CN114397156A - Sample pretreatment method for detecting trace metal ions in PTFE (polytetrafluoroethylene) and application thereof - Google Patents
Sample pretreatment method for detecting trace metal ions in PTFE (polytetrafluoroethylene) and application thereof Download PDFInfo
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- 229920001343 polytetrafluoroethylene Polymers 0.000 title claims abstract description 79
- 239000004810 polytetrafluoroethylene Substances 0.000 title claims abstract description 79
- 238000002203 pretreatment Methods 0.000 title claims abstract description 19
- 229910021655 trace metal ion Inorganic materials 0.000 title claims abstract description 19
- -1 polytetrafluoroethylene Polymers 0.000 title claims description 29
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 62
- 229910021645 metal ion Inorganic materials 0.000 claims abstract description 43
- 238000002791 soaking Methods 0.000 claims abstract description 17
- 238000012360 testing method Methods 0.000 claims abstract description 17
- 238000000034 method Methods 0.000 claims abstract description 12
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 claims abstract description 6
- 239000000243 solution Substances 0.000 claims description 30
- 239000011347 resin Substances 0.000 claims description 27
- 229920005989 resin Polymers 0.000 claims description 27
- 238000005245 sintering Methods 0.000 claims description 25
- 239000012086 standard solution Substances 0.000 claims description 25
- 238000001816 cooling Methods 0.000 claims description 16
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- 238000005520 cutting process Methods 0.000 claims description 12
- 238000001514 detection method Methods 0.000 claims description 9
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- 238000002360 preparation method Methods 0.000 claims description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 7
- 229910052742 iron Inorganic materials 0.000 claims description 7
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 claims description 6
- PTFCDOFLOPIGGS-UHFFFAOYSA-N Zinc dication Chemical compound [Zn+2] PTFCDOFLOPIGGS-UHFFFAOYSA-N 0.000 claims description 6
- 229910001422 barium ion Inorganic materials 0.000 claims description 6
- WLZRMCYVCSSEQC-UHFFFAOYSA-N cadmium(2+) Chemical compound [Cd+2] WLZRMCYVCSSEQC-UHFFFAOYSA-N 0.000 claims description 6
- 229910001430 chromium ion Inorganic materials 0.000 claims description 6
- 229910001431 copper ion Inorganic materials 0.000 claims description 6
- 229910001437 manganese ion Inorganic materials 0.000 claims description 6
- 229910001453 nickel ion Inorganic materials 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 238000007873 sieving Methods 0.000 claims description 4
- 238000001704 evaporation Methods 0.000 claims description 3
- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 claims 1
- 238000001556 precipitation Methods 0.000 abstract description 13
- 239000000843 powder Substances 0.000 abstract description 7
- 239000012528 membrane Substances 0.000 abstract description 4
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 230000008092 positive effect Effects 0.000 abstract description 2
- 238000000926 separation method Methods 0.000 abstract 1
- 239000000523 sample Substances 0.000 description 45
- 239000010408 film Substances 0.000 description 30
- 239000007788 liquid Substances 0.000 description 20
- 239000012535 impurity Substances 0.000 description 13
- 230000000052 comparative effect Effects 0.000 description 12
- 239000007789 gas Substances 0.000 description 10
- 239000000725 suspension Substances 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 239000012496 blank sample Substances 0.000 description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 6
- 239000004065 semiconductor Substances 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- WAEMQWOKJMHJLA-UHFFFAOYSA-N Manganese(2+) Chemical compound [Mn+2] WAEMQWOKJMHJLA-UHFFFAOYSA-N 0.000 description 5
- 239000012159 carrier gas Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000005070 sampling Methods 0.000 description 5
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- 229910021641 deionized water Inorganic materials 0.000 description 4
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- 150000002500 ions Chemical class 0.000 description 3
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- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
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- 229910052804 chromium Inorganic materials 0.000 description 1
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- 239000012530 fluid Substances 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 229920002313 fluoropolymer Polymers 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
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- 229910052748 manganese Inorganic materials 0.000 description 1
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- 238000001819 mass spectrum Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000011895 specific detection Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
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- 239000011701 zinc Substances 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/42—Low-temperature sample treatment, e.g. cryofixation
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/44—Sample treatment involving radiation, e.g. heat
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
- G01N27/626—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using heat to ionise a gas
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- Chemical & Material Sciences (AREA)
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- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
- Sampling And Sample Adjustment (AREA)
Abstract
The invention provides a sample pretreatment method for detecting trace metal ions in PTFE and application thereof. According to the invention, PTFE powder is prepared into a film, so that PTFE can be more easily immersed into concentrated hydrochloric acid; the PTFE membrane is sintered at high temperature to destroy the end group of PTFE, which is beneficial to the soaking and separation of metal ions by hydrochloric acid; the PTFE film in a high-temperature state is rapidly cooled, so that the specific surface area of the film is increased, and a positive effect on the precipitation of metal ions is achieved. The sample to be tested is tested by ICP-MS, the test result is accurate, and the method is widely applicable to the determination of trace metal ions in PTFE.
Description
Technical Field
The invention relates to the field of fluorine chemical industry, in particular to a sample pretreatment method for detecting trace metal ions in polytetrafluoroethylene and application thereof.
Background
Polytetrafluoroethylene (PTFE) is a major variety of fluoroplastics, and is used in various fields such as chemical industry, electronics, and electricity because of its excellent comprehensive properties such as high temperature resistance, corrosion resistance, non-adhesiveness, and self-lubricity. Particularly, with the rapid development of the semiconductor industry, the chemical resistance and low metal ion precipitation performance of PTFE play an irreplaceable role in the practical application of semiconductors. The problem of the purity of semiconductor chemicals can be well solved through the polytetrafluoroethylene material. For example, in the process of manufacturing silicon wafers, pipes and the like made of high-purity polytetrafluoroethylene can enable cleaning agents to clean parts through the pipes, and pollution is avoided to a great extent. In addition, various containers and storage bottles made of polytetrafluoroethylene can store and transport chemical products required in the semiconductor manufacturing process, and ensure the purity of the chemicals, thereby avoiding the pollution of fluid to components.
For the polytetrafluoroethylene suspension resin, the metal ion precipitation is an important index for detecting the purity of the polytetrafluoroethylene suspension resin, and whether the material is applied to the semiconductor industry can be determined. Chinese patent CN102033101A discloses a method for detecting metal impurities in a high-purity MgO film material by adopting ICP-MS, which comprises the following steps: (1) preparing a solution to be detected of the MgO film material; (2) preparing a series of standard solution samples containing impurities and different concentrations; (3) selecting the working conditions of the inductively coupled plasma mass spectrometer, and selecting the isotopes of elements to be detected, Ca, Fe and As in H2Measuring Al, Ti, V, Cr, Mn, Ni, Co, Cu, Zn, Zr, Mo, Cd, Sn, Sb, W, Pb and Bi in an Ar mode, analyzing a series of standard solution samples to obtain a working curve Y of corresponding impuritiesn＝aXn+ b, analyzing the solution to be detected of the MgO membrane material to obtain an impurity concentration value; (4) and according to the concentration value of the impurity, calculating to obtain the mass percentage content of the impurity element to be detected. However, for the PTFE powder, the PTFE powder is insoluble in water, resistant to acid and alkali, and floats on the surface of an aqueous solution, and the traditional concentrated hydrochloric acid-soaked PTFE powder cannot better precipitate metal ions, and it is important to develop a rapid and reliable PTFE metal ion precipitation test method in the face of rapid development of the semiconductor industry.
Disclosure of Invention
Aiming at the problem of detecting trace metal ions in PTFE, the invention provides a method for determining metal ion impurities in PTFE by adopting an inductively coupled plasma mass spectrometer (ICP-MS), which can better separate out metal ions and has the advantages of simple sample treatment, high instrument sensitivity and real and reliable detection result.
The invention provides a sample pretreatment method for detecting trace metal ions in PTFE, which has the following specific technical scheme:
a1: pressing: placing PTFE resin in a mould for pressing;
a2: and (3) sintering: placing the demoulded resin in a sintering furnace for sintering and preserving heat;
a3: cooling: after the heat preservation is finished, cooling the sample;
a4: rotary cutting: and after the temperature reduction is finished, carrying out rotary cutting on the sample to form a film.
In step a1, the resin is screened prior to pressing; the sieving treatment is to sieve the polytetrafluoroethylene suspension resin through a 10-mesh screen after the polytetrafluoroethylene suspension resin is kept at the constant temperature of 24 ℃ for 24 hours; the mass of the resin is 200 plus or minus 0.5 g; the mould is a hollow rod mould; the pressing speed is 10 mm/min; the pressing pressure is 30 MPa; the pressing process needs 300s of pressure maintaining.
In the step A2, the resin is demoulded, then is kept stand for 4 hours, and then is sintered; the sintering temperature rise rate is 60-120 ℃/h; the sintering temperature is 360-380 ℃; the heat preservation time is 3-5h, and after high-temperature sintering, the end group in the PTFE is destroyed, so that the subsequent metal ions are soaked and separated out by hydrochloric acid solution.
In the step A3, the environment temperature of cooling is not more than 0 ℃, and rapid cooling reduces the crystallinity of the PTFE sample, increases the porosity, improves the specific surface area of the film, and is more beneficial to the precipitation of metal ions.
Preferably, the ambient temperature for cooling is-10 ℃.
In the step A4, the thickness of the film is 0.5 +/-0.05 mm, the thicker the film is, the smaller the specific surface area is, and the poorer the effect of metal ion precipitation in the concentrated hydrochloric acid soaking process is.
The invention also provides application of the sample pretreatment method for detecting trace metal ions in PTFE. The sample pretreatment method can be applied to detection of trace metal ions in PTFE, and the specific application method is as follows:
s1, sample pretreatment:
the sample pretreatment method for detecting trace metal ions in PTFE is adopted for treatment.
S2, preparation of a standard solution:
accurately measuring 20uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the solubility of 10 ppb; accurately measuring 40uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the concentration of 20 ppb; accurately measuring 60uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the concentration of 30 ppb; a100 uL liquid transfer gun is used for accurately measuring 80uL of mixed standard solution, the volume is determined in a 100mL volumetric flask, and the solution with the concentration of 40ppb is prepared.
Wherein the concentration of the mixed standard solution is 50mg/L
S3, preparation of a sample to be detected:
cutting the polytetrafluoroethylene film after the pretreatment into small pieces, putting the small pieces into a PFA bottle, adding concentrated hydrochloric acid for soaking for 7 days; concentrated hydrochloric acid was evaporated by heating with an electric mantle (temperature 80 ℃), 9-11g of water was added to the bottle, and after filtration and purification, the sample was labeled for testing.
S4, sample injection detection:
(1) starting the inductively coupled plasma mass spectrum, and setting the working conditions of the inductively coupled plasma as follows: the high-frequency power is 1.2kW, the sampling depth is 5.0mm, the plasma gas is 9.0L/min, the auxiliary gas is 1.1L/min, the carrier gas is 0.7L/min, and the temperature of a fog chamber is 5.0 ℃.
(2) After the instrument is stabilized, blank samples are firstly injected from low concentration to high concentration in sequence, and then a standard curve is generated according to concentration-intensity.
The linear correlation coefficients of the standard curves are all larger than 0.999, wherein I is the intensity of the sample.
(3) And sequentially testing each sample to be tested, and directly obtaining the concentration of the metal ions in the tested sample according to a standard curve equation.
In step S3, the mass of the polytetrafluoroethylene film chip is 1-1.1 g; the mass of the concentrated hydrochloric acid is 4-5 g; the concentrated hydrochloric acid is electronic grade; the water is ultrapure water; the evaporation time is 2-5 h; the filtration purification is to adopt a 0.22 mu m organic microporous filter membrane for filtration.
In step S4, the metal ions to be detected are: barium ion, cadmium ion, chromium ion, copper ion, iron ion, manganese ion, nickel ion, and zinc ion.
The invention has the following beneficial effects:
according to the invention, PTFE is prepared into a film, so that the PTFE can be more easily soaked in concentrated hydrochloric acid; the PTFE film is subjected to high-temperature sintering treatment to destroy the PTFE end group and better separate out metal ions; after high-temperature sintering, the film is rapidly cooled, the porosity of the film is increased, the specific surface area is improved, and the precipitation of metal ions is facilitated. The process overcomes the problem that in the PTFE detection method in the prior art, powder floats on the surface of an aqueous solution, so that concentrated hydrochloric acid is difficult to play a role in soaking out metal ions, and the PTFE detection method is high in instrument sensitivity and accurate and stable in data.
Drawings
FIG. 1 is a standard curve of concentration-intensity of each metal ion
Detailed Description
Example 1:
(1) sample pretreatment: two different polytetrafluoroethylene suspension resins were prepared to obtain two samples. After the samples 1 and 2 were respectively kept at a constant temperature of 24 ℃ for 24 hours, they were sieved through a 10-mesh sieve, 200g of the resin was weighed, and added to a hollow bar mold, and pressed at a pressing speed of 10mm/min to 30MPa, and the pressure was maintained for 300 seconds. And standing for 4 hours after demolding, and sintering in a sintering furnace at the temperature rise rate of 120 ℃/h and the sintering temperature of 380 ℃ for 4 hours. And after the heat preservation is finished, the hollow rod is placed in an environment with the temperature of minus 10 ℃ for rapid cooling. And after the temperature reduction is finished, taking out the hollow rod, and carrying out rotary cutting on a numerical control machine tool to obtain the hollow rod with the thickness of 0.53 mm.
(2) Preparation of a standard curve: accurately measuring 20uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the solubility of 10 ppb; accurately measuring 40uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the concentration of 20 ppb; accurately measuring 60uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the concentration of 30 ppb; a100 uL liquid transfer gun is used for accurately measuring 80uL of mixed standard solution, the volume is determined in a 100mL volumetric flask, and the solution with the concentration of 40ppb is prepared.
(3) Preparing a sample to be tested: cutting the treated polytetrafluoroethylene film into small pieces with the mass of 1g, then putting the small pieces into a PFA bottle, adding electronic grade concentrated hydrochloric acid for soaking for 7 days, then evaporating the concentrated hydrochloric acid by using a water bath kettle at the temperature of 80 ℃ for 4 hours, adding 10g of deionized water into the bottle, taking out the solution by using a filter head, and marking the sample for testing.
(4) Inductively coupled plasma mass spectrometry conditions: the high-frequency power is 1.2kW, the sampling depth is 5.0mm, the plasma gas is 9.0L/min, the auxiliary gas is 1.1L/min, the carrier gas is 0.7L/min, and the temperature of a fog chamber is 5.0 ℃.
Secondly, after the instrument is stabilized, blank samples are firstly introduced, then samples are sequentially introduced from low concentration to high concentration, and then a standard curve is generated according to the concentration-intensity, as shown in figure 1, the linear correlation coefficients of the samples are all larger than 0.999, wherein I is the intensity of the sample.
And thirdly, sequentially testing each sample to be tested, and directly obtaining the concentration of the metal ions in the tested sample according to each formula below the standard curve graph.
The metal ions to be detected are as follows: barium ion, cadmium ion, chromium ion, copper ion, iron ion, manganese ion, nickel ion, and zinc ion.
The detected ion content is shown in table 1.
Table 1 stability of test results for each sample
Wherein, the sample 1 is a film without impurity points, and the surface of the film is free of impurity points;
sample 2 is a thin film containing impurity spots, and the surface thereof contains impurity spots.
To demonstrate the accuracy of the instrument, three tests were performed on each sample, and the mean of the results of the three tests was taken as the final data for the sample. As can be seen from Table 1, the ionic contents of the samples in the table are almost the same, and the data are accurate and stable.
Comparative example 1:
to confirm that rapid cooling does positively affect the precipitation of metal ions, this comparative example was compared using room temperature cooling as a comparison, and the other steps were the same as in example 1.
The specific operation steps are as follows:
(1) sample pretreatment: and (3) keeping the temperature of the polytetrafluoroethylene suspension resin at 24 ℃ for 24 hours, sieving the polytetrafluoroethylene suspension resin by a sieve with 10 meshes, weighing 200g of the resin, adding the resin into a hollow rod die, pressing the resin to 30MPa at the pressing speed of 10mm/min, and maintaining the pressure for 300 s. And standing for 4h after demolding, and sintering in a sintering furnace at the sintering temperature of 380 ℃ for 4h at the heating rate of 120 ℃/h. And after the heat preservation is finished, taking out the hollow rod, cooling the hollow rod to room temperature in an air cooling mode, and performing rotary cutting on a numerical control machine tool to obtain the hollow rod with the thickness of 0.53 mm.
(2) Preparation of a standard curve: accurately measuring 20uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the solubility of 10 ppb; accurately measuring 40uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the concentration of 20 ppb; accurately measuring 60uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the concentration of 30 ppb; a100 uL liquid transfer gun is used for accurately measuring 80uL of mixed standard solution, the volume is determined in a 100mL volumetric flask, and the solution with the concentration of 40ppb is prepared.
(3) Preparing a sample to be tested: cutting the treated polytetrafluoroethylene film into small pieces with the mass of 1g, then putting the small pieces into a PFA bottle, adding electronic grade concentrated hydrochloric acid for soaking for 7 days, then utilizing an electrothermal sleeve to heat and evaporate the concentrated hydrochloric acid at the temperature of 80 ℃ for 4 hours, adding 10g of deionized water into the bottle, taking out the solution by using a filter head, and marking the sample for testing.
(4) Inductively coupled plasma mass spectrometry conditions: the high-frequency power is 1.2kW, the sampling depth is 5.0mm, the plasma gas is 9.0L/min, the auxiliary gas is 1.1L/min, the carrier gas is 0.7L/min, and the temperature of a fog chamber is 5.0 ℃.
Secondly, after the instrument is stabilized, blank samples are firstly injected from low concentration to high concentration, and then a standard curve is generated according to concentration-intensity.
And thirdly, sequentially testing each sample to be tested, and directly obtaining the concentration of the metal ions in the tested sample according to each formula below the standard curve graph.
The metal ions to be detected are as follows: barium ion, cadmium ion, chromium ion, copper ion, iron ion, manganese ion, nickel ion, and zinc ion.
Comparative example 2:
to confirm that high temperature sintering does positively affect the precipitation of metal ions, this comparative example was compared with a non-sintered PTFE membrane as comparative example, with the other steps being the same as example 1.
The specific operation steps are as follows:
(1) sample pretreatment: and (3) keeping the temperature of the polytetrafluoroethylene suspension resin at 24 ℃ for 24 hours, sieving the polytetrafluoroethylene suspension resin by a sieve with 10 meshes, weighing 200g of the resin, adding the resin into a hollow rod die, pressing the resin to 30MPa at the pressing speed of 10mm/min, and maintaining the pressure for 300 s. Taking out the hollow bar, and rotary cutting on a numerical control machine tool to obtain the hollow bar with the thickness of 0.53 mm.
(2) Preparation of a standard curve: accurately measuring 20uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the solubility of 10 ppb; accurately measuring 40uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the concentration of 20 ppb; accurately measuring 60uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the concentration of 30 ppb; a100 uL liquid transfer gun is used for accurately measuring 80uL of mixed standard solution, the volume is determined in a 100mL volumetric flask, and the solution with the concentration of 40ppb is prepared.
(3) Preparing a sample to be tested: cutting the treated polytetrafluoroethylene film into small pieces with the mass of 1g, then putting the small pieces into a PFA bottle, adding concentrated hydrochloric acid for soaking for 7 days, then utilizing an electrothermal sleeve to heat and evaporate the concentrated hydrochloric acid at the temperature of 80 ℃ for 4 hours, adding 10g of deionized water into the bottle, taking out the solution by using a filter head, and marking the sample for testing.
(4) Inductively coupled plasma mass spectrometry conditions: the high-frequency power is 1.2kW, the sampling depth is 5.0mm, the plasma gas is 9.0L/min, the auxiliary gas is 1.1L/min, the carrier gas is 0.7L/min, and the temperature of a fog chamber is 5.0 ℃.
Secondly, after the instrument is stabilized, blank samples are firstly injected from low concentration to high concentration, and then a standard curve is generated according to concentration-intensity.
And thirdly, sequentially testing each sample to be tested, and directly obtaining the concentration of the metal ions in the tested sample according to each formula below the standard curve graph.
The metal ions to be detected are as follows: barium ion, cadmium ion, chromium ion, copper ion, iron ion, manganese ion, nickel ion, and zinc ion.
Comparative example 3:
to confirm that the film formation from PTFE does have a positive effect on the precipitation of metal ions, this comparative example was compared using PTFE powder as the comparative example.
The specific operation is as follows:
(1) sample pretreatment: the polytetrafluoroethylene suspension resin is kept at the constant temperature of 24 ℃ for 24 hours, sieved by a screen with 10 meshes, and 200g of the resin is weighed and put into a sintering furnace for sintering, wherein the sintering temperature is 380 ℃, the heat preservation time is 4 hours, and the heating rate is 120 ℃/h. And after the heat preservation is finished, rapidly cooling at the temperature of minus 10 ℃.
(2) Preparation of a standard curve: accurately measuring 20uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the solubility of 10 ppb; accurately measuring 40uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the concentration of 20 ppb; accurately measuring 60uL of mixed standard solution by using a 100uL liquid transfer gun, fixing the volume in a 100mL volumetric flask, and preparing the solution with the concentration of 30 ppb; a100 uL liquid transfer gun is used for accurately measuring 80uL of mixed standard solution, the volume is determined in a 100mL volumetric flask, and the solution with the concentration of 40ppb is prepared.
(3) Preparing a sample to be tested: 1g of the treated polytetrafluoroethylene is put into a PFA bottle and soaked in electronic grade concentrated hydrochloric acid for 7 days, then the concentrated hydrochloric acid is evaporated by an electrothermal sleeve at the temperature of 80 ℃ for 4 hours, 10g of deionized water is added into the bottle, the solution is taken out by a filter head, and a sample is marked for testing.
(4) Inductively coupled plasma mass spectrometry conditions: the high-frequency power is 1.2kW, the sampling depth is 5.0mm, the plasma gas is 9.0L/min, the auxiliary gas is 1.1L/min, the carrier gas is 0.7L/min, and the temperature of a fog chamber is 5.0 ℃.
Secondly, after the instrument is stabilized, blank samples are firstly injected from low concentration to high concentration, and then a standard curve is generated according to concentration-intensity.
And thirdly, sequentially testing each sample to be tested, and directly obtaining the concentration of the metal ions in the tested sample according to each formula below the standard curve graph.
The metal ions to be detected are as follows: barium ion, cadmium ion, chromium ion, copper ion, iron ion, manganese ion, nickel ion, and zinc ion.
TABLE 2 content of metal ions detected under different sample pretreatment conditions
Wherein, the blank sample does not contain a film and only contains concentrated hydrochloric acid;
table 2 shows the metal ion contents of the above examples and comparative examples, and it can be seen from the table that:
(1) the content of metal ions obtained by the test of the embodiment 1 is far higher than that obtained by the test of the comparative example 1, so that the porosity of the film can be increased by rapidly cooling the PTFE film, and the precipitation of the metal ions is facilitated;
(2) as can be seen from example 1 and comparative example 2, the precipitation of metal ions from the PTFE film can be positively influenced by high-temperature sintering;
(3) according to the embodiment 1 and the comparative example 3, the PTFE powder is prepared into a film, so that the problem that PTFE floats on the surface of concentrated hydrochloric acid, so that the concentrated hydrochloric acid is difficult to act and soak out metal ions can be effectively solved.
Experimental example 1:
in order to more fully separate out metal ions, different solutions are adopted to soak a sample to be detected in the experimental example, and the content of ions separated out is detected.
The specific procedure was the same as in example 1.
TABLE 3 content of metal ions measured by soaking in different solutions
And (4) analyzing results: in order to highlight the advantages of soaking in concentrated hydrochloric acid, samples containing films with impurity spots are respectively soaked in concentrated hydrochloric acid, pure water and concentrated sulfuric acid to serve as comparison samples, and the results are shown in table 3; as can be seen from Table 3, the content of each ion is greatly increased when the PTFE film is soaked in concentrated hydrochloric acid compared with the film containing the impurity spots after being soaked in pure water, which indicates that the content of trace metal ions in the PTFE film can be more easily measured by adopting the method of soaking the PTFE film in concentrated hydrochloric acid.
Experimental example 2:
in order to obtain the influence of the soaking time of the concentrated hydrochloric acid on the precipitation of the PTFE metal ions, the PTFE soaked in the concentrated hydrochloric acid for different times is subjected to metal ion content detection, the specific detection steps are the same as those in example 1, and the obtained detection results are shown in Table 4.
TABLE 4
And (4) analyzing results:
as can be seen from table 4, as the soaking time of the PTFE film in the concentrated hydrochloric acid was prolonged, the detected content of the metal ions was higher; when the soaking time is prolonged to 7 days, the detected content of the metal ions reaches the highest; when the soaking time is extended again, the detected content of the metal ions hardly changes. This indicates that a soaking time of the PTFE film in concentrated hydrochloric acid of 7 days is the optimum soaking time.
Claims (10)
1. A sample pretreatment method for detecting trace metal ions in PTFE is characterized by comprising the following steps:
a1: pressing: placing PTFE resin in a mould for pressing;
a2: and (3) sintering: placing the demolded PTFE resin in a sintering furnace for sintering and heat preservation;
a3: cooling: after the heat preservation is finished, cooling the sample;
a4: rotary cutting: and after the temperature reduction is finished, carrying out rotary cutting on the sample to form a film.
2. The sample pretreatment method for detecting the trace metal ions in the PTFE according to claim 1, wherein in the step A1, the resin is subjected to a sieving treatment before being pressed; the mould is a hollow rod mould; the pressing speed is 10 mm/min; the pressing pressure is 30 MPa; the pressing process needs 300s of pressure maintaining.
3. The sample pretreatment method for detecting the trace metal ions in the PTFE according to claim 1, wherein in the step A2, the resin is left standing for 4 hours after being demoulded and then is subjected to sintering treatment.
4. The sample pretreatment method for detecting the trace metal ions in the PTFE according to claim 3, wherein the sintering temperature rise rate is 60-120 ℃/h; the sintering temperature is 360-380 ℃; the heat preservation time is 3-5 h.
5. The sample pretreatment method for detecting the trace metal ions in the PTFE according to claim 1, wherein in the step A3, the ambient temperature of cooling is not more than 0 ℃; preferably, the environment temperature for cooling is-10 ℃.
6. The sample pretreatment method for detecting the trace metal ions in the PTFE according to claim 1, wherein in the step A4, the thickness of the film is 0.5 ± 0.05 mm.
7. The application of the sample pretreatment method according to any one of claims 1 to 6, characterized in that the sample pretreatment method can be applied to detection of trace metal ions in PTFE.
8. The application of the sample pretreatment method according to claim 7, wherein the method for detecting trace metal ions in PTFE comprises the following steps:
s1: sample pretreatment: a film prepared according to any one of claims 1 to 6;
s2: preparation of a standard solution: respectively preparing solutions with the concentrations of 10ppb, 20ppb, 30ppb and 40 ppb;
s3: preparation of a sample to be tested: cutting the film obtained in the step S1 into PTFE sheets, adding into concentrated hydrochloric acid for soaking, heating and evaporating the concentrated hydrochloric acid, filtering and purifying;
s4: sample introduction detection:
(1) opening the ICP-MS and setting working conditions;
(2) measuring a standard curve;
(3) and testing the concentration of the metal ions in the sample to be tested.
9. The use of the sample pretreatment method according to claim 8, wherein the mass of said PTFE sheet in step S3 is 1 to 1.1 g.
10. The application of the sample pretreatment method according to claim 8, wherein in step S4(3), the metal ions are barium ions, cadmium ions, chromium ions, copper ions, iron ions, manganese ions, nickel ions, and zinc ions.
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