A method for detecting the carbon chain distribution and EO number of oleylamine polyoxyethylene ether (2)

Abstract

The application belongs to the technical field of chemical analysis and detection, and discloses a detection method for carbon chain distribution and EO number of oleylamine polyoxyethylene ether (2). The detection method is as follows: oleylamine polyoxyethylene ether (2) raw material is taken and injected into a high performance liquid chromatograph for separation; a quadrupole mass spectrometer is used for detection; the mass chromatogram of each component is extracted, the relative content of each component is calculated by using the area normalization method, and the carbon chain distribution and the EO number are calculated. The detection method can realize good separation of different carbon chain and EO number compounds and their isomers in the oleylamine polyoxyethylene ether (2) raw material, and has the advantages of simple operation, good separation effect, excellent peak shape, accurate quantification, good reproducibility, and the like, and is suitable for raw material warehouse detection, batch consistency control, industrial quality control, supplier management and process optimization in industrial production, and has significant industrial application value.

Description

Technical Field

[0001] This invention relates to the field of chemical analysis and detection technology, specifically to a method for detecting the carbon chain distribution and EO number of oleylamine polyoxyethylene ether (2). Background Technology

[0002] Oleamide polyoxyethylene ether (2) is an important nonionic / weakly cationic amphoteric surfactant widely used in metalworking fluids, textile auxiliaries, and pesticide emulsifiers. Its molecular structure consists of a C18 unsaturated carbon chain (mainly containing oleic acid groups), short-chain ethoxy groups (with an average EO number of approximately 2), and amino groups. Due to the randomness of ethylene oxide addition reactions and the complexity of the source of the oleamide carbon chain, industrial-grade products are actually complex mixtures containing different carbon chain lengths (C12-C20), different degrees of unsaturation (C18:1, C18:2, etc.), and different EO addition numbers. The differences in the distribution of these components directly determine the product performance and stability in downstream applications such as metalworking fluids and textile auxiliaries. Therefore, establishing a detection method that can simultaneously distinguish between carbon chain isomers and EO number distribution is crucial.

[0003] However, existing detection technologies have significant limitations and cannot meet the analytical requirements of oleoamine polyoxyethylene ether (2). Traditional detection methods, such as chemical titration and spectroscopy, can only roughly determine macroscopic parameters such as total amine value and average EO number. They cannot effectively identify impurities with similar carbon chains and EO numbers as the main components, nor can they obtain detailed content of compounds with different carbon chains and EO numbers in the raw materials, and they cannot compare the microscopic differences between different batches.

[0004] For the detection of polyoxyethylene ether surfactants, the literature mainly reports the following two types of methods, but neither of them can be directly applied to oleylamine polyoxyethylene ethers (2): For the analysis of aliphatic amine polyoxyethylene ethers with high EO numbers (e.g., EO>5), existing technologies (such as Chinese invention patent CN119000969A) mostly employ hydrophilic interaction chromatography (HILIC) or amino / amide columns. These methods utilize the partitioning effect between the polar groups of the solute (EO chains and amine groups) and the stationary phase for separation. While they can effectively distinguish components with different EO numbers, their ability to resolve different carbon chains and double bond structures within the same EO number is severely insufficient. Data from Chinese invention patent CN119000969A shows that in HILIC mode, the retention times of different carbon chain components with the same EO number are extremely close, even exhibiting co-elution. More importantly, for unsaturated C18u-EO2 components, multiple double bond position or geometric configuration isomers (such as cis / trans, double bond position isomers) typically exist internally, and HILIC mode cannot identify these subtle structural differences and cannot distinguish isomers.

[0005] For fatty alcohol polyoxyethylene ethers or common amine compounds, silica gel columns are usually used for detection and analysis. However, because oleylamine polyoxyethylene ether (2) contains weakly basic amine groups, it will have a strong secondary interaction with the residual silanol groups in the silica gel matrix, resulting in severe peak tailing, broadening, failure to adsorb peaks, and inaccurate quantification.

[0006] In summary, there is an urgent need to develop a detection method that can simultaneously meet the following requirements: effectively retain and separate weakly polar amine compounds with low EO numbers (EO=2); completely eliminate peak tailing caused by amine groups to obtain symmetrical peak shapes; possess extremely high selectivity to distinguish minute differences in the number, position, and geometry of double bonds in the carbon chain (i.e., separating different isomers such as C18:2); and accurately reflect the structural differences of raw materials from different manufacturers and batches for strict quality control. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for detecting the carbon chain distribution and EO number of oleoamine polyoxyethylene ether (2). This method has high specificity, high separation degree and good reproducibility. Specifically, it is a method for detecting the carbon chain isomers, EO number distribution and accurate quantification of aliphatic amine polyoxyethylene ether surfactants with low ethoxylation degree (EO≈2) using liquid chromatography-mass spectrometry (LC-MS).

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for detecting the carbon chain distribution and EO number of oleylamine polyoxyethylene ether (2), comprising the following steps: S1. Take oleylamine polyoxyethylene ether (2) as raw material and inject it into a high performance liquid chromatograph for separation; The separation was performed using a carbamate-intercalated C18 column with acetonitrile-isopropanol as the organic phase and formic acid / ammonium formate aqueous solution as the aqueous phase, followed by gradient elution. S2. Detection was performed using a quadrupole mass spectrometer with an electrospray ionization source (ESI) in positive ion mode (ESI+). S3. Extract the mass chromatograms of each component, calculate the relative content of each component using the area normalization method, and calculate the carbon chain distribution and EO number.

[0009] This invention uses a C18 chromatographic column (such as MicroPulite XP RP 18Plus) with polar carbamate embedded in it. In a specific mobile phase system, it can achieve good separation of compounds with different carbon chains and EO numbers and their isomers in oleamine polyoxyethylene ether (2) raw materials. The sensitivity meets the test requirements, and the fingerprint spectrum of the raw materials can be compared.

[0010] As a preferred embodiment of the method for detecting the carbon chain distribution and EO number of oleamine polyoxyethylene ether (2) according to the present invention, in step S1, the oleamine polyoxyethylene ether (2) raw material is first pretreated; the pretreatment method is: dissolving the oleamine polyoxyethylene ether (2) raw material in an organic solvent to prepare a solution with a concentration of 200 μg / mL-1 mg / mL; and then filtering.

[0011] As a further preferred embodiment of the method for detecting the carbon chain distribution and EO number of oleamine polyoxyethylene ether (2) of the present invention, the oleamine polyoxyethylene ether (2) raw material is dissolved in an organic solvent by ultrasonication; the ultrasonication time is 20 min-40 min and the frequency is 35 kHz-55 kHz; the organic solvent is ethanol; the filtration process uses a 0.22 μm organic phase microporous filter membrane.

[0012] Preferably, the ultrasound duration is 30 minutes and the frequency is 45 kHz.

[0013] As a preferred embodiment of the method for detecting the carbon chain distribution and EO number of oleamine polyoxyethylene ether (2) according to the present invention, in step S1, the urethane-intercalated C18 column is a MicroPulite XP RP 18 Plus column with a specification of 2.1×150 mm and 1.7 μm.

[0014] In a preferred embodiment of the method for detecting the carbon chain distribution and EO number of oleoamine polyoxyethylene ether (2) according to the present invention, in step S1, the mobile phase used for separation includes mobile phase A, mobile phase B and mobile phase C; mobile phase A is a mixture of acetonitrile and isopropanol with a volume ratio of (5-20):1; mobile phase B is a 0.1% formic acid solution; mobile phase C is a 30 mM-100 mM ammonium formate solution containing 0.1% formic acid.

[0015] Preferably, the volume ratio of acetonitrile to isopropanol is any one or a range of two of the following: 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, and 20:1; and the concentration of the ammonium formate solution is any one or a range of two of the following: 30 mM, 40 mM, 50 mM, 60 mM, 70 mM, 80 mM, 90 mM, and 100 mM.

[0016] In a preferred embodiment of the method for detecting the carbon chain distribution and EO number of oleoamine polyoxyethylene ether (2) according to the present invention, in step S1, the injection volume during separation is 1 μL-3 μL; the flow rate is 0.2 mL / min-0.4 mL / min; and the column temperature is 30℃-45℃.

[0017] As a further preferred embodiment of the method for detecting the carbon chain distribution and EO number of oleoamine polyoxyethylene ether (2) according to the present invention, the injection volume is 2 μL; the flow rate is 3 mL / min; and the column temperature is 40℃.

[0018] In a preferred embodiment of the method for detecting the carbon chain distribution and EO number of oleylamine polyoxyethylene ether (2) according to the present invention, in step S1, the gradient elution procedure is as follows:

[0019] As a preferred embodiment of the detection method for carbon chain distribution and EO number of oleoamine polyoxyethylene ether (2) of the present invention, in step S2, the settings parameters of the quadrupole mass spectrometer for detection are as follows: the electrospray ionization source is in positive ion mode (ESI+), the ionization voltage is 3.0 kV-5.0 kV, the drying gas temperature is 250℃-400℃, the nebulizing gas pressure is 30 psi-40 psi; the drying gas flow rate is 12 L / min; the quadrupole temperature is 100℃; and the scanning range is 150 m / z-600 m / z.

[0020] Preferably, the ionization voltage is 4.0 kV, the drying gas temperature is 300 °C, and the atomizing gas pressure is 35 psi.

[0021] Secondly, the present invention applies the method for detecting the carbon chain distribution and EO number of oleamine polyoxyethylene ether (2) described in the first aspect to the industrial analysis or quality control of oleamine polyoxyethylene ether (2) raw materials.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) For the first time, high selectivity separation of low EO number (EO≈2) oleamine polyoxyethylene ether has been achieved. It can effectively separate and identify different carbon chain lengths, different EO numbers and carbon chain isomers at the same time. It solves the technical problem that existing technologies cannot distinguish complex isomers such as C18:1 and C18:2. The separation selectivity and resolution have been significantly improved.

[0023] (2) By using a carbamate-intercalated C18 column and combining it with an isopropanol-modified organic phase and a formic acid-ammonium formate buffer system, the secondary adsorption between the amine group and the stationary phase was well suppressed, effectively improving the problems of peak tailing, peak bifurcation and peak broadening. The target component peaks were symmetrical and sharp, and the quantitative accuracy and detection sensitivity were greatly improved.

[0024] (3) The method has good stability and high reproducibility. It can accurately determine the relative content of each component, carbon chain distribution and average EO number, and establish characteristic fingerprint spectra of raw materials from different manufacturers and batches. It can intuitively reflect the subtle differences in the source of carbon chain, hydrogenation process and EO addition reaction control level of raw materials, and provide key data support for raw material traceability, supplier selection, production process optimization and end product quality stability control.

[0025] (4) The pretreatment is simple and the analysis process is efficient. No complicated derivatization operation is required. It is suitable for daily quality testing and purity analysis of industrial-grade oleamine polyoxyethylene ether (2). It fills the technical gap of simultaneous detection of carbon chain distribution and EO number of low EO number fatty amine polyoxyethylene ether compounds, and has important practical value and promotion prospects. Attached Figure Description

[0026] Figure 1 The figure shows the total ion current chromatogram in Example 2; in the figure, a is the total ion current (TIC) chromatogram, and be is the extracted ion current chromatogram of the corresponding component.

[0027] Figure 2 The figure shows the total ion current chromatogram in Example 3; in the figure, a is the total ion current (TIC) chromatogram, and be is the extracted ion current chromatogram of the corresponding component.

[0028] Figure 3 The figure shows the total ion current chromatogram in Example 4; in the figure, a is the total ion current (TIC) chromatogram, and be is the extracted ion current chromatogram of the corresponding component.

[0029] Figure 4 The figure shows the total ion current chromatogram in Example 5; in the figure, a is the total ion current (TIC) chromatogram, and be is the extracted ion current chromatogram of the corresponding component.

[0030] Figure 5 The figures show comparative chromatograms of batch 4 from manufacturer A and batch 1 from manufacturer G in the application example; in the figures, a is the total ion chromatogram of batch 4 from manufacturer A and b is the total ion chromatogram of batch 1 from manufacturer G.

[0031] Figure 6 The total ion current chromatogram is shown in Comparative Example 1; Figure 7 The total ion current chromatogram is shown in Comparative Example 2; Figure 8The total ion current chromatogram is shown in Comparative Example 3; Figure 9 The total ion current chromatogram is shown in Comparative Example 4; Figure 10 The total ion current chromatogram is shown in Comparative Example 5; Figure 11 The total ion current chromatogram is shown in Comparative Example 6; Figure 12 The total ion current chromatogram is shown in Comparative Example 7; Figure 13 The total ion current chromatogram is shown in Comparative Example 8. Detailed Implementation

[0032] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0033] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified. Furthermore, unless otherwise specified, the raw materials used in parallel experiments are from the same batch. The average EO number is calculated as the sum of the products of the EO number of each component and the peak area ratio.

[0034] The high-performance liquid chromatograph 12060 Infinity and 6120 quadrupole mass spectrometer involved in the examples were purchased from Agilent Technologies, USA; the MS105 electronic balance was purchased from Mettler Toledo; the KQ5200DE ultrasonic cleaner was purchased from Kunshan Ultrasonic Instrument Co., Ltd.; and the PURELAB flex pure water system was purchased from ELGA LabWater, UK.

[0035] Acetonitrile and isopropanol involved in the examples were mass spectrometry grade and purchased from Merck GmbH, Germany; ammonium formate and formic acid were mass spectrometry grade and purchased from Fisher GmbH; and the raw material of oleoamine polyoxyethylene ether (2) involved was purchased from Lianhong New Material Technology Co., Ltd.

[0036] The chromatographic columns involved in the examples include MicroPulite XP RP 18 Plus columns with specifications of 2.1×150 mm, 1.7 μm, or other equivalent specifications.

[0037] Example 1: Sample Pretreatment Weigh 100 mg of oleylamine polyoxyethylene ether (2) raw material and place it in a 100 mL volumetric flask. Add ethanol to make up the volume and sonicate at 45 kHz for 30 min to prepare a stock solution with a total concentration of 1 mg / mL. Then dilute with ethanol to a concentration of 200 μg / mL. After passing through a 0.22 μm organic phase filter membrane, collect the filtrate to obtain the test solution.

[0038] Example 2: Sample Detection The test solution treated in Example 1 was analyzed by high performance liquid chromatography-quadrupole mass spectrometry: The chromatographic conditions are as follows: Column: MicroPulite XP RP 18 Plus (2.1×150mm, 1.7μm) Mobile phase A: Acetonitrile: Isopropanol (10:1, V / V). Mobile phase B: An aqueous solution containing 0.1% formic acid. Mobile phase C: is a 50 mM ammonium formate aqueous solution containing 0.1% (v / v) formic acid; Column temperature: 40℃; The flow rate was 0.3 mL / min; The injection volume was 1 μL; The elution program is gradient elution, and the gradient elution program is shown in Table 1: Table 1 Gradient elution program Mass spectrometry conditions are: The electrospray ionization source was in positive ion mode (ESI+), with an ionization voltage of 4.0 kV, a drying gas temperature of 300 ℃, and an atomizing gas pressure of 35 psi; the drying gas flow rate was 12 L / min; the quadrupole temperature was 100 ℃; and the scanning range (m / z) was 150~600.

[0039] The oleylamine polyoxyethylene ether (2) pretreated solution from Example 1 was analyzed under the above conditions, and the total ion chromatogram (TIC) obtained is shown below. Figure 1 As shown. The chromatographic data are shown in Tables 2 and 3: Table 2 Chromatographic data Table 3 Chromatographic data The results above show that: 1) The peak time distribution of each component is reasonable, the peak shape is symmetrical and sharp, and there is no obvious tailing. The tailing factor of most components is between 0.8 and 1.7, and most of them are concentrated between 1.0 and 1.3, which ensures the accuracy of quantification. 2) By extracting characteristic ion chromatograms and mass spectrometry analysis, the separation and qualitative analysis of components with different carbon chain lengths and different EO adsorption numbers in oleamine polyoxyethylene ether (2) were successfully achieved. The isomers of C18:2-2EO, C18:2-3EO, C18:1-2EO, and C18:1-3EO were all separated at the baseline. 3) The components with different carbon chains and different EO numbers can be quantified by the area normalization method. At the same time, the proportion of each carbon chain (such as C18:1 having the highest proportion of 70.81%) and the average EO number (2.28) were calculated, which are consistent with the theoretical value of the raw material.

[0040] Example 3: The Influence of Flow Relative Detection Results The only difference between this embodiment and Example 2 is that the molar concentration of ammonium formate in mobile phase C is changed. In this embodiment, the molar concentration of ammonium formate in mobile phase C is increased from 50 mM in Example 2 to 100 mM, that is, mobile phase C in this embodiment is a 100 mM aqueous solution of ammonium formate containing 0.1% by volume formic acid. All other conditions (including the composition of the chromatographic column, mobile phase A and mobile phase B, elution program, flow rate, column temperature and mass spectrometry detection conditions) are the same as in Example 2.

[0041] The oleylamine polyoxyethylene ether (2) pretreated solution from Example 1 was analyzed under the above conditions, and the resulting chromatogram is shown below. Figure 2 As shown, the chromatographic data are presented in Tables 4 and 5.

[0042] Table 4 Chromatographic data Table 5 Chromatographic data The results above show that the increase in the molar concentration of ammonium formate in mobile phase C is also applicable to the separation of oleoamine polyoxyethylene ether (2) raw materials: 1) Compared with Example 2, the retention times of all components have been delayed to varying degrees. For example, the retention time of the main component C18:1-2EO has been extended from 15.881 min in Example 2 to 19.805 min in this example. This indicates that ammonium formate helps retain positively charged amine compounds. 2) The separation degree of isomers remains good, with a slight increase in value. This indicates that increasing the buffer salt concentration within a certain range will change the retention window, but will not destroy the overall separation ability of the method. 3) The calculated carbon chain ratios (e.g., C18:1 accounts for 72.00%) are highly consistent with those of Example 2 (C18:1 accounts for 70.81%), and the average EO number (2.27) is also highly consistent with those of Example 1 (2.27).

[0043] Example 4: The Influence of Flow Relative Detection Results The only difference between this embodiment and Example 2 is that the molar concentration of ammonium formate in mobile phase C is changed. In this embodiment, the molar concentration of ammonium formate in mobile phase C is reduced from 50 mM in Example 2 to 30 mM, that is, mobile phase C in this embodiment is a 30 mM aqueous solution of ammonium formate containing 0.1% by volume formic acid. All other conditions (including the composition of the chromatographic column, mobile phase A and mobile phase B, elution program, flow rate, column temperature and mass spectrometry detection conditions) are the same as in Example 2.

[0044] The oleylamine polyoxyethylene ether (2) pretreated solution from Example 1 was analyzed under the above conditions, and the resulting chromatogram is shown below. Figure 3 As shown, the chromatographic data are presented in Tables 6 and 7.

[0045] Table 6 Chromatographic data Table 7 Chromatographic data The results above show that when the molar concentration of ammonium formate in mobile phase C is reduced to 30 mM, it is also applicable to the separation of oleoamine polyoxyethylene ether (2) raw materials: 1) Compared with Example 2, the retention times of all components have shifted to different degrees. This further illustrates that ammonium formate helps retain positively charged amine compounds. 2) The resolution still meets the analytical requirements, and the peak shape symmetry is good (USP tailing factor is close to 1.0). The quantitative results of the carbon chain ratio (C18:1 accounts for 70.49%) and the calculated results of the EO number (2.27) are very close to those of Examples 2 and 3, indicating that the results are accurate and reliable.

[0046] Example 5: The impact of gradient elution procedure on detection results The only difference between this embodiment and Embodiment 2 is that the gradient elution program is adjusted, and the proportion of mobile phase A at the elution endpoint is changed from 60% to 45%. All other conditions (including column, mobile phase composition, flow rate, column temperature, and mass spectrometry detection conditions) remain the same as in Embodiment 2. The specific gradient elution program is shown in Table 8. Table 8 Elution Procedure The oleylamine polyoxyethylene ether (2) pretreated solution from Example 1 was analyzed under the above conditions, and the resulting chromatogram is shown below. Figure 4 As shown, the chromatographic data are presented in Tables 9 and 10.

[0047] Table 9 Chromatographic Data Table 10 Chromatographic data The results above show that when the rate of change of mobile phase A slows down, the retention capacity of oleylamine polyoxyethylene ether (2) is enhanced, with analytes appearing in the front, middle, and rear sections, and the main substances concentrated in the middle section. The overall resolution further increases. In addition to baseline separation, the isomers of C18:2-2EO, C18:2-3EO, C18:1-2EO, and C18:1-3EO were found to have other isomers at the second chromatographic peaks at m / z 356.3 and m / z 400.3. This indicates that the oleylamine polyoxyethylene ether (2) raw material has many unsaturated carbon chain isomers and complex composition. The overall peak area ratio, carbon chain distribution, and EO number calculation results are basically consistent with those of the previous examples.

[0048] Example 6: The Influence of Flow Relative Detection Results The only difference between this embodiment and Example 5 is that the ratio of acetonitrile to isopropanol in mobile phase A is adjusted to 20:1. All other conditions (including chromatographic column, mobile phase composition, flow rate, column temperature and mass spectrometry detection conditions) remain the same as in Example 5.

[0049] The chromatographic data obtained by analyzing the pretreated oleamine polyoxyethylene ether (2) solution in Example 1 under the above conditions are shown in Tables 11 and 12.

[0050] Table 11 Chromatographic data Table 12 Chromatographic data The results above show that when the proportion of isopropanol in mobile phase A decreases, the retention capacity of oleylamine polyoxyethylene ether (2) weakens slightly. This phenomenon is not entirely consistent with the common understanding that isopropanol has a stronger elution capacity than acetonitrile in conventional reversed-phase chromatography. In conventional C18 column systems, isopropanol has a higher viscosity, and its addition will significantly increase the system column pressure. However, when the MicroPulite XPRP 18 Plus column was used for testing in this invention, it was found that the introduction of isopropanol into the mobile phase actually caused a significant decrease in the overall system pressure. This may be because isopropanol is embedded in the alkyl chain layer of the high-density C18 stationary phase, which improves the effective hydrophobicity of the stationary phase and enhances the hydrophobic retention of the target analyte. This effect exceeds the strong elution capacity of isopropanol itself, and ultimately, the higher the proportion of isopropanol, the stronger the retention.

[0051] Example 7: The Influence of Flow Relative Detection Results The only difference between this embodiment and Example 5 is that the ratio of acetonitrile to isopropanol in mobile phase A is adjusted to 5:1. All other conditions (including chromatographic column, mobile phase composition, flow rate, column temperature and mass spectrometry detection conditions) remain the same as in Example 5.

[0052] The chromatographic data obtained by analyzing the oleamine polyoxyethylene ether (2) pretreated in Example 1 under the above conditions are shown in Tables 13 and 14.

[0053] Table 13 Chromatographic data Table 14 Chromatographic data The results above show that as the proportion of isopropanol in mobile phase A increases, the retention capacity of oleylamine polyoxyethylene ether (2) on the stationary phase increases synchronously, which is consistent with the pattern shown in Example 6. It can be seen from the spectra and the data in the table that a volume ratio of acetonitrile to isopropanol of 5:1 meets the analytical requirements.

[0054] As shown in the explanation of Example 6, when the ratio of isopropanol in the mobile phase is slightly increased to 5:1 or slightly decreased to 20:1, it only affects the retention time of the compound. The overall peak area ratio, carbon chain distribution, and EO number calculation results are basically consistent with those of the previous examples, indicating that the method has strong tolerance and wide applicability.

[0055] Example 8: Precision Test The oleamine polyoxyethylene ether (2) raw material prepared in Example 1 was subjected to multiple injections using the method of Example 2, for a total of 6 injections. The RSD value of each chromatographic peak was calculated, as shown in Table 15. Table 15 Chromatographic data As shown in the table above, after six parallel repeated injections, the relative standard deviation (RSD) of retention time for each characteristic component was ≤0.35%, and the relative standard deviation (RSD) of peak area ratio was ≤5.00%. The experimental data demonstrate that the detection method of this invention exhibits excellent chromatographic peak stability, good reproducibility of component separation, and high quantitative detection accuracy. It can stably and accurately distinguish and quantitatively detect various components with different carbon chains and different ethylene oxide addition numbers in oleylamine polyoxyethylene ether.

[0056] Application example: Using the detection steps and conditions of Example 5, ten different batches of oleylamine polyoxyethylene ether (2) raw materials from seven different manufacturers were tested. The differences in the content of each component, the carbon chain distribution, and the average EO number in the raw materials from different manufacturers and batches were compared. For the comparison spectrum of batch 4 from manufacturer A and batch 1 from manufacturer G, please refer to [link to relevant documentation]. Figure 5 a and b. See Table 16-19 for detailed data.

[0057] Table 16 Chromatographic Data Table 17 Chromatographic Data Table 18 Chromatographic Data Table 19 Chromatographic Data The results above show that there are still slight fluctuations between different batches from the same manufacturer. For example, the C16 content of manufacturer A fluctuates by about 1.1% between batch 1 (8.61%) and batch 3 (9.71%), and the C18:1 content fluctuates by about 2.5% between batch 2 (73.33%) and batch 3 (70.81%). The differences in carbon chain content between different manufacturers are even more obvious. For example, the C16 content differs by about 2.38% between manufacturer C (7.59%) and manufacturer F (9.97%), and the C18 content differs by about 3.42% between batch 3 (4.61%) of manufacturer A and manufacturer G (8.03%). This reflects both the slight fluctuations in the production process of the same manufacturer and the subtle differences in the source of carbon chain in the raw materials of different manufacturers. Regarding the average EO number, the values ​​for batches 2 from manufacturers C, D, E, F, G, and manufacturer A were all concentrated between 1.99 and 2.01, very close to the target value of 2, and the number of components was relatively small, with no high EO number components detected. However, the average EO number of the three batches from manufacturer A and the raw material from manufacturer B was 2.18-2.26, significantly higher than the target value of 2. This further illustrates that different manufacturers have different capabilities in controlling the EO addition reaction during the production of this raw material, and relatively speaking, the processes of manufacturers C, D, E, F, and G may be better.

[0058] Comparative Example 1: The only difference between this comparative example and Example 2 is that the chromatographic conditions used are as follows: Chromatographic column: Waters ACQUITY UPLC BEH C18 column (2.1 × 100 mm, 1.7 μm).

[0059] Mobile phase A: Acetonitrile.

[0060] Mobile phase B: 10 mM ammonium acetate aqueous solution containing 0.1% formic acid by volume.

[0061] The gradient elution procedure is shown in Table 20: Table 20 Gradient Elution Procedure The oleylamine polyoxyethylene ether (2) pretreated solution from Example 1 was analyzed under the above conditions, and the resulting chromatogram is shown below. Figure 6 As shown: As can be seen from the figure, the chromatographic conditions cannot meet the analytical requirements for carbon chain isomers and EO (ethylene oxide) adduct numbers in the oleoamine polyoxyethylene ether (2) raw material. The specific defects are as follows: 1) Insufficient separation ability, the sample components failed to achieve good separation, and some components did not elute; 2) The chromatographic peaks of the main components are too broad and have poor shapes; 3) The main components that have elute are highly concentrated at the end of the gradient (12-15 min), that is, the strong elution stage with a high proportion of acetonitrile (95%). This shows that this method cannot solve the separation problem of complex amine mixtures such as oleoamine polyoxyethylene ether at all.

[0062] Comparative Example 2: The only difference between this comparative example and Example 2 is that the chromatographic conditions used are as follows: Chromatographic column: Waters ACQUITY UPLC BEH HILIC column (2.1 × 100 mm, 1.7 μm) Mobile phase A: Acetonitrile (in HILIC mode, the high organic phase is a weak solvent used for retention). Mobile phase B: An aqueous solution containing 0.1% formic acid. Mobile phase C: 50 mM ammonium formate aqueous solution containing 0.1% formic acid (the high aqueous phase is a strong solvent used for elution).

[0063] The gradient elution procedure is shown in Table 21: Table 21 Gradient elution program The oleylamine polyoxyethylene ether (2) pretreated solution from Example 1 was analyzed under the above conditions, and the resulting chromatogram is shown below. Figure 7 As shown: As can be seen from the figure, the target compound exhibits extremely strong non-specific retention on the HILIC column. Within the 12-18 min range, unlike reversed-phase chromatography, all components do not separate sequentially according to carbon chain length or double bond position, but instead pile up to form a large, unseparated broad peak. This indicates that the HILIC mechanism mainly relies on the interaction between the polar groups of the solute (EO chains and amine groups) and the stationary phase. Because the components in oleoamine polyoxyethylene ether (2) have similar short EO chains and amine groups, their retention behavior on the HILIC column is highly consistent, leading to a loss of selectivity. Furthermore, within the broad peak, components from different raw material sources, such as C18:1, C18:2, and C18:3, are completely co-eluted. The crucial C18:2-2EO isomer is completely invisible in the figure, submerged in the broad envelope peak.

[0064] The above results indicate that although the HILIC column can retain polar molecules, its separation is based on polarity differences. For oleylamine polyoxyethylene ether (2), the structural differences are mainly reflected in the hydrophobic tail chain (carbon chain length, double bond position / configuration), rather than the hydrophilic head group. The HILIC column forces all isomers with the same EO number to merge into a single peak.

[0065] Comparative Example 3: The only difference between this comparative example and Example 2 is that the mobile phase A used is acetonitrile.

[0066] The oleylamine polyoxyethylene ether (2) pretreated solution from Example 1 was analyzed under the above conditions, and the resulting chromatogram is shown below. Figure 8 As shown: As can be seen from the figure, the separation effect of the oleylamine polyoxyethylene ether (2) raw material is not satisfactory when isopropanol is missing in mobile phase A. Specifically, most components cannot be eluted or separated, the main components in the raw material do not show peaks under these conditions, the baseline is extremely flat and there is no effective signal, and only two weak chromatographic peaks appear around 15 min. Mass spectrometry confirmed that these two peaks are C12-2EO and C12-3EO (m / z 274.2 and 318.2, respectively).

[0067] Comparative Example 4: The only difference between this comparative example and Example 2 is that the mobile phase B used is water, and the mobile phase C is a 50 mM ammonium formate aqueous solution.

[0068] The oleylamine polyoxyethylene ether (2) pretreated solution from Example 1 was analyzed under the above conditions, and the resulting chromatogram is shown below. Figure 9 As shown: As can be seen from the figure, without the addition of formic acid to the mobile phase, the chromatographic behavior deteriorated significantly. The reactant components were not completely eluted, indicating insufficient elution capacity of the mobile phase. Some chromatographic peaks showed bifurcation and extreme broadening, with numerous peak spikes. Repeated injections revealed retention time drift. This indicates that the acidic environment provided by formic acid is crucial for inhibiting the dissociation of amine compounds, shielding the silanol effect, and maintaining sharp peak shapes.

[0069] Comparative Example 5: The only difference between this comparative example and Example 2 is that the mobile phase C used is a 10 mM ammonium formate aqueous solution containing 0.1% by volume formic acid.

[0070] The oleylamine polyoxyethylene ether (2) pretreated solution from Example 1 was analyzed under the above conditions, and the resulting chromatogram is shown below. Figure 10 As shown.

[0071] As can be seen from the figure, when the mobile phase C uses a 10 mM ammonium formate aqueous solution containing 0.1% formic acid (v / v), all components of the raw material are eluted within 10 minutes. The retention capacity of each component in the stationary phase of the column used in this invention is insufficient, resulting in co-elution of target components with different carbon chains and different EO addition numbers. This leads to overlapping chromatographic peaks and poor resolution; for example, the chromatographic peaks of C18:1-3EO and C18:1-2EO completely overlap, C18:2-2EO and C18:2-3EO cannot be separated, and C16-2EO and C16-3EO cannot be separated. Therefore, effective separation and individual quantification of multiple components cannot be achieved. Thus, this mobile phase salt concentration condition is not suitable for the simultaneous detection of multiple components of oleylamine polyoxyethylene ether in this invention.

[0072] Comparative Example 6: The only difference between this comparative example and Example 2 is that the mobile phase C used is a 150 mM ammonium formate aqueous solution containing 0.1% by volume formic acid.

[0073] The oleylamine polyoxyethylene ether (2) pretreated solution from Example 1 was analyzed under the above conditions, and the resulting chromatogram is shown below. Figure 11 As shown.

[0074] As can be seen from the figure, when the mobile phase C uses a 150 mM ammonium formate aqueous solution containing 0.1% formic acid by volume, although the raw material can be completely eluted within the program, the excessively high ionic strength of the mobile phase significantly weakens the hydrophobic retention between the target analyte and the stationary phase of the column. The separation degree of target components with different carbon chain lengths and different EO addition numbers decreases significantly, and the overall separation effect is worse than that under the buffer salt concentration conditions of Example 2 of this invention. For example, the chromatographic peaks of the two components C18:1-3EO and C18:1-2EO completely overlap, making separation impossible. It is difficult to intuitively distinguish the component distribution differences of oleamine polyoxyethylene ether raw materials from different manufacturers and batches based on the total ion current (TIC) chromatogram, which cannot meet the requirements for qualitative identification and accurate quantitative detection of multiple components.

[0075] Comparative Example 7: The only difference between this comparative example and Example 2 is that the volume ratio of acetonitrile to isopropanol in mobile phase A is 3:1.

[0076] The oleylamine polyoxyethylene ether (2) pretreated solution from Example 1 was analyzed under the above conditions, and the resulting chromatogram is shown below. Figure 12 As shown: As shown in the figure, when the ratio of acetonitrile to isopropanol in mobile phase A is 3:1, although all components of the raw material can be eluted within the elution program with narrow peaks, the chromatographic peaks of components C18:1-3EO and C18:1-2EO completely overlap and cannot be separated. Under these conditions, it is difficult to visually distinguish the component distribution differences of oleylamine polyoxyethylene ether raw materials from different manufacturers and batches using total ion current (TIC) chromatograms, thus failing to meet analytical requirements.

[0077] Comparative Example 8: The only difference between this comparative example and Example 2 is that the volume ratio of acetonitrile to isopropanol in mobile phase A is 25:1.

[0078] The oleylamine polyoxyethylene ether (2) pretreated solution from Example 1 was analyzed under the above conditions, and the resulting chromatogram is shown below. Figure 13 As shown: As shown in the figure, when the ratio of acetonitrile to isopropanol in mobile phase A is 25:1, although all components of the raw material can be eluted within the elution program, the retention times of C18-2EO and C18-3EO are significantly enhanced, and their elution positions are greatly delayed. Simultaneously, the chromatographic peaks of both components exhibit peak broadening, reduced peak height, and thicker peak shapes, resulting in decreased component response sensitivity and difficulty in achieving accurate quantification. Overall, this condition is not suitable for oleylamine polyoxyethylene ether raw materials.

[0079] The method for detecting the carbon chain distribution and EO number of oleamine polyoxyethylene ether (2) of the present invention overcomes the problem that the prior art cannot perform carbon chain distribution, EO number distribution and isomer comparison analysis on oleamine polyoxyethylene ether (2) with low EO number. It is simple to operate, has good separation effect, excellent peak shape, accurate quantification and good reproducibility. It can realize rapid, accurate and comprehensive characterization of oleamine polyoxyethylene ether (2) raw materials. It is suitable for raw material warehousing inspection, batch consistency control, industrial quality control, supplier management and process optimization in industrial production, and has significant industrial application value.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for detecting the carbon chain distribution and EO number of oleylamine polyoxyethylene ether (2), characterized in that, Includes the following steps: S1. Take oleamine polyoxyethylene ether (2) raw material and inject it into a high performance liquid chromatograph for separation; the oleamine polyoxyethylene ether (2) raw material is first pretreated; the pretreatment method is: dissolve the oleamine polyoxyethylene ether (2) raw material in an organic solvent to prepare a solution with a concentration of 200 μg / mL-1 mg / mL; then filter it; the organic solvent is ethanol; The separation was performed using a MicroPulite XP RP 18 Plus column with gradient elution of the mobile phase. The mobile phase consisted of mobile phase A, mobile phase B, and mobile phase C. Mobile phase A was a mixture of acetonitrile and isopropanol in a volume ratio of (5-20):

1. Mobile phase B was a 0.1% formic acid solution. Mobile phase C was a 30 mM-100 mM ammonium formate solution containing 0.1% formic acid. The gradient elution procedure is as follows: When the elution time is 0 min, the volume percentage of mobile phase A is 35%, mobile phase B is 55-65%, and mobile phase C is 5-10%; when the elution time is 5 min, the volume percentage of mobile phase A is 40%, mobile phase B is 50-60%, and mobile phase C is 5-10%; when the elution time is 40 min, the volume percentage of mobile phase A is 45-60%, mobile phase B is 30-55%, and mobile phase C is 5-10%. S2. Detection was performed using a quadrupole mass spectrometer with an electrospray ionization source (ESI) in positive ion mode (ESI+). S3. Extract the mass chromatograms of each component, calculate the relative content of each component using the area normalization method, and calculate the carbon chain distribution and EO number.

2. The method for detecting the carbon chain distribution and EO number of oleoamine polyoxyethylene ether (2) according to claim 1, characterized in that, The oleoamine polyoxyethylene ether (2) raw material is dissolved in an organic solvent by ultrasonication; the ultrasonication time is 20 min-40 min and the frequency is 35 kHz-55 kHz; the filtration process uses a 0.22 μm organic phase microporous filter membrane.

3. The method for detecting the carbon chain distribution and EO number of oleoamine polyoxyethylene ether (2) according to claim 1, characterized in that, In step S1, the MicroPulite XP RP 18 Plus column has dimensions of 2.1 × 150 mm and 1.7 μm.

4. The method for detecting the carbon chain distribution and EO number of oleoamine polyoxyethylene ether (2) according to claim 1, characterized in that, In step S1, the injection volume during separation is 1 μL-3 μL; the flow rate is 0.2 mL / min-0.4 mL / min; and the column temperature is 30℃-45℃.

5. The method for detecting the carbon chain distribution and EO number of oleoamine polyoxyethylene ether (2) according to claim 4, characterized in that, The injection volume is 2 μL; the flow rate is 3 mL / min; and the column temperature is 40 °C.

6. The method for detecting the carbon chain distribution and EO number of oleoamine polyoxyethylene ether (2) according to claim 1, characterized in that, In step S2, the settings for the quadrupole mass spectrometer are as follows: the electrospray ionization source is in positive ion mode (ESI+), the ionization voltage is 3.0 kV-5.0 kV, the drying gas temperature is 250℃-400℃, the nebulizing gas pressure is 30 psi-40 psi, the drying gas flow rate is 12 L / min, the quadrupole temperature is 100℃, and the scanning range is 150 m / z-600 m / z.

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