Method for detecting esterquats

Abstract

The invention discloses a detection method of ester quaternary ammonium salt, and belongs to the technical field of chemical component analysis. According to the method, an analysis method based on reversed-phase ultra-high performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS) is innovatively established, the accurate mass determination capacity of high-resolution mass spectrometry is fully played, ester quaternary ammonium salt homologues with similar molecular weights can be accurately distinguished, and the separation and identification problem in a complex matrix in a traditional method is solved; baseline separation of quaternary ammonium salts with different esterification degrees (monoester, diester and triester) is realized, the analysis time is shortened to 23 minutes, and the efficiency is remarkably improved compared with that of a conventional HPLC (High Performance Liquid Chromatography) method; the interference of other surfactants can be avoided in the detection process of the detergent, and the reliability of an analysis result is ensured.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of chemical component analysis, and particularly relates to a detection method of ester-based quaternary ammonium salt. BACKGROUND

[0002] In the detergent industry, with the increasing requirements of consumers for product softness, antistatic performance and environmental friendliness, ester-based quaternary ammonium salt (Esterquats) as a green and degradable cationic surfactant is widely used in softener, shampoo, hair conditioner and laundry care products. Compared with traditional quaternary ammonium salt, the ester-based quaternary ammonium salt has a hydrolysable ester bond in the molecular structure, which makes it more easily degradable in the environment, while still providing excellent softness, antistatic and conditioning effects.

[0003] However, the chemical structure of ester-based quaternary ammonium salt is complex, and the industrial raw material usually contains various homologues and by-products, such as monoester, diester and triester quaternary ammonium salt, and even unreacted fatty acids or alcohols. The differences of these components will affect the performance stability of the product, such as dispersibility, compatibility and hydrolysis tendency during storage. In addition, since the ester-based quaternary ammonium salt is usually present in low content in the formula and is compounded with nonionic surfactants, silicone oil, fragrances and other ingredients, it brings great challenges to its accurate quantitative analysis.

[0004] At present, there is a lack of standardized detection method for ester-based quaternary ammonium salt in the market, and traditional high performance liquid chromatography (HPLC) or two-phase titration method often has difficulty in distinguishing similar quaternary ammonium salt derivatives, and is easily interfered by the matrix. For example, the method disclosed in CN118759107A improves the shortcomings of traditional analysis by using high performance liquid chromatography (HPLC) combined with evaporative light scattering detector (ELSD) technology, but still has obvious limitations: not only the sensitivity is insufficient to meet the trace analysis demand, but also the qualitative method depending on retention time is easy to produce misjudgment in complex sample analysis, and the strong corrosiveness of trifluoroacetic acid in the mobile phase also brings additional operation safety hazards. Therefore, it is of great significance to develop an analysis method with high selectivity and high sensitivity to realize accurate content determination and structure identification of ester-based quaternary ammonium salt for product quality control, formula optimization and market supervision. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a detection method of ester-based quaternary ammonium salt which can effectively separate and identify ester-based quaternary ammonium salt in detergents.

[0006] To achieve the above-mentioned purpose, in the first aspect of the present application, the present application provides a detection method of ester-based quaternary ammonium salt, which uses reversed-phase ultra-high performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry to determine the detection object.

[0007] The conditions of the reverse ultra-high performance liquid chromatography are as follows:

[0008] The chromatographic column is a reverse C8 chromatographic column;

[0009] The mobile phase A is an isopropanol solution containing 0.05-0.15% volume percentage of formic acid, and the mobile phase B is an acetonitrile aqueous solution containing 0.05-0.15% volume percentage of formic acid; wherein the volume ratio of acetonitrile to water in the acetonitrile aqueous solution is (70-40):(30-60).

[0010] The elution program is gradient elution;

[0011] The column temperature is 35-45℃;

[0012] The flow rate is 0.3-0.4 mL / min.

[0013] The present application researches and finds that the reverse ultra-high performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry can effectively separate and identify different ester-based quaternary ammonium salts in the detection object, and has fast analysis speed, high sensitivity and strong specificity.

[0014] As a preferred embodiment of the detection method of the present application, the mobile phase A is an isopropanol solution containing 0.1% volume percentage of formic acid, and the mobile phase B is an acetonitrile aqueous solution containing 0.1% volume percentage of formic acid.

[0015] As a preferred embodiment of the detection method of the present application, the column temperature is 40℃.

[0016] As a preferred embodiment of the detection method of the present application, the flow rate is 0.3 mL / min.

[0017] As a preferred embodiment of the detection method of the present application, the chromatographic column is a 2.1 mm x 100 mm, 1.7 μm Waters BEH C8 chromatographic column.

[0018] The present application researches and finds that further selecting the conditions of the reverse ultra-high performance liquid chromatography within the above range can achieve a faster analysis rate, and the separation degree between the obtained substances is better, i.e. the sensitivity is higher and the specificity is stronger.

[0019] As a preferred embodiment of the detection method of the present application, the volume ratio of acetonitrile to water in the acetonitrile aqueous solution is (50-60):(50-40). For example, it can be 50:50, 60:40, etc.

[0020] The present application researches and finds that further selecting the volume ratio of acetonitrile to water in the acetonitrile aqueous solution in the mobile phase B within the above range can improve the efficiency and make the separation degree of ester-based quaternary ammonium salt better.

[0021] As a preferred embodiment of the detection method of the present application, the sample injection volume is 1-3 μL; preferably, the sample injection volume is 2 μL.

[0022] As a preferred embodiment of the detection method of the present application, the gradient elution is:

[0023] 0 min, 28-32% mobile phase A and 72-68% mobile phase B;

[0024] 0.5 min, 28-32% mobile phase A and 72-68% mobile phase B;

[0025] 2 min, 38-42% mobile phase A and 62-58% mobile phase B;

[0026] 10 min, 48-52% mobile phase A and 52-48% mobile phase B;

[0027] 11 min, 54-56% mobile phase A and 46-44% mobile phase B;

[0028] 14 min, 59-61% mobile phase A and 41-39% mobile phase B;

[0029] 17 min, 64-66% mobile phase A and 36-34% mobile phase B;

[0030] 20 min, 67-69% mobile phase A and 33-31% mobile phase B;

[0031] 21 min, 28-32% mobile phase A and 72-68% mobile phase B;

[0032] 22 min, 28-32% mobile phase A and 72-68% mobile phase B.

[0033] The present application has found that within the gradient elution range given above, good separation and detection results can be achieved.

[0034] As a preferred embodiment of the detection method of the present application, the mass spectrometry conditions are:

[0035] The mode is positive ion mode;

[0036] The ionization voltage is 3-5 kV;

[0037] The ion source temperature is 135-200°C;

[0038] The desolvation gas temperature is 250-450°C;

[0039] The cone gas flow is 50±2 L / h;

[0040] The desolvation gas flow is 600±10 L / h;

[0041] The collision gas is argon;

[0042] The scanning range is 50-1200;

[0043] The scanning time is 0.2s.

[0044] The present application researches and finds that the mass spectrum under the above conditions can well analyze the components of monoester, diester and polyesters in the detection object.

[0045] As a preferred embodiment of the detection method of the present application, the detection object comprises a detergent.

[0046] Exemplarily, the detergent can be a personal care detergent, a fabric care detergent, a home care detergent, etc.

[0047] As a preferred embodiment of the detection method of the present application, before being determined by reverse ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry, the detection method further comprises a process of extracting the detection object to obtain a to-be-tested solution.

[0048] As a preferred embodiment of the detection method of the present application, the extraction is ultrasonic extraction of the detection object in an extraction solution, followed by filtration, collection of the filtrate and dilution to obtain the to-be-tested solution.

[0049] As a preferred embodiment of the detection method of the present application, the extraction solution comprises a mixed solution of isopropanol and acetonitrile in a volume ratio of (0.5-3):1.

[0050] As a preferred embodiment of the detection method of the present application, the ultrasonic extraction time is 10-30min and the power is 40-50kHz.

[0051] As a preferred embodiment of the detection method of the present application, the filtration is through a 0.22μm or 0.45μm organic phase filter membrane.

[0052] As a preferred embodiment of the detection method of the present application, the dilution is dilution with a mixed solution of isopropanol and acetonitrile in a volume ratio of (0.5-3):1.

[0053] As a preferred embodiment of the detection method of the present application, the mass volume concentration of the ester-based quaternary ammonium salt in the to-be-tested solution is 2-8μg / mL.

[0054] Compared with the prior art, the present application has the following beneficial effects:

[0055] (1) innovatively established an analysis method based on reversed-phase ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), which fully utilizes the accurate mass determination capability of high-resolution mass spectrometry, can accurately distinguish homologues of ester quaternary ammonium salt with similar molecular weights, and solves the separation and identification problems in complex matrixes by traditional methods;

[0056] (2) By optimizing the reversed-phase ultra-high performance liquid chromatography conditions, baseline separation of quaternary ammonium salts with different esterification degrees (monoester, diester, triester) is realized, and the analysis time is shortened to 23 min, which is significantly more efficient than the conventional HPLC method;

[0057] (3) By optimizing the collision energy of secondary mass spectrometry, characteristic fragment ions are obtained, which provide reliable basis for the structure confirmation of ester quaternary ammonium salt;

[0058] (4) By optimizing the analysis process, the running time is reduced, the consumption of solvents and the waste of energy are effectively reduced by the present application, and no corrosive additives are needed, which conforms to the core concept of green chemistry;

[0059] (5) The present application is successfully applied to the testing of actual market products of detergents, and the method has excellent sensitivity, accuracy and specificity, can effectively distinguish ester quaternary ammonium salt and its structural analogues, completely avoids the interference of other surfactants in detergent formula, ensures the reliability of the analysis results, meets the detection needs of different application scenarios, and provides strong technical support and solutions for related industries. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 The liquid chromatogram of the detection method provided for Example 1;

[0061] Figure 2 The liquid chromatogram of the detection method provided for Example 2;

[0062] Figure 3 The liquid chromatogram of the detection method provided for Example 3;

[0063] Figure 4 The liquid chromatogram of the detection method provided for Example 4;

[0064] Figure 5 The liquid chromatogram of the detection method provided for Example 5;

[0065] Figure 6 The liquid chromatogram of the detection method provided for Example 6;

[0066] Figure 7 The liquid chromatogram of the detection method provided for Example 7;

[0067] Figure 8Liquid chromatogram of the detection method provided for Comparative Example 1;

[0068] Figure 9 Liquid chromatogram of the detection method provided for Comparative Example 2;

[0069] Figure 10 Liquid chromatogram of the detection method provided for Comparative Example 3;

[0070] Figure 11 Liquid chromatogram of the detection method provided for Comparative Example 4;

[0071] Figure 12 Liquid chromatogram of the detection method provided for Comparative Example 5;

[0072] Figure 13 Liquid chromatogram of the detection method provided for Application Example 1;

[0073] Figure 14 Liquid chromatogram of the detection method provided for Application Example 2. DETAILED DESCRIPTION

[0074] For the purpose of better illustrating the object, technical scheme and advantages of the present application, the present application will be further described in conjunction with specific embodiments.

[0075] The reagents, methods and devices employed in the present application are all conventional reagents, methods and devices in the art unless otherwise specified, and the raw materials used in parallel experiments are the same batch of raw materials unless otherwise specified.

[0076] Specifically, the main reagents and sources are as follows:

[0077] Ester quaternary ammonium salt raw material (containing monoester, diester and a small amount of triester component): Stepan Company;

[0078] Isopropyl alcohol: chromatographically pure, Fisher Company;

[0079] Acetonitrile: chromatographically pure, Merck Company, Germany;

[0080] Formic acid: chromatographically pure, Fisher Company;

[0081] Main instruments:

[0082] Ultra-high performance liquid chromatograph Waters ACQUITY UPLC system with Xevo G2-S QTof high-resolution mass spectrometer: Waters Company, USA;

[0083] MS105 electronic balance: Mettler-Toledo Company;

[0084] Heidolph Multi Reax vortex mixer: Heidolph Company, Germany;

[0085] KQ5200DE ultrasonic cleaner: Kunshan Ultrasonic Instrument Co., Ltd.

[0086] PURELAB flex pure water instrument: ELGA LabWater Co., Ltd. in the United Kingdom.

[0087] Example 1

[0088] The embodiment of the present application provides a detection method of ester-based quaternary ammonium salt, and the detection method comprises the following steps:

[0089] (1) 100 mg of ester-based quaternary ammonium salt raw material is weighed and placed in a 100 mL volumetric flask, extraction liquid (a mixed solution of isopropyl alcohol and acetonitrile, and the volume ratio of isopropyl alcohol to acetonitrile is 1:1) is added to constant volume to the scale, ultrasonic cleaning is carried out at 45 kHz for 15 min, and a stock solution with a total concentration of 1 mg / mL is prepared; then the extraction liquid is diluted to a solution with an ester-based quaternary ammonium salt concentration of 5 μg / mL, then a 0.22 μm organic phase filter membrane is used, the filtrate is collected, and a to-be-tested solution is obtained;

[0090] (2) The to-be-tested solution is subjected to reversed-phase ultra-high performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry detection;

[0091] The chromatographic conditions are as follows:

[0092] The chromatographic column is 2.1 mm x 100 mm, 1.7 μm Waters BEH C8;

[0093] The mobile phase A is isopropyl alcohol containing 0.1% volume fraction of formic acid, and the mobile phase B is acetonitrile water solution (the volume ratio of acetonitrile to water is 60:40) containing 0.1% volume fraction of formic acid;

[0094] The column temperature is 40°C;

[0095] The flow rate is 0.3 mL / min;

[0096] The injection amount is 2 μL;

[0097] The elution program is gradient elution, and the gradient elution program is as follows:

[0098] 0 min, 30% mobile phase A and 70% mobile phase C;

[0099] 0.5 min, 30% mobile phase A and 70% mobile phase B;

[0100] 2 min, 40% mobile phase A and 60% mobile phase B;

[0101] 10 min, 50% mobile phase A and 50% mobile phase B;

[0102] 11 min, 55% mobile phase A and 45% mobile phase B;

[0103] 14 min, 60% mobile phase A and 40% mobile phase B;

[0104] 17 min, 65% mobile phase A and 35% mobile phase B;

[0105] 20 min, 68% mobile phase A and 32% mobile phase B;

[0106] 21 min, 30% mobile phase A and 70% mobile phase B;

[0107] 22 min, 30% mobile phase A and 70% mobile phase B;

[0108] The mass spectrometry conditions are as follows:

[0109] The mode is positive ion mode (ESI+);

[0110] The ionization voltage is 3 kV;

[0111] The ion source temperature is 135°C;

[0112] The desolvation gas temperature is 250°C;

[0113] The cone gas flow is 50 L / h;

[0114] The desolvation gas flow is 600 L / h;

[0115] The collision gas is argon;

[0116] The scan range is 50-1200;

[0117] The scan time is 0.2 s.

[0118] The chromatogram obtained from Example 1 is shown in Figure 1 The peak time, mass-to-charge ratio, molecular formula and normalized data of each component are shown in Table 1.

[0119] Table 1

[0120]

[0121]

[0122]

[0123] From Figure 1 It can be seen from the above and Table 1 that the method provided by the present application has excellent separation effect on the ester-based quaternary ammonium salt raw material, the peak is sharp and has good separation effect, and the program running time is shorter, and the peak can be obtained within 23 min.

[0124] Example 2

[0125] The detection method of the ester-based quaternary ammonium salt provided by the embodiment of the present application is different from that of embodiment 1 in that the gradient elution procedure is different, and the gradient elution procedure of the present embodiment is as follows:

[0126] 0 min, 30% of mobile phase A and 70% of mobile phase C;

[0127] 0.5 min, 30% of mobile phase A and 70% of mobile phase B;

[0128] 2 min, 40% of mobile phase A and 60% of mobile phase B;

[0129] 8 min, 47.5% of mobile phase A and 52.5% of mobile phase B;

[0130] 12 min, 52.5% of mobile phase A and 47.5% of mobile phase B;

[0131] 16 min, 58% of mobile phase A and 42% of mobile phase B;

[0132] 18 min, 62% of mobile phase A and 38% of mobile phase B;

[0133] 21 min, 75% of mobile phase A and 25% of mobile phase B;

[0134] 22 min, 75% of mobile phase A and 25% of mobile phase B;

[0135] 25 min, 30% of mobile phase A and 70% of mobile phase B.

[0136] The obtained chromatogram is shown in Figure 2 , and the peak time and mass-to-charge ratio of each component are shown in Table 2;

[0137] Table 2

[0138]

[0139]

[0140] From Figure 2 and Table 2, it can be seen that the detection method provided by the present application can effectively improve the peak time and accelerate the detection efficiency, and the obtained chromatographic peak is symmetrical in peak shape, has good resolution, and can be completely eluted.

[0141] Embodiment 3

[0142] The detection method of the ester-based quaternary ammonium salt provided by the embodiment of the present application is different from that of embodiment 2 in that the volume ratio of acetonitrile to water in the mobile phase B is different, and the volume ratio of acetonitrile to water in the present embodiment is 50:50;

[0143] The obtained chromatogram is shown in Figure 3 The elution time and mass-to-charge ratio of each component are shown in Table 3.

[0144] Table 3

[0145]

[0146] From Figure 3 As can be seen from Table 3, when the volume ratio of acetonitrile and water in the mobile phase B is changed to 50:50, compared with Example 2, the retention time of monoester, diester and triester is delayed by about 1 min, and the separation degree and theoretical plate number do not change significantly. It is speculated that when the acetonitrile ratio is within the range of Example 2-3, the elution strength of the mobile phase and the hydrophobic interaction of the analyte on the C8 stationary phase reach a dynamic balance, that is, the slight adjustment of the acetonitrile ratio has little effect on the retention behavior, and the retention time changes little because the adsorption-desorption balance of the stationary phase is buffered.

[0147] Example 4

[0148] The detection method of the ester-based quaternary ammonium salt provided by the embodiment of the present application differs from that of Example 2 in that the volume ratio of acetonitrile and water in the mobile phase B is different, and in this embodiment, the volume ratio of acetonitrile and water is 70:30.

[0149] The obtained chromatogram is shown in Figure 4 The elution time and mass-to-charge ratio of each component are shown in Table 4.

[0150] Table 4

[0151]

[0152]

[0153] From Figure 4 As can be seen from Table 4, when the volume ratio of acetonitrile and water in the mobile phase B is changed to 70:30, compared with Example 2, the increase of the organic phase ratio significantly enhances the elution strength of the mobile phase, the retention time of all components is shortened as a whole, and some chromatographic peaks in the monoester component are combined due to insufficient separation degree; the separation degree between the triester components is improved because the selectivity of the mobile phase to the difference in hydrophobicity is enhanced under the condition of high organic phase, but at the same time, the peak interval between the triester peaks appears to be distributed loosely due to the significant shortening of the retention time; the elution time span of the strongly polar monoester and the hydrophobic triester is increased, which prolongs the analysis time and reduces the efficiency. However, the overall efficiency is relatively high, and the separation effect is relatively good.

[0154] Example 5

[0155] The detection method of the ester-based quaternary ammonium salt provided by the embodiment of the present application differs from that of Example 2 in that the column temperature, and in this embodiment, the column temperature is 35℃.

[0156] The obtained chromatogram is shown in Fig. 4, and the peak time and mass-to-charge ratio of each component are shown in Table 5. Figure 5

[0157] Table 5

[0158]

[0159]

[0160] From Figure 5 As can be seen from Table 5, when the column temperature is changed to 35℃, compared with Example 2, low temperature enhances the hydrophobic interaction, so that the analyte is retained more strongly on the stationary phase, the peak is delayed, and the analysis time is slightly prolonged, but the overall difference is not large.

[0161] Example 6

[0162] The detection method of the ester-based quaternary ammonium salt provided by the embodiment of the present application differs from that of Example 2 in that the column temperature is 45℃;

[0163] The obtained chromatogram is shown in Fig. 4, and the peak time and mass-to-charge ratio of each component are shown in Table 5. Figure 6 Table 6

[0164]

[0165]

[0166]

[0167] From Figure 6 As can be seen from Table 6, when the column temperature is changed to 45℃, compared with Example 2, high temperature reduces the viscosity of the mobile phase, accelerates the mass transfer rate, and simultaneously weakens the hydrophobic interaction between the analyte and the stationary phase, so that the ester-based quaternary ammonium salt (especially the tri-ester with stronger hydrophobicity) is eluted faster, but the overall difference is not large.

[0168] Example 7

[0169] The detection method of the ester-based quaternary ammonium salt provided by the embodiment of the present application differs from that of Example 2 in that the flow rate is 0.4mL / min;

[0170] The obtained chromatogram is shown in Fig. 4, and the peak time and mass-to-charge ratio of each component are shown in Table 5. Figure 7 Table 7

[0171]

[0172]

[0173]

[0174] From​​​Figure 7 As can be seen from Table 7, when the flow rate is changed to 0.4 mL / min, the following changes are observed compared to Example 2: first, the retention time of the ester-based quaternary ammonium salt is shortened as a whole, and the analysis efficiency is significantly improved; second, although the separation degree of mono-ester and di-ester decreases slightly, the separation degree of tri-ester is significantly improved. However, there is a significant technical bottleneck in this optimization scheme: under this flow rate condition, the system pressure continuously exceeds 10,000 psi, with a maximum of 13,000 psi, close to the upper limit of the system pressure, which may cause damage to the chromatographic column and instrument hardware, thereby affecting the stability and reproducibility of the analysis method.

[0175] Comparative Example 1

[0176] The detection method of the ester-based quaternary ammonium salt provided by the present application has a difference from Example 2 in that the chromatographic column is 2.1 x 150 mm, 1.7 μm Waters ACQUITY UPLC BEH ShieldRP18 chromatographic column.

[0177] The obtained chromatogram is shown in Figure 8 The peak time and mass-to-charge ratio of each component are shown in Table 8;

[0178] Table 8

[0179]

[0180] As can be seen from Figure 8 and Table 8, when the chromatographic column used is changed, compared with Example 2, the chromatographic column used in Comparative Example 1 introduces hydrophilic groups at the end of the C18 long chain through polar end group modification technology, which can theoretically enhance the retention of polar compounds through hydrogen bonding. However, under the test conditions of the present application, the retention time of the target compound is significantly shortened compared with the other two chromatographic columns, and part of the components are not detected. After analysis, this phenomenon may be caused by the following factors: first, the polar end group modification may weaken the hydrophobic interaction of the stationary phase, resulting in weakened interaction of the components with strong hydrophobicity with the stationary phase; second, part of the ester bond isomers may be difficult to penetrate due to high density of the bonded phase in the long chain C18 bonded phase due to large molecular volume, resulting in insufficient retention or co-elution. Therefore, the detection effect obtained is worse than that of Example 2.

[0181] Comparative Example 2

[0182] The detection method of the ester-based quaternary ammonium salt provided by the present application has a difference from Example 2 in that the chromatographic column is 2.1 x 100 mm, 1.7 μm Waters ACQUITY UPLC BEH C18 chromatographic column.

[0183] The obtained chromatogram is shown in Figure 9 The elution time and mass-to-charge ratio of each component are shown in Table 9.

[0184] Table 9

[0185]

[0186] From Figure 9 As can be seen from Table 9, compared with Example 2, the C18 column used in Comparative Example 2 exhibits stronger retention under the same conditions, the elution time of the target compound is significantly delayed, part of the components are not eluted due to exceeding the analysis time, and the chromatographic peaks are obviously broadened and tailed. This is because the long carbon chain structure of C18 causes too strong hydrophobic interaction between the stationary phase and the sample molecules, and the electrostatic interaction (secondary interaction) between the residual silanol group and the ester quaternary ammonium salt exacerbates the peak abnormality. The long chain structure can also cause an increase in mass transfer resistance, leading to uneven molecular diffusion and further peak broadening.

[0187] Comparative Example 3

[0188] The present comparative example provides a detection method for ester quaternary ammonium salt, which differs from Example 2 in that the volume ratio of acetonitrile to water in mobile phase B is different, and the volume ratio of acetonitrile to water in this example is 40:60.

[0189] The obtained chromatogram is shown in Figure 10 The elution time and mass-to-charge ratio of each component are shown in Table 10.

[0190] Table 10

[0191]

[0192]

[0193] From Figure 10 As can be seen from Table 10, compared with Example 2, when the volume ratio of acetonitrile to water in mobile phase B is changed to 40:60, the polarity of the mobile phase is enhanced and the elution strength is reduced due to the decrease in the proportion of acetonitrile, the interaction time of monoester and diester with the stationary phase is prolonged, and the difference in retention time is amplified due to the difference in polarity, resulting in improved separation degree and sharp peak shape. For hydrophobic triesters, the hydrophobic interaction between the triesters and the stationary phase is too strong under low acetonitrile conditions, which can cause saturation of the adsorption sites of the stationary phase or intermolecular hydrophobic aggregation, resulting in a decrease in the difference in interaction between the components and the stationary phase, a close retention time, and serious peak merging and decreased separation degree. If complete separation of triesters is to be achieved, the analysis time needs to be extended, which will reduce the efficiency.

[0194] Comparative Example 4

[0195] The present application provides a detection method of ester-based quaternary ammonium salt, which is different from Example 2 in that the flow rate is 0.2 mL / min;

[0196] The obtained chromatogram is shown in Figure 11 The peak time and mass-to-charge ratio of each component are shown in Table 11;

[0197] Table 11

[0198]

[0199]

[0200] From Figure 11 It can be seen from Table 11 that when the flow rate is changed to 0.2 mL / min, the retention time of the ester-based quaternary ammonium salt is significantly prolonged compared with Example 2. Although the separation degree of monoester and diester remains stable, the peak time of triester is compressed to peak within 3 minutes, resulting in a decrease in separation degree. This flow rate adjustment not only prolongs the retention time of the ester-based quaternary ammonium salt chromatographic peak, but also fails to improve the separation performance of triester. If baseline separation of triester is to be achieved under this condition, the analysis time needs to be significantly prolonged, which will inevitably cause a significant decrease in overall analysis efficiency.

[0201] Comparative Example 5

[0202] The present application provides a detection method of ester-based quaternary ammonium salt, which is different from Example 2 in that no formic acid is added in mobile phase A and mobile phase B;

[0203] The obtained chromatogram is shown in Figure 12 The peak time and mass-to-charge ratio of each component are shown in Table 12;

[0204] Table 12

[0205]

[0206] From Figure 12As shown in Table 12, when formic acid is not added to the mobile phase, the pH of the mobile phase increases to neutral compared to Example 2. At this time, the silanol groups (-SiOH) on the surface of the silica matrix partially dissociate into negatively charged -SiO- due to the increased pH. The positively charged quaternary ammonium salt cations generate strong electrostatic attraction with -SiO-, resulting in a prolonged retention time. Specifically, the monoester component, due to its strong polarity and the presence of hydrophilic groups, easily combines with silanol groups through hydrogen bonds or dipole interactions in addition to electrostatic attraction, causing some chromatographic peaks to be masked due to excessive retention. The diester component has moderate polarity, and the hydrophobic interaction and moderate electrostatic interaction of silanol groups reach equilibrium, resulting in the separation of some small peaks due to differences in interaction. The trimer component is mainly hydrophobic, and the electrostatic effect of silanol groups is relatively weak. However, due to insufficient elution capacity of the mobile phase, the component has an excessively long retention time in the column, which leads to increased molecular diffusion and mass transfer resistance, resulting in peak broadening or even merging.

[0207] Application Example 1

[0208] This invention provides a method for detecting ester-based quaternary ammonium salts. The difference between this method and Example 1 lies in the sample being a commercially available fabric softener (a conventional fabric softener in which the mass percentage of ester-based quaternary ammonium salts is approximately 5%) and the treatment in step (1). In this example, step (1) is as follows: 200 mg of the commercially available conventional fabric softener is placed in a 100 mL volumetric flask, and an extraction solution (a mixed solution of isopropanol and acetonitrile, with a volume ratio of 1:1) is added and the solution is brought to the mark. The solution is then sonicated at 45 kHz for 15 min to prepare a stock solution with a total concentration of approximately 0.1 mg / mL of ester-based quaternary ammonium salts in the actual fabric softener sample. The solution is then diluted with the extraction solution to a concentration of approximately 5 μg / mL of ester-based quaternary ammonium salts in the sample. Finally, the solution is filtered through a 0.22 μm organic phase filter membrane, and the filtrate is collected to obtain the test solution.

[0209] The obtained test results are as follows Figure 13 As shown; from Figure 13 It can be clearly seen that when the detection method provided by this invention is used to detect actual samples, the chromatographic peaks of each component (monoester, diester, and triester) of the ester-based quaternary ammonium salt achieve good separation and are not affected by the matrix of the surfactant complex system, exhibiting excellent peak shape symmetry and repeatability.

[0210] Application Example 2

[0211] This invention provides a method for detecting ester-based quaternary ammonium salts. The difference between this method and Example 1 lies in the sample being a commercially available fabric softener (concentrated fabric softener, wherein the mass percentage of ester-based quaternary ammonium salts is approximately 15%) and the treatment in step (1). In this example, step (1) is as follows: 100 mg of commercially available concentrated fabric softener is placed in a 100 mL volumetric flask, and an extraction solution (a mixed solution of isopropanol and acetonitrile, with a volume ratio of 1:1) is added and the solution is brought to the mark. The solution is then sonicated at 45 kHz for 15 min to prepare a stock solution with a total concentration of ester-based quaternary ammonium salts of 0.15 mg / mL in the actual fabric softener sample. The solution is then diluted with the extraction solution to a concentration of 5 μg / mL of ester-based quaternary ammonium salts in the sample. The solution is then filtered through a 0.22 μm organic phase filter membrane, and the filtrate is collected to obtain the test solution.

[0212] The obtained test results are as follows Figure 14 As shown; from Figure 14 It can be clearly seen that when the detection method provided by this invention is used to detect actual samples, the chromatographic peaks of each component (monoester, diester, and triester) of the ester-based quaternary ammonium salt achieve good separation and are not affected by the matrix of the surfactant complex system, exhibiting excellent peak shape symmetry and repeatability.

[0213] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention and not 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 ester-based quaternary ammonium salts, characterized by, The detection method is to use reversed-phase ultra-high performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry to determine the detection object. The reversed-phase ultra-high performance liquid chromatography conditions are as follows: The chromatographic column is a reversed-phase C8 chromatographic column. The mobile phase A is an isopropanol solution containing 0.05-0.15% volume percentage of formic acid, and the mobile phase B is an acetonitrile aqueous solution containing 0.05-0.15% volume percentage of formic acid; wherein the volume ratio of acetonitrile to water in the acetonitrile aqueous solution is (70-40):(30-60). The elution program is gradient elution. The column temperature is 35-45°C. The flow rate is 0.3-0.4 mL / min.

2. The detection method according to claim 1, characterized in that, The chromatographic column is a 2.1 mm x 100 mm, 1.7 μm Waters BEH C8 chromatographic column.

3. The method of claim 1, wherein, The volume ratio of acetonitrile to water in the acetonitrile aqueous solution is (50-60):(50-40).

4. The method of claim 1, wherein, The gradient elution is as follows: 0 min, 28-32% mobile phase A and 72-68% mobile phase B; 0.5 min, 28-32% mobile phase A and 72-68% mobile phase B; 2 min, 38-42% mobile phase A and 62-58% mobile phase B; 10 min, 48-52% mobile phase A and 52-48% mobile phase B; 11 min, 54-56% mobile phase A and 46-44% mobile phase B; 14 min, 59-61% mobile phase A and 41-39% mobile phase B; 17 min, 64-66% mobile phase A and 36-34% mobile phase B; 20 min, 67-69% mobile phase A and 33-31% mobile phase B; 21 min, 28-32% mobile phase A and 72-68% mobile phase B; 22 min, 28-32% mobile phase A and 72-68% mobile phase B.

5. The method of claim 1, wherein The mass spectrometry conditions are as follows: The mode is positive ion mode; The ionization voltage is 3-5 kV; The ion source temperature is 135-200°C; The desolvation gas temperature is 250-450°C; The cone gas flow rate is 50±2 L / h; The desolvation gas flow rate is 600±10 L / h; The collision gas is argon; The scan range is 50-1200; The scan time is 0.2 s.

6. The method of claim 1, wherein, The detection object includes a detergent.

7. The method of claim 1, wherein, Before being determined by reversed-phase ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry, the process of extracting the detection object to obtain a test solution is further included.

8. The detection method according to claim 7, characterized in that, The extraction is to place the detection object in an extraction liquid for ultrasonic extraction, then filter, collect the filtrate and dilute to obtain the test solution.

9. The detection method according to claim 8, characterized in that, The extraction liquid includes a mixed solution of isopropanol and acetonitrile with a volume ratio of (0.5-3):

1.

10. The detection method of claim 8, wherein, The ultrasonic extraction time is 10-30 min, and the power is 40-50 kHz.

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