A qualitative identification method of polyvinyl alcohol based on py-gc / ms

Abstract

The application discloses a polyvinyl alcohol qualitative identification method based on Py-GC / MS, and belongs to the technical field of analysis and detection, which comprises the following steps: (1) placing a sample to be tested in a cracker, pyrolyzing under the protection of an inert atmosphere at a high temperature of 300-600 DEG C, introducing pyrolysis products into a gas chromatograph-mass spectrometer for analysis to obtain a TIC graph; (2) if polyvinyl alcohol characteristic pyrolysis components including methyl conjugated polyene aldehyde are all identified in the TIC graph, it is indicated that the sample to be tested contains polyvinyl alcohol. The application does not need a sample pretreatment step, can quickly realize accurate qualitative identification of polyvinyl alcohol in the sample, and can provide significant characteristic pyrolysis components and basis for accurately identifying polyvinyl alcohol by using a pyrolysis method, such as octa-2, 4, 6-triene aldehyde and other methyl conjugated polyene aldehydes.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of analytical detection technology, and particularly relates to a polyvinyl alcohol qualitative identification method based on Py-GC / MS. BACKGROUND

[0002] Polyvinyl alcohol (PVA) has the advantages of high strength, good toughness and strong impact resistance, and is widely used in PVA blending, sizing, paper, composite film, textile fiber and sensor material fields. PVA is also used as an ingredient of adhesives or emulsifiers, as a water-soluble protective film, and as a starting material for other resins. However, polyvinyl alcohol is difficult to biodegrade and pollutes the environment, and some countries have explicitly prohibited the use of PVA. Therefore, it is very important to establish a scientific and accurate qualitative identification method.

[0003] A Chinese patent document with publication number CN101303310A discloses a method for determining the content of polyvinyl alcohol in water. First, an excess of sulfuric acid is added under neutral heating conditions (60-90℃) to hydrolyze and remove the starch in the sample that interferes with the determination. At the same time, the excess acid reacts with the polyvinyl alcohol in the sample to form an ester. In the presence of boric acid, both the ester produced by the reaction of polyvinyl alcohol with sulfuric acid and polyvinyl alcohol can react with boric acid-iodine-potassium iodide solution to form a stable blue-green complex. The absorbance of the complex is determined at a specific wavelength of 645 nm by a spectrophotometer, and the content of polyvinyl alcohol in the test sample can be calculated according to the standard curve.

[0004] A Chinese patent document with publication number CN103901027A discloses a method for detecting PVA in textile sizing components. This invention uses chemical analysis and color reaction to identify the presence of PVA. In the sizing process, the sizing components are often a combination of multiple sizing agents and chemical additives, and some sizing agents and chemical additives can interfere with the detection results of PVA. However, this method can effectively solve the interference problem of sizing agents and chemical additives, and accurately detect the presence of PVA.

[0005] A Chinese patent document with publication number CN113504196A discloses a method for detecting the content of polyvinyl alcohol by spectrophotometry. This method uses chloramine or chloramine derivatives and metal ions as color developing agents to detect the content of medicinal polyvinyl alcohol. The chloramine derivatives are methyl chloramine, ethyl chloramine or isopropyl chloramine. However, this method is suitable for the detection of all PVA that has not been completely alcoholized.

[0006] However, the above methods have complex steps and poor reliability in qualitative identification. Therefore, it is necessary to develop a simple, fast, reliable and environmentally friendly qualitative identification method for polyvinyl alcohol. SUMMARY

[0007] The application provides a polyvinyl alcohol qualitative identification method based on Py-GC / MS.

[0008] The specific technical scheme is as follows:

[0009] A polyvinyl alcohol qualitative identification method based on Py-GC / MS comprises the following steps:

[0010] (1) placing a sample to be measured in a pyrolyzer, pyrolyzing at 300-600 DEG C under the protection of an inert atmosphere, introducing pyrolysis products into a gas chromatograph-mass spectrometer for analysis to obtain a TIC graph;

[0011] (2) if polyvinyl alcohol characteristic pyrolysis components including methyl conjugated polyene aldehyde are all identified in the TIC graph, it is indicated that the sample to be measured contains polyvinyl alcohol.

[0012] The sample to be measured comprises unknown polymers, pulp, paper, composite films, textile fibers or sensor materials.

[0013] The application utilizes pyrolysis-gas chromatography / mass spectrometry (Py-GC / MS) technology, pyrolyzes polymers into small molecule compounds with volatility at high temperature, separates by gas chromatography, identifies characteristic pyrolysis components by mass spectrometry, realizes qualitative identification of polymers, especially octa-2,4,6-triene aldehyde and other methyl conjugated polyene aldehydes formed at a specific pyrolysis temperature, and can provide significant characteristic pyrolysis components and basis for accurately identifying polyvinyl alcohol by using Py-GC / MS technology.

[0014] Preferably, the inert atmosphere is a nitrogen atmosphere, a helium atmosphere or an argon atmosphere, and further preferably a helium atmosphere.

[0015] Preferably, the pyrolysis condition is 300-400 DEG C, and the pyrolysis time is 10-60 s. Under the above preferred condition, it is beneficial to the formation of methyl conjugated polyene aldehyde.

[0016] Further preferably, the pyrolysis condition is 400 DEG C, and the pyrolysis time is 20-30 s. Under the above further preferred condition, the pyrolysis characteristic is most significant.

[0017] Preferably, the characteristic pyrolysis component comprises acetaldehyde, acetone, 2,5-dihydrofuran, butenal, ethylene ketone, benzaldehyde, phenylacetone, methylbenzaldehyde or methyl conjugated polyene aldehyde.

[0018] Further, the methyl conjugated polyene aldehyde includes 2,4-hexadienal, octa-2,4,6-trienal, dec-2,4,6,8-tetraenal, 2,4,6,8,10-dodecane pentene aldehyde or 2,4,6,8,10,12-tetradecane hexene aldehyde.

[0019] Further, the methyl conjugated polyene aldehyde includes 2,4-hexadienal, octa-2,4,6-trienal, dec-2,4,6,8-tetraenal, 2,4,6,8,10-dodecane pentene aldehyde or 2,4,6,8,10,12-tetradecane hexene aldehyde.

[0020] Preferably, the gas chromatography-mass spectrometer analysis of the pyrolysis product is as follows:

[0021] The chromatographic conditions are as follows: the injection port temperature is 300 DEG C; the split ratio is 20:1; the helium carrier gas flow rate is 1 mL / min; the column temperature program is that the initial temperature is 40 DEG C (maintained for 5 min), and then increased to 300 DEG C (maintained for 5 min) at a rate of 10 DEG C / min; and the chromatographic column is DB-5MS (30 m*0.25 mm*0.25 um).

[0022] The mass spectrometric conditions are as follows: the ion source temperature is 230 DEG C; the quadrupole temperature is 150 DEG C; the mass spectrometric interface temperature is 300 DEG C; the electron impact energy is 70 eV; and the mass scan mode is SCAN / SIM, and the mass scan range is m / z 15-450.

[0023] The application further provides the use of methyl conjugated polyene aldehyde as a characteristic pyrolysis component in the qualitative identification of polyvinyl alcohol, and the methyl conjugated polyene aldehyde includes 2,4-hexadienal, octa-2,4,6-trienal, dec-2,4,6,8-tetraenal, 2,4,6,8,10-dodecane pentene aldehyde or 2,4,6,8,10,12-tetradecane hexene aldehyde.

[0024] Compared with the prior art, the application has the beneficial effects that:

[0025] The method of the application can directly sample and analyze without pretreatment of the sample, and has the advantages of simple steps, easy implementation, small sample dosage (as low as 0.1-0.5 mg), instant pyrolysis of the sample, fast detection speed, accurate qualitative identification of polyvinyl alcohol in the sample, simplicity, rapidness, high efficiency and sensitivity, and suitability for the detection of polyvinyl alcohol in various samples. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is the total ion current chromatogram of the pyrolysis of polyvinyl alcohol in Example 1.

[0027] Figure 2 Pyrolysis total ion chromatogram of poly(lactic acid) / polyvinyl alcohol blend film in Example 2.

[0028] Figure 3 Pyrolysis total ion chromatogram of wool keratin / polyvinyl alcohol blend film in Example 3.

[0029] Figure 4 Pyrolysis total ion chromatogram of polyamide 66 / polyvinyl alcohol composite fiber in Example 4.

[0030] Figure 5 Pyrolysis total ion chromatogram of gelatin / polyvinyl alcohol blend hydrogel in Example 5.

[0031] Figure 6 Pyrolysis total ion chromatogram of starch / polyvinyl alcohol mixed slurry in Example 6.

[0032] Figure 7 Pyrolysis total ion chromatogram of heat-sealed paper in Example 7. DETAILED DESCRIPTION

[0033] The present application will be further clarified by the following examples, which are intended to be exemplary of the present application. It should be understood that these examples are in no way limiting of the scope of the present application. Methods of operation, which are not specifically noted in the examples below, are generally performed according to conventional methods or according to the manufacturer's instructions.

[0034] The equipment and instrument parameters used in the examples are shown below, and the samples to be tested are derived from the laboratory or the market.

[0035] 1. Equipment and instruments

[0036] PY-3030D pyrolyzer; Agilent 7890B-5977A gas chromatograph-mass spectrometer; DB-5ms quartz capillary column (30 m x 0.25 mm x 0.25 μm).

[0037] 2. Instrument parameters

[0038] Chromatographic conditions: inlet temperature 300℃; split ratio 20:1; helium carrier gas flow rate 1 mL / min; column temperature program initial temperature 40℃, hold for 5 min, then increase to 300℃ at 10℃ / min, hold for 5 min;

[0039] Mass spectrometric conditions: ion source temperature 230℃; quadrupole temperature 150℃; mass spectrometer interface temperature 300℃; electron impact energy 70 eV; mass scan mode SCAN / SIM, mass scan range m / z 15-450.

[0040] Example 1

[0041] Polyvinyl alcohol 0.18 mg was placed in a pyrolyzer, pyrolyzed at 400 °C for 30 s under the protection of inert atmosphere, and the pyrolysis products were introduced into a gas chromatograph-mass spectrometer for analysis to obtain a TIC graph as shown in Figure 1 The mass spectrum analysis results of the pyrolysis products showed that the pyrolysis products included acetaldehyde, acetone, 2,5-dihydrofuran, butenal, ethylidene ketone, benzaldehyde, acetophenone, methylbenzaldehyde, and 2,4-hexadienal, octa-2,4,6-trienal, dec-2,4,6,8-tetraenal, 2,4,6,8,10-dodecadienal, 2,4,6,8,10,12-tetradecadienal; the peak area relative percentage of several methyl conjugated polyene aldehyde products was in the order of 2,4-hexadienal (88.27%) > octa-2,4,6-trienal (6.99%) > dec-2,4,6,8-tetraenal (3.44%) > 2,4,6,8,10-dodecadienal (1.19%) > 2,4,6,8,10,12-tetradecadienal (0.10%).

[0042] Example 2

[0043] Poly (lactic acid) / polyvinyl alcohol blend film was used as the sample to be tested, 0.13 mg of poly (lactic acid) / polyvinyl alcohol blend film was placed in a pyrolyzer, pyrolyzed at 400 °C for 36 s under the protection of inert atmosphere, and the pyrolysis products were introduced into a gas chromatograph-mass spectrometer for analysis to obtain a TIC graph as shown in Figure 2 The mass spectrum analysis results of the pyrolysis products showed that the pyrolysis products included acetaldehyde, acetone, 2,5-dihydrofuran, butenal, ethylidene ketone, benzaldehyde, acetophenone, methylbenzaldehyde, and 2,4-hexadienal, octa-2,4,6-trienal, dec-2,4,6,8-tetraenal, 2,4,6,8,10-dodecadienal, 2,4,6,8,10,12-tetradecadienal; the peak area relative percentage of several methyl conjugated polyene aldehyde products was in the order of 2,4-hexadienal (87.68%) > octa-2,4,6-trienal (8.25%) > dec-2,4,6,8-tetraenal (2.80%) > 2,4,6,8,10-dodecadienal (1.14%) > 2,4,6,8,10,12-tetradecadienal (0.13%). It indicated that polyvinyl alcohol was present in the sample to be tested.

[0044] Example 3

[0045] Wool keratin / polyvinyl alcohol blend film was used as the sample to be tested, 0.30 mg of wool keratin / polyvinyl alcohol blend film was placed in a pyrolyzer, pyrolyzed at 350 °C for 30 s under the protection of inert atmosphere, and the pyrolysis products were introduced into a gas chromatograph-mass spectrometer for analysis to obtain a TIC graph as shown in Figure 3The TIC chart is shown. According to the mass spectrum analysis results of the cracking products, the cracking products include: acetaldehyde, acetone, 2,5-dihydrofuran, butenal, ethylidene ketone, benzaldehyde, acetophenone, methylbenzaldehyde and 2,4-hexadienal, octa-2,4,6-trienal, dec-2,4,6,8-tetraenal, 2,4,6,8,10-dodecane pentenal, 2,4,6,8,10,12-tetradecane hexenal; the peak area relative percentage of several methyl conjugated polyene aldehyde products is in the order of 2,4-hexadienal (87.68%) > octa-2,4,6-trienal (8.25%) > dec-2,4,6,8-tetraenal (2.80%) > 2,4,6,8,10-dodecane pentenal (1.14%) > 2,4,6,8,10,12-tetradecane hexenal (0.13%). It shows that there is polyvinyl alcohol in the sample to be tested.

[0046] Example 4

[0047] Take polyamide 66 / polyvinyl alcohol composite fiber as the sample to be tested, 0.21 mg of polyamide 66 / polyvinyl alcohol composite fiber is placed in the cracking device, and is cracked at a high temperature of 300°C for 60 s under the protection of an inert atmosphere. The cracking products are introduced into a gas chromatograph-mass spectrometer for analysis to obtain a TIC chart as shown. Figure 4 The TIC chart is shown. According to the mass spectrum analysis results of the cracking products, the cracking products include: acetaldehyde, acetone, 2,5-dihydrofuran, butenal, ethylidene ketone, benzaldehyde, acetophenone, methylbenzaldehyde and 2,4-hexadienal, octa-2,4,6-trienal, dec-2,4,6,8-tetraenal, 2,4,6,8,10-dodecane pentenal, 2,4,6,8,10,12-tetradecane hexenal; the peak area relative percentage of several methyl conjugated polyene aldehyde products is in the order of 2,4-hexadienal (87.68%) > octa-2,4,6-trienal (8.25%) > dec-2,4,6,8-tetraenal (2.80%) > 2,4,6,8,10-dodecane pentenal (1.14%) > 2,4,6,8,10,12-tetradecane hexenal (0.13%). It shows that there is polyvinyl alcohol in the sample to be tested.

[0048] Example 5

[0049] Take gelatin / polyvinyl alcohol blended hydrogel as the sample to be tested, 0.16 mg of gelatin / polyvinyl alcohol blended hydrogel is placed in the cracking device, and is cracked at a high temperature of 380°C for 42 s under the protection of an inert atmosphere. The cracking products are introduced into a gas chromatograph-mass spectrometer for analysis to obtain a TIC chart as shown. Figure 5The TIC chart is shown. According to the mass spectrum analysis results of the cracking products, the cracking products include: acetaldehyde, acetone, 2,5-dihydrofuran, butenal, ethylidene ketone, benzaldehyde, acetophenone, methylbenzaldehyde and 2,4-hexadienal, octa-2,4,6-trienal, dec-2,4,6,8-tetraenal, 2,4,6,8,10-dodecadienal, 2,4,6,8,10,12-tetradecadienal; the peak area relative percentage of several methyl conjugated polyene aldehyde products is in the order of 2,4-hexadienal (89.01%) > octa-2,4,6-trienal (8.14%) > dec-2,4,6,8-tetraenal (1.83%) > 2,4,6,8,10-dodecadienal (0.93%) > 2,4,6,8,10,12-tetradecadienal (0.09%). It is indicated that there is polyvinyl alcohol in the sample to be tested.

[0050] Example 6

[0051] The starch / polyvinyl alcohol mixed textile size is used as the sample to be tested. 0.19 mg of the starch / polyvinyl alcohol mixed textile size is placed in a cracking device, and is cracked at a high temperature of 400°C for 30 s under the protection of an inert atmosphere. The cracking products are introduced into a gas chromatograph-mass spectrometer for analysis to obtain a TIC chart as shown in the figure. Figure 6 The TIC chart is shown. According to the mass spectrum analysis results of the cracking products, the cracking products include: acetaldehyde, acetone, 2,5-dihydrofuran, butenal, ethylidene ketone, benzaldehyde, acetophenone, methylbenzaldehyde and 2,4-hexadienal, octa-2,4,6-trienal, dec-2,4,6,8-tetraenal, 2,4,6,8,10-dodecadienal, 2,4,6,8,10,12-tetradecadienal; the peak area relative percentage of several methyl conjugated polyene aldehyde products is in the order of 2,4-hexadienal (89.01%) > octa-2,4,6-trienal (8.14%) > dec-2,4,6,8-tetraenal (1.83%) > 2,4,6,8,10-dodecadienal (0.93%) > 2,4,6,8,10,12-tetradecadienal (0.09%). It is indicated that there is polyvinyl alcohol in the sample to be tested.

[0052] Example 7

[0053] The heat-sealing paper is used as the sample to be tested. 0.12 mg of the heat-sealing paper is placed in a cracking device, and is cracked at a high temperature of 330°C for 54 s under the protection of an inert atmosphere. The cracking products are introduced into a gas chromatograph-mass spectrometer for analysis to obtain a TIC chart as shown in the figure. Figure 7The TIC chart is shown. According to the mass spectrum analysis results of the cleavage products, the cleavage products include: acetaldehyde, acetone, 2,5-dihydrofuran, butenal, ethyl ketone, benzaldehyde, acetophenone, methylbenzaldehyde and 2,4-hexadienal, octa-2,4,6-trienal, dec-2,4,6,8-tetraenal, 2,4,6,8,10-dodecane pentenal, 2,4,6,8,10,12-tetradecane hexenal; the peak area relative percentage of several methyl conjugated polyene aldehyde products is in the order of 2,4-hexadienal (87.71%) > octa-2,4,6-trienal (8.54%) > dec-2,4,6,8-tetraenal (2.58%) > 2,4,6,8,10-dodecane pentenal (1.06%) > 2,4,6,8,10,12-tetradecane hexenal (0.11%). It is shown that there is polyvinyl alcohol in the sample to be tested.

[0054] The above-described embodiments of the present application are described in detail, it should be understood that the above-described only for the specific embodiments of the present application, and not for limiting the present application, any modification, supplement or similar way of substitution, etc. made within the scope of the principles of the present application, should be included in the scope of protection of the present application.

Claims

1. A qualitative identification method of polyvinyl alcohol based on Py-GC / MS, characterized by, The method comprises the following steps: (1) placing a sample to be tested in a pyrolyzer, pyrolyzing the sample at a high temperature of 300-400 DEG C for 10-60 s under protection of an inert atmosphere, and introducing pyrolysis products into a gas chromatograph-mass spectrometer for analysis to obtain a TIC graph; (2) if polyvinyl alcohol characteristic pyrolysis components including methyl conjugated polyene aldehyde are all identified in the TIC graph, it is indicated that the sample to be tested contains polyvinyl alcohol; The conditions for analyzing the pyrolysis products by the gas chromatograph-mass spectrometer are as follows: Chromatographic conditions: injection port temperature 300 DEG C; split ratio 20:1; helium carrier gas flow rate 1 mL / min; column temperature program: initial temperature 40 DEG C, maintained for 5 min, then increased to 300 DEG C at a rate of 10 DEG C / min, maintained for 5 min; chromatographic column DB-5MS 30 m x 0.25 mm x 0.25 um; Mass spectrometric conditions: ion source temperature 230 DEG C; quadrupole temperature 150 DEG C; mass spectrometer interface temperature 300 DEG C; electron impact energy 70 eV; mass scan mode SCAN / SIM, mass scan range m / z 15-450; The characteristic pyrolysis components include acetaldehyde, acetone, 2,5-dihydrofuran, butenal, ethylidene ketone, benzaldehyde, acetophenone, methylbenzaldehyde and methyl conjugated polyene aldehyde, and the methyl conjugated polyene aldehyde is 2,4-hexadienal, octa-2,4,6-trienal, dec-2,4,6,8-tetraenal, 2,4,6,8,10-dodecane pentenal and 2,4,6,8,10,12-tetradecane hexenal.

2. The method for qualitative identification of polyvinyl alcohol based on Py-GC / MS according to claim 1, characterized in that, The sample to be tested includes an unknown polymer, slurry, paper, composite film, textile fiber or sensor material.

3. The method for qualitative identification of polyvinyl alcohol based on Py-GC / MS according to claim 1, characterized in that, The inert atmosphere is a nitrogen atmosphere, a helium atmosphere or an argon atmosphere.

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