A method for detecting the content of perfluoropolyether carboxylic acid in perfluoropolyether carboxylic acid

Abstract

The present application relates to the technical field of fluorine-containing fine chemicals, and particularly relates to a method for detecting content of perfluoropolyether acyl fluoride in perfluoropolyether carboxylic acid, comprising the following steps: (1) establishing a relationship curve equation between the concentration of perfluoropolyether acyl fluoride in a mixed solution of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride and the absorbance value of the mixed solution at ultraviolet wavelength; (2) determining the absorbance value at ultraviolet wavelength in the perfluoropolyether carboxylic acid sample to be detected, and substituting the absorbance value into the relationship curve equation in step (1) to calculate the content of perfluoropolyether acyl fluoride in the perfluoropolyether carboxylic acid sample to be detected. The detection method is simple in operation, time-saving and labor-saving, high in detection efficiency, low in detection cost, and capable of realizing rapid detection of the purity of the perfluoropolyether carboxylic acid sample to be detected; moreover, the detection result is high in accuracy and basically consistent with the existing GC detection result.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fluorine-containing fine chemicals, in particular to a method for detecting the content of perfluoropolyether acyl fluoride in perfluoropolyether carboxylic acid. BACKGROUND

[0002] Perfluoropolyether carboxylic acid is a kind of fluorine-containing compound with wide application, which can be used as a surfactant, a water and oil repellent, and an intermediate for synthesizing fluoropolymer, and can be used as a dispersant for dispersing polymerized fluorinated monomers in an aqueous polymerization medium, and for preparing various fluororesins. Due to the environmental problems caused by traditional fluorine-containing surfactants perfluorooctanoic acid and salt solutions, perfluoropolyether carboxylic acid and carboxylic acid salt are considered as an important new type of green fluorocarbon surfactant because of their easier degradation, and have wide application value in the fields of fluorine-containing polymer preparation, waterproof and oil-proof, oil exploitation, etc. The high-purity perfluoropolyether carboxylic acid in the present application is applied in the synthesis of top anti-reflective layer and bottom anti-reflective layer of photoresist supporting materials, and the purity and impurity control requirements are very strict.

[0003] The main industrial synthesis method of high-purity 3 / 4 / 5 / 6 polyperfluoropolyether carboxylic acid is electrochemical fluorination, that is, high-purity 3 / 4 / 5 / 6 polyperfluoroacyl fluoride is reacted with water to prepare. Therefore, the prepared high-purity 3 polyperfluoropolyether carboxylic acid, 4 polyperfluoropolyether carboxylic acid, 5 polyperfluoropolyether carboxylic acid, 6 polyperfluoropolyether carboxylic acid and 7 polyperfluoropolyether carboxylic acid will be doped with perfluoropolyether acyl fluoride with their respective corresponding polymerization degree, and other polymerization degree of perfluoropolyether acyl fluoride will not be doped.

[0004] The content of a small amount of perfluoropolyether acyl fluoride in the existing perfluoropolyether carboxylic acid is usually tested by separation through chromatographic techniques such as GC, GC-MS, LC, LC-MS, etc. Among them, for low molecular weight and low boiling point perfluoropolyether carboxylic acid, GC and GC-MS can be used to detect the content of a small amount of perfluoropolyether acyl fluoride; there are certain requirements for the corrosion and pollution of perfluoropolyether carboxylic acid to the GC chromatographic column, the GC chromatographic column needs to be maintained and replaced regularly, the detection cost is high, and the detection time is long, the efficiency is low. For the content of high molecular weight and high boiling point perfluoropolyether acyl fluoride, GC and GC-MS cannot be used for detection, and usually LC and LC-MS are used to detect the content of a small amount of perfluoropolyether acyl fluoride, but perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride have strong thermal stability, and most polar and non-polar solvents are difficult to dissolve, therefore, when LC and LC-MS are used for detection, perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride need to be modified to improve their solubility, and then LC and LC-MS are used for detection, therefore, the sample pretreatment before detection is complex, the detection time is long, the efficiency is low, and the cost is high; and due to the potential pollution problem (such as fluorine-containing polymer coating on the sealing gasket) in the LC system, the accuracy of the detection result is affected, and the accuracy of the detection result is low. In view of the problems and deficiencies in the prior art, it is urgent to provide a method for simply and quickly detecting the content of perfluoropolyether acyl fluoride in perfluoropolyether carboxylic acid. SUMMARY

[0005] In view of the problems and deficiencies in the prior art, the present application aims to provide a method for detecting the content of perfluoropolyether acyl fluoride in perfluoropolyether carboxylic acid.

[0006] To achieve the purpose of the application, the technical scheme adopted by the present application is as follows:

[0007] A method for detecting the content of perfluoropolyether acyl fluoride in perfluoropolyether carboxylic acid, comprising the following steps:

[0008] (1) establishing a relationship curve equation between the concentration of perfluoropolyether acyl fluoride in the mixed solution of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride and the absorbance value of the mixed solution at ultraviolet wavelength;

[0009] (2) measuring the absorbance value at ultraviolet wavelength in the sample to be detected, substituting the absorbance value into the relationship curve equation in step (1), and calculating the content of perfluoropolyether acyl fluoride in the sample to be detected.

[0010] Further, the ultraviolet wavelength is preferably 226 nm.

[0011] Further, the perfluoropolyether acyl fluoride is a perfluoropolyether acyl fluoride of one degree of polymerization or a mixture of perfluoropolyether acyl fluorides of different degrees of polymerization.

[0012] Further, the perfluoropolyether carboxylic acid is one or more of perfluoropolyether carboxylic acids with a polymerization degree of 0-7.

[0013] Further, in step (1), the perfluoropolyether carboxylic acid is one with a polymerization degree.

[0014] Further, the perfluoropolyether carboxylic acid is one of perfluoropolyether carboxylic acids with a polymerization degree of 0-7.

[0015] Further, when the perfluoropolyether carboxylic acid is 3-poly perfluoropolyether carboxylic acid, the relationship curve equation is y=0.2646x+0.0139.

[0016] Further, when the perfluoropolyether carboxylic acid is 4-poly perfluoropolyether carboxylic acid, the relationship curve equation is y=0.2675x+0.0214.

[0017] Further, when the perfluoropolyether carboxylic acid is 5-poly perfluoropolyether carboxylic acid, the relationship curve equation is y=0.2676x+0.022.

[0018] Further, when the perfluoropolyether carboxylic acid is 6-poly perfluoropolyether carboxylic acid, the relationship curve equation is y=0.268x+0.0267.

[0019] Further, the specific operation of step (1) is:

[0020] The perfluoropolyether carboxylic acid is used as a solvent to dilute the perfluoropolyether carboxylic acid to obtain a mixed solution with different perfluoropolyether carboxylic acid concentrations, the absorbance value of the mixed solution under ultraviolet wavelength is detected, and a relationship curve equation is established according to the absorbance value of the mixed solution and the concentration of the perfluoropolyether carboxylic acid.

[0021] Further, in step (1), the purity of the perfluoropolyether carboxylic acid is ≥99%.

[0022] Compared with the prior art, the present application has the following positive and beneficial effects:

[0023] The present application firstly establishes a relationship curve equation between the concentration of perfluoropolyether carboxylic acid and the absorbance value of the mixed solution at the ultraviolet wavelength in the mixed solution of perfluoropolyether carboxylic acid and perfluoropolyether carboxylic acid fluoride at the ultraviolet wavelength, the content of perfluoropolyether carboxylic acid fluoride in the perfluoropolyether carboxylic acid sample to be detected can be quickly detected by detecting the absorbance value of the perfluoropolyether carboxylic acid sample to be detected at the ultraviolet wavelength and substituting the absorbance value into the relationship curve equation, and the purity of the perfluoropolyether carboxylic acid to be detected can be further calculated. Therefore, compared with the existing chromatographic detection technologies such as GC, GC-MS, LC, LC-MS and the like, the detection method of the present application is simple in operation, time-saving and labor-saving, high in detection efficiency, low in detection cost, and can realize the rapid detection of the purity of the perfluoropolyether carboxylic acid sample to be detected; moreover, the detection result is high in accuracy and basically consistent with the existing GC detection result. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a relationship curve equation between the content of 3-poly perfluoropolyether carboxylic acid fluoride and the absorbance in 3-poly perfluoropolyether carboxylic acid;

[0025] Figure 2 is a relationship curve equation between the content of 4-poly perfluoropolyether carboxylic acid fluoride and the absorbance in 4-poly perfluoropolyether carboxylic acid;

[0026] Figure 3 is a relationship curve equation between the content of 5-poly perfluoropolyether carboxylic acid fluoride and the absorbance in 5-poly perfluoropolyether carboxylic acid;

[0027] Figure 4 is a relationship curve equation between the content of 6-poly perfluoropolyether carboxylic acid fluoride and the absorbance in 6-poly perfluoropolyether carboxylic acid;

[0028] Figure 5 is a relationship curve equation between the content of 3-poly, 4-poly perfluoropolyether carboxylic acid fluoride and the absorbance in 3-poly perfluoropolyether carboxylic acid. DETAILED DESCRIPTION

[0029] The following detailed description is exemplary in nature and is intended to provide further description of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0030] It is to be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, components, and / or groups thereof.

[0031] The experimental methods in the following examples not specified in the specific conditions, using conventional techniques in the art, or according to the manufacturer's recommended conditions; the reagents or instruments used, not specified by the manufacturer, are conventional products that can be obtained by market.

[0032] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in conjunction with specific examples.

[0033] Example 1:

[0034] A method for detecting the content of 3-polyfluoropolyether carboxylic acid in 3-polyfluoropolyether carboxylic acid, the specific steps are:

[0035] (1) 3-polyfluoropolyether carboxylic acid (purity ≥ 99%) as a solvent for dilution of 3-polyfluoropolyether carboxylic acid (purity ≥ 99%), 3-polyfluoropolyether carboxylic acid (purity ≥ 99%) is diluted to 8 gradient standard solutions with concentrations of 0.1%, 0.3%, 0.5%, 1.0%, 2%, 4%, 6%, 8%; The absorbance value of the 8 gradient standard solutions is detected under ultraviolet wavelength 226 nm (the detection results are shown in Table 1, and the absorbance value in Table 1 is the average value of three experiments), according to the relationship between the absorbance value and the concentration of 3-polyfluoropolyether carboxylic acid (purity ≥ 99%), the relationship curve equation between the concentration of 3-polyfluoropolyether carboxylic acid and the absorbance is established, and the relationship curve equation obtained is y = 0.2646x + 0.0139 (as shown in Figure 1 ).

[0036] Table 1 Absorbance of standard solution with different 3-polyfluoropolyether carboxylic acid concentration

[0037]

[0038] (2) The absorbance value of the sample to be tested under ultraviolet wavelength is measured, and the absorbance value is substituted into the relationship curve equation y = 0.2646x + 0.0139 described in step (1) to calculate the content of 3-polyfluoropolyether carboxylic acid in the sample to be tested.

[0039] To verify the accuracy of the detection method of the embodiment, 3-polyfluoropolyether carboxylic acid (purity ≥ 99%) was used as a solvent to dilute 3-polyfluoropolyether acyl fluoride (purity ≥ 99%) into six concentration gradient samples of 0.2%, 0.4%, 1.2%, 2.3%, 3.6%, and 4.5%. The above six samples were used as the samples to be detected, and the absorbance of the samples was detected at a UV wavelength of 226 nm. The absorbance was substituted into the relationship curve equation y = 0.2646x + 0.0139 to calculate the concentration of 3-polyfluoropolyether acyl fluoride in the sample. At the same time, in order to make a comparison, the embodiment also used GC to detect the concentration of 3-polyfluoropolyether acyl fluoride in the above six samples (the GC detection conditions were: Shimadzu GC-2030 gas chromatograph, HP-5 chromatographic column, initial temperature 120°C, retention 2 min, rate 10°C / min, retention 5 min, rate 20°C / min, injection port temperature 280°C, detector temperature 310°C). The detection results are shown in Table 2 (the absorbance values in Table 2 are the average values of three experiments).

[0040] Table 2 Detection results of the concentration of 3-polyfluoropolyether acyl fluoride in 3-polyfluoropolyether carboxylic acid samples

[0041]

[0042] As can be seen from Table 2, the detection results of the concentration of 3-polyfluoropolyether acyl fluoride in the six samples detected by the detection method of the embodiment are basically consistent with the GC detection results and the actual concentration of the samples. This shows that using 3-polyfluoropolyether carboxylic acid as a solvent and detecting the absorbance at a UV absorption wavelength of 226 nm can detect the content of a small amount of 3-polyfluoropolyether acyl fluoride in 3-polyfluoropolyether carboxylic acid.

[0043] Embodiment 2:

[0044] A method for detecting the content of 4-polyfluoropolyether acyl fluoride in 4-polyfluoropolyether carboxylic acid, the specific steps are:

[0045] (1) 4-polyfluoropolyether carboxylic acid (purity ≥ 99%) was used as a solvent to dilute 4-polyfluoropolyether acyl fluoride (purity ≥ 99%) into eight gradient standard solutions with concentrations of 0.1%, 0.3%, 0.5%, 0.7%, 2%, 4%, 6%, and 8%. The absorbance values of the eight gradient standard solutions were detected at a UV wavelength of 226 nm (the detection results are shown in Table 3, and the absorbance values in Table 3 are the average values of three experiments). According to the relationship between the absorbance value and the concentration of 4-polyfluoropolyether acyl fluoride (purity ≥ 99%), a relationship curve equation of the concentration of 4-polyfluoropolyether acyl fluoride and the absorbance was established, and the relationship curve equation obtained was y = 0.2675x + 0.0214 (as shown in Figure 2

[0046] ​Table 3 Absorbance of standard solution of different 4-polyfluoropolyether acyl fluoride concentrations

[0047]

[0048] (2) The absorbance value of the sample to be tested at the ultraviolet wavelength is determined, and the absorbance value is substituted into the relational curve equation y = 0.2675x + 0.0214 to calculate the content of 4-polyfluoropolyether acyl fluoride in the sample of 4-polyfluoropolyether carboxylic acid to be tested.

[0049] To verify the accuracy of the detection method of the present embodiment, 4-polyfluoropolyether acyl fluoride (purity ≥ 99%) was diluted into 6 concentration gradients of 0.2%, 0.4%, 0.6%, 1.0%, 3.2%, and 4.8% using 4-polyfluoropolyether carboxylic acid (purity ≥ 99%) as the solvent. The above 6 samples were used as the samples to be tested, and the absorbance of the detector was detected at a wavelength of 226 nm. The absorbance was substituted into the relational curve equation y = 0.2675x + 0.0214 to calculate the concentration of 4-polyfluoropolyether acyl fluoride in the sample. At the same time, for comparison, the present embodiment also uses GC to detect the concentration of 4-polyfluoropolyether acyl fluoride in the above 6 samples (the GC detection conditions are: Shimadzu GC-2030 gas chromatograph, HP-5 chromatographic column, initial temperature 120°C, retention 2 min, rate 10°C / min, retention 5 min, rate 20°C / min, injection port temperature 280°C, detector temperature 310°C). The detection results are shown in Table 4 (the absorbance values in Table 4 are the average values of three experiments).

[0050] Table 4 Detection results of 4-polyfluoropolyether acyl fluoride concentration in 4-polyfluoropolyether carboxylic acid samples

[0051]

[0052]

[0053] As can be seen from Table 4, the detection results of the concentration of 4-polyfluoropolyether acyl fluoride in the 6 samples detected by the detection method of the present embodiment are basically consistent with the GC detection results and the actual concentration of the samples. Therefore, it is shown that the detection of a small amount of 4-polyfluoropolyether acyl fluoride content in 4-polyfluoropolyether carboxylic acid can be carried out by detecting the absorbance at a wavelength of 226 nm under ultraviolet absorption.

[0054] Example 3:

[0055] A method for detecting the content of 5-polyfluoropolyether acyl fluoride in 5-polyfluoropolyether carboxylic acid, the specific steps are:

[0056] (1) Using 5% poly(perfluoropolyether) carboxylic acid (purity ≥ 99%) as a solvent, 5% poly(perfluoropolyether) acyl fluoride (purity ≥ 99%) was diluted to prepare eight gradient standard solutions with concentrations of 0.1%, 0.3%, 0.5%, 0.7%, 2%, 4%, 6%, and 8%. The absorbance values ​​of the eight gradient standard solutions (0.1%, 0.3%, 0.5%, 0.7%, 2%, 4%, 6%, and 8%) were measured at a UV wavelength of 226 nm (the results are shown in Table 5, where the absorbance values ​​are the average of three experiments). Based on the relationship between absorbance values ​​and the concentration of 5% poly(perfluoropolyether) acyl fluoride (purity ≥ 99%), a curve equation relating the concentration of 5% poly(perfluoropolyether) acyl fluoride and absorbance was established. The obtained curve equation is y = 0.2676x + 0.022 (e.g., ...). Figure 3 (As shown).

[0057] Table 5. Absorbance of standard solutions with different concentrations of 5-perfluoropolyether fluoride.

[0058]

[0059] (2) Measure the absorbance value of the 5-perfluoropolyether carboxylic acid sample under ultraviolet wavelength, substitute the absorbance value into the relationship curve equation y=0.2676x+0.022 described in step (1), and calculate the content of 5-perfluoropolyether acyl fluoride in the 5-perfluoropolyether carboxylic acid sample.

[0060] To verify the accuracy of the detection method in this embodiment, 5-perfluoropolyether carboxylic acid (purity ≥99%) was diluted to six concentration gradients: 0.2%, 0.4%, 0.6%, 1.0%, 3.2%, and 4.8%, using 5-perfluoropolyether carboxylic acid (purity ≥99%) as the solvent. These six samples were used as analytes, and their absorbance was measured at 226 nm UV wavelength. The absorbance was then substituted into the relationship curve equation y = 0.2676x + 0.022 to calculate the concentration of 5-perfluoropolyether fluoride in the samples. For comparison, this embodiment also used GC to detect the concentration of 5-perfluoropolyether fluoride in the six samples (GC detection conditions: Shimadzu GC-2030 gas chromatograph, HP-5 column, initial temperature 120℃, retention time 2 min, rate 10℃ / min, retention time 5 min, rate 20℃ / min, injection port temperature 300℃, detector temperature 320℃). The test results are shown in Table 6.

[0061] Table 6. Detection results of 5-perfluoropolyether acyl fluoride concentration in 5-perfluoropolyether carboxylic acid samples

[0062]

[0063] As shown in Table 6, the detection results of the 5-polyfluoropolyether carboxylic acid concentration in 5 samples detected by the detection method of the present application are basically consistent with the detection results of GC and the actual concentration of the samples. Thus, it is shown that the detection of a small amount of 5-polyfluoropolyether carboxylic acid in 5-polyfluoropolyether carboxylic acid can be performed by using 5-polyfluoropolyether carboxylic acid as a solvent and detecting the absorbance at an ultraviolet absorption wavelength of 226 nm.

[0064] Example 4:

[0065] A method for detecting the content of 6-polyfluoropolyether carboxylic acid in 6-polyfluoropolyether carboxylic acid, the specific steps are:

[0066] (1) 6-polyfluoropolyether carboxylic acid (purity ≥ 99%) is used as a solvent to dilute 6-polyfluoropolyether carboxylic acid (purity ≥ 99%), and the 6-polyfluoropolyether carboxylic acid (purity ≥ 99%) is diluted into eight gradient standard solutions with concentrations of 0.1%, 0.3%, 0.5%, 0.7%, 2%, 4%, 6%, and 8%. The absorbance values of the eight gradient standard solutions of 0.1%, 0.3%, 0.5%, 1.0%, 2%, 4%, 6%, and 8% are detected at an ultraviolet wavelength of 226 nm (the detection results are shown in Table 7, and the absorbance values in Table 7 are the average values of three experiments), and a relationship curve equation between the 6-polyfluoropolyether carboxylic acid concentration and the absorbance is established according to the relationship between the absorbance value and the 6-polyfluoropolyether carboxylic acid (purity ≥ 99%) concentration, and the obtained relationship curve equation is y = 0.268x + 0.0267 as shown in Table 7. Figure 4

[0067] Table 7 Absorbance of standard solution with different 6-polyfluoropolyether carboxylic acid concentrations

[0068]

[0069] (2) The absorbance value of the 6-polyfluoropolyether carboxylic acid sample to be detected at the ultraviolet wavelength is determined, the absorbance value is substituted into the relationship curve equation y = 0.268x + 0.0267 described in step (1), and the content of 6-polyfluoropolyether carboxylic acid in the 6-polyfluoropolyether carboxylic acid sample to be detected is calculated.

[0070] ​In order to verify the accuracy of the detection method of the embodiment, 6-polyfluoropolyether carboxylic acid (purity ≥ 99%) was used as the solvent, and 6-polyfluoropolyether acyl fluoride (purity ≥ 99%) was diluted into three concentration gradient samples of 0.2%, 0.4% and 0.6%. The above six samples were used as the samples to be detected, and the absorbance of the detector was detected at a ultraviolet wavelength of 226 nm. The absorbance was substituted into the relationship curve equation y = 0.268x + 0.0267 to calculate the concentration of 6-polyfluoropolyether acyl fluoride in the sample. At the same time, in order to make a comparison, the concentration of 6-polyfluoropolyether acyl fluoride in the above three samples was also detected by LC-MS (for the detection conditions of LC-MS, please refer to the literature “Research on the detection method of perfluoroalkyl ether carboxylic acid in water by ultra-high performance liquid chromatography-tandem mass spectrometry”, Journal of Analysis and Test, Vol. 41, No. 1, January 2022). The detection results are shown in Table 8.

[0071] Table 8 Detection results of 6-polyfluoropolyether acyl fluoride concentration in 6-polyfluoropolyether carboxylic acid samples

[0072]

[0073] As can be seen from Table 8, the detection results of the concentration of 6-polyfluoropolyether acyl fluoride in the three samples detected by the detection method of the present application are basically consistent with the detection results of LC-MS and the actual concentration of the sample. Therefore, it is proved that using 6-polyfluoropolyether carboxylic acid as the solvent, detecting the absorbance at a ultraviolet absorption wavelength of 226 nm, the detection of a small amount of 6-polyfluoropolyether acyl fluoride content in 6-polyfluoropolyether carboxylic acid can be carried out.

[0074] Embodiment 5:

[0075] A method for detecting the total content of 3-polyfluoropolyether acyl fluoride and 4-polyfluoropolyether acyl fluoride in 3-polyfluoropolyether carboxylic acid, the specific steps are:

[0076] (1) 3-polyfluoropolyether carboxylic acid (purity ≥ 99%) was used as the solvent to dilute the mixed solution of 3-polyfluoropolyether acyl fluoride (purity ≥ 99%) and 4-polyfluoropolyether acyl fluoride (purity ≥ 99%) (the mass ratio of 3-polyfluoropolyether acyl fluoride and 4-polyfluoropolyether acyl fluoride in the mixed solution was 1:1), and the mixed solution of 3-polyfluoropolyether acyl fluoride (purity ≥ 99%) and 4-polyfluoropolyether acyl fluoride (purity ≥ 99%) was diluted into eight gradient standard solutions with concentrations of 0.1%, 0.3%, 0.5%, 0.7%, 2%, 4%, 6% and 8%; the absorbance values of the eight gradient standard solutions were detected at a ultraviolet wavelength of 226 nm (the detection results are shown in Table 9, and the absorbance values in Table 9 are the average values of three experiments), and the relationship curve equation of the concentration of perfluoropolyether acyl fluoride (purity ≥ 99%) and the absorbance was established according to the relationship between the absorbance value and the concentration of perfluoropolyether acyl fluoride (purity ≥ 99%), and the relationship curve equation obtained was y = 0.2618x + 0.0211 (as shown in Figure 5 Table 9 Absorbance values of 8 gradient standard solutions of 3-polyfluoropolyether acyl fluoride and 4-polyfluoropolyether acyl fluoride

[0077] Table 9 Absorbance of standard solution of different perfluoropolyether acyl fluoride concentration

[0078]

[0079] (2) The absorbance value of the sample to be tested at the ultraviolet wavelength is determined, and the absorbance value is substituted into the relational curve equation y = 0.2618x + 0.0211 described in step (1) to calculate the total content of perfluoropolyether acyl fluoride in the sample of 3-poly perfluoropolyether carboxylic acid to be tested.

[0080] In order to verify the accuracy of the detection method of the embodiment, a mixture of 3-poly perfluoropolyether acyl fluoride (purity ≥ 99%) and 4-poly perfluoropolyether acyl fluoride (purity ≥ 99%) (the mass ratio of 3-poly perfluoropolyether acyl fluoride and 4-poly perfluoropolyether acyl fluoride in the mixture is 1:1) is diluted into 6 concentration gradient samples of 0.2%, 0.4%, 0.6%, 1.0%, 3.2%, and 4.8%. The above 6 samples are used as the samples to be tested, the absorbance of the detector is detected at the ultraviolet wavelength of 226 nm, and the absorbance is substituted into the relational curve equation y = 0.26x + 0.021 to calculate the total concentration of perfluoropolyether acyl fluoride in the sample. At the same time, in order to make a comparison, the total concentration of perfluoropolyether acyl fluoride in the above 6 samples is also detected by GC (the GC detection condition is: Shimadzu GC-2030 gas chromatograph, HP-5 chromatographic column, initial temperature 120°C, retention 2 min, rate 10°C / min, retention 5 min, rate 20°C / min, injection port temperature 280°C, detector temperature 310°C). The detection results are shown in Table 10 (the absorbance values in Table 10 are the average values of three experiments).

[0081] Table 10 Detection results of 3-poly perfluoropolyether acyl fluoride concentration in 3-poly perfluoropolyether carboxylic acid sample

[0082]

[0083] As can be seen from Table 10, the detection results of the total concentration of perfluoropolyether acyl fluoride in the 6 samples detected by the detection method of the present application are basically consistent with the total concentration of acyl fluoride detected by GC and the actual concentration of the sample. Therefore, it is proved that the detection of a small amount of perfluoropolyether acyl fluoride content in 3-poly perfluoropolyether carboxylic acid can be carried out by detecting the absorbance at the ultraviolet absorption wavelength of 226 nm with 3-poly perfluoropolyether carboxylic acid as the solvent.

[0084] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for detecting the content of perfluoropolyether acyl fluoride in a perfluoropolyether carboxylic acid, characterized in that, The method comprises the following steps: (1) establishing a curve equation of the relationship between the concentration of perfluoropolyether carboxylic acid and the absorbance value of the mixed solution at the ultraviolet wavelength in the mixed solution of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride; (2) determining the absorbance value of the perfluoropolyether carboxylic acid sample at the ultraviolet wavelength, and substituting the absorbance value into the curve equation of the relationship in step (1) to calculate the content of perfluoropolyether acyl fluoride in the perfluoropolyether carboxylic acid sample; wherein the ultraviolet wavelength is 226 nm; The perfluoropolyether acyl fluoride is a perfluoropolyether acyl fluoride with a certain degree of polymerization or a mixture of perfluoropolyether acyl fluorides with different degrees of polymerization; the perfluoropolyether acyl fluoride is one or more of perfluoropolyether acyl fluorides with a degree of polymerization of 0-7; in step (1), the perfluoropolyether carboxylic acid is a perfluoropolyether carboxylic acid with a certain degree of polymerization; the perfluoropolyether carboxylic acid is any one of perfluoropolyether carboxylic acids with a degree of polymerization of 0-7.

2. The method of detecting the content of perfluoropolyether carboxylic acid in perfluoropolyether carboxylic acid fluoride according to claim 1, characterized by, When the perfluoropolyether carboxylic acid is 3-poly perfluoropolyether carboxylic acid, the curve equation of the relationship is y=0.2646x+0.0139; when the perfluoropolyether carboxylic acid is 4-poly perfluoropolyether carboxylic acid, the curve equation of the relationship is y=0.2675x+0.0214; when the perfluoropolyether carboxylic acid is 5-poly perfluoropolyether carboxylic acid, the curve equation of the relationship is y=0.2676x+0.022; when the perfluoropolyether carboxylic acid is 6-poly perfluoropolyether carboxylic acid, the curve equation of the relationship is y=0.268x+0.0267.

3. The method of detecting the content of perfluoropolyether carboxylic acid in perfluoropolyether carboxylic acid according to claim 2, characterized by, The specific operation of step (1) is: The perfluoropolyether acyl fluoride is diluted with perfluoropolyether carboxylic acid as a solvent to obtain a mixed solution with different concentrations of perfluoropolyether acyl fluoride, and the absorbance value of the mixed solution at the ultraviolet wavelength is detected, and a curve equation of the relationship between the absorbance value of the mixed solution and the concentration of perfluoropolyether acyl fluoride is established.

4. The method of detecting perfluoropolyether acyl fluoride content in perfluoropolyether carboxylic acid according to claim 3, characterized by, In step (1), the purity of the perfluoropolyether carboxylic acid is ≥99%.

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