Method for detecting impurities in ethylene glycol antimony

Abstract

This invention discloses a method for detecting impurities in antimony glycol, comprising the following steps: (1) drying the antimony glycol sample; (2) placing the dried antimony glycol sample from step (1) on a carrier, compacting it, and then loading it into the sample chamber of a glow discharge mass spectrometer, followed by vacuum treatment; (3) pushing the vacuum-treated sample from step (2) into the sample chamber of the glow discharge mass spectrometer, cooling it with liquid nitrogen, and then detecting it using a glow discharge mass spectrometer. This invention uses glow discharge mass spectrometry, which reduces the exposure time of antimony glycol at room temperature and pressure, thus saving sample pretreatment time, avoiding hydrolysis of antimony glycol, and preventing human operation contamination, ensuring the accuracy of the detection results; this invention uses a glow discharge mass spectrometer for detection, which does not require any pretreatment, and only requires a small amount of powder sample to be pressed slightly on a high-purity indium sheet, making the pretreatment simple and fast.

Description

Technical Field

[0001] This invention belongs to the field of analytical chemistry technology, and specifically relates to a method for detecting impurities in antimony glycol. Background Technology

[0002] Antimony glycolate is a key catalyst in polyester synthesis, and its purity directly affects the molecular weight distribution and color of PET products. When the content of metal impurities exceeds 0.1 ppm, it will lead to: a decrease in the polycondensation reaction rate; and an increase in the yellowing index (YI) of the final product by 3-5 units.

[0003] Traditional atomic absorption spectrometry (AAS) is limited by the flame atomization efficiency, with a detection limit of only 1 ppm for elements such as calcium, iron, arsenic, and lead, which cannot meet the production requirements of food-grade polyester.

[0004] Inductively coupled plasma mass spectrometry (ICP-MS) requires complex sample pretreatment. The complete digestion of antimony glycol takes about 4 hours. The pretreatment for digestion requires weighing and other operations. During this process, antimony glycol will rapidly absorb moisture, resulting in the final result not matching the actual value. Furthermore, the acid or alkali dissolution method can introduce impurities, making it impossible to detect the content of all elements in the sample.

[0005] Currently, the core standards for antimony glycol only cover the determination of the antimony content of the main component, limits of key impurities, and physical performance indicators (appearance, melting point, solubility). There are few reports on the detection of impurities in antimony glycol.

[0006] Glow discharge mass spectrometry (GD-MS) is a direct analysis technique for solid samples. It has advantages such as high sensitivity, low detection limit, and the ability to detect multiple elements simultaneously, and has been widely used in the high-purity analysis of metallic materials.

[0007] However, when using glow discharge mass spectrometry to detect antimony glycolate, due to the physicochemical properties of antimony glycolate, such as its hygroscopic nature and subsequent reaction after absorbing water to decompose into antimony trioxide and ethylene glycol, improper sample processing or poor control of detection conditions can easily lead to unstable matrix Sb signals, failure to detect, and excessively long detection times. Summary of the Invention

[0008] The purpose of this invention is to provide a method for detecting impurities in antimony glycol.

[0009] The above-mentioned objective of this invention can be achieved by the following technical solution: a method for detecting impurities in antimony glycol, comprising the following steps:

[0010] (1) Dry the antimony glycol sample;

[0011] (2) Place the antimony glycol sample dried in step (1) on the carrier, compact it, and then put it into the sample injection chamber of the glow discharge mass spectrometer and perform vacuum treatment.

[0012] (3) The sample after vacuum treatment in step (2) is pushed into the sample chamber of the glow discharge mass spectrometer. After being cooled by liquid nitrogen, the impurities in antimony glycol are detected by glow discharge mass spectrometer.

[0013] In the above methods for detecting impurities in antimony glycol:

[0014] Preferably, the drying process in step (1) is a vacuum drying process, wherein the pressure of the vacuum drying process is -0.8~0.9 bar, the temperature is 60~65℃, and the drying time is 12~15 h.

[0015] Preferably, the carrier in step (2) is an indium sheet with a purity of 7-7.5N.

[0016] More preferably, the carrier in step (2) is an indium sheet with a purity of 7N.

[0017] Preferably, the area of ​​the antimony glycolate sample in step (2) accounts for 1 / 5 to 2 / 5 of the total area of ​​the indium wafer sputtering surface.

[0018] More preferably, the area of ​​the antimony glycolate sample in step (2) accounts for 1 / 5 of the total area of ​​the indium wafer sputtering surface.

[0019] Preferably, the indium sheet described in step (2) is first etched with UP-grade nitric acid for 2-3 minutes before use, then washed with ultrapure water and UP-grade ethanol in sequence, and then dried with cold air.

[0020] Preferably, the cooling time with liquid nitrogen in step (3) is 15~20 min.

[0021] The core purpose of liquid nitrogen cooling is to suppress sample thermal volatilization, stabilize glow discharge, and significantly reduce gas background and polyatomic ion interference through the cold trap effect.

[0022] Preferably, the glow discharge mass spectrometer in step (3) is a DC glow discharge mass spectrometer.

[0023] Preferably, the current of the glow discharge mass spectrometer in step (3) is 1.2-1.8mA and the voltage is 1000V-1200V.

[0024] Preferably, the sputtering time of the glow discharge mass spectrometer in step (3) is 30~40 min.

[0025] Preferably, in step (3), a glow discharge mass spectrometer is used to detect impurities in antimony glycolate and to perform quantitative analysis of impurity elements in the antimony glycolate sample. The impurities include Mg, Al, Ca, Fe, Cl, As, Sn, Pb and Bi.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) By drying the antimony glycol sample, the moisture adsorbed on the sample surface and inside can be effectively removed, avoiding the interference of moisture on the detection process and improving the stability of the detection results.

[0028] (2) Since antimony glycol is hygroscopic and decomposes into antimony trioxide and ethylene glycol after absorbing water, the pretreatment time of antimony glycol should not be too long when detecting impurities. This invention uses glow discharge mass spectrometry to reduce the exposure time of antimony glycol at room temperature and pressure, which not only saves sample pretreatment time, but also avoids hydrolysis of antimony glycol and avoids human operation contamination, thus ensuring the accuracy of detection results.

[0029] (3) The present invention uses glow discharge mass spectrometry (GDMS) for detection, which does not require any pretreatment. Only a small amount of powder sample needs to be pressed slightly on a high-purity indium sheet. The pretreatment is simple and fast.

[0030] (4) In this invention, a small amount of sample is placed on 7N-7.5N high-purity indium. The laying range should be smaller than the glow discharge sputtering area and the laying area should be 1 / 5-2 / 5 to avoid reducing the sample ionization efficiency.

[0031] (5) Since the physicochemical properties of organometallic compounds are different from those of inorganic compounds, the detection parameters for detecting impurities in antimony glycol in this invention are different from those for ordinary inorganic compounds. By optimizing the discharge parameters, this invention can quantitatively detect trace elements in antimony glycol.

[0032] (6) Due to its higher ion extraction efficiency and lower matrix suppression effect, glow discharge mass spectrometry (GD-MS) exhibits higher sensitivity than inductively coupled plasma mass spectrometry (ICP-MS) in continuous operation mode. Attached Figure Description

[0033] Figure 1 This is the antimony glycolate sample laid on an indium sheet in Example 1;

[0034] Figure 2 This is the antimony glycolate sample laid on an indium sheet in Example 2;

[0035] Figure 3 This is the antimony glycolate sample laid on an indium sheet in Example 3. Detailed Implementation

[0036] The present invention will be further described below through specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not depart from the basic idea of ​​the present invention, they are all within the scope of the present invention.

[0037] Unless otherwise mentioned, all reagents listed below are commercially available raw materials.

[0038] Example 1

[0039] The method for detecting impurities in antimony glycol provided in this embodiment includes the following steps:

[0040] (1) Before testing, the antimony glycol sample was dried in a vacuum drying oven and then sealed and stored in a desiccator;

[0041] The vacuum drying process was carried out at a pressure of -0.9 bar, a temperature of 65°C, and a time of 12 hours.

[0042] (2) Remove the antimony glycolate from the desiccator, place a certain amount of sample on a 7N purity indium sheet, press the sample and indium sheet firmly, and then load it directly into the instrument (Nu Instruments Astrum Swift is recommended but not limited to). Vacuum the sample chamber. This process will allow the ethanol on the sample surface to evaporate and be removed (the vacuum of the glow discharge chamber is 1×10). -4 mbar);

[0043] The antimony glycolate sample's sputtering area accounts for 1 / 5 of the total area of ​​the indium wafer's sputtering surface, such as... Figure 1 As shown;

[0044] Before use, 7N purity indium sheets are first etched with UP-grade nitric acid for 2 minutes, then washed with ultrapure water and UP-grade ethanol in sequence, and then dried with cold air.

[0045] (3) Then the sample was pushed into the sample cell and cooled with liquid nitrogen for 20 min. The sample was then analyzed using a DC glow discharge mass spectrometer with the set glow discharge parameters of 1.5 mA and 1100 V.

[0046] The core purpose of liquid nitrogen cooling is to suppress sample thermal volatilization, stabilize glow discharge, and significantly reduce gas background and polyatomic ion interference through the cold trap effect.

[0047] Table 1 shows the detection data. As can be seen from Table 1, the data results tend to stabilize as the collection time increases. When the last 2-3 sets of data results are relatively stable, the data collection can be terminated. After 30 minutes of sputtering, the surface contamination of the sample surface is basically completely removed. Even for trace elements, the relative standard deviation of the elements is within 10%.

[0048] Table 1 Detection Data

[0049] Mg 4.20 0.89 0.47 0.39 0.31 0.30 0.31 1.3 Al 0.67 0.50 0.42 0.41 0.39 0.36 0.38 5.2 Ca 11.74 3.78 3.01 3.10 2.71 2.69 2.70 0.5 Fe 0.83 0.87 0.75 0.87 0.82 0.91 0.84 6.4 Cl 146.10 26.50 9.81 9.92 7.95 7.27 7.61 6.4 As 2.80 1.93 1.50 1.46 1.47 1.41 1.44 2.7 Sn 4.44 4.34 3.96 4.95 4.74 4.74 4.53 7.8 Pb 7.99 5.70 6.36 5.94 5.78 6.20 6.00 4.7 Bi 12.50 10.52 13.72 13.47 12.46 12.43 12.44 0.2

[0050] Example 2

[0051] The method for detecting impurities in antimony glycol provided in this embodiment includes the following steps:

[0052] (1) Before testing, the antimony glycol sample was dried in a vacuum drying oven and then sealed and stored in a desiccator;

[0053] The vacuum drying process was carried out at a pressure of -0.8 bar, a temperature of 60°C, and a drying time of 15 hours.

[0054] (2) Take antimony glycolate out of the desiccator, take a certain amount of sample and place it on a 7.5N purity indium sheet, press the sample and indium sheet firmly, put it into the sample holder and put it directly into the machine, and evacuate the sample chamber. This process will cause the ethanol on the sample surface to evaporate and be removed.

[0055] The antimony glycolate sample's sputtering area accounts for 3 / 10 of the total area of ​​the indium wafer's sputtering surface, such as... Figure 2 As shown;

[0056] Before use, 7.5N purity indium sheets are first etched with UP-grade nitric acid for 3 minutes, then washed with ultrapure water and UP-grade ethanol in sequence, and then dried with cold air.

[0057] (3) Then the sample was pushed into the sample cell, cooled with liquid nitrogen for 15 min, and analyzed using a DC glow discharge mass spectrometer with the set glow discharge parameters of 1.2 mA and 1000 V.

[0058] Table 2 shows the detection data. As can be seen from Table 2, the data results tend to stabilize as the collection time increases. When the last 2-3 sets of data results are relatively stable, the data collection can be terminated. After 30 minutes of sputtering, the surface contamination of the sample surface is basically completely removed. Even for trace elements, the relative standard deviation of the elements is within 10%.

[0059] Table 2 Detection Data

[0060] Mg 3.95 0.82 0.44 0.37 0.3 0.29 0.3 1.2 Al 0.63 0.48 0.4 0.39 0.37 0.35 0.37 5 Ca 11.28 3.65 2.92 3.02 2.65 2.63 2.64 0.4 Fe 0.8 0.85 0.73 0.84 0.8 0.88 0.82 6.2 Cl 139.8 25.2 9.42 9.55 7.68 7.05 7.38 6.3 As 2.68 1.85 1.45 1.41 1.42 1.37 1.4 2.5 Sn 4.32 4.21 3.85 4.82 4.65 4.63 4.41 7.6 Pb 7.75 5.52 6.18 5.78 5.62 6.05 5.85 4.5 Bi 12.28 10.35 13.55 13.3 12.25 12.22 12.23 0.2

[0061] Example 3

[0062] The method for detecting impurities in antimony glycol provided in this embodiment includes the following steps:

[0063] (1) Before testing, the antimony glycol sample was dried in a vacuum drying oven and then sealed and stored in a desiccator;

[0064] The vacuum drying process was carried out at a pressure of -0.85 bar, a temperature of 63°C, and a time of 13 hours.

[0065] (2) Take antimony glycolate out of the desiccator, take a certain amount of sample and place it on a 7N purity indium sheet, press the sample and indium sheet firmly, put it into the sample holder and put it directly into the machine, and evacuate the sample chamber. This process will allow the ethanol on the sample surface to evaporate and be removed.

[0066] The antimony glycolate sample's sputtering area accounts for 2 / 5 of the total area of ​​the indium wafer's sputtering surface, such as... Figure 3 As shown;

[0067] Before use, 7N purity indium sheets are first etched with UP-grade nitric acid for 2.5 minutes, then washed with ultrapure water and UP-grade ethanol in sequence, and then dried with cold air.

[0068] (3) Then the sample was pushed into the sample cell and cooled with liquid nitrogen for 17 min. The sample was then analyzed using a DC glow discharge mass spectrometer with the set glow discharge parameters of 1.2 mA and 1000 V.

[0069] Table 3 shows the detection data. As can be seen from Table 3, the data results tend to stabilize as the collection time increases. When the last 2-3 sets of data results are relatively stable, the data collection can be terminated. After 30 minutes of sputtering, the surface contamination of the sample surface is basically completely removed. Even for trace elements, the relative standard deviation of the elements is within 10%.

[0070] Table 3 Detection Data

[0071] Mg 4.35 0.93 0.49 0.41 0.33 0.32 0.32 1.4 Al 0.7 0.52 0.44 0.43 0.41 0.38 0.4 5.3 Ca 12.15 3.9 3.1 3.18 2.78 2.75 2.76 0.5 Fe 0.85 0.89 0.77 0.89 0.84 0.93 0.86 6.5 Cl 152.3 27.8 10.15 10.25 8.2 7.5 7.85 6.5 As 2.92 2.01 1.55 1.51 1.52 1.45 1.48 2.8 Sn 4.55 4.45 4.05 5.05 4.85 4.83 4.63 7.9 Pb 8.2 5.85 6.5 6.1 5.9 6.35 6.15 4.8 Bi 12.7 10.7 13.9 13.65 12.65 12.6 12.62 0.2

[0072] Comparative Example 1

[0073] Unlike Example 1, the drying process in step (1) is omitted.

[0074] Because antimony glycolate readily absorbs water, the discharge becomes unstable after absorbing water. Even after half an hour of sputtering, the signal of the substrate Sb remains unstable, making it impossible to test the sample.

[0075] Comparative Example 2

[0076] Unlike Example 1, the antimony glycol sample had a sputtering area that accounted for 3 / 5 of the total area of ​​the indium wafer sputtering surface.

[0077] Since antimony glycolate is an insulator, a large sample amount is not conducive to glow discharge. When the area of ​​antimony glycolate sample covers 3 / 5 of the total area of ​​the indium wafer sputtering surface, even after half an hour of sputtering, the substrate Sb signal still cannot be stabilized, and the sample cannot be tested.

[0078] Comparative Example 3

[0079] Unlike Example 1, in step (3), the current of the glow discharge mass spectrometer is 2.0 mA and the voltage is 1500 V.

[0080] Since antimony glycolate is an insulator, larger discharge parameters are not conducive to the stability of the substrate Sb signal. When the discharge parameters are set to 2.0mA / 1500V, even after half an hour of sputtering, the substrate Sb signal still cannot be stabilized, and the sample cannot be tested.

[0081] Comparative Example 4

[0082] Unlike Example 1, in step (3), the current of the glow discharge mass spectrometer is 1.0 mA and the voltage is 800 V.

[0083] The sputtering rate of the sample is affected by the discharge parameters. Smaller discharge current and voltage result in a slower sputtering rate, longer sample surface contamination removal time, and increased sample detection time. The detection results at a discharge parameter of 1.0 mA / 800 V are shown in Table 4. As can be seen from Table 4, it took 1 hour of sputtering for the contamination on the sample surface to be removed.

[0084] Table 4 Detection Data

[0085] Mg 2.1 1.55 1.05 0.75 0.52 0.4 0.33 0.31 0.31 0.9 Al 1.5 1.2 0.82 0.61 0.52 0.41 0.39 0.38 0.38 3.8 Ca 6.85 5.95 4.85 4.25 3.65 3.15 2.75 2.7 2.7 0.3 Fe 2.5 2.1 1.6 1.2 0.95 0.85 0.84 0.84 0.84 1.8 Cl 78.5 65.5 42.5 28.5 18.5 12.5 8.25 7.6 7.61 4.2 As 2.15 1.98 1.85 1.75 1.65 1.55 1.46 1.44 1.44 1.8 Sn 4.5 4.48 4.52 4.55 4.51 4.53 4.53 4.53 4.53 0.4 Pb 6.05 5.98 6.02 5.99 6.03 6.01 6 6 6 0.3 Bi 12.48 12.45 12.46 12.44 12.45 12.43 12.44 12.44 12.44 0.1

[0086] The above examples illustrate specific embodiments of the present invention. It is important to note that these specific embodiments are only for further explanation and do not constitute a limitation on the scope of protection of the present invention. Non-essential modifications and adjustments made by others based on the present invention still fall within the scope of protection of the present invention.

Claims

1. A method for detecting impurities in antimony glycol, characterized in that, Includes the following steps: (1) Dry the antimony glycol sample; (2) Place the antimony glycol sample dried in step (1) on the carrier, compact it, and then put it into the sample injection chamber of the glow discharge mass spectrometer and perform vacuum treatment. (3) The sample after vacuum treatment in step (2) is pushed into the sample chamber of the glow discharge mass spectrometer. After being cooled by liquid nitrogen, the impurities in antimony glycol are detected by glow discharge mass spectrometer.

2. The method for detecting impurities in antimony glycol according to claim 1, characterized in that, The drying process described in step (1) is a vacuum drying process, wherein the pressure of the vacuum drying process is -0.8~0.9 bar, the temperature is 60~65℃, and the time is 12~15h.

3. The method for detecting impurities in antimony glycol according to claim 1, characterized in that, The carrier in step (2) is an indium sheet with a purity of 7-7.5N.

4. The method for detecting impurities in antimony glycol according to claim 3, characterized in that, The area of ​​the antimony glycolate sample in step (2) accounts for 1 / 5 to 5 / 2 of the total area of ​​the indium wafer sputtering surface.

5. The method for detecting impurities in antimony glycol according to claim 3, characterized in that, The indium sheet described in step (2) is first etched with UP-grade nitric acid for 2-3 minutes before use, then washed with ultrapure water and UP-grade ethanol in sequence, and then dried with cold air.

6. The method for detecting impurities in antimony glycol according to claim 1, characterized in that, In step (3), the cooling time with liquid nitrogen is 15-20 minutes.

7. The method for detecting impurities in antimony glycol according to claim 1, characterized in that, The glow discharge mass spectrometer mentioned in step (3) is a DC glow discharge mass spectrometer.

8. The method for detecting impurities in antimony glycol according to claim 1 or 7, characterized in that, The current of the glow discharge mass spectrometer mentioned in step (3) is 1.2-1.8mA and the voltage is 1000V-1200V.

9. The method for detecting impurities in antimony glycol according to claim 1, characterized in that, The sputtering time of the glow discharge mass spectrometer in step (3) is 30~40 min.

10. The method for detecting impurities in antimony glycol according to claim 1, characterized in that, In step (3), a glow discharge mass spectrometer is used to detect impurities in antimony glycolate and to perform quantitative analysis of impurity elements in the antimony glycolate sample. The impurities include Mg, Al, Ca, Fe, Cl, As, Sn, Pb and Bi.

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