory methods for photometric testing of lead to improve its selectivity.)

1. The method for determining the lead-containing water sample is characterized by comprising the following operation steps of:

s1: acquiring a water sample to be detected, and adding nitric acid and hydrogen peroxide for digestion pretreatment;

s2: adding a mixed solution and octohydroxyquinoline to remove ionic interference, wherein the mixed solution comprises a neutralizer and a mixed masking agent, the neutralizer is sodium hydroxide, the PH of a water sample to be detected is adjusted to be 12, and the mixed masking agent is composed of sodium sulfite, trisodium citrate and sodium pyrophosphate;

s3: adding color developing agent TPPS₄Carrying out color development treatment in a water bath;

s4: and (3) carrying out absorbance detection on the lead in the water sample, wherein the detection wavelength is 470 nm.

2. The method for determining the lead-containing water sample according to claim 1, wherein the concentration of the sodium hydroxide is 3g/L, the concentration of the sodium sulfite is 5g/L, the concentration of the trisodium citrate is 25g/L, the concentration of the sodium pyrophosphate is 2.5g/L, and the volume ratio of the mixed solution to the water sample to be determined is 1: 10.

3. The method for determining the lead-containing water sample according to claim 1, wherein the concentration of the octahydroxyquinoline is 0.5g/L, and the volume ratio of the octahydroxyquinoline to the water sample to be detected is 1: 10.

4. The method for determining the lead-containing water sample according to claim 1, wherein the TPPS is used for determining the concentration of the lead-containing water sample₄Is 0.045g/L, the TPPS₄The volume ratio of the water sample to be detected to the water sample to be detected is 1: 10.

5. The method for determining the lead-containing water sample according to claim 1, wherein the temperature of the color development treatment is 40 ℃, and the time of the color development treatment is 300 s.

6. The method for determining the lead-containing water sample according to claim 1, wherein the absorbance detection is performed by using an ultraviolet-visible spectrophotometer.

Technical Field

The invention relates to the technical field of lead ion detection, in particular to a method for determining a lead-containing water sample.

Background

Lead is an accumulated poison, is easily absorbed by intestines and stomach, and influences metabolism of enzymes and cells through blood. Excessive lead intake will seriously affect human health, with the main toxicities being anemia, neurological dysfunction and kidney damage. The lead in natural water is mostly from the pollution of mining, metallurgy, chemical engineering, electroplating and other waste water, and the lead content in drinking water can be increased by using a pipeline with high lead content or a plastic pipe containing a lead compound as a tap water pipe. According to the regulations of sanitary standards for drinking water in China, the lead content in ground water and drinking water cannot exceed 0.05mg/L, and the limit value of class V water in the environmental quality standards for surface water is 0.1 mg/L. The limit value of V-type water in the Integrated wastewater discharge Standard is 1 mg/L. Therefore, the content of lead in the environment, especially the content of lead in an environmental water sample, is an important index for monitoring and controlling the environment.

The existing national environmental standard monitoring method stipulates that the determination of water quality lead comprises a dithizone spectrophotometry and a flame atomic absorption spectrophotometry, and the lowest detected concentration can reach 10 mu g/L. However, because the content of lead in water is low, the methods can not meet the requirement for measuring trace lead in an environmental water sample, the dithizone method has the disadvantages of complex operation, poor selectivity and low sensitivity, and potassium cyanide and organic solvents which are highly toxic reagents are used, so that the dithizone method is difficult to be accepted by analysts. The detection limit of the atomic absorption method generally cannot meet the requirement of trace analysis, and the sample needs to be pre-separated and enriched, but the enrichment method needs to consume a large amount of reagents and analysis time, the analysis operation is complex, large-scale equipment is needed, and the acquisition and maintenance cost is high. It is therefore desirable to develop a method that is sensitive, cost effective, and relatively simple to test.

Tetraphenylporphyrin tetrasulfonic acid (TPPS)₄) The color developing agent is a high-sensitivity water-soluble color developing agent, can be used for measuring metal ions such as Cd, Co, Cu, Pb, Zn, Ni, Hg and the like, but has poor selectivity, and is easily interfered by copper ions, zinc ions and the like to cause a low measurement result when measuring lead, so that complex steps such as separation and extraction of an APDC/MIBK extraction system are required when measuring lead.

For TPPS₄The invention mainly establishes TPPS for testing the defect of poor lead selectivity₄Laboratory methods for photometric testing of lead to improve its selectivity. After the water sample is pretreated by digestion, alkali liquor and a masking agent are added, and direct measurement can be carried out. Is suitable for the fields of surface water and industrial wastewater. The method does not need large-scale analytical equipment, has no extraction step, has high selectivity, and canEffectively eliminating the interference of other coexisting ions. The range of the measurable lead-containing water sample is 0-0.2mg/L, and the lower limit of the quantification is superior to that of the existing national standard dithizone spectrophotometry and is as low as 0.005 mg/L. A method with simple steps and quick response is needed in the field of emergency monitoring and on-line monitoring, and the method provides a solution for quickly determining lead.

Therefore, a method for measuring a lead-containing water sample is provided.

Disclosure of Invention

The invention aims to provide a method for determining a lead-containing water sample, which aims at TPPS₄Testing the defect of poor lead selectivity and establishing TPPS₄Laboratory methods for photometric testing of lead to improve its selectivity.

In order to achieve the above purpose, the invention provides the following technical scheme:

a method for measuring a lead-containing water sample comprises the following operation steps:

s1: acquiring a water sample to be detected, and adding nitric acid and hydrogen peroxide for digestion pretreatment;

s2: adding a mixed solution and octohydroxyquinoline to remove ionic interference, wherein the mixed solution comprises a neutralizer and a mixed masking agent, the neutralizer is sodium hydroxide, the PH of a water sample to be detected is adjusted to be 12, and the mixed masking agent is composed of sodium sulfite, trisodium citrate and sodium pyrophosphate;

s3: adding color developing agent TPPS₄Carrying out color development treatment in a water bath;

s4: and (3) carrying out absorbance detection on the lead in the water sample, wherein the detection wavelength is 470 nm.

Preferably, the concentration of the sodium hydroxide is 3g/L, the concentration of the sodium sulfite is 5g/L, the concentration of the trisodium citrate is 25g/L, the concentration of the sodium pyrophosphate is 2.5g/L, and the volume ratio of the mixed solution to the water sample to be detected is 1: 10.

Preferably, the concentration of the octahydroxyquinoline is 0.5g/L, and the volume ratio of the octahydroxyquinoline to the water sample to be detected is 1: 10.

Preferably, the TPPS₄Is 0.045g/L, the TPPS₄The volume ratio of the water sample to be detected to the water sample to be detected is 1: 10.

Preferably, the temperature of the color development treatment is 40 ℃, and the time of the color development treatment is 300 s.

Preferably, the absorbance detection is performed by using an ultraviolet-visible spectrophotometer.

The invention has the beneficial effects that:

(1) the invention aims to overcome the defects of TPPS₄The selectivity is poor, the interference of copper, cadmium, zinc and other ions with similar properties in a water sample can be easily caused, the interference of the copper, cadmium, zinc and other ions can be effectively catalyzed and masked compared with the direct color development of the water sample by selecting and optimizing a mixed masking agent and the octahydroxyquinoline and selecting the sodium sulfite, the trisodium citrate, the sodium pyrophosphate and the octahydroxyquinoline, and the trace lead in the water sample can be better determined;

(2) when the PH of the water sample to be detected is 12, the TPPS₄The complex can form a 1:1 complex with lead, has maximum and stable absorbance, and can ensure the data stability of subsequent absorbance determination;

(3) the method does not need large-scale analysis equipment, has no extraction step, has high selectivity, can effectively eliminate the interference of other coexisting ions, can accurately measure the water sample within the range of 0-0.2mg/L by using the method for determining lead, has reliable determination result and cannot be interfered by the mixed ions in the water sample.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the following embodiments, unless otherwise specified, the technical means used are conventional means well known to those skilled in the art.

A method for measuring a lead-containing water sample comprises the following operation steps:

s1: obtaining a water sample to be detected, and adding nitric acid and hydrogen peroxide for digestion pretreatment;

wherein, the dosage of the nitric acid and the hydrogen peroxide and the digestion step refer to HJ677-2013 digestion nitric acid digestion method for water quality metal total amount.

S2: adding mixed solution and octohydroxyquinoline to remove ion interference;

the method for the complexity requirement of the ion components of the actual water sample has certain anti-interference capability, and Cd, Cu, Zn and other ions coexisting in the water sample can also be combined with TPPS₄A complex is formed, and the color development of lead is suppressed. For TPPS₄The selectivity is improved when the lead is measured, usually, a masking agent is added, and then, complex steps such as extraction and the like are adopted to specifically refer to the chromogenic reaction of Zhao Shihao, Zhang Hongshan, 4-sulfophenyl porphyrin and lead to measure the trace lead [ J ] in food]Manufactured by china, 2007,173: 72-74; after the water sample is pretreated by the method, the method is described in the following documents: determination of trace lead [ J ] in food by chromogenic reaction of Zhao Shihao, Zhang Hongdong, 4-sulfophenyl porphyrin and lead]"China manufacture, 2007,173:72-74 and Yan Junying. Hough et al]Physicochemical detection-chemical breakdown, 1998,11:492-49, directly testing after masking with phenanthroline (and ammonia water mixed masking) and hydroxylamine hydrochloride respectively, preparing 0.1mg/L of the following mixed standard containing interfering ions with different concentrations by referring to HJ762-2015 technical requirements and detection method of automatic lead water quality monitor, and testing results are shown in the following table 1.

TABLE 1 measurement of non-extracted after masking

Experiments prove that the scheme is free from extraction, the influence of interference ions on the test result cannot be effectively eliminated, and particularly 0.1mg/L of lead cannot be tested even in the presence of copper and zinc.

A large number of experiments prove that the masking agents such as sodium potassium tartrate, ammonium thiocyanate, thiourea, diethanolamine, ammonia water, phenanthroline and the like can not effectively mask interfering ions such as copper, zinc and the like, and when lead is measured, trisodium citrate is added in the presence of sodium sulfite,Sodium pyrophosphate and octohydroxyquinoline masking agent capable of improving TPPS (thermoplastic polystyrene)₄The test results are shown in Table 2 for the selectivity to lead, thereby establishing TPPS₄A simple method for testing the lead content in a water sample.

TABLE 2 interfering ions and their concentrations

S3: adding color developing agent TPPS₄Fully shaking up, and developing in a water bath kettle at 40 ℃ for 300 s;

s4: and when the absorbance detection is used for detecting the lead in the water sample, an ultraviolet-visible spectrophotometer is adopted for detection, the wavelengths of 470nm are used for respectively measuring the absorbance, a standard curve is drawn, and linear regression calculation is carried out.

Further, the operation steps of the standard curve of the invention are that 5ml (0mg/L, 0.01mg/L, 0.05mg/L, 0.1mg/L, 0.15mg/L, 0.2mg/L) of lead standard solution is respectively taken to be put into 6 groups of 10ml cuvettes, then sodium hydroxide and mixed masking agent are added, 0.5ml of octahydroxyquinoline and 0.5ml of color developing agent TPPS are added₄Mixing, and developing in water bath at constant temperature of 40 deg.C for 300 s; the absorbance was measured on an ultraviolet-visible spectrophotometer using a wavelength of 470nm and a standard curve was drawn, respectively, to perform linear regression calculation.

The required reagents of the invention are:

reagent A: mixed liquor (3g/L sodium hydroxide 5g/L sodium sulfite 25g/L trisodium citrate and 2.5g/L sodium pyrophosphate)

And (3) reagent B: 0.5g/L Octaquinolinol

And (3) reagent C: 0.045g/L TPPS₄

The following examples 1 to 4 all used the above reagents for the determination of a sample of water containing lead.