A method for simultaneously determining 5-hydroxymethylfurfural and its oxidation products

Abstract

The present invention provides a method for simultaneously determining 5-hydroxymethylfurfural and its oxidation product, including: providing a reaction mixture obtained after 5-hydroxymethylfurfural is oxidized, the reaction mixture comprising 5-hydroxymethylfurfural and its oxidation product; filtering the reaction mixture to obtain a filtrate and a filter residue; preparing the filtrate as a first solution to be tested, mixing the filter residue with an inorganic base so that the insoluble oxidation product in the filter residue undergoes a salt-forming reaction and dissolves, and preparing the filtrate as a second solution to be tested; performing high performance liquid chromatography analysis on the first solution to be tested and the second solution to be tested, respectively, the conditions for high performance liquid chromatography analysis comprising: an organic acid analytical column as the stationary phase, and a column temperature of 25°C to 60°C; an inorganic acid aqueous solution as the mobile phase, and a flow rate of the mobile phase of 0.4 to 1 mL / min; an injection volume of 1 μL to 20 μL; and adopting dual wavelength detection, with a first detection wavelength of 200 nm to 240 nm and a second detection wavelength of 250 nm to 300 nm. The method provided by the present invention has good separation, high accuracy, and high precision.

Description

Technical Field

[0001] The invention belongs to the technical field of furan bio-based compound content determination, and particularly relates to a method for simultaneously determining 5-hydroxymethylfurfural and its oxidation products. Background Art

[0002] 5-Hydroxymethylfurfural (HMF) is a bio-based intermediate with an aromatic furan structure. It is a platform compound with high technical content, great application potential, and is clean and environmentally friendly. It is expected to lead the chemical industry from the "benzene era" to the cleaner and more environmentally friendly "furan era." 2,5-Furandicarboxylic acid (FDCA) is a bio-based chemical with long-term and widespread application potential. Experts believe it is an important candidate for sustainable chemicals to replace existing petrochemicals. It has broad application prospects in polyester plastics, coatings, fiber fabrics, and other fields. Compared with traditional petrochemicals, FDCA has lower carbon emissions, better biodegradability, and a wider range of resource sources. Finding a green and efficient method for preparing FDCA has become a research hotspot.

[0003] Currently, there are multiple routes for synthesizing FDCA. The most widely studied and widely used route is the oxidation reaction using HMF as a raw material. It is also considered the most promising route for large-scale production of FDCA, offering significant economic benefits. However, this reaction is prone to the production of byproducts. In addition to FDCA, other oxidation byproducts are typically 5-hydroxymethyl-2-furoic acid (HMFCA), 5-formyl-2-furoic acid (FFCA), fumaric acid (FA), and maleic acid (MA). FDCA, HMFCA, and FFCA share similar structures, and current high-performance liquid chromatography (HPLC) methods have low separation between the three, making accurate determination difficult. Furthermore, the ring-opening oxidation products FA and MA do not produce effective UV absorption at the wavelengths of other oxidation products, resulting in qualitative and quantitative inaccuracies. This makes it difficult to effectively separate and determine the multiple oxidation components of 5-hydroxymethylfurfural simultaneously. Summary of the Invention

[0004] In order to solve all or part of the above technical problems, the present invention provides the following technical solutions:

[0005] One of the objects of the present invention is to provide a method for simultaneously determining 5-hydroxymethylfurfural and its oxidation products, comprising:

[0006] Providing a reaction mixture obtained after an oxidation reaction of 5-hydroxymethylfurfural, the reaction mixture comprising 5-hydroxymethylfurfural and an oxidation product thereof, wherein the oxidation product comprises one or more of 2,5-furandicarboxylic acid, 2,5-furandicarboxaldehyde, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, fumaric acid, and maleic acid;

[0007] The reaction mixture is filtered to obtain a filtrate and a filter residue; the filtrate is prepared as a first test solution, the filter residue is mixed with an inorganic base to cause the insoluble oxidation product in the filter residue to undergo a salt reaction and dissolve, and the mixture is prepared as a second test solution;

[0008] performing high performance liquid chromatography analysis on the first test solution and the second test solution respectively to perform qualitative and / or quantitative detection of substances contained in the reaction mixture;

[0009] Among them, the conditions of the high performance liquid chromatography analysis include: the stationary phase is an organic acid analytical column, the column temperature is 25°C to 60°C; the mobile phase is an inorganic acid aqueous solution, the flow rate of the mobile phase is 0.4 to 1 mL / min; the injection volume is 1 μL to 20 μL; dual-wavelength detection is used, the first detection wavelength is 200 nm to 240 nm, and the second detection wavelength is 250 nm to 300 nm.

[0010] The reaction mixture from the oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid may produce a large number of oxidation byproducts. 5-hydroxymethylfurfural and its various oxidation products have similar structures and are difficult to qualitatively and quantitatively detect. In addition, the reaction product obtained from the oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid usually contains insoluble substances. For example, when acetic acid is used for the reaction, the oxidation products of 5-hydroxymethylfurfural have limited solubility in acetic acid, and direct detection of liquid components may result in inaccurate detection. The method provided by the present invention separates the filtrate and the filter residue to detect 5-hydroxymethylfurfural and its oxidation products in the filtrate and the filter residue respectively, thereby achieving accurate detection of the reaction mixture. By adding an inorganic base, such as a monobasic inorganic base, the 2,5-furandicarboxylic acid, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, fumaric acid, and maleic acid in the filter residue are salted and dissolved, thereby improving the accuracy of the determination of the 5-hydroxymethylfurfural oxidation products in the filter residue. By using dual-wavelength detection, 5-hydroxymethylfurfural and its oxidation products can effectively absorb ultraviolet light, making the detection results more accurate. Therefore, the method provided by the present invention has high separation, detection accuracy and precision for 5-hydroxymethylfurfural and its various oxidation products.

[0011] In some embodiments, the concentration of the inorganic acid in the aqueous inorganic acid solution is 1-20 mM.

[0012] In some embodiments, the inorganic acid includes one or more of hydrochloric acid, nitric acid, boric acid, sulfuric acid, carbonic acid or phosphoric acid, preferably includes one or more of boric acid, sulfuric acid or phosphoric acid.

[0013] In some embodiments, the conductivity of water in the inorganic acid aqueous solution is 0-5 μS / cm, preferably 0-2 μS / cm.

[0014] In some embodiments, the stationary phase is an Aminex HPX-87H chromatographic column.

[0015] In some embodiments, the method specifically includes: subjecting a mixture containing filter residue, inorganic base and water to ultrasonic dissolution treatment for 1 to 30 minutes, and then adding inorganic base until the oxidation product of 5-hydroxymethylfurfural in the filter residue is fully dissolved to obtain the second sample solution to be tested.

[0016] In some embodiments, the amount of the inorganic base is more than twice the amount of 2,5-furandicarboxylic acid in the filter residue, for example, twice the amount of 2,5-furandicarboxylic acid in the filter residue.

[0017] In some embodiments, the ultrasonic dissolution treatment lasts for 10 to 15 minutes, preferably 10 minutes.

[0018] In some embodiments, the amount of filter cake used is 5 to 50 mg, preferably 5 to 20 mg, and more preferably 10 mg.

[0019] Exemplarily, the preparation method of the first test solution and the second test solution includes:

[0020] The reaction mixture after oxidation of 5-hydroxymethylfurfural is filtered to obtain a filtrate and a filter cake;

[0021] The filtrate is dissolved in water and diluted to a 250 ml volumetric flask, shaken and cooled to room temperature, and then diluted twice. 100 μL-1000 μL of the solution is transferred to a 100 ml volumetric flask, dissolved in water and diluted to a 100 ml volumetric flask, shaken and cooled to room temperature. This is the first test solution;

[0022] After the filter cake is dried, a sample is taken, and water is used as the solvent and an appropriate amount of inorganic base is added until the 2,5-furandicarboxylic acid, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, fumaric acid, and maleic acid in the filter residue are dissolved into salts. After ultrasonic dissolution, the volume is adjusted to a 100 ml volumetric flask, shaken well, and cooled to room temperature to prepare the second solution.

[0023] In some embodiments, the method performs quantitative detection based on the relationship between the chromatographic peak area and the concentration of the corresponding substance.

[0024] In some embodiments, the method specifically includes: taking standard samples of 5-hydroxymethylfurfural, 2,5-furandicarboxylic acid, 2,5-furandicarboxaldehyde, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, fumaric acid, and maleic acid, preparing a series of standard sample solutions of different concentrations for each substance, performing high performance liquid chromatography under the conditions of the high performance liquid chromatography analysis, and obtaining a standard curve of the relationship between peak area and concentration with the peak area as the ordinate and the concentration of the corresponding substance in the standard sample solution as the abscissa;

[0025] The corresponding substances in the first test solution and the second test solution are quantified according to the standard curve.

[0026] When preparing the standard sample solution, an appropriate amount of inorganic base can be added to fully dissolve 2,5-furandicarboxylic acid, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, fumaric acid, and maleic acid.

[0027] In some embodiments, the conditions for the HPLC analysis include: the stationary phase is an Aminex HPX-87H column, the column temperature is 40°C; the mobile phase is a 5 mM H2SO4 aqueous solution, the flow rate of the mobile phase is 0.6 mL / min; the injection volume is 5 μL; dual-wavelength detection is used, the first detection wavelength is 210 nm, and the second detection wavelength is 280 nm.

[0028] In some embodiments, under the conditions of the HPLC analysis, the standard curve equation of the corresponding substance is as follows:

[0029] 5-Hydroxymethylfurfural: y = 61,480.3781x + 15.3701;

[0030] 2,5-Furandicarboxylic acid: y = 24,254.4768x - 59.6930;

[0031] 2,5-Furandicarboxaldehyde: y = 63,226.5523x + 2.9948;

[0032] 5-Hydroxymethyl-2-furancarboxylic acid: y = 8,835.6258x + 0.2834;

[0033] 5-Formyl-2-furancarboxylic acid: y = 63,819.1784x - 8.4367;

[0034] Fumaric acid: y = 57617.8012x - 46.9584;

[0035] Maleic acid: y = 56483.3873x - 177.376;

[0036] In the standard curve equation, y represents the peak area in mAu·s; x represents the concentration of the corresponding substance in g / L.

[0037] In some embodiments, under the conditions of the HPLC analysis, the retention time of 5-hydroxymethylfurfural is 33.88 min, the retention time of 2,5-furandicarboxylic acid is 18.09 min, the retention time of 2,5-furandicarboxaldehyde is 42.49 min, the retention time of 5-hydroxymethyl-2-furancarboxylic acid is 22.57 min, the retention time of 5-formyl-2-furancarboxylic acid is 25.49 min, the retention time of fumaric acid is 11.67 min, and the retention time of maleic acid is 6.19 min.

[0038] A second object of the present invention is to provide a method for simultaneously determining 5-hydroxymethylfurfural and its oxidation products, comprising:

[0039] Providing a sample to be tested, wherein the sample to be tested contains 5-hydroxymethylfurfural and further contains one or more of 2,5-furandicarboxylic acid, 2,5-furandicarboxaldehyde, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, fumaric acid or maleic acid;

[0040] The sample to be tested is subjected to high performance liquid chromatography analysis, and the conditions of the high performance liquid chromatography analysis include: the stationary phase is an organic acid analytical column, and the column temperature is 25°C to 60°C; the mobile phase is an inorganic acid aqueous solution, and the flow rate of the mobile phase is 0.4 to 1 mL / min; the injection volume is 1 μL to 20 μL; dual-wavelength detection is adopted, the first detection wavelength is 200 nm to 240 nm, and the second detection wavelength is 250 nm to 300 nm.

[0041] In some embodiments, the method includes: adding an inorganic base to the sample to be tested to fully dissolve 2,5-furandicarboxylic acid, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, fumaric acid, and maleic acid.

[0042] Further solutions of the method provided in the second object of the present invention, such as more specific chromatographic conditions, have been described in detail in part one of the objects of the present invention and will not be repeated here.

[0043] The method of the present invention can be used for qualitative and / or quantitative detection of 2,5-furandicarboxylic acid, 5-hydroxymethylfurfural and oxidation by-products in a reaction mixture for oxidizing 5-hydroxymethylfurfural to synthesize 2,5-furandicarboxylic acid.

[0044] Compared with the prior art, the present invention has at least the following beneficial effects: the method provided by the present invention can simultaneously detect samples containing 5-hydroxymethylfurfural and its oxidation products, with good separation, high accuracy, and high precision. The method is suitable for detecting a reaction mixture in which 5-hydroxymethylfurfural is used as a raw material to oxidize and synthesize 2,5-furandicarboxylic acid. The method can qualitatively and / or quantitatively detect 2,5-furandicarboxylic acid, 5-hydroxymethylfurfural, and oxidation byproducts (2,5-furandicarboxaldehyde, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, fumaric acid, and maleic acid) in the reaction mixture, thereby resolving the problems in the prior art of low separation due to the similar structures of 5-hydroxymethylfurfural and its oxidation products, and inaccurate qualitative and quantitative determination of the ring-opening oxidation products FA and MA. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0046] Figure 1 1 is a flow chart of a detection method in one embodiment of the present invention;

[0047] Figure 2 This is a liquid chromatogram of a sample containing HMF, FDCA, DFF, HMFCA, and FFCA in one embodiment of the present invention;

[0048] Figure 3 This is a liquid chromatogram of a sample containing both FA and MA according to an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The technical solutions of the present invention are described in detail below in conjunction with specific embodiments so that those skilled in the art can better understand and implement the technical solutions of the present invention. The specific functional details disclosed herein should not be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching those skilled in the art to employ the present invention in various ways in virtually any appropriate detailed embodiment.

[0050] In addition, unless otherwise specified, the various raw materials used in the following examples can be purchased from the market, and the various production and testing equipment used are also known in the art. The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0051] Some of the raw materials and medicines used in the specific implementation are as follows:

[0052] HMF standard (purity > 99%, Aladdin); FDCA standard (purity > 98%, Aladdin); DFF standard (purity > 98%, Aladdin); HMFCA standard (purity > 98%, Aladdin); FFCA standard (purity > 98%, Aladdin); FA standard (purity > 99.5%, Aladdin); MA standard (purity > 99%, J&K); methanol (AR, Shanghai Titan Technology Co., Ltd.); deionized water.

[0053] The experimental instruments and equipment used are as follows:

[0054] High performance liquid chromatograph: Agilent 1260 (including online degasser, quaternary pump, autosampler, column oven, UV detector, and chromatographic workstation); chromatographic column: Aminex HPX-87H; analytical balance 0.0001 g (Mettler-Toledo Instrument Co., Ltd.); ultrasonic cleaner (Shanghai Kedao Ultrasonic Instrument Co., Ltd.).

[0055] Example 1

[0056] In this example, high performance liquid chromatography was used to analyze the contents of related substances in a mixture containing HMF and its various oxidation products.

[0057] The chromatographic conditions used in the test process of this embodiment are:

[0058] Stationary phase: Aminex HPX-87H column;

[0059] Mobile phase: single channel, 5 mM H2SO4;

[0060] Detection wavelength: 210nm and 280nm;

[0061] Flow rate: 0.6 mL / min;

[0062] Injection volume: 5 μL;

[0063] Column temperature: 40℃.

[0064] 1. Standard curve drawing

[0065] (1) Drawing of standard curves for HMF, FDCA, DFF, HMFCA, and FFCA

[0066] Accurately weigh 38.5 mg of HMF, 9.6 mg of FDCA, 9.4 mg of DFF, 5.7 mg of HMFCA, and 5.6 mg of FFCA, respectively, and add them together into a 100 mL volumetric flask. Add 8.13 mg of NaOH, dissolve in deionized water, and dilute to the mark. Ultrasonicate to assist dissolution, and cool to room temperature before use.

[0067] Prepare five standard solutions of increasing concentration by diluting 6.25 mL, 12.5 mL, 25 mL, and 50 mL of the mother solution into a 100 mL volumetric flask. Analyze under the aforementioned chromatographic conditions, injecting each sample twice and recording the peak area of ​​each substance.

[0068] The standard curve was drawn with the peak area Y (mAu) axis as the ordinate and the standard sample concentration X (mg / L) axis as the abscissa, and regression processing was performed.

[0069] The standard curves of HMF, FDCA, DFF, HMFCA, and FFCA were obtained as shown in Table 1.

[0070] Table 1(2) FA and MA standard curve drawing

[0071] Related substances Regression equation <![CDATA[Coefficient of correlation R 2 > HMF y=61,480.3781x+15.3701 0.9999 FDCA y=24,254.4768x-59.6930 0.9990 DFF y=63,226.5523x+2.9948 0.9999 HMFCA y=8,835.6258x+0.2834 0.9999 FFCA y=63,819.1784x-8.4367 0.9999

[0072] Accurately weigh 17.7 mg of FA and 18.1 mg of MA respectively into a 100 mL volumetric flask, and add 24.69 mg of NaOH. Dissolve in deionized water and dilute to the mark. Sonicate to assist dissolution. Cool to room temperature and set aside.

[0073] Prepare five standard solutions of increasing concentration by diluting 6.25 mL, 12.5 mL, 25 mL, and 50 mL of the mother solution into a 100 mL volumetric flask. Analyze under the aforementioned chromatographic conditions, injecting each sample twice and recording the peak area of ​​each substance.

[0074] The standard curve was drawn with the peak area Y (mAu) axis as the ordinate and the standard sample concentration X (mg / L) axis as the abscissa, and regression processing was performed.

[0075] Obtain the standard curves for FA and MA as described in Table 2.

[0076] Table 2

[0077]

[0078]

[0079] 2. Separation test

[0080] The separation degree of the high performance liquid chromatography analysis method provided in this embodiment was tested in the following steps:

[0081] Accurately weigh 30.0 mg of HMF, 10.0 mg of FDCA, 10.0 mg of DFF, 5.0 mg of HMFCA, and 5.0 mg of FFCA, respectively, into a 100 ml volumetric flask. Add 5.4 mg of NaOH and dissolve in deionized water until the volume is filled to the mark. Ultrasonicate to assist dissolution. Cool to room temperature and set aside. This is referred to as test solution A.

[0082] HPLC analysis of test solution A was performed using the above-described column conditions, and the resolution was calculated. The resolution was calculated using the formula: α = 2(t2 - t1) / (w1 + w2). Here, t1 and t2 are the retention times of the two components, and w1 and w2 are the peak widths of the two components.

[0083] The results of the separation calculation are shown in Table 3.

[0084] Table 3

[0085] Peak Compound name Separation 1 FDCA / 2 HMFCA 2.63 3 FFCA 4.39 4 DFF 5.67 5 HMF 6.65

[0086] Figure 2 is the liquid chromatogram of test solution A.

[0087] Accurately weigh 10 mg of MA and FA respectively into a 100 ml volumetric flask, add 13.8 mg of NaOH, dissolve in deionized water and dilute to the mark, sonicate, cool to room temperature and set aside. This is referred to as test solution B.

[0088] The above-mentioned chromatographic column conditions were used to perform HPLC detection on the test solution B, and the separation was calculated according to the same method as above. The separation calculation results are shown in Table 4.

[0089] Table 4

[0090] Peak Compound name Separation 1 MA / 2 FA 13.41

[0091] Figure 3 is the liquid chromatogram of test solution B.

[0092] 3. Precision test

[0093] (1) Precision test of HMF determination (n=6)

[0094] Weigh 10 mg of HMF, record the exact mass, dissolve it in water, and dilute to a 100 mL volumetric flask. This solution is then mixed to form a 0.01 wt% HMF aqueous solution. This solution is then shaken to prepare the test sample solution. The solution is filtered through a 0.45 μm filter membrane and measured six times on an HPLC system. The HMF content and relative standard deviation (RSD) of the HMF content are calculated. The test results are shown in Table 5.

[0095] Table 5

[0096]

[0097] As can be seen from the above table, the HMF content in the sample remains basically unchanged, and its RSD value is % = 0.2386, which is less than 1%, indicating that the precision of the determination of HMF using this method is high.

[0098] (2) Precision test of FDCA determination (n=6)

[0099] Weigh 5 mg of FDCA and record the exact mass. Add 2.57 mg of NaOH, dissolve in water, and dilute to a 100 ml volumetric flask to prepare a 0.005 wt% FDCA aqueous solution. Shake well to prepare the test sample solution. Filter through a 0.45 μm filter membrane and repeat the HPLC measurement six times. Calculate the FDCA content and relative standard deviation (RSD) of FDCA. The test results are shown in Table 6.

[0100] Table 6

[0101]

[0102]

[0103] As can be seen from the above table, the FDCA content in the sample remained basically unchanged, and its RSD value was 0.1626%, which was less than 1%, indicating that the precision of the determination of FDCA using this method was high.

[0104] (3) Precision test of DFF determination (n=6)

[0105] Weigh 5 mg of DFF, dissolve it in water, and dilute to a 100 ml volumetric flask. This solution is then mixed to create a 0.005 wt% DFF aqueous solution. This solution is then shaken to prepare the test sample solution. The solution is filtered through a 0.45 μm filter membrane and measured six times by HPLC. The DFF content and relative standard deviation (RSD) of the DFF content are calculated. The test results are shown in Table 7.

[0106] Table 7

[0107]

[0108] As can be seen from the above table, the DFF content in the sample remained basically unchanged, and its RSD value was 0.2229%, which was less than 1%, indicating that the precision of DFF determination using this method was high.

[0109] (4) Precision test of HMFCA determination (n=6)

[0110] 5 mg of HMFCA was weighed and the exact mass recorded. 1.41 mg of NaOH was added, dissolved in water, and the volume was adjusted to a 100 ml volumetric flask to prepare a 0.005 wt % HMFCA aqueous solution. After shaking, the sample solution was filtered through a 0.45 μm filter membrane and measured six times on an HPLC system. The HMFCA content and relative standard deviation (RSD) of HMFCA were calculated after conversion. The test results are shown in Table 8.

[0111] Table 8

[0112]

[0113]

[0114] As can be seen from the above table, the HMFCA content in the sample remained basically unchanged, and its RSD value was 0.2735%, which was less than 1%, indicating that the precision of the determination of HMFCA using this method was high.

[0115] (5) Precision test of FFCA assay (n=6)

[0116] Weigh approximately 5 mg of FFCA and record the exact mass. Add 1.43 mg of NaOH, dissolve in water, and dilute to a 100 ml volumetric flask to prepare a 0.005 wt% FFCA aqueous solution. Shake well to prepare the test sample solution. Filter through a 0.45 μm filter membrane and perform six replicate HPLC measurements. The FFCA content and relative standard deviation (RSD) of FFCA were calculated. The test results are shown in Table 9.

[0117] Table 9

[0118]

[0119] As can be seen from the table above, the FFCA content in the sample remained basically unchanged, with an RSD value of 0.4139%, which is less than 1%, indicating that the precision of the determination of FFCA using this method is high.

[0120] (6) Precision test of FA determination (n=6)

[0121] Weigh approximately 5 mg of FA and record the exact mass. Add 3.45 mg of NaOH, dissolve in water, and dilute to a 100 ml volumetric flask to prepare a 0.005 wt% FA aqueous solution. Shake well to prepare the sample solution. Filter through a 0.45 μm filter membrane and repeat the HPLC determination six times. The FA content and relative standard deviation (RSD) of FA were calculated after conversion. The test results are shown in Table 10.

[0122] Table 10

[0123]

[0124] As can be seen from the above table, the FA content in the sample remained basically unchanged, and its RSD value was 0.1524%, which was less than 1%, indicating that the precision of FA determination using this method was high.

[0125] (7) Precision test of MA determination (n=6)

[0126] Weigh approximately 5 mg of MA and record the exact mass. Add 3.45 mg of NaOH, dissolve in water, and dilute to a 100 ml volumetric flask to prepare a 0.005 wt% MA aqueous solution. Shake well to prepare the sample solution. Filter through a 0.45 μm filter membrane and repeat the HPLC determination six times. The MA content and relative standard deviation (RSD) of MA are calculated after conversion. The test results are shown in Table 11.

[0127] Table 11

[0128]

[0129]

[0130] It can be seen from the above table that the MA content in the sample remains basically unchanged, and its RSD value is 0.1629%, which is less than 1%, indicating that the precision of MA determination using this method is high.

[0131] 4. Spike recovery test

[0132] To determine the accuracy of the test method, spike recovery tests were conducted on HMF and its oxidation products FDCA, DFF, HMFCA, FFCA, FA, and MA.

[0133] (1) HMF sample spike recovery test (n=3)

[0134] 1) Prepare a 0.5 g / kg HMF sample by adding 0.50 g of pure HMF to 999.5 g of water, dissolve it with ultrasonic assistance, and cool it to room temperature to prepare sample A;

[0135] 2) To 100 g of sample A, 0.05 g of pure HMF was added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was added to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After HPLC analysis, the HMF content in sample B was calculated as the HMF assay value: HMF recovery = (mass of HMF after spiked - mass of HMF in sample) / amount of HMF spiked × 100%. Repeat three times.

[0136] 3) To 100 g of sample A, 0.1 g of pure HMF was added, sonicated, and cooled to room temperature to prepare sample C. 5 g of sample C was transferred to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After HPLC analysis, the HMF content in sample C was calculated as the HMF assay value: HMF recovery = (mass of HMF after spiked - mass of HMF in sample) / amount of HMF spiked × 100%. Repeat three times.

[0137] 4) To 100 g of sample A, 0.2 g of pure HMF was added, sonicated, and cooled to room temperature to prepare sample D. 5 g of sample D was added to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After HPLC analysis, the HMF content in sample D was calculated as the HMF assay value: HMF recovery = (mass of HMF after spiked - mass of HMF in sample) / amount of HMF spiked × 100%. Repeat three times.

[0138] The results of the spike recovery test of HMF are shown in Table 12.

[0139] Table 12

[0140]

[0141]

[0142] As can be seen from the above table, in the HMF recovery test, the relative standard deviation of HMF is less than 1%; and the measured recovery rate is between 90% and 110%, which proves that this method has high accuracy.

[0143] (2) FDCA sample spike recovery test (n=3)

[0144] 1) Prepare a 0.2 g / kg FDCA sample by adding 0.20 g FDCA and 0.10 g NaOH to 999.7 g water, dissolve with ultrasonic aid, and cool to room temperature to prepare sample A;

[0145] 2) To 100 g of sample A, 0.02 g of pure FDCA and 0.01 g of NaOH were added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was transferred to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After analysis by HPLC, the FDCA content in sample B was calculated as the FDCA assay value: FDCA recovery = (mass of FDCA after spiked - mass of FDCA in sample) / amount of FDCA spiked × 100%. Repeat three times.

[0146] 3) To 100 g of sample A, 0.04 g of pure FDCA and 0.02 g of NaOH were added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was transferred to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After analysis by HPLC, the FDCA content in sample B was calculated as the FDCA assay value: FDCA recovery = (mass of spiked FDCA - mass of FDCA in sample) / amount of spiked FDCA × 100%. Repeat three times.

[0147] 4) To 100 g of sample A, 0.08 g of pure FDCA and 0.04 g of NaOH were added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was transferred to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After analysis by HPLC, the FDCA content in sample B was calculated as the FDCA assay value: FDCA recovery = (mass of FDCA after spiked - mass of FDCA in sample) / amount of FDCA spiked × 100%. Repeat three times.

[0148] The results of the spike recovery test of FDCA are shown in Table 13.

[0149] Table 13

[0150]

[0151] As can be seen from the above table, in the FDCA recovery test, the relative standard deviation of FDCA is less than 1%; and the measured recovery rate is between 90% and 110%, which proves that this method has high accuracy.

[0152] (3) DFF sample spike recovery test (n=3)

[0153] 1) Prepare a 0.2 g / kg DFF sample by adding 0.20 g DFF to 999.8 g water, dissolve it with ultrasonic aid, and cool it to room temperature to prepare sample A;

[0154] 2) To 100 g of sample A, 0.02 g of pure FDCA was added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was transferred to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After HPLC analysis, the DFF content in sample B was calculated as the DFF assay value: DFF recovery = (mass of DFF after spiked - mass of DFF in sample) / amount of DFF spiked × 100%. Repeat three times.

[0155] 3) To 100 g of sample A, 0.04 g of pure DFF was added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was transferred to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After HPLC analysis, the DFF content in sample B was calculated as the DFF assay value: DFF recovery = (mass of DFF after spiked - mass of DFF in sample) / amount of DFF spiked × 100%. Repeat three times.

[0156] 4) To 100 g of sample A, 0.08 g of pure DFF was added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was transferred to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After HPLC analysis, the DFF content in sample B was calculated as the DFF assay value: DFF recovery = (mass of DFF after spiked - mass of DFF in sample) / amount of DFF spiked × 100%. Repeat three times.

[0157] The results of the spike recovery test of DFF are shown in Table 14.

[0158] Table 14

[0159]

[0160] As can be seen from the above table, in the DFF recovery test, the relative standard deviation of DFF is less than 1%; and the measured recovery rate is between 90% and 110%, proving that this method has high accuracy.

[0161] (4) HMFCA sample spike recovery test (n=3)

[0162] 1) Prepare a 0.2 g / kg HMFCA sample by adding 0.20 g HMFCA and 0.05 g NaOH to 999.75 g water, dissolve with ultrasonication, and cool to room temperature to prepare sample A;

[0163] 2) To 100 g of sample A, 0.02 g of pure HMFCA and 0.005 g of NaOH were added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was added to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. The HMFCA content in sample B, i.e., the HMFCA measured value, was calculated by HPLC analysis: HMFCA recovery = (mass of HMFCA after spiked - mass of HMFCA in sample) / amount of HMFCA spiked × 100%. This was repeated three times.

[0164] 3) 100 g of sample A was added with 0.04 g of pure HMFCA and 0.01 g of NaOH, and the mixture was solubilized with ultrasonication. The mixture was cooled to room temperature to prepare sample B. 5 g of sample B was added to a 100 ml volumetric flask, dissolved with water, and the volume was adjusted to the mark. The HMFCA content in sample B was calculated by HPLC analysis, i.e., the HMFCA measured value: HMFCA recovery = (mass of HMFCA after spiked - mass of HMFCA in sample) / amount of HMFCA spiked × 100%. This was repeated three times.

[0165] 4) 100 g of sample A was added with 0.08 g of pure HMFCA and 0.02 g of NaOH, and the solution was sonicated and cooled to room temperature to prepare sample B. 5 g of sample B was added to a 100 ml volumetric flask, dissolved with water, and the volume was adjusted to the mark. The HMFCA content in sample B was calculated by HPLC analysis (i.e., the HMFCA measured value): HMFCA recovery = (mass of HMFCA after spiked - mass of HMFCA in sample) / amount of HMFCA spiked × 100%), and the solution was repeated three times.

[0166] The recovery of HMFCA spiked samples is shown in Table 15.

[0167] Table 15

[0168]

[0169] As can be seen from the table above, in the HMFCA recovery test, the relative standard deviation of HMFCA is less than 1%; and the measured recovery rate is between 90% and 110%, proving that this method has high accuracy.

[0170] (5) FFCA sample spike recovery test (n=3)

[0171] 1) Prepare a 0.2 g / kg FFCA sample by adding 0.20 g FFCA and 0.05 g NaOH to 999.75 g water, dissolve with ultrasonic aid, and cool to room temperature to prepare Sample A;

[0172] 2) To 100 g of sample A, 0.02 g of pure FFCA and 0.005 g of NaOH were added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was transferred to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After analysis by HPLC, the FFCA content in sample B was calculated as the FFCA assay value: HMFCA recovery = (mass of FFCA after spiked - mass of FFCA in sample) / spiked amount of FFCA × 100%. Repeat three times.

[0173] 3) To 100 g of sample A, 0.04 g of pure FFCA and 0.01 g of NaOH were added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was transferred to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After analysis by HPLC, the FFCA content in sample B was calculated as the FFCA assay value. FFCA recovery = (mass of spiked FFCA - mass of FFCA in sample) / spiked FFCA amount × 100%. Repeat three times.

[0174] 4) To 100 g of sample A, 0.08 g of pure FFCA and 0.02 g of NaOH were added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was transferred to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After analysis by HPLC, the FFCA content in sample B was calculated as the FFCA assay value. FFCA recovery = (mass of FFCA after spiked - mass of FFCA in sample) / spiked amount of FFCA × 100%. Repeat three times.

[0175] The results of the FFCA spike recovery experiment are shown in Table 16.

[0176] Table 16

[0177]

[0178] As can be seen from the table above, in the FFCA recovery test, the relative standard deviation of FFCA is less than 1%; and the measured recovery rate is between 90% and 110%, proving that this method has high accuracy.

[0179] (6) FA sample spike recovery test (n=3)

[0180] 1) Prepare a 0.4 g / kg FA sample by adding 0.40 g FA to 999.6 g water, dissolve it with ultrasonic aid, and cool it to room temperature to prepare sample A;

[0181] 2) To 100 g of sample A, 0.04 g of pure FA was added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was transferred to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After HPLC analysis, the FA content in sample B was calculated as follows: FA recovery = (mass of FA after spiked - mass of FA in sample) / spiked amount of FA × 100%. Repeat three times.

[0182] 3) To 100 g of sample A, add 0.08 g of pure FA, dissolve with ultrasonication, and cool to room temperature to prepare sample B. 5 g of sample B is transferred to a 100 ml volumetric flask, dissolved with water, and dilute to the mark. After analysis by HPLC, the FA content in sample B (i.e., the FA determination value) is calculated: FA recovery = (mass of FA after spiked - mass of FA in sample) / spiked amount of FA × 100%. Repeat three times.

[0183] 4) To 100 g of sample A, 0.12 g of pure FA was added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was transferred to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After analysis by HPLC, the FA content in sample B (i.e., the FA determination value) was calculated: FA recovery = (mass of FA after spiked - mass of FA in sample) / spiked amount of FA × 100%. Repeat three times.

[0184] The results of the FA spike recovery experiment are shown in Table 17.

[0185] Table 17

[0186]

[0187] As can be seen from the above table, in the FA recovery test, the relative standard deviation of FA is less than 1%; and the measured recovery rate is between 90% and 110%, proving that this method has high accuracy.

[0188] (7) MA sample spike recovery test (n=3)

[0189] 1) Prepare a 0.4 g / kg MA sample by adding 0.40 g MA to 999.6 g water, dissolve it with ultrasonic aid, and cool it to room temperature to prepare sample A;

[0190] 2) To 100 g of sample A, add 0.04 g of pure MA, dissolve with ultrasonication, and cool to room temperature to prepare sample B. 5 g of sample B is added to a 100 ml volumetric flask, dissolved with water, and dilute to the mark. After HPLC analysis, the MA content in sample B, i.e., the measured MA value, is calculated: MA recovery = (mass of MA after spiked - mass of MA in sample) / amount of MA spiked × 100%. Repeat three times.

[0191] 3) To 100 g of sample A, add 0.08 g of pure MA, sonicate, and cool to room temperature to prepare sample B. 5 g of sample B is transferred to a 100 ml volumetric flask, dissolved with water, and dilute to the mark. After HPLC analysis, the FA content in sample B, i.e., the MA value, is calculated: MA recovery = (mass of MA after spiked - mass of MA in sample) / amount of MA spiked × 100%. Repeat three times.

[0192] 4) To 100 g of sample A, 0.12 g of pure MA was added, sonicated, and cooled to room temperature to prepare sample B. 5 g of sample B was added to a 100 ml volumetric flask, dissolved with water, and diluted to the mark. After HPLC analysis, the MA content in sample B, i.e., the measured MA value, was calculated: MA recovery = (mass of MA after spiked addition - mass of MA in sample) / amount of MA spiked × 100%. Repeat three times.

[0193] The results of the MA spike recovery experiment are shown in Table 18.

[0194] Table 18

[0195]

[0196] As can be seen from the above table, in the MA recovery test, the relative standard deviation of MA is less than 1%; and the measured recovery rate is between 90% and 110%, proving that this method has high accuracy.

[0197] 5. Real sample testing

[0198] Figure 1 A schematic flow chart of the method for detecting the reaction product of HMF oxidation to FDCA is shown.

[0199] The test sample is the reaction product of HMF oxidation to FDCA. The synthesis reaction conditions are as follows: 1g HMF and 0.5g catalyst are added to 30ml acetic acid, and the reaction is carried out at 150°C for 1h under 1Mpa oxygen atmosphere.

[0200] The reaction product after HMF oxidation was filtered to obtain a filtrate and a filter cake. Water was added to the filtrate to a 250 mL volumetric flask, shaken, and cooled to room temperature before dilution. 1000 μL of the dilution solution was transferred to a 25 mL volumetric flask, and water was added to a 25 mL volumetric flask. The solution was shaken, cooled to room temperature, and retained for later use. The solution was filtered through a 0.451 μm membrane to obtain a first test solution, which was then analyzed by HPLC.

[0201] After the filter cake is partially dried, a sample is taken, 5.13 mg of NaOH is added to water as the solvent, and the volume is adjusted to a 100 ml volumetric flask after ultrasonic dissolution. The solution is shaken and filtered through a 0.45 μm filter membrane after cooling to room temperature to obtain the second test solution, which is then measured by HPLC.

[0202] The test results are shown in Tables 19 and 20.

[0203] Table 19

[0204]

[0205]

[0206] In summary, the present invention provides a method for simultaneously determining HMF and its oxidation products (FDCA, DFF, HMFCA, FFCA, FA, and MA) in a reaction mixture following the oxidation of 5-hydroxymethylfurfural. This method offers excellent separation, lacks interference from impurities, and is highly feasible. It can simultaneously and accurately determine the contents of HMF and its oxidation products in a reaction solution following HMF oxidation, demonstrating its practical application.

[0207] The various aspects, embodiments, features and examples of the present invention should be considered as illustrative in all respects and are not intended to limit the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0208] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0209] Although the present invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions, and / or additions may be made and that substantial equivalents may be substituted for the elements of the embodiments without departing from the spirit and scope of the present invention. Additionally, many modifications may be made to adapt specific circumstances or materials to the teachings of the present invention without departing from the scope of the present invention. Therefore, it is not intended herein to limit the present invention to the disclosed specific embodiments for carrying out the present invention, but rather to include all embodiments within the scope of the appended claims. Furthermore, unless specifically stated, any use of the terms first, second, etc. does not indicate any order or importance, but rather uses the terms first, second, etc. to distinguish one element from another.

Claims

1. A method for simultaneously determining 5-hydroxymethylfurfural and its oxidation products, characterized in that: include: A reaction mixture obtained after an oxidation reaction of 5-hydroxymethylfurfural is provided, wherein the reaction mixture is a reaction product of oxidizing 5-hydroxymethylfurfural to synthesize 2,5-furandicarboxylic acid. The synthesis reaction conditions are as follows: 1 g of 5-hydroxymethylfurfural and 0.5 g of a catalyst are added to 30 ml of acetic acid, and the mixture is reacted at 150° C. for 1 hour under a 1 MPa oxygen atmosphere. The reaction mixture contains 5-hydroxymethylfurfural and its oxidation products, wherein the oxidation products include 2,5-furandicarboxylic acid, 2,5-furandicarboxaldehyde, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, fumaric acid, and maleic acid. The reaction mixture is filtered to obtain a filtrate and a filter residue; the filtrate is prepared as a first test solution, the filter residue is mixed with an inorganic base to cause the insoluble oxidation product in the filter residue to undergo a salt reaction and dissolve, and the mixture is prepared as a second test solution; performing high performance liquid chromatography analysis on the first test solution and the second test solution respectively to perform qualitative and / or quantitative detection of substances contained in the reaction mixture; Among them, the conditions of the high performance liquid chromatography analysis include: the stationary phase is an Aminex HPX-87H chromatographic column, the column temperature is 25°C~60°C, the mobile phase is an inorganic acid aqueous solution, the flow rate of the mobile phase is 0.4~1mL / min, the injection volume is 1μL~20μL, and dual-wavelength detection is adopted, the first detection wavelength is 200nm~240nm, and the second detection wavelength is 250nm~300nm.

2. The method according to claim 1, wherein: The concentration of the inorganic acid in the inorganic acid aqueous solution is 1-20 mM.

3. The method according to claim 1, wherein: The inorganic acid includes one or a combination of hydrochloric acid, nitric acid, boric acid, sulfuric acid, carbonic acid or phosphoric acid.

4. The method according to claim 3, wherein: The inorganic acid includes one or a combination of more of boric acid, sulfuric acid or phosphoric acid.

5. The method according to claim 1, wherein: The electrical conductivity of water in the inorganic acid aqueous solution is 0-5 μS / cm.

6. The method according to claim 5, characterized in that: The electrical conductivity of water in the inorganic acid aqueous solution is 0-2 μS / cm.

7. The method according to claim 1, characterized in that Specifically include: The mixture containing the filter residue, the inorganic base and water is subjected to ultrasonic dissolution treatment for 1 to 30 minutes, and then the inorganic base is added until the oxidation product of 5-hydroxymethylfurfural in the filter residue is fully dissolved to obtain the second test solution.

8. The method according to claim 7, wherein: The amount of the inorganic base used is more than twice the amount of 2,5-furandicarboxylic acid in the filter residue.

9. The method according to claim 1, wherein: The method performs quantitative detection based on the relationship between the chromatographic peak area of ​​the corresponding substance and its concentration.

10. The method according to claim 9, characterized in that Specifically include: Taking standard samples of 5-hydroxymethylfurfural, 2,5-furandicarboxylic acid, 2,5-furandicarboxaldehyde, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, fumaric acid, and maleic acid, a series of standard sample solutions of different concentrations were prepared for each substance, and high performance liquid chromatography was performed under the conditions of high performance liquid chromatography analysis. A standard curve of the relationship between peak area and concentration was obtained with the peak area as the ordinate and the concentration of the corresponding substance in the standard sample solution as the abscissa; The contents of the corresponding substances in the first test solution and the second test solution are calculated according to the standard curve.

11. The method according to claim 1 or 10, characterized in that: The conditions for the HPLC analysis include: the stationary phase is Aminex HPX-87H, the column temperature is 40°C; the mobile phase is a 5 mM H2SO4 aqueous solution, the flow rate of the mobile phase is 0.6 mL / min; the injection volume is 5 μL; and dual-wavelength detection is used, with the first detection wavelength being 210 nm and the second detection wavelength being 280 nm.

12. The method according to claim 11, characterized in that Under the conditions of the HPLC analysis, the standard curve equation of the corresponding substance is as follows: 5-Hydroxymethylfurfural: y=61,480.3781 x +15.3701; 2,5-Furandicarboxylic acid: y= 24,254.4768 x -59.6930; 2,5-Furandicarboxaldehyde: y= 63,226.5523 x+ 2.9948; 5-Hydroxymethyl-2-furancarboxylic acid: y =8,835.6258 x +0.2834; 5-Formyl-2-furancarboxylic acid: y =63,819.1784 x- 8.4367; Fumaric acid: y =57617.8012 x -46.9584; Maleic acid: y =56483.3873 x -177.376; Wherein, y in the standard curve equation represents the peak area, and the unit is mAu∙s; x Represents the concentration of the corresponding substance in g / L.

13. The method according to claim 11, wherein: Under the conditions of the high performance liquid chromatography analysis, the retention time of 5-hydroxymethylfurfural is 33.88 min, the retention time of 2,5-furandicarboxylic acid is 18.09 min, the retention time of 2,5-furandicarboxaldehyde is 42.49 min, the retention time of 5-hydroxymethyl-2-furancarboxylic acid is 22.57 min, the retention time of 5-formyl-2-furancarboxylic acid is 25.49 min, the retention time of fumaric acid is 11.67 min, and the retention time of maleic acid is 6.19 min.

14. A method for simultaneously determining 5-hydroxymethylfurfural and its oxidation products, characterized in that: include: Providing a sample to be tested, wherein the sample to be tested is a reaction product of oxidizing 5-hydroxymethylfurfural to synthesize 2,5-furandicarboxylic acid, and the synthesis reaction conditions are as follows: adding 1 g of 5-hydroxymethylfurfural to 30 ml of acetic acid, adding 0.5 g of a catalyst, and reacting at 150° C. for 1 hour under a 1 MPa oxygen atmosphere. The sample to be tested contains 5-hydroxymethylfurfural and its oxidation products, and the oxidation products include 2,5-furandicarboxylic acid, 2,5-furandicarboxaldehyde, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, fumaric acid, and maleic acid; The sample to be tested is subjected to high performance liquid chromatography analysis, and the conditions of the high performance liquid chromatography analysis include: the stationary phase is an Aminex HPX-87H chromatographic column, the column temperature is 25°C~60°C; the mobile phase is an inorganic acid aqueous solution, and the flow rate of the mobile phase is 0.4~1 mL / min; the injection volume is 1 μL~20 μL; dual-wavelength detection is adopted, the first detection wavelength is 200nm~240nm, and the second detection wavelength is 250nm~300nm.

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