Method for detecting sorbitol in wastewater

Abstract

The invention relates to a method for detecting sorbitol in wastewater, which comprises the following steps of: testing a sample by adopting a Karl Fischer method to obtain the percentage content nh of water in the sample; testing the sample by adopting a thermogravimetric analysis method to obtain the percentage content nTGA of the inorganic salt in the sample; carrying out water removal treatment on the sample to obtain a water-free sample; testing the anhydrous sample by adopting a thermal cracking-gas chromatography-mass spectrometry method to obtain the percentage content nr of the resin in the sample; the anhydrous sample is tested through gas chromatography-mass spectrometry, the percentage content nq of the sorbitol in the small molecule organic matter is obtained, the percentage content ns of the sorbitol in the sample is obtained by combining the test result, and the calculation formula is ns = nq (1-nh-nTGA-nr). According to the method, through combined use of multiple testing instruments, complex sample pretreatment operation is avoided, the content of sorbitol in the wastewater can be accurately detected, and the method is good in accuracy, high in precision and high in application value.

Description

Technical Field

[0001] The invention relates to the technical field of analytical chemistry, and in particular to a method for detecting sorbitol in wastewater. Background Art

[0002] Sorbitol is a sugar alcohol that can be metabolized slowly by humans. It has a similar structure to monosaccharides and can be obtained by reducing the aldehyde group on glucose to a hydroxyl group. Sorbitol can be used as a chemical raw material and is also commonly used in the food and pharmaceutical industries. Currently, the detection methods for sorbitol include potassium periodate titration, thin layer chromatography, high performance liquid chromatography, gas chromatography, enzyme colorimetry, etc.

[0003] CN101329337A discloses a method for determining the concentration of sorbitol by an enzyme colorimetric method, the principle of which is as follows: sorbitol and coenzyme generate sorbose and reduced coenzyme under the action of sorbitol dehydrogenase; the final reactant is placed under an ultraviolet / visible light analyzer or a semi- or fully automatic biochemical analyzer, the degree / speed of the increase in absorbance at the main wavelength of 340nm is detected, and the concentration measurement result of sorbitol is calculated.

[0004] An article discloses a method for determining the sorbitol content in compound sodium lactate sorbitol injection by gas chromatography: sorbitol is derivatized with acetic anhydride to form sorbitol hexaethyl ester with a lower boiling point, which is then separated using an HP-5 capillary column and detected using a flame ionization detector. This method achieves the separation of sorbitol from glucose, fructose, lactose, xylitol, and mannitol.

[0005] In the prior art, the detection of sorbitol is mostly focused on the fields of medicine and food. The types of impurities in the samples are relatively single, mostly small molecular organic matter. However, the components in industrial wastewater are complex, including inorganic salts and macromolecular resin substances. The above method cannot be applied to the detection of wastewater systems. Therefore, a detection method suitable for sorbitol in wastewater is provided to improve the precision and accuracy of the detection, which has high application value. Summary of the invention

[0006] To solve the above technical problems, the present invention provides a method for detecting sorbitol in wastewater. The present invention avoids complicated sample pretreatment operations by combining multiple testing instruments, can accurately detect the sorbitol content in wastewater, has good accuracy and high precision, and has high application value.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for detecting sorbitol in wastewater, the method comprising the following steps:

[0009] The Karl Fischer method was used to test the sample and the percentage of water in the sample was obtained. h; Thermogravimetric analysis was used to test the sample and the percentage of inorganic salt in the sample was obtained. TGA ;

[0010] The sample is dehydrated to obtain an anhydrous sample; the anhydrous sample is tested by thermal pyrolysis-gas chromatography-mass spectrometry to obtain the percentage of resin in the sample. r ;

[0011] The anhydrous sample was tested by gas chromatography-mass spectrometry to obtain the percentage of sorbitol in the small molecule organic matter. q , combined with the above test results, the percentage of sorbitol in the sample is obtained s , the calculation formula is:

[0012] n s =n q (1-n h -n TGA -n r ).

[0013] The wastewater detected by the present invention is wastewater discharged from the water circulation system of a swimming pool, which is a complex solution system optionally containing resin macromolecules (such as polyurethane, polyacrylamide, epoxy resin and phenolic resin, etc.), small molecule organic matter (such as fatty acids, lubricants, antioxidants, plasticizers, etc.) and inorganic salts (such as sodium salts, calcium salts and silicates, etc.). The detection of the sorbitol content therein is interfered by multiple substances and is very difficult.

[0014] In the present invention, during the thermogravimetric analysis test, water in the sample is vaporized, organic matter is decomposed, and the non-weight-loss part is inorganic salt, and then the percentage content of the inorganic salt in the sample is obtained; because water can hydrolyze the chromatographic column, it is necessary to first perform water removal treatment, and then perform PY-GC-MS and GC-MS tests. During the PY-GC-MS test, the ratio of the resin to the organic matter (excluding water and inorganic salt) is obtained by the ratio of the peak area of ​​the resin in the chromatogram to the peak area of ​​the total substance, and the percentage content of the resin in the sample is obtained by combining the percentage content of water and inorganic salt in the sample; in the GC-MS test, the percentage content of sorbitol to the small molecular compound (excluding water, inorganic salt and resin) is obtained by the ratio of the peak area of ​​sorbitol to the total substance in the chromatographic column; and the content of sorbitol in the wastewater can be obtained by summarizing and calculating various test data.

[0015] The present invention avoids complicated sample pretreatment operations by combining a variety of testing instruments, and can achieve accurate detection of the sorbitol content in wastewater with good accuracy and high precision, thus having high application value.

[0016] Preferably, the Karl Fischer method comprises a volumetric method, a coulometric method or a coulometric heating method, preferably a volumetric method.

[0017] Preferably, the thermogravimetric analysis is performed in a nitrogen atmosphere and an oxygen atmosphere, respectively.

[0018] Preferably, the heating program under the nitrogen atmosphere is: initial temperature 30-50°C (for example, 32°C, 35°C, 38°C, 40°C, 42°C, 45°C, 48°C, etc.), constant temperature 8-12min (for example, 8.5min, 9min, 9.5min, 10min, 10.5min, 11min, 11.5min, etc.), heating to 500-700°C (for example, 525°C, 550°C, 575°C, 600°C, 625°C, 650°C, 675°C, etc.) at 8-12°C / min (for example, 8.5°C / min, 9°C / min, 9.5°C / min, 10°C / min, 10.5°C / min, 11°C / min, 11.5°C / min, etc.).

[0019] Preferably, the heating program under the oxygen atmosphere is: initial temperature 500-700°C (for example, it can be 525°C, 550°C, 575°C, 600°C, 625°C, 650°C, 675°C, etc.), heating at 8-12°C / min (for example, it can be 8.5°C / min, 9°C / min, 9.5°C / min, 10°C / min, 10.5°C / min, 11°C / min, 11.5°C / min, etc.) to 750-950°C (for example, it can be 775°C, 800°C, 825°C, 850°C, 875°C, 900°C, 925°C, etc.), and maintaining the temperature for 0.5-2min (for example, it can be 0.8min, 1min, 1.2min, 1.5min, 1.8min, etc.).

[0020] Preferably, the dehydration treatment method includes any one of drying, distillation or reagent dehydration, or a combination of at least two of them.

[0021] Preferably, the drying temperature is 80-105°C (for example, 85°C, 90°C, 95°C, 100°C, etc.), and the drying time is 20-120 min (for example, 40 min, 60 min, 80 min, 100 min, etc.).

[0022] Preferably, the distillation temperature is 100-110°C (for example, 102°C, 104°C, 106°C, 108°C, etc.), and the distillation time is 1.5-2.5h (for example, 1.6h, 1.8h, 2h, 2.2h, 2.4h, etc.).

[0023] Preferably, the reagent comprises anhydrous sodium sulfate.

[0024] In the present invention, drying and distillation are preferably used for dehydration, which improves the dehydration efficiency and has a better dehydration effect compared with reagent dehydration.

[0025] Preferably, in the thermal cracking-gas chromatography-mass spectrometry method, the thermal cracking temperature is 300-600°C (for example, it can be 350°C, 400°C, 450°C, 500°C, 550°C, etc.), and the time is 0.15-0.3min (for example, it can be 0.16min, 0.18min, 0.2min, 0.22min, 0.24min, 0.26min, 0.28min, etc.).

[0026] In the present invention, too low or too high a pyrolysis temperature is not conducive to the detection of resinous substances in wastewater samples. The precision and accuracy of sorbitol content detection can be improved within the temperature range specified by the present invention.

[0027] Preferably, in the pyrolysis-gas chromatography-mass spectrometry method, the split ratio of the gas chromatography is (20-60):1 (for example, it can be 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, etc.).

[0028] Preferably, in the pyrolysis-gas chromatography-mass spectrometry, the temperature raising program of the gas chromatography is: the initial temperature is 30-50°C (for example, it can be 32°C, 35°C, 38°C, 40°C, 42°C, 45°C, 48°C, etc.), maintained for 2-4min (for example, it can be 2.2min, 2.5min, 2.8min, 3min, 3.2min, 3.5min, 3.8min, etc.), and the temperature is raised to 13°C / min at 8-12°C / min (for example, it can be 8.5°C / min, 9°C / min, 9.5°C / min, 10°C / min, 10.5°C / min, 11°C / min, 11.5°C / min, etc.). 0-150℃ (for example, it can be 132℃, 135℃, 138℃, 140℃, 142℃, 145℃, 148℃, etc.), then increase the temperature at 18-22℃ / min (for example, it can be 18.5℃ / min, 19℃ / min, 19.5℃ / min, 20℃ / min, 20.5℃ / min, 21℃ / min, 21.5℃ / min, etc.) to 300-320℃ (for example, it can be 302℃, 305℃, 308℃, 310℃, 312℃, 315℃, 318℃, etc.), and maintain for 5-10min (for example, it can be 6min, 7min, 8min, 9min, etc.).

[0029] Preferably, in the gas chromatography-mass spectrometry test, the anhydrous sample is first diluted with a solvent and then tested.

[0030] Preferably, the solvent includes any one of methanol, acetonitrile, diethyl ether or dichloromethane, or a combination of at least two thereof.

[0031] Preferably, in the gas chromatography-mass spectrometry test, the split ratio of the gas chromatography is (20-60):1 (for example, it can be 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, etc.).

[0032] In the present invention, a higher or lower split ratio will affect the peak shape. Within the range defined by the present invention, the detection effect is better.

[0033] Preferably, in the gas chromatography-mass spectrometry test, the temperature rising program of the gas chromatography is: the initial temperature is 40-60°C (for example, it can be 42°C, 45°C, 48°C, 50°C, 52°C, 55°C, 58°C, etc.), maintained for 1-3min (for example, it can be 1.2min, 1.5min, 1.8min, 2min, 2.2min, 2.5min, 2.8min, etc.), and the temperature is increased at 8-12°C / min (for example, it can be 8.5°C / min, 9°C / min, 9.5°C / min, 10°C / min, 10.5°C / min, 11°C / min, 11.5°C / min, etc.) to 140-160°C (for example, it can be 142°C, 145°C, 148°C, 150°C, 152°C, 15 The temperature may be 5°C, 158°C, etc.), maintained for 0.5-1.5min (for example, it may be 0.6min, 0.8min, 1min, 1.2min, 1.4min, etc.), then heated to 300-320°C (for example, it may be 302°C, 305°C, 308°C, 310°C, 312°C, 315°C, 318°C, etc.) at 18-22°C / min (for example, it may be 18.5°C / min, 19°C / min, 19.5°C / min, 20°C / min, 20.5°C / min, 21°C / min, 21.5°C / min, etc.), maintained for 3-7min (for example, it may be 3.5min, 4min, 4.5min, 5min, 5.5min, 6min, 6.5min, etc.).

[0034] In the present invention, the gas chromatography adopts a two-stage temperature rising program, and the obtained peak shape is better, which is conducive to the detection of sorbitol content.

[0035] Preferably, the detection method comprises the following steps:

[0036] The Karl Fischer method was used to test the sample and the percentage of water in the sample was obtained. h ; Thermogravimetric analysis was used to test the sample and the percentage of inorganic salt in the sample was obtained. TGA ;

[0037] The sample is dehydrated to obtain an anhydrous sample; the anhydrous sample is tested by thermal pyrolysis-gas chromatography-mass spectrometry to obtain the percentage of resin in the sample. r ;

[0038] The anhydrous sample was tested by gas chromatography-mass spectrometry to obtain the percentage of sorbitol in the small molecule organic matter. q , combined with the above test results, the percentage of sorbitol in the sample is obtained s , the calculation formula is:

[0039] n s =n q (1-n h -n TGA -n r )

[0040] The conditions of the thermogravimetric analysis are as follows:

[0041] The heating program is carried out in nitrogen atmosphere and oxygen atmosphere in turn; the heating program in nitrogen atmosphere is: initial temperature 30-50°C, constant temperature 8-12min, heating to 500-700°C at 8-12°C / min; the heating program in oxygen atmosphere is: initial temperature 500-700°C, heating to 750-950°C at 8-12°C / min, constant temperature 0.5-2min;

[0042] The test conditions of the pyrolysis-gas chromatography-mass spectrometry are as follows:

[0043] The temperature of thermal cracking is 300-600°C, and the time is 0.15-0.3min; the split ratio of gas chromatography is (20-60):1, and the temperature program is: the initial temperature is 30-50°C, maintained for 2-4min, heated to 130-150°C at 8-12°C / min, and then heated to 300-320°C at 18-22°C / min, and maintained for 5-10min;

[0044] The test conditions of the gas chromatography-mass spectrometry are as follows:

[0045] The split ratio of the gas chromatography is (20-60):1, and the temperature program of the gas chromatography is: the initial temperature is 40-60°C, maintained for 1-3 minutes, heated to 140-160°C at 8-12°C / min, maintained for 0.5-1.5 minutes, and then heated to 300-320°C at 18-22°C / min, maintained for 3-7 minutes.

[0046] Compared with the prior art, the present invention has at least the following beneficial effects:

[0047] The present invention obtains the contents of water, inorganic salts and resin in the wastewater sample through Karl Fischer test, thermogravimetric analysis test and thermal cracking-gas chromatography-mass spectrometry test, and obtains the content of sorbitol in the sample in combination with gas chromatography-mass spectrometry test; the present invention avoids complicated sample pretreatment operations through the combined use of multiple testing instruments, can realize accurate detection of the sorbitol content in the wastewater, has good accuracy and high precision, and has high application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is the thermogravimetric analysis diagram in Example 1.

[0049] Figure 2 It is the gas chromatogram of step (3) in Example 1.

[0050] Figure 3 It is the gas chromatogram of step (4) in Example 1. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0052] Example 1

[0053] This embodiment provides a method for detecting sorbitol in wastewater, the detection method comprising the following steps:

[0054] (1) The sample is tested using the Karl Fischer volumetric method. The sample is accurately weighed and titrated automatically using a moisture meter to obtain the percentage of water in the sample. h ;

[0055] (2) The sample was tested by thermogravimetric analysis to obtain the percentage of inorganic salt in the sample. TGA The conditions of thermogravimetric analysis are as follows: the temperature program is carried out in nitrogen atmosphere and oxygen atmosphere in turn. The temperature program in nitrogen atmosphere is: initial temperature 40°C, constant temperature for 10 min, heating to 600°C at 10°C / min, and the temperature program in oxygen atmosphere is: initial temperature 600°C, heating to 850°C at 10°C / min, constant temperature for 1 min; the flow rate of nitrogen or oxygen is 50 mL / min;

[0056] (3) Take 1 g of sample and dry it at 90°C for 1 h to obtain an anhydrous sample; use thermal pyrolysis-gas chromatography-mass spectrometry to test and obtain the percentage of resin in the sample. r; The test conditions of thermal pyrolysis-gas chromatography-mass spectrometry are as follows: the temperature of thermal pyrolysis is 400°C, and the time is 0.2 min; the chromatographic column of the gas chromatography is Rtx-5MS (30m*0.25mm*0.25μm), the split ratio is 40:1, and the heating program is: the initial temperature is 40°C for 3 min, the temperature is increased to 140°C at 10°C / min, and then the temperature is increased to 310°C at 20°C / min, and maintained for 8 min; the ion source temperature of the mass spectrometer is 230°C, the interface temperature is 310°C, the ionization mode is electron bombardment (70ev), the acquisition time is 1-28 min, and the scanning range is 29-600m / z;

[0057] (4) The anhydrous sample obtained in step (3) was diluted with methanol, filtered through a 0.22 μm microporous filter membrane, and then tested by gas chromatography-mass spectrometry to obtain the percentage of sorbitol in the small molecule organic matter. q ,The test conditions of gas chromatography-mass spectrometry are as follows: the chromatographic column of gas chromatography is HP-5MS (30.0m*250μm*0.25μm), the split ratio is 40:1, and the temperature program of gas chromatography is: the initial temperature is 50℃ and maintained for 2min, then the temperature is increased to 150℃ at 10℃ / min, maintained for 1min, and then the temperature is increased to 310℃ at 20℃ / min, maintained for 5min; the ion source temperature of mass spectrometry is 230℃, the interface temperature is 310℃, the ionization mode is electron bombardment (70ev), the acquisition time is 28min, and the scanning range is 29-600m / z;

[0058] (5) Combined with the above test results, the percentage of sorbitol in the sample is obtained. s , the calculation formula is as follows:

[0059] n s =n q (1-n h -n TGA -n r )

[0060] Among them, n q is the percentage of the peak area of ​​sorbitol in the gas chromatogram obtained by gas chromatography-mass spectrometry to the peak area of ​​all substances; n TGA The final residue weight (i.e., inorganic salt portion) in the thermogravimetric analysis is the percentage of the total weight; S 树脂 , S 总 They are respectively the peak area of ​​the resin and the peak area of ​​all substances in the gas chromatogram obtained from the test of thermal pyrolysis-gas chromatography-mass spectrometry.

[0061] Thermogravimetric analysis chart Figure 1 As shown, the non-weight-loss portion is inorganic salt.

[0062] Gas chromatograms in pyrolysis-gas chromatography-mass spectrometry tests are shown in Figure 1. Figure 2 shown.

[0063] Gas chromatogram in gas chromatography-mass spectrometry test Figure 3 shown.

[0064] Example 2

[0065] This embodiment provides a method for detecting sorbitol in wastewater, the detection method comprising the following steps:

[0066] (1) The sample is tested using the Karl Fischer volumetric method. The sample is accurately weighed and titrated automatically using a moisture meter to obtain the percentage of water in the sample. h ;

[0067] (2) The sample was tested by thermogravimetric analysis to obtain the percentage of inorganic salt in the sample. TGA The conditions of thermogravimetric analysis are as follows: the temperature program is carried out in nitrogen atmosphere and oxygen atmosphere in turn. The temperature program in nitrogen atmosphere is: initial temperature 30°C, constant temperature 8min, heating to 500°C at 8°C / min, and the temperature program in oxygen atmosphere is: initial temperature 500°C, heating to 750°C at 8°C / min, constant temperature 0.5min; the flow rate of nitrogen or oxygen is 50mL / min;

[0068] (3) Take 1.5 g of sample and dry it at 105°C for 20 min to obtain an anhydrous sample; use thermal pyrolysis-gas chromatography-mass spectrometry to test and obtain the percentage of resin in the sample. r ; The test conditions of thermal pyrolysis-gas chromatography-mass spectrometry are as follows: the temperature of thermal pyrolysis is 300°C, the time is 0.3 min; the chromatographic column of gas chromatography is Rtx-5MS (30m*0.25mm*0.25μm), the split ratio is 20:1, and the heating program is: the initial temperature is 30°C for 2 min, the temperature is increased to 130°C at 8°C / min, and then the temperature is increased to 300°C at 18°C / min, and maintained for 5 min; the ion source temperature of the mass spectrometer is 230°C, the interface temperature is 310°C, the ionization mode is electron bombardment (70ev), the acquisition time is 1-28min, and the scanning range is 29-600m / z;

[0069] (4) The anhydrous sample obtained in step (3) was diluted with methanol, filtered through a 0.22 μm microporous filter membrane, and then tested by gas chromatography-mass spectrometry to obtain the percentage of sorbitol in the small molecule organic matter. qThe test conditions of gas chromatography-mass spectrometry are as follows: the chromatographic column of the gas chromatography is HP-5MS (30.0m*250μm*0.25μm), the split ratio is 20:1, and the temperature program of the gas chromatography is: the initial temperature is 40℃ and maintained for 1min, then the temperature is increased to 140℃ at 8℃ / min, maintained for 0.5min, and then the temperature is increased to 300℃ at 18℃ / min, maintained for 3min; the ion source temperature of the mass spectrometer is 230℃, the interface temperature is 310℃, the ionization mode is electron bombardment (70ev), the acquisition time is 28min, and the scanning range is 29-600m / z;

[0070] (5) Combined with the above test results, the percentage of sorbitol in the sample is obtained. s , the calculation formula is as follows:

[0071] n s =n q (1-n h -n TGA -n r )

[0072] Among them, n q is the percentage of the peak area of ​​sorbitol in the gas chromatogram obtained by gas chromatography-mass spectrometry to the peak area of ​​all substances; n TGA The final residue weight (i.e., inorganic salt portion) in the thermogravimetric analysis is the percentage of the total weight; S 树脂 , S 总 They are respectively the peak area of ​​the resin and the peak area of ​​all substances in the gas chromatogram obtained from the test of thermal pyrolysis-gas chromatography-mass spectrometry.

[0073] Example 3

[0074] This embodiment provides a method for detecting sorbitol in wastewater, the detection method comprising the following steps:

[0075] (1) The sample is tested using the Karl Fischer volumetric method. The sample is accurately weighed and titrated automatically using a moisture meter to obtain the percentage of water in the sample. h ;

[0076] (2) The sample was tested by thermogravimetric analysis to obtain the percentage of inorganic salt in the sample. TGA The conditions of thermogravimetric analysis are as follows: the temperature program is carried out in nitrogen atmosphere and oxygen atmosphere in turn. The temperature program in nitrogen atmosphere is: initial temperature 50°C, constant temperature for 12 min, heating to 700°C at 12°C / min, and the temperature program in oxygen atmosphere is: initial temperature 700°C, heating to 950°C at 12°C / min, and constant temperature for 2 min; the flow rate of nitrogen or oxygen is 50 mL / min;

[0077] (3) Take 2 g of sample, dry it at 100°C for 1 h to obtain an anhydrous sample; use thermal pyrolysis-gas chromatography-mass spectrometry to test and obtain the percentage of resin in the sample n r ; The test conditions of thermal pyrolysis-gas chromatography-mass spectrometry are as follows: the temperature of thermal pyrolysis is 600°C, and the time is 0.15 min; the chromatographic column of gas chromatography is Rtx-5MS (30m*0.25mm*0.25μm), the split ratio is 60:1, and the heating program is: the initial temperature is 50°C for 4 min, the temperature is increased to 150°C at 12°C / min, and then the temperature is increased to 320°C at 22°C / min, and maintained for 10 min; the ion source temperature of mass spectrometry is 230°C, the interface temperature is 310°C, the ionization mode is electron bombardment (70ev), the acquisition time is 28 min, and the scanning range is 29-600m / z;

[0078] (4) The anhydrous sample obtained in step (3) was diluted with methanol, filtered through a 0.22 μm microporous filter membrane, and then tested by gas chromatography-mass spectrometry to obtain the percentage of sorbitol in the small molecule organic matter. q ,The test conditions of gas chromatography-mass spectrometry are as follows: the chromatographic column of gas chromatography is HP-5MS (30.0m*250μm*0.25μm), the split ratio is 60:1, and the temperature program of gas chromatography is: initial temperature 60℃ for 3min, heating to 160℃ at 12℃ / min, holding for 1.5min, and then heating to 320℃ at 22℃ / min, holding for 7min; the ion source temperature of mass spectrometry is 230℃, the interface temperature is 310℃, the ionization mode is electron bombardment (70ev), the acquisition time is 28min, and the scanning range is 29-600m / z;

[0079] (5) Combined with the above test results, the percentage of sorbitol in the sample is obtained. s , the calculation formula is as follows:

[0080] n s =n q (1-n h -n TGA -n r )

[0081] Among them, n q is the percentage of the peak area of ​​sorbitol in the gas chromatogram obtained by gas chromatography-mass spectrometry to the peak area of ​​all substances; n TGA The final residue weight (i.e., inorganic salt portion) in the thermogravimetric analysis is the percentage of the total weight; S 树脂 , S 总 They are respectively the peak area of ​​the resin and the peak area of ​​all substances in the gas chromatogram obtained from the test of thermal pyrolysis-gas chromatography-mass spectrometry.

[0082] Example 4

[0083] This embodiment provides a method for detecting sorbitol in wastewater, which differs from Embodiment 1 only in that, in step (3), 1 g of sample is taken, and after assembling the distillation apparatus, a heating jacket is used to maintain 100° C. for continuous distillation for 2 h to obtain an anhydrous sample. Other operations are similar to those of Embodiment 1.

[0084] Example 5

[0085] This embodiment provides a method for detecting sorbitol in wastewater, which differs from Embodiment 1 only in that, in step (3), 1 g of sample is taken, 5 times the mass of anhydrous sodium sulfate is added, and the mixture is allowed to stand for 24 hours to obtain an anhydrous sample.

[0086] Example 6

[0087] This embodiment provides a method for detecting sorbitol in wastewater, which differs from Embodiment 1 only in that the temperature of thermal cracking in step (3) is 200° C., and other operations refer to Embodiment 1.

[0088] Example 7

[0089] This embodiment provides a method for detecting sorbitol in wastewater, which differs from Embodiment 1 only in that the temperature of thermal cracking in step (3) is 800° C., and other operations refer to Embodiment 1.

[0090] Example 8

[0091] This embodiment provides a method for detecting sorbitol in wastewater, which differs from Embodiment 1 only in that the split ratio of the gas chromatography in step (4) is 10:1, and other operations refer to Embodiment 1.

[0092] Example 9

[0093] This embodiment provides a method for detecting sorbitol in wastewater, which differs from Embodiment 1 only in that the split ratio of the gas chromatography in step (4) is 100:1, and other operations refer to Embodiment 1.

[0094] Example 10

[0095] This embodiment provides a method for detecting sorbitol in wastewater, which differs from Embodiment 1 only in that the gas chromatography temperature raising program in step (4) is: the initial temperature is 50°C, maintained for 2 min, then heated to 310°C at a rate of 15°C / min, and maintained for 5 min. The other operations refer to Embodiment 1.

[0096] Comparative Example 1

[0097] This comparative example provides a method for detecting sorbitol in wastewater, and the detection method comprises the following steps:

[0098] (1) Chloroform was selected as the extraction solvent, 0.5 g of the sample was taken into a 10 mL volumetric flask, and chloroform was added to make the volume to 10 mL to obtain a sample solution to be tested. When loading the sample, the bottom chloroform layer was taken for testing; at the same time, a sorbitol standard with a purity of 99.99% was selected to prepare a standard solution, 10 mg of sorbitol was taken into a 10 mL volumetric flask, and chloroform was added to make the volume to 10 mL to obtain a 1000 ppm mother solution, which was diluted to five standard solutions of different gradients of 10 ppm, 30 ppm, 80 ppm, 100 ppm, and 300 ppm in sequence based on the mother solution;

[0099] (2) The above standard solutions and the sample solutions to be tested are uniformly tested by gas chromatography-mass spectrometry (test parameters refer to Example 1) to obtain a five-point calibration curve, wherein the calibration curve must meet R 2 ≈0.999, the sample data was brought into the standard curve to obtain the specific content of sorbitol in the sample; the GCMS acquisition mode initially required a full scan of a standard solution, and then the selected ion mode (SIM) was selected to test the complete standard solution and sample solution.

[0100] Test Example 1

[0101] Precision test

[0102] The wastewater samples were tested according to the detection methods provided in Examples 1-10 and Comparative Example 1. The experimental results are shown in Table 1.

[0103] Table 1

[0104] Implementation conditions Number of measurements Average content (%) RSD(%) Example 1 5 41.0 4.9 Example 2 5 39.4 5.7 Example 3 5 39.7 5.3 Example 4 5 41.3 6.1 Example 5 5 54.5 15.4 Example 6 5 43.8 7.4 Example 7 5 38.9 6.6 Example 8 5 42.1 5.9 Example 9 5 38.6 8.2 Example 10 5 43.4 6.8 Comparative Example 1 5 42.6 6.1

[0105] The test results show that:

[0106] (1) It can be seen from Examples 1 to 10 that the present invention can accurately detect the content of sorbitol in wastewater by combining multiple testing instruments, and the experimental operation is simple and the precision is high.

[0107] (2) By comparing Example 1, Example 4 and Example 5, it can be seen that the present invention can remove water from the sample in a relatively short time by using the drying or distillation dehydration operation, thereby improving the detection efficiency;

[0108] By comparing Example 1 with Examples 6-7, it can be seen that a pyrolysis temperature that is too low or too high is not conducive to the detection of resinous substances in wastewater samples, thereby reducing the precision of sorbitol content detection;

[0109] By comparing Example 1 with Examples 8-9, it can be seen that the split ratio is large, the peak shape is wide, and the peak intensity is low; the split ratio is low, the peak shape is asymmetric, and peak supersaturation and miscellaneous peaks appear, which are not conducive to the detection of sorbitol content;

[0110] It can be seen from the comparison between Example 1 and Example 10 that when only a one-stage temperature increase program is used in the gas chromatography, the peak shape is deteriorated, thereby affecting the precision of the detection.

[0111] (3) By comparing Example 1 with Comparative Example 1, it can be seen that the present invention not only realizes the accurate detection of the sorbitol content in the complex system of wastewater by combining multiple detection instruments, but also avoids the complicated operation of building a standard curve, thereby improving the detection efficiency.

[0112] Test Example 2

[0113] Accuracy test

[0114] Take two wastewater samples, each 1 g, and add 0.1 g of sorbitol standard (purity 99.99%) to one of them. Test the wastewater samples according to the detection methods provided in Examples 1-10 and Comparative Example 1, and calculate the recovery rate. The experimental results are shown in Table 2.

[0115] Table 2

[0116]

[0117]

[0118] It can be seen from the test results that the detection method provided by the present invention has an excellent recovery rate, indicating that the detection method provided by the present invention has high accuracy and can meet the detection requirements of sorbitol content in wastewater.

[0119] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for detecting sorbitol in wastewater, It is characterized in that The detection method comprises the following steps: The Karl Fischer method was used to test the sample and the percentage of water in the sample was obtained. h ; Thermogravimetric analysis was used to test the sample and the percentage of inorganic salt in the sample was obtained. TGA ; The sample is dehydrated to obtain an anhydrous sample; the anhydrous sample is tested by thermal pyrolysis-gas chromatography-mass spectrometry to obtain the percentage of resin in the sample. r ; The anhydrous sample was tested by gas chromatography-mass spectrometry to obtain the percentage of sorbitol in the small molecule organic matter. q , combined with the above test results, the percentage of sorbitol in the sample is obtained s , the calculation formula is: n s =n q (1-n h -n TGA -n r )。 2. The test method according to claim 1, It is characterized in that The Karl Fischer method includes a volumetric method, a coulometric method or a coulometric heating method, and the volumetric method is preferred.

3. The test method according to claim 1 or 2, It is characterized in that The thermogravimetric analysis was performed in nitrogen atmosphere and oxygen atmosphere respectively; Preferably, the heating program under the nitrogen atmosphere is: initial temperature 30-50°C, constant temperature 8-12min, heating to 500-700°C at 8-12°C / min; Preferably, the temperature rising program under the oxygen atmosphere is: initial temperature 500-700°C, heating to 750-950°C at 8-12°C / min, and maintaining the temperature for 0.5-2min.

4. The detection method according to any one of claims 1 to 3, It is characterized in that The dehydration treatment method includes any one or a combination of at least two of drying, distillation or reagent dehydration; Preferably, the drying temperature is 80-105°C and the drying time is 20-120min; Preferably, the distillation temperature is 100-110°C and the time is 1.5-2.5h; Preferably, the reagent comprises anhydrous sodium sulfate.

5. The detection method according to any one of claims 1 to 4, It is characterized in that In the thermal cracking-gas chromatography-mass spectrometry method, the thermal cracking temperature is 300-600° C. and the time is 0.15-0.3 min.

6. The detection method according to any one of claims 1 to 5, It is characterized in that In the thermal pyrolysis-gas chromatography-mass spectrometry, the split ratio of the gas chromatography is (20-60):1; Preferably, in the pyrolysis-gas chromatography-mass spectrometry, the temperature raising program of the gas chromatography is: the initial temperature is 30-50°C, maintained for 2-4 minutes, heated to 130-150°C at 8-12°C / min, and then heated to 300-320°C at 18-22°C / min, and maintained for 5-10 minutes.

7. The detection method according to any one of claims 1 to 6, It is characterized in that In the gas chromatography-mass spectrometry test, the anhydrous sample is first diluted with a solvent and then tested; Preferably, the solvent includes any one of methanol, acetonitrile, diethyl ether or dichloromethane, or a combination of at least two thereof.

8. The detection method according to any one of claims 1 to 7, It is characterized in that In the gas chromatography-mass spectrometry test, the split ratio of the gas chromatography is (20-60):

1.

9. The detection method according to any one of claims 1 to 8, It is characterized in that In the gas chromatography-mass spectrometry test, the temperature rising program of the gas chromatography is: the initial temperature is 40-60°C, maintained for 1-3 minutes, heated to 140-160°C at 8-12°C / min, maintained for 0.5-1.5 minutes, and then heated to 300-320°C at 18-22°C / min, maintained for 3-7 minutes.

10. The detection method according to any one of claims 1 to 9, It is characterized in that The detection method comprises the following steps: The Karl Fischer method was used to test the sample and the percentage of water in the sample was obtained. h ; Thermogravimetric analysis was used to test the sample and the percentage of inorganic salt in the sample was obtained. TGA ; The sample is dehydrated to obtain an anhydrous sample; the anhydrous sample is tested by thermal pyrolysis-gas chromatography-mass spectrometry to obtain the percentage of resin in the sample. r ; The anhydrous sample was tested by gas chromatography-mass spectrometry to obtain the percentage of sorbitol in the small molecule organic matter. q , combined with the above test results, the percentage of sorbitol in the sample is obtained s , the calculation formula is: n s =n q (1-n h -n TGA -n r ) The conditions of the thermogravimetric analysis are as follows: The heating program is carried out in nitrogen atmosphere and oxygen atmosphere in turn; the heating program in nitrogen atmosphere is: initial temperature 30-50°C, constant temperature 8-12min, heating to 500-700°C at 8-12°C / min; the heating program in oxygen atmosphere is: initial temperature 500-700°C, heating to 750-950°C at 8-12°C / min, constant temperature 0.5-2min; The test conditions of the pyrolysis-gas chromatography-mass spectrometry are as follows: The temperature of thermal cracking is 300-600°C, and the time is 0.15-0.3min; the split ratio of gas chromatography is (20-60):1, and the temperature program is: the initial temperature is 30-50°C, maintained for 2-4min, heated to 130-150°C at 8-12°C / min, and then heated to 300-320°C at 18-22°C / min, and maintained for 5-10min; The test conditions of the gas chromatography-mass spectrometry are as follows: The split ratio of the gas chromatography is (20-60):1, and the temperature program of the gas chromatography is: the initial temperature is 40-60°C, maintained for 1-3 minutes, heated to 140-160°C at 8-12°C / min, maintained for 0.5-1.5 minutes, and then heated to 300-320°C at 18-22°C / min, maintained for 3-7 minutes.

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