CN115824765A - Method for determining lead in soil through wet digestion - Google Patents

Abstract

The invention discloses a method for determining lead in soil by wet digestion, which belongs to the technical field of analysis and comprises the following operation steps: s1: sample treatment: adding an acid reagent into the sample, carrying out pre-digestion overnight, and carrying out wet digestion; cooling after digesting by a wet method, and adding a 50% hydrochloric acid solution for redissolving; then adding ammonium salt as a matrix improver, and carrying out constant volume to obtain a sample solution to be measured; the acid reagent is nitric acid, hydrofluoric acid and perchloric acid, and the 50% hydrochloric acid solution is hydrochloric acid in a volume ratio of: the first-stage water is 1:1, and the ammonium salt is 5% diammonium hydrogen phosphate solution. According to the method for determining the lead in the soil by wet digestion, the lead in the soil is digested by a wet method, the lead content in the sample is detected after the soil sample is processed by a triacid digestion method, and the sensitivity of determining the lead content in the soil by a graphite furnace atomic absorption spectrophotometry is high, and the result is accurate and reliable.

Description

Method for determining lead in soil through wet digestion

Technical Field

The invention relates to the technical field of analysis, in particular to a method for digesting and measuring lead in soil by a wet method.

Background

The method adopted by the existing method for analyzing the lead content in the soil has long time consumption, large reagent consumption amount and incomplete dissolved sample in the sample digestion process; although the subsequent microwave digestion method shortens the digestion time, the soil sample has complex components, so that the sample is difficult to digest completely, the subsequent determination of lead is influenced, and the determination error is generated. The method is improved aiming at the defect of sample pretreatment, and the soil sample is measured after pretreatment by adopting a method of adding single acid for multiple times to fully exert the digestion efficiency of each acid.

Disclosure of Invention

The invention mainly aims to provide a method for digesting and measuring lead in soil by a wet method, which can effectively solve the problems in the background technology.

In order to realize the purpose, the invention adopts the technical scheme that:

1. a method for measuring lead in soil by wet digestion comprises the following operation steps:

s1: sample treatment: adding an acid reagent into the sample, carrying out early digestion overnight, and then carrying out wet digestion; cooling after wet digestion, and adding 50% hydrochloric acid solution for redissolving; then adding ammonium salt as a matrix improver, and carrying out constant volume to obtain a sample solution to be measured; the acid reagent is nitric acid, hydrofluoric acid and perchloric acid, and the 50% hydrochloric acid solution is hydrochloric acid in a volume ratio of: the first-stage water is 1:1, preparing ammonium salt which is 5 percent diammonium hydrogen phosphate solution;

s2: and (3) sample determination: and (3) taking the sample solution to be detected in the step (S1) to perform determination on a graphite furnace atomic absorption spectrophotometer.

Preferably, the determination on the graphite furnace atomic absorption spectrophotometer comprises the following steps:

(1) Preparing a standard solution:

taking a lead standard stock solution, diluting the lead standard stock solution by using a nitric acid solution with the volume percentage of 1-2%, and preparing a lead standard solution A, B, C, D, E, F, G with different concentrations;

(2) Sample pretreatment:

1) Taking a sample into a polytetrafluoroethylene cup, adding 5-10mL of nitric acid, and covering with a cover overnight;

2) After the sample is pre-digested overnight, opening a cover and placing on an electric hot plate, and digesting to about 3-5mL at 100-120 ℃;

3) Adding hydrofluoric acid, and digesting at 140-150 ℃ until the residue is almost dissolved;

4) Adding perchloric acid, covering and covering the cup, digesting at 160-180 ℃ until the solution is clear and transparent, and the cup wall and the cup bottom have no black carbide and the like;

5) Uncovering to remove acid until the solution is as large as soybean (0.5-1 mL);

6) Cooling, adding 50% hydrochloric acid solution for redissolution, adding 5% diammonium phosphate solution, and diluting to constant volume with primary water;

(3) Testing and data processing:

testing on a computer, setting instrument parameters after a graphite furnace atomic absorption spectrophotometer is debugged, and testing the standard solution A, B, C, D, E, F, G prepared in the step (1) under specified operating conditions to obtain a linear equation Y = aX + b of lead concentration and light absorption intensity in the solution, wherein Y is the lead concentration in the sample, ug/L is unit, and X is a lead element detection response value in the sample; detecting the solution obtained in the step (2) by using an ink furnace atomic absorption spectrophotometer, detecting by using an instrument to obtain a light absorption intensity value of lead content in the solution, substituting the value into a standard curve formula for calculation to obtain lead concentration in the solution, and substituting the concentration into the formula: lead content mg/kg = (c × V)/m, wherein V is a mobile volume unit mL and m is a sample weight unit g.

Preferably, in the pretreatment of the sample in the step S2, the sample weighing amount is 0.1-0.2g, and the content of HNO3 in the nitric acid is 65-68%; the content of HF in the hydrofluoric acid is more than or equal to 40 percent, and the content of HClO4 in the perchloric acid is 65-68 percent; the HCl content in the hydrochloric acid is more than or equal to 40 percent; the content of NH4H2PO4 in the diammonium phosphate is more than or equal to 40 percent.

Preferably, the parameters of the graphite furnace atomic absorption spectrophotometer are as follows;

1) Light source: lead hollow cathode lamp

2) Wavelength: 283.3;

3) And (4) background buckling: a deuterium lamp;

4) Current: 10.0A;

4) Flow rate of atomizing gas Ar: 0.79mL/min;

5) Flow rate of cooling gas Ar: 13.8mL/min;

6) The sampling volume is: 5mm;

7) Temperature of the atomization chamber: 0 to 4 ℃;

8) Sampling mode: fully quantifying;

9) The scanning mode is as follows: jumping peaks;

10 Scan times): 10-100 times;

11 Number of measurements): 3 times;

12 Atomizer: a concentric atomizer;

13 Atomizing chamber: a swirling flow atomizing chamber;

16 Test mode): and (4) standard mode.

Preferably, the electric heating plate digests, and the specific temperature and the corresponding time are as follows:

a first stage: heating to 100-120 deg.C for 10-30min, and maintaining for 90-120min; two stages: after hydrofluoric acid is added, heating at 140-150 ℃ for 5-10min, and keeping for 10-20min; three stages: after perchloric acid is added, heating at 160-180 ℃ for 5-10min, and keeping for 60-120min; the fourth stage: acid is removed to the size of the soybeans (0.5-1 mL).

Compared with the prior art, the invention has the following beneficial effects:

in the invention, the sample treatment process is mainly divided into two steps of sample pretreatment and computer test; the pretreatment is carried out for pre-digestion to avoid detection loss caused by overflow of a sample solution due to over violent reaction during temperature-rising digestion; after pre-digestion, because the digestion system adopts single acid for acidolysis, hydrofluoric acid can be added into the digestion system after the oxidizability of nitric acid and the digestion speed of organic matters in the sample are ensured, the digested sample is desilicated to destroy the mineral lattices of soil, then perchloric acid is added to completely digest black carbides, and finally 50% hydrochloric acid solution is added for melting and dissolving to ensure that all elements to be detected in the sample enter the test solution, thereby reducing the loss of the objects to be detected in the digestion process. After the sample is processed, testing by using a graphite furnace atomic spectrophotometer with high sensitivity;

the wet digestion technology used in the determination method has the characteristics of improving timeliness, reducing acid amount, being capable of batch operation and the like, and optimizes the existing method.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.

Example 1

(I) laboratory instruments and reagents

(1) An experimental instrument: the devices used were graphite furnace atomic absorption spectrophotometer (model: 240FSAA, manufacturer: agent) and Beijing Yongguang medical device, inc. stainless steel electric heating plate.

(2) Experimental reagent: nitric acid, hydrofluoric acid, perchloric acid, hydrochloric acid, diammonium hydrogen phosphate, ultrapure water and lead standard solution.

(II) conditions of the Instrument parameters

(1) Graphite furnace atomic absorption spectrophotometer instrument parameters

ICP-MS instrument parameters

(III) drawing of standard curve

Taking 1.0mL of 100mg/L iron standard stock solution (China institute of metrology science), using 1% nitric acid solution (volume percentage of high-grade pure concentrated nitric acid and first-grade water) to fix the volume to 100mL, respectively taking 0, 0.1, 0.2, 0.4, 0.8 and 1.0mL, using 1% nitric acid solution to fix the volume to 100mL, making a standard curve with the gradient of 0, 10, 20, 40, 80 and 100ug/L, calculating a formula of the standard curve, and obtaining Y =0.002X-16.146, wherein Y is the concentration of iron in a sample, unit ug/L and X is the detection response value of iron elements in the sample.

(IV) sample pretreatment

Putting 0.2006g of sample into a polytetrafluoroethylene beaker, adding 6mL of nitric acid, covering overnight, after the cover is opened, volatilizing the sample to about 3mL at 110 ℃ on an electric heating plate, adding 5mL of hydrofluoric acid, heating to 140 ℃, digesting for 15min until the solution is clear, adding 2mL of perchloric acid, covering, heating to 170 ℃, digesting for 90min until the digestion solution is white, and covering the cover to remove acid to 1mL. 3mL of 50% hydrochloric acid solution was removed, cooled to room temperature, and 3mL of 5% ammonium dihydrogen phosphate solution was added to the solution to a volume of 25mL.

(V) test and data processing

Testing on a computer, testing the standard curve prepared in the step (III) under the specified operating condition after the graphite furnace atomic absorption spectrophotometer is debugged to obtain a linear equation of the lead concentration and the light absorption intensity value in the solution; detecting the solution obtained in the step (IV) by using a graphite furnace atomic absorption spectrophotometer, detecting by using an instrument to obtain a light absorption intensity value of the lead content in the solution, substituting the value into a standard curve formula for calculation to obtain the lead concentration in the solution, and substituting the concentration into the formula: lead content mg/kg = (c-c 0 × V)/(m × 1000), where V is the mobile volume unit mL and m is the weight unit g of the weight.

Calculating the lead content in the sample by a formula as follows: 206.44mg/kg.

Example 2

(I) laboratory instruments and reagents

(1) An experimental instrument: the instruments used were graphite furnace atomic absorption spectrophotometer (model: 240FSAA, manufacturer: agent) and stainless steel electric heating plate of Yongguanming medical instruments, inc. of Beijing.

(2) Experimental reagent: nitric acid, hydrofluoric acid, perchloric acid, hydrochloric acid, diammonium hydrogen phosphate, ultrapure water and lead standard solution.

(II) Instrument parameter Condition

(1) Graphite furnace atomic absorption spectrophotometer instrument parameters

ICP-MS instrument parameters

(III) drawing of standard curve

Taking 1.0mL of 100mg/L iron standard stock solution (China institute of metrology science), using 1% nitric acid solution (volume percentage of high-grade pure concentrated nitric acid and first-grade water) to perform constant volume to 100mL, respectively taking 0, 0.1, 0.2, 0.4, 0.8 and 1.0mL, using 1% nitric acid solution to perform constant volume to 100mL, making a standard curve with the gradient of 0, 10, 20, 40, 80 and 100ug/L, calculating a formula of the standard curve, and obtaining Y =0.002X-16.146, wherein Y is the concentration of iron in a sample, unit ug/L and X is the detection response value of the iron element in the sample.

(IV) sample pretreatment

Putting 0.2006g of sample into a polytetrafluoroethylene beaker, adding 8mL of nitric acid, covering overnight, volatilizing the sample to about 3mL at 120 ℃ on an electric heating plate after the cover is opened, adding 5mL of hydrofluoric acid, heating to 150 ℃ for digestion for 15min until the solution is clear, adding 2mL of perchloric acid for covering, heating to 180 ℃ for digestion for 90min until the digestion solution is white, and covering the cover to remove acid to 1mL. 3mL of 50% hydrochloric acid solution was removed, cooled to room temperature, and 3mL of 5% ammonium dihydrogen phosphate solution was added to the solution to a volume of 25mL.

(V) test and data processing

Testing on a computer, testing the standard curve prepared in the step (III) under the specified operating condition after the graphite furnace atomic absorption spectrophotometer is debugged to obtain a linear equation of the lead concentration and the light absorption intensity value in the solution; detecting the solution obtained in the step (four) by using a graphite furnace atomic absorption spectrophotometer, detecting by using an instrument to obtain a light absorption intensity value of lead content in the solution, substituting the value into a standard curve formula for calculation to obtain lead concentration in the solution, and substituting the concentration into the formula: lead content mg/kg = (c-c 0 × V)/(m × 1000), where V is the mobile volume unit mL and m is the weight unit g of the weight.

Calculating the lead content in the sample by a formula as follows: 206.44mg/kg.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (5)

1. A method for determining lead in soil by wet digestion is characterized by comprising the following steps: the method comprises the following operation steps:

s1: sample treatment: adding an acid reagent into the sample, carrying out pre-digestion overnight, and carrying out wet digestion; cooling after wet digestion, and adding 50% hydrochloric acid solution for redissolving; then adding ammonium salt as a matrix improver, and performing constant volume to obtain a sample solution to be measured; the acid reagent is nitric acid, hydrofluoric acid and perchloric acid, and the 50% hydrochloric acid solution is hydrochloric acid in a volume ratio of: the first-stage water is 1:1, preparing ammonium salt which is 5 percent diammonium hydrogen phosphate solution;

s2: and (3) sample determination: and (3) taking the sample solution to be detected in the step (S1) to perform determination on a graphite furnace atomic absorption spectrophotometer.

2. The method for measuring lead in soil through wet digestion according to claim 1, characterized by comprising the following steps: the determination on the graphite furnace atomic absorption spectrophotometer comprises the following steps:

(1) Preparing a standard solution:

taking a lead standard stock solution, diluting the lead standard stock solution by using a nitric acid solution with the volume percentage of 1-2%, and preparing a lead standard solution A, B, C, D, E, F, G with different concentrations;

(2) Sample pretreatment:

1) Taking a sample into a polytetrafluoroethylene cup, adding 5-10mL of nitric acid, and covering with a cover overnight;

2) After the sample is pre-digested overnight, opening a cover and placing on an electric hot plate, and digesting to about 3-5mL at 100-120 ℃;

3) Adding hydrofluoric acid, and digesting at 140-150 ℃ until the residue is almost dissolved;

4) Adding perchloric acid, covering and covering the cup, digesting at 160-180 ℃ until the solution is clear and transparent, and the cup wall and the cup bottom have no black carbide and the like;

5) Uncovering to remove acid until the solution is as large as soybean (0.5-1 mL);

6) Cooling, adding 50% hydrochloric acid solution for redissolution, adding 5% diammonium phosphate solution, and diluting to constant volume with primary water;

(3) Testing and data processing:

testing on a computer, setting instrument parameters after a graphite furnace atomic absorption spectrophotometer is debugged, and testing the standard solution A, B, C, D, E, F, G prepared in the step (1) under specified operating conditions to obtain a linear equation Y = aX + b of lead concentration and light absorption intensity in the solution, wherein Y is the lead concentration in the sample, ug/L is unit, and X is a lead element detection response value in the sample; detecting the solution obtained in the step (2) by using an ink furnace atomic absorption spectrophotometer, detecting by using an instrument to obtain a light absorption intensity value of lead content in the solution, substituting the value into a standard curve formula for calculation to obtain lead concentration in the solution, and substituting the concentration into the formula: lead content mg/kg = (c × V)/m, wherein V is a mobile volume unit mL and m is a sample weight unit g.

3. The method for measuring lead in soil through wet digestion according to claim 2, characterized by comprising the following steps: in the step S2, in the sample pretreatment, the sample weighing amount is 0.1-0.2g, and the content of HNO3 in the nitric acid is 65-68%; the content of HF in the hydrofluoric acid is more than or equal to 40 percent, and the content of HClO4 in the perchloric acid is 65-68 percent; the HCl content in the hydrochloric acid is more than or equal to 40 percent; the content of NH4H2PO4 in the diammonium phosphate is more than or equal to 40 percent.

4. The method for measuring lead in soil through wet digestion according to claim 2, characterized by comprising the following steps: the parameters of the graphite furnace atomic absorption spectrophotometer are as follows;

1) Light source: lead hollow cathode lamp

2) Wavelength: 283.3;

3) And (4) background buckling: a deuterium lamp;

4) Current: 10.0A;

4) Flow rate of atomizing gas Ar: 0.79mL/min;

5) Flow rate of cooling gas Ar: 13.8mL/min;

6) The sampling volume is: 5mm;

7) Temperature of the atomization chamber: 0 to 4 ℃;

8) The sampling mode is as follows: fully quantifying;

9) The scanning mode is as follows: jumping peaks;

10 Scan times): 10-100 times;

11 Number of measurements): 3 times;

12 Atomizer: a concentric atomizer;

13 Atomizing chamber: a swirling flow atomizing chamber;

16 Test mode): and (4) standard mode.

5. The method for measuring lead in soil through wet digestion according to claim 2, characterized by comprising the following steps: the electric heating plate digestion is carried out at the following specific temperature and corresponding time:

a first stage: heating to 100-120 deg.C for 10-30min, and maintaining for 90-120min; two stages: after hydrofluoric acid is added, heating at 140-150 ℃ for 5-10min, and keeping for 10-20min; three stages: after perchloric acid is added, heating at 160-180 ℃ for 5-10min, and keeping for 60-120min; the fourth stage: acid is removed to the size of the soybeans (0.5-1 mL).