Method for detecting content of free amine in fatty acid amide propyl dimethyl betaine

Abstract

The invention relates to the field of chemical analysis, in particular to a method for detecting the content of free amine in fatty acid amide propyl dimethyl betaine. The method comprises the following steps: extracting free amine in fatty acid amide propyl dimethyl betaine by using ethyl acetate to obtain an oil phase which is a solution to be detected, and performing gas chromatographic analysis on the solution to be detected to obtain the content of the free amine in the solution to be detected. According to the method, the content of free amine in fatty acid amide propyl dimethyl betaine can be rapidly and accurately detected, the detection efficiency and reliability are remarkably improved, the analysis time is shortened, the rapid detection requirement in large-scale production is met, and efficient detection can be achieved on an industrial production line.

Description

Technical Field

[0001] The invention relates to the field of chemical analysis, and in particular to a method for detecting the free amine content in fatty amide propyl dimethyl betaine. Background Art

[0002] Fatty amide propyl dimethyl betaine (PCDMA) is a zwitterionic surfactant with excellent surface activity, which is widely used in detergents, personal care products, industrial cleaning and agricultural additives. Its chemical structure contains both hydrophilic betaine groups and hydrophobic fatty amide groups, which makes it show good surface activity, mildness and biodegradability under various environmental conditions. However, in the production process of PCDMA, the residual problem of intermediate free amines not only affects the quality and performance of the product, but also may bring negative effects such as irritation and bad odor. Even if the process is optimized, trace amounts of free amine residues are still inevitable. However, relevant product standards require that the free amine content is ≤0.5%. Therefore, how to accurately and quickly detect the content of free amines in the product has become a key link in production quality control.

[0003] At present, the detection methods for free amines in PCDMA mainly include: (1) direct titration method for determining the content of active substances and free tertiary amines in PCDMA products ("Daily Chemical Industry" 2011 Issue 01, pages 68-72). The residual free amide content in PCDMA is low (≤0.5%). The direct titration subtraction method is simple to operate, but has low sensitivity and selectivity, is easily interfered by other alkaline impurities, has large detection errors, and cannot accurately detect the free amide content; (2) the standard "Fatty Amidopropyl Dimethyl Betaine" QB / T 4082-2010 5.3 adopts ether-n-butanol extraction, water bath evaporation, and potentiometric titration method to detect free amides, but the detection method is complicated, the detection time is long (about 4 hours), the selectivity is poor, it is easily interfered by impurity fatty acids, the result error is large, and ether solvent is used in the detection process, and the experimental safety is low.

[0004] Although existing methods can meet the detection needs to a certain extent, they generally have problems such as insufficient sensitivity, complex operation or poor selectivity, and are difficult to fully adapt to the requirements of rapid, simple and efficient detection in industrial production. Therefore, it is urgent to develop a free amide residue detection method with high sensitivity, high selectivity, simple operation and suitable for batch detection to improve the quality control level of PCDMA and meet the requirements of green chemistry and environmental protection. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. For this purpose, the present invention provides a method for detecting the content of free amine in fatty amide propyl dimethyl betaine. This method can quickly and accurately detect the content of free amine in fatty amide propyl dimethyl betaine, significantly improve the detection efficiency and reliability, shorten the analysis time, meet the rapid detection requirements in large-scale production, and achieve efficient detection on the industrial production line.

[0006] For this purpose, the present invention provides a method for detecting the content of free amine in fatty amide propyl dimethyl betaine, comprising the following steps:

[0007] Use ethyl acetate to extract the free amine in fatty amide propyl dimethyl betaine, and the obtained oil phase is the test solution. Perform gas chromatography analysis on the test solution to measure the content of free amine in the test solution.

[0008] Aiming at the problems of insufficient sensitivity, poor selectivity, and complex operation in the existing detection technology for residual free amide in PCDMA, the present invention provides the above detection method. By pretreating fatty amide propyl dimethyl betaine, that is, using ethyl acetate to extract the free amine in the sample in one step, obtaining the test sample through simple centrifugation separation, and then performing gas chromatography analysis on the test sample, the content of free amine in PCDMA can be measured. This pretreatment can be completed within 10 minutes, realizing the efficient extraction of free amine in the sample, reducing the sample pretreatment steps, greatly reducing the operation complexity, and solving the technical bottleneck of rapid and direct detection in the industrial production of free amine. Combining with gas chromatography, this method has the advantages of high selectivity and strong anti-interference ability, while reducing the safety risk in the experimental process, having good chemical stability, environmental friendliness, and cost-effectiveness. The recovery rate of this method is 90.0%-106%, the repeatability RSD≤4.04%, and the detection limit is 0.0008%.

[0009] According to an embodiment of the present invention, the detection method further comprises:

[0010] Dissolve the free amine in ethyl acetate to prepare free amine standard solutions with different concentrations;

[0011] Use ethyl acetate to extract the free amine in fatty amide propyl dimethyl betaine, and the obtained oil phase is the test solution;

[0012] Perform gas chromatography analysis on free amine standard solutions with different concentrations, and obtain a standard curve according to the test results;

[0013] Perform gas chromatography analysis on the test solution, and obtain the content of free amine in fatty amide propyl dimethyl betaine according to the test results and the standard curve;

[0014] Wherein, the gas chromatography analysis conditions are:

[0015] The chromatographic column is a medium-polarity capillary chromatographic column;

[0016] The inlet temperature is 200 - 350 °C;

[0017] The detector temperature is 280 - 330 °C;

[0018] The chromatographic column is programmed to increase the temperature. The initial temperature is 150 - 250 °C, hold for 0 - 5 min, then increase the temperature to 280 - 350 °C, and hold for 1 - 30 min;

[0019] The injection volume is 0.1 - 2 μL;

[0020] The column flow rate is 0.4 - 1.5 mL / min;

[0021] The carrier gas is nitrogen, hydrogen or helium. Thus, the detection time is greatly shortened, the costs of reagents, instruments, labor, etc. are reduced, the contradiction that the existing methods cannot balance cost and efficiency is solved, and the requirements for high-frequency batch detection in industrial production can be met.

[0022] According to an embodiment of the present invention, the free amine includes at least one of C 8 -C 18 fatty amide propyl dimethyl tertiary amine.

[0023] According to an embodiment of the present invention, the free amine includes at least one of octanamide propyl dimethyl tertiary amine, decanamide propyl dimethyl tertiary amine, lauramide propyl dimethyl tertiary amine, myristamide propyl dimethyl tertiary amine, palmitamide propyl dimethyl tertiary amine, stearamide propyl dimethyl tertiary amine.

[0024] According to an embodiment of the present invention, the mass-volume ratio of the fatty amide propyl dimethyl betaine to ethyl acetate is (0.01 - 0.5) g:1 mL.

[0025] According to an embodiment of the present invention, the preparation method further includes: mixing the fatty amide propyl dimethyl betaine with a sodium chloride solution and a sodium hydroxide solution, mixing the obtained mixed solution with ethyl acetate, and performing extraction treatment.

[0026] According to an embodiment of the present invention, the stationary phase of the medium-polarity capillary chromatographic column is 5% phenyl - 95% methyl polysiloxane.

[0027] According to an embodiment of the present invention, the chromatographic column includes at least one of DB-5HT 20 m × 0.18 mm × 0.18 μm and DB-5 30 m × 0.25 mm × 0.25 μm.

[0028] According to an embodiment of the present invention, during the programmed temperature increase of the chromatographic column, the heating rate is 5 - 25 °C / min.

[0029] According to an embodiment of the present invention, in the gas chromatography analysis conditions, the injection split ratio is (5-20):1.

[0030] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0032] Figure 1 The gas chromatogram of sample A in Example 1 of the present invention is shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Embodiments of the present invention will be described in detail below. The embodiments described below are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0034] It should be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Further, in the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0035] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0036] To make the present invention easier to understand, certain technical and scientific terms are specifically defined below. Unless otherwise clearly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by those of ordinary skill in the art to which the present invention pertains.

[0037] In this document, the term "comprising" or "including" is an open expression, that is, it includes the content specified by the present invention, but does not exclude other aspects.

[0038] According to an embodiment of the present invention, the present invention provides a method for detecting the free amine content in fatty amide propyl dimethyl betaine, comprising the following steps:

[0039] Extract the free amine in fatty amide propyl dimethyl betaine with ethyl acetate. The obtained oil phase is the test solution, and perform gas chromatography analysis on the test solution to measure the content of free amine in the test solution.

[0040] The present invention optimizes the sample pretreatment process, adopts a method of directly extracting the free amide in the sample with ethyl acetate in one step and simply centrifuging to obtain the test sample. The pretreatment time can be completed within 10 minutes, realizing the efficient extraction of free amide in the sample. By reducing the sample treatment steps, the operation complexity is greatly reduced, and the technical bottleneck of rapid and direct detection in the industrial production of free amide is solved. This method uses gas chromatography for separation and detection, has high selectivity and strong anti-interference ability, and can realize the trace detection of C 8 -C 18 in fatty amide propyl dimethyl tertiary amine, effectively monitoring the product.

[0041] According to a specific embodiment of the present invention, the detection method further includes:

[0042] Dissolve the free amine in ethyl acetate to prepare free amine standard solutions with different concentrations;

[0043] Extract the free amine in fatty amide propyl dimethyl betaine with ethyl acetate. The obtained oil phase is the test solution;

[0044] Perform gas chromatography analysis on free amine standard solutions with different concentrations, and obtain a standard curve according to the test results;

[0045] Perform gas chromatography analysis on the test solution, and obtain the content of free amine in fatty amide propyl dimethyl betaine according to the test results and the standard curve;

[0046] Among them, the gas chromatography analysis conditions are:

[0047] The chromatographic column is a medium-polarity capillary chromatographic column;

[0048] The inlet temperature is 200 - 350 °C;

[0049] The detector temperature is 280 - 330 °C;

[0050] The chromatographic column is programmed to heat. The initial temperature is 150 - 250 °C, hold for 0 - 5 minutes, then heat to 280 - 350 °C, and hold for 1 - 30 minutes;

[0051] The injection volume is 0.1 - 2 μL;

[0052] The column flow rate is 0.4 - 1.5 mL / min;

[0053] The carrier gas is nitrogen, hydrogen or helium.

[0054] According to specific embodiments of the present invention, the type of the free amine is not particularly limited and includes, but is not limited to, C 8 -C 18 fatty amide propyl dimethyl tertiary amine, specifically such as octanamide propyl dimethyl tertiary amine, decanamide propyl dimethyl tertiary amine, lauramide propyl dimethyl tertiary amine, myristamide propyl dimethyl tertiary amine, palmitamide propyl dimethyl tertiary amine, stearamide propyl dimethyl tertiary amine.

[0055] According to specific embodiments of the present invention, the mass-volume ratio of the fatty amide propyl dimethyl betaine to ethyl acetate is (0.01 - 0.5) g:1 mL, thereby achieving a better extraction effect.

[0056] According to specific embodiments of the present invention, the preparation method further includes: mixing the fatty amide propyl dimethyl betaine with a sodium chloride solution and a sodium hydroxide solution, and mixing the obtained mixed solution with ethyl acetate for extraction treatment. Thereby improving the extraction efficiency. Among them, sodium chloride is a strong electrolyte, which can significantly increase the ionic strength of the aqueous phase, thereby reducing the mutual solubility between the aqueous phase and the organic phase, reducing the emulsifying ability, and further enhancing the separation effect between the two phases.

[0057] According to specific embodiments of the present invention, the stationary phase of the medium-polarity capillary chromatographic column is 5% phenyl - 95% methyl polysiloxane.

[0058] According to specific embodiments of the present invention, the chromatographic column includes at least one of DB-5HT 20 m×0.18 mm×0.18 μm and DB-5 30 m×0.25 mm×0.25 μm.

[0059] According to specific embodiments of the present invention, in the programmed temperature rise of the chromatographic column, the heating rate is 5 - 25 °C / min.

[0060] According to specific embodiments of the present invention, in the gas chromatography analysis, split injection can be adopted, and the injection split ratio can be (5 - 20):1, or non-split injection can also be selected, which does not affect the subsequent analysis effect.

[0061] Next, the solutions of the present invention will be explained with reference to the examples. Those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those not specified in the examples regarding specific techniques or conditions, they shall be carried out according to the techniques or conditions described in the literature in the art or according to the product specifications. For reagents or instruments not specified in terms of the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0062] Example 1

[0063] This embodiment provides a rapid detection method for free amines in fatty amide propyl dimethyl betaine, comprising the following steps:

[0064] (1) Reagent preparation:

[0065] Standard stock solution: Prepare an ethyl acetate solution containing 357 mg / L of octanamide propyl dimethyl tertiary amine, 311.5 mg / L of decanamide propyl dimethyl tertiary amine, 2491 mg / L of lauramide propyl dimethyl tertiary amine, 844.5 mg / L of tetradecanamide propyl dimethyl tertiary amine, 437 mg / L of hexadecanamide propyl dimethyl tertiary amine, and 500 mg / L of octadecanamide propyl dimethyl tertiary amine;

[0066] Standard solution 1: Prepare an ethyl acetate solution containing 3.57 mg / L of octanamide propyl dimethyl tertiary amine, 3.115 mg / L of decanamide propyl dimethyl tertiary amine, 24.91 mg / L of lauramide propyl dimethyl tertiary amine, 8.445 mg / L of tetradecanamide propyl dimethyl tertiary amine, 4.37 mg / L of hexadecanamide propyl dimethyl tertiary amine, and 5.00 mg / L of octadecanamide propyl dimethyl tertiary amine;

[0067] Standard solution 2: Prepare an ethyl acetate solution containing 7.14 mg / L of octanamide propyl dimethyl tertiary amine, 6.23 mg / L of decanamide propyl dimethyl tertiary amine, 49.82 mg / L of lauramide propyl dimethyl tertiary amine, 16.89 mg / L of tetradecanamide propyl dimethyl tertiary amine, 8.74 mg / L of hexadecanamide propyl dimethyl tertiary amine, and 10.00 mg / L of octadecanamide propyl dimethyl tertiary amine;

[0068] Standard solution 3: Prepare an ethyl acetate solution containing 17.85 mg / L of octanamide propyl dimethyl tertiary amine, 15.58 mg / L of decanamide propyl dimethyl tertiary amine, 124.55 mg / L of lauramide propyl dimethyl tertiary amine, 42.23 mg / L of tetradecanamide propyl dimethyl tertiary amine, 21.86 mg / L of hexadecanamide propyl dimethyl tertiary amine, and 25.00 mg / L of octadecanamide propyl dimethyl tertiary amine;

[0069] Standard solution 4: Prepare an ethyl acetate solution containing 35.71 mg / L of octanamide propyl dimethyl tertiary amine, 31.16 mg / L of decanamide propyl dimethyl tertiary amine, 249.10 mg / L of lauramide propyl dimethyl tertiary amine, 84.47 mg / L of tetradecanamide propyl dimethyl tertiary amine, 43.71 mg / L of hexadecanamide propyl dimethyl tertiary amine, and 50.00 mg / L of octadecanamide propyl dimethyl tertiary amine;

[0070] Standard solution 5: Prepare an ethyl acetate solution containing 71.41 mg / L of octanamidopropyl dimethyl tertiary amine, 62.31 mg / L of decanamidopropyl dimethyl tertiary amine, 498.20 mg / L of lauramidopropyl dimethyl tertiary amine, 168.94 mg / L of tetradecanamidopropyl dimethyl tertiary amine, 87.42 mg / L of hexadecanamidopropyl dimethyl tertiary amine, and 100.00 mg / L of octadecanamidopropyl dimethyl tertiary amine;

[0071] Sodium chloride solution (5 mol / L NaCl): Weigh 292 g of sodium chloride into a 2000 mL beaker, add 900 mL of water, stir to dissolve, make up the volume to 1000 mL with water in a volumetric flask, and shake well;

[0072] Sodium hydroxide solution (400 g / L NaOH): Weigh 400 g of sodium hydroxide into a 2000 mL beaker, add 900 mL of water, stir to dissolve, cool and dilute to 1000 mL, and stir evenly.

[0073] (2) Preparation of the test solution:

[0074] Weigh 1.0 g of sample A (accurate to 0.0001 g) by the subtraction method into a beaker, add 5 mL of sodium chloride solution, 1 mL of sodium hydroxide solution, add 5 mL of deionized water, transfer to a separatory funnel, and rinse the beaker with 10 mL of water respectively. The rinsing solution is incorporated into the separatory funnel, and 15 mL of ethyl acetate is added. Plug the stopper and shake vigorously for at least 1 min (pay attention to relieving pressure), let it stand for layering completely, discard the lower aqueous phase, and pour the upper extraction solution into a dry 25 mL volumetric flask (pay attention to preventing water droplets from entering the volumetric flask). At the same time, rinse the separatory funnel with a small amount of ethyl acetate, incorporate the rinsing solution into the volumetric flask, make up the volume to the mark with ethyl acetate, and shake well for standby.

[0075] (3) Gas chromatography test:

[0076] Set the gas chromatography conditions as follows. After equilibrating the chromatographic column and obtaining a stable baseline for the gas chromatography system, inject the sample for detection, record the chromatogram, and process the data with a chromatographic workstation.

[0077] Chromatographic column: DB-5HT 20 m × 0.18 mm × 0.18 μm;

[0078] Injector temperature: 300 °C

[0079] Detector temperature: 330 °C

[0080] Column oven program:

[0081]

[0082] Injection volume: 1.0 μL;

[0083] Split ratio: 5:1;

[0084] Column flow rate: 0.6 mL / min;

[0085] Carrier gas: N 2 ;

[0086] Needle washing solvent: acetone.

[0087] By performing gas chromatography analysis on the standard solution, a standard curve was obtained: octylamidopropyl dimethyl tertiary amine y=2.9384x-0.5874, decylamidopropyl dimethyl tertiary amine y=2.8995x-0.4024, laurylamidopropyl dimethyl tertiary amine y=2.9908x-4.004, tetradecylamidopropyl dimethyl tertiary amine y=2.9935x-2.1766, hexadecylamidopropyl dimethyl tertiary amine y=3.0042x-1.8535, octadecylamidopropyl dimethyl tertiary amine y=3.0176x-6.5869, and the linear relationship of each standard curve was >0.999.

[0088] Calculation of free amine residue: Calculate the free amine residue in the sample by using the standard curve and the test results of the solution to be tested. The gas chromatogram of sample A is shown in Figure 1 .

[0089] Repeatability verification: The test solutions were sampled and tested 7 times, and the standard deviation (SD) and relative standard deviation (RSD) were calculated.

[0090] Accuracy verification: The recovery rate indicator is used to test the accuracy of the method.

[0091] The reproducibility data of free amine residues in the same batch of fatty amide propyl dimethyl betaine are shown in Table 1-2. Among them, C8-PKO is octylamide propyl dimethyl tertiary amine, C10-PKO is caprylamidopropyl dimethyl tertiary amine, C12-PKO is lauramide propyl dimethyl tertiary amine, C14-PKO is tetradecylamide propyl dimethyl tertiary amine, C16-PKO is hexadecylamide propyl dimethyl tertiary amine, and C18-PKO is octadecylamide propyl dimethyl tertiary amine.

[0092] Table 1

[0093]

[0094] Table 2

[0095]

[0096]

[0097] Example 2

[0098] This embodiment provides a method for rapid detection of free amines in fatty amide propyl dimethyl betaine, comprising the following steps:

[0099] (1) Reagent preparation:

[0100] Standard stock solution: prepare an ethyl acetate solution containing 357 mg / L octanamidopropyl dimethyl tertiary amine, 311.5 mg / L decanoamidopropyl dimethyl tertiary amine, 2491 mg / L lauramidopropyl dimethyl tertiary amine, 844.5 mg / L tetradecanoamidopropyl dimethyl tertiary amine, 437 mg / L hexadecanoamidopropyl dimethyl tertiary amine, and 500 mg / L octadecanoamidopropyl dimethyl tertiary amine;

[0101] Standard solution 1: prepare an ethyl acetate solution containing 3.57 mg / L octanamidopropyl dimethyl tertiary amine, 3.115 mg / L decanoamidopropyl dimethyl tertiary amine, 24.91 mg / L lauramidopropyl dimethyl tertiary amine, 8.445 mg / L tetradecanoamidopropyl dimethyl tertiary amine, 4.37 mg / L hexadecanoamidopropyl dimethyl tertiary amine, and 5.00 mg / L octadecanoamidopropyl dimethyl tertiary amine;

[0102] Standard solution 2: prepare an ethyl acetate solution containing 7.14 mg / L octanamidopropyl dimethyl tertiary amine, 6.23 mg / L decanoamidopropyl dimethyl tertiary amine, 49.82 mg / L lauramidopropyl dimethyl tertiary amine, 16.89 mg / L tetradecanoamidopropyl dimethyl tertiary amine, 8.74 mg / L hexadecanoamidopropyl dimethyl tertiary amine, and 10.00 mg / L octadecanoamidopropyl dimethyl tertiary amine;

[0103] Standard solution 3: prepare an ethyl acetate solution containing 17.85 mg / L of octylamidopropyl dimethyl tertiary amine, 15.58 mg / L of decylamidopropyl dimethyl tertiary amine, 124.55 mg / L of laurylamidopropyl dimethyl tertiary amine, 42.23 mg / L of tetradecylamidopropyl dimethyl tertiary amine, 21.86 mg / L of hexadecylamidopropyl dimethyl tertiary amine, and 25.00 mg / L of octadecylamidopropyl dimethyl tertiary amine;

[0104] Standard solution 4: prepare an ethyl acetate solution containing 35.71 mg / L of octylamidopropyl dimethyl tertiary amine, 31.16 mg / L of decylamidopropyl dimethyl tertiary amine, 249.10 mg / L of laurylamidopropyl dimethyl tertiary amine, 84.47 mg / L of tetradecylamidopropyl dimethyl tertiary amine, 43.71 mg / L of hexadecylamidopropyl dimethyl tertiary amine, and 50.00 mg / L of octadecylamidopropyl dimethyl tertiary amine;

[0105] Standard solution 5: prepare an ethyl acetate solution containing 71.41 mg / L octanamidopropyl dimethyl tertiary amine, 62.31 mg / L decanoamidopropyl dimethyl tertiary amine, 498.20 mg / L lauramidopropyl dimethyl tertiary amine, 168.94 mg / L tetradecanoamidopropyl dimethyl tertiary amine, 87.42 mg / L hexadecanoamidopropyl dimethyl tertiary amine, and 100.00 mg / L octadecanoamidopropyl dimethyl tertiary amine;

[0106] Sodium chloride solution (5 mol / L NaCl): weigh 292 g of sodium chloride into a 2000 mL beaker, add 900 mL of water, stir to dissolve, dilute to 1000 mL with water, and shake well;

[0107] Sodium hydroxide solution (400g / L NaOH): Weigh 400g of sodium hydroxide into a 2000mL beaker, add 900mL of water, stir to dissolve, dilute to 1000mL after cooling, and stir evenly.

[0108] (2) Preparation of test solution:

[0109] Weigh 1.0g of sample B (accurate to 0.0001g) in a beaker using the reduction method, add 5mL of sodium chloride solution, 1mL of sodium hydroxide solution, add 5mL of deionized water, transfer to a separatory funnel, and rinse the beaker with 10mL of water respectively, merge the rinse into the separatory funnel, and transfer 15mL of ethyl acetate. Plug in the stopper and shake vigorously for at least 1min (pay attention to pressure relief), let stand for stratification, discard the lower aqueous phase, and pour the upper extract into a dry 25mL volumetric flask (be careful to prevent water drops from entering the volumetric flask), and at the same time rinse the separatory funnel with a small amount of ethyl acetate, merge the rinse into the volumetric flask, dilute to the mark with ethyl acetate, shake well for later use.

[0110] (3) Gas chromatography test:

[0111] Set up the gas chromatography conditions as follows, balance the chromatographic column, allow the gas chromatography system to obtain a stable baseline, inject samples for testing, record the chromatogram, and process the data using the chromatography workstation.

[0112] Chromatographic column: DB-5HT 20m×0.18mm×0.18μm;

[0113] Inlet temperature: 300°C

[0114] Detector temperature: 330°C

[0115] Oven Program:

[0116]

[0117] Injection volume: 1.0 μL;

[0118] Split ratio: 5:1;

[0119] Column flow rate: 0.6 mL / min;

[0120] Carrier gas: N 2 ;

[0121] Needle washing solvent: acetone.

[0122] The standard solution was analyzed by gas chromatography to obtain a standard curve.

[0123] Calculation of free amine residue: Calculate the free amine residue in the sample based on the standard curve and the test results of the test solution.

[0124] Repeatability verification: The test solutions were sampled and tested 7 times, and the standard deviation (SD) and relative standard deviation (RSD) were calculated.

[0125] Accuracy verification: The recovery rate indicator is used to test the accuracy of the method.

[0126] The repeatability data of free amine residue in the same batch of fatty amide propyl dimethyl betaine are shown in Table 3-4.

[0127] Table 3

[0128]

[0129] Table 4

[0130]

[0131]

[0132] Example 3

[0133] This embodiment provides a method for rapid detection of free amines in fatty amide propyl dimethyl betaine, comprising the following steps:

[0134] (1) Reagent preparation:

[0135] Standard stock solution: prepare an ethyl acetate solution containing 357 mg / L octanamidopropyl dimethyl tertiary amine, 311.5 mg / L decanoamidopropyl dimethyl tertiary amine, 2491 mg / L lauramidopropyl dimethyl tertiary amine, 844.5 mg / L tetradecanoamidopropyl dimethyl tertiary amine, 437 mg / L hexadecanoamidopropyl dimethyl tertiary amine, and 500 mg / L octadecanoamidopropyl dimethyl tertiary amine;

[0136] Standard solution 1: prepare an ethyl acetate solution containing 3.57 mg / L octanamidopropyl dimethyl tertiary amine, 3.115 mg / L decanoamidopropyl dimethyl tertiary amine, 24.91 mg / L lauramidopropyl dimethyl tertiary amine, 8.445 mg / L tetradecanoamidopropyl dimethyl tertiary amine, 4.37 mg / L hexadecanoamidopropyl dimethyl tertiary amine, and 5.00 mg / L octadecanoamidopropyl dimethyl tertiary amine;

[0137] Standard solution 2: prepare an ethyl acetate solution containing 7.14 mg / L octanamidopropyl dimethyl tertiary amine, 6.23 mg / L decanoamidopropyl dimethyl tertiary amine, 49.82 mg / L lauramidopropyl dimethyl tertiary amine, 16.89 mg / L tetradecanoamidopropyl dimethyl tertiary amine, 8.74 mg / L hexadecanoamidopropyl dimethyl tertiary amine, and 10.00 mg / L octadecanoamidopropyl dimethyl tertiary amine;

[0138] Standard solution 3: prepare an ethyl acetate solution containing 17.85 mg / L of octylamidopropyl dimethyl tertiary amine, 15.58 mg / L of decylamidopropyl dimethyl tertiary amine, 124.55 mg / L of laurylamidopropyl dimethyl tertiary amine, 42.23 mg / L of tetradecylamidopropyl dimethyl tertiary amine, 21.86 mg / L of hexadecylamidopropyl dimethyl tertiary amine, and 25.00 mg / L of octadecylamidopropyl dimethyl tertiary amine;

[0139] Standard solution 4: prepare an ethyl acetate solution containing 35.71 mg / L of octylamidopropyl dimethyl tertiary amine, 31.16 mg / L of decylamidopropyl dimethyl tertiary amine, 249.10 mg / L of laurylamidopropyl dimethyl tertiary amine, 84.47 mg / L of tetradecylamidopropyl dimethyl tertiary amine, 43.71 mg / L of hexadecylamidopropyl dimethyl tertiary amine, and 50.00 mg / L of octadecylamidopropyl dimethyl tertiary amine;

[0140] Standard solution 5: prepare an ethyl acetate solution containing 71.41 mg / L octanamidopropyl dimethyl tertiary amine, 62.31 mg / L decanoamidopropyl dimethyl tertiary amine, 498.20 mg / L lauramidopropyl dimethyl tertiary amine, 168.94 mg / L tetradecanoamidopropyl dimethyl tertiary amine, 87.42 mg / L hexadecanoamidopropyl dimethyl tertiary amine, and 100.00 mg / L octadecanoamidopropyl dimethyl tertiary amine;

[0141] Sodium chloride solution (5 mol / L NaCl): weigh 292 g of sodium chloride into a 2000 mL beaker, add 900 mL of water, stir to dissolve, dilute to 1000 mL with water, and shake well;

[0142] Sodium hydroxide solution (400g / L NaOH): Weigh 400g of sodium hydroxide into a 2000mL beaker, add 900mL of water, stir to dissolve, dilute to 1000mL after cooling, and stir evenly.

[0143] (2) Preparation of test solution:

[0144] Weigh 1.0g of sample C (accurate to 0.0001g) in a beaker using the reduction method, add 5mL of sodium chloride solution, 1mL of sodium hydroxide solution, add 5mL of deionized water, transfer to a separatory funnel, and rinse the beaker with 10mL of water respectively, merge the rinse into the separatory funnel, and transfer 15mL of ethyl acetate. Plug in the stopper and shake vigorously for at least 1min (pay attention to pressure relief), let stand for stratification, discard the lower aqueous phase, and pour the upper extract into a dry 25mL volumetric flask (be careful to prevent water drops from entering the volumetric flask), and at the same time rinse the separatory funnel with a small amount of ethyl acetate, merge the rinse into the volumetric flask, dilute to the mark with ethyl acetate, shake well for later use.

[0145] (3) Gas chromatography test:

[0146] Set up the gas chromatography conditions as follows, balance the chromatographic column, allow the gas chromatography system to obtain a stable baseline, inject samples for testing, record the chromatogram, and process the data using the chromatography workstation.

[0147] Chromatographic column: DB-5 30m×0.25mm×0.25μm;

[0148] Inlet temperature: 300°C

[0149] Detector temperature: 330°C

[0150] Oven Program:

[0151]

[0152] Injection volume: 1.0 μL;

[0153] Split ratio: 5:1;

[0154] Column flow rate: 0.6 mL / min;

[0155] Carrier gas: N 2 ;

[0156] Needle washing solvent: acetone.

[0157] The standard solution was analyzed by gas chromatography to obtain a standard curve.

[0158] Calculation of free amine residue: Calculate the free amine residue in the sample based on the standard curve and the test results of the test solution.

[0159] Repeatability verification: The test solutions were sampled and tested 7 times, and the standard deviation (SD) and relative standard deviation (RSD) were calculated.

[0160] Accuracy verification: The recovery rate indicator is used to test the accuracy of the method.

[0161] The repeatability data of free amine residue in the same batch of fatty amide propyl dimethyl betaine are shown in Table 5-6.

[0162] Table 5

[0163]

[0164] Table 6

[0165]

[0166]

[0167] Example 4

[0168] This embodiment provides a rapid detection method for free amines in fatty amide propyl dimethyl betaine, which differs from Example 1 only in that sample A is replaced by sample D, the carrier gas is hydrogen, and the repeatability data of the free amine residues in the same batch of fatty amide propyl dimethyl betaine are measured as shown in Table 7-8.

[0169] Table 7

[0170]

[0171] Table 8

[0172]

[0173]

[0174] Example 5

[0175] This embodiment provides a rapid detection method for free amines in fatty amide propyl dimethyl betaine, which differs from Embodiment 1 only in that: sample A is replaced by sample E, the carrier gas is helium, and the repeatability data of the free amine residues in the same batch of fatty amide propyl dimethyl betaine are measured as shown in Tables 9-10.

[0176] Table 9

[0177]

[0178]

[0179] Table 10

[0180]

[0181] Example 6

[0182] This embodiment provides a rapid detection method for free amines in fatty amide propyl dimethyl betaine, which differs from Example 1 only in that: sample A is replaced with sample F, the column flow rate is 0.4 mL / min, and the repeatability data of the free amine residues in the same batch of fatty amide propyl dimethyl betaine are measured as shown in Tables 11-12.

[0183] Table 11

[0184]

[0185] Table 12

[0186]

[0187]

[0188] Example 7

[0189] This embodiment provides a rapid detection method for free amines in fatty amide propyl dimethyl betaine, which differs from Example 1 only in that: sample A is replaced with sample G, the column flow rate is 1.2 mL / min, and the repeatability data of the free amine residues in the same batch of fatty amide propyl dimethyl betaine are measured as shown in Tables 13-14.

[0190] Table 13

[0191]

[0192] Table 14

[0193]

[0194]

[0195] Example 8

[0196] This embodiment provides a rapid detection method for free amines in fatty amide propyl dimethyl betaine, which differs from Example 1 only in that sample A is replaced with sample H, the column flow rate is 1.5 mL / min, and the repeatability data of the free amine residues in the same batch of fatty amide propyl dimethyl betaine are measured as shown in Tables 15-16.

[0197] Table 15

[0198]

[0199]

[0200] Table 16

[0201]

[0202]

[0203] Example 9

[0204] This embodiment provides a rapid detection method for free amines in fatty amide propyl dimethyl betaine, which differs from embodiment 1 only in that sample A is replaced with sample I, and the column box program is:

[0205]

[0206] The repeatability data of free amine residue in the same batch of fatty amide propyl dimethyl betaine are shown in Tables 17-18.

[0207] Table 17

[0208]

[0209] Table 18

[0210]

[0211]

[0212] Example 10

[0213] This embodiment provides a rapid detection method for free amines in fatty amide propyl dimethyl betaine, which differs from embodiment 1 only in that sample A is replaced with sample J, and the column box program is:

[0214]

[0215] The repeatability data of free amine residue in the same batch of fatty amide propyl dimethyl betaine are shown in Tables 19-20.

[0216] Table 19

[0217]

[0218] Table 20

[0219]

[0220]

[0221] Embodiment 11

[0222] The detection limit was determined according to the standard curve y=2.9384x-0.5874 corresponding to the octanamidopropyl dimethyl tertiary amine measured in Example 1, specifically using the noise method, and the concentration of the detection limit corresponding to the three times noise was 0.0008%.

[0223] Comparative Example 1

[0224] The difference between this comparative example and Example 1 is that:

[0225] Step (2): Preparation of test solution:

[0226] Weigh 1.0g of sample A (accurate to 0.0001g) in a beaker using the reduction method, add 5mL of sodium chloride solution and 1mL of sodium hydroxide solution, stir to dissolve, and dilute to a 25mL volumetric flask with water. Since the main components of the sample include fatty amide propyl dimethyl betaine and residual free amines, free fatty acids, chloroacetic acid and its by-products, the composition is complex and chromatographic separation is difficult. At the same time, the addition of sodium chloride and sodium hydroxide to the test solution also has a certain impact on the chromatographic test, so the free amine content in fatty amide propyl dimethyl betaine cannot be measured.

[0227] Comparative Example 2

[0228] This comparative example adopts the method of detecting free amine in fatty amide propyl dimethyl betaine according to the standard "Fatty Acid Amidopropyl Dimethyl Betaine" QB / T 4082-2010 5.3, which is as follows:

[0229] Weigh 10g-15g of sample J (accurate to 0.001g) in a beaker using the reduction method, add 10mL of water, 15mL of sodium chloride solution and 2 drops of phenolphthalein indicator solution, shake well and neutralize with sodium hydroxide solution until the solution turns pink, then add 1mL of sodium hydroxide solution in excess. Place the beaker in a water bath and heat to 35℃-40℃, stir evenly to make it fully react, then transfer to a separatory funnel, and rinse the beaker with 20mL of water and 30mL, respectively, and add the rinse solution into the separatory funnel. Put the stopper on and shake vigorously for at least 1 minute. After standing and stratifying, put the lower aqueous phase into another separatory funnel, add 30mL of ether-n-butanol mixed solution (volume ratio is 2:1), repeat the extraction twice, collect the upper liquid of the three extractions and put it into the same separatory funnel, let it stand for 30 minutes, discard the lower aqueous phase, and pour the upper extract into a dry volumetric flask (be careful to prevent water droplets from entering the volumetric flask), and rinse the separatory funnel with a small amount of ether, add the rinse liquid into the volumetric flask, dilute to the mark with ether, shake well and set aside. Use a pipette to transfer 20.0mL of the above extract into a 250mL beaker, place it in a water bath to heat and drive out the solvent, and blow it dry with nitrogen or compressed air, add 5mL of anhydrous ethanol to the residue, and heat and blow it dry again. Add 100 mL of ethanol solution to the beaker and place it on an electromagnetic stirrer for stirring. Then perform potentiometric titration with a standard hydrochloric acid titration solution (hydrochloric acid concentration is 0.05 mol / L) and draw a titration curve. The maximum jump point of the potential value between pH 6-7 is the titration end point. Record the volume of the consumed hydrochloric acid standard titration solution. At the same time, perform a blank test and record the volume of the consumed hydrochloric acid standard titration solution.

[0230] This method can only detect the total free amine content in fatty amide propyl dimethyl betaine, but cannot distinguish the specific free amine type. The repeatability data of free amine residues in the same batch of fatty amide propyl dimethyl betaine are shown in Table 21-22.

[0231] Table 21

[0232]

[0233] Table 22

[0234]

[0235] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0236] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for detecting the free amine content in fatty amide propyl dimethyl betaine, characterized in that: The following steps are involved: The free amine in the fatty amide propyl dimethyl betaine is extracted with ethyl acetate, and the obtained oil phase is the test solution. The test solution is subjected to gas chromatography analysis to measure the content of the free amine in the test solution.

2. The detection method according to claim 1, characterized in that: The detection method further comprises: Dissolve the free amine in ethyl acetate to prepare free amine standard solutions of different concentrations; Ethyl acetate was used to extract the free amine in fatty amide propyl dimethyl betaine, and the obtained oil phase was the test solution; Perform gas chromatography analysis on free amine standard solutions of different concentrations, and obtain a standard curve based on the test results; Performing gas chromatography analysis on the solution to be tested, and obtaining the free amine content in fatty amide propyl dimethyl betaine according to the test results and the standard curve; Wherein, the gas chromatography analysis conditions are: The chromatographic column is a medium polarity capillary column; The injection port temperature is 200-350°C; Detector temperature is 280-330°C; The column temperature was programmed to rise from 150-250°C for 0-5 min, then to 280-350°C for 1-30 min. The injection volume is 0.1-2 μL; Column flow rate is 0.4-1.5mL / min; The carrier gas is nitrogen, hydrogen or helium.

3. The detection method according to claim 1, characterized in that: The free amines include C8-C 18 At least one of fatty amide propyl dimethyl tertiary amine.

4. The detection method according to claim 1, characterized in that: The free amine includes at least one of octylamidopropyl dimethyl tertiary amine, caprylamidopropyl dimethyl tertiary amine, laurylamidopropyl dimethyl tertiary amine, myristicamidopropyl dimethyl tertiary amine, hexadecylamidopropyl dimethyl tertiary amine, and octadecylamidopropyl dimethyl tertiary amine.

5. The detection method according to claim 1, characterized in that: The mass volume ratio of the fatty amide propyl dimethyl betaine to ethyl acetate is (0.01-0.5) g:1 mL.

6. The detection method according to claim 1, characterized in that: The detection method further comprises: mixing the fatty amide propyl dimethyl betaine with a sodium chloride solution and a sodium hydroxide solution, and mixing the obtained mixed solution with ethyl acetate for extraction treatment.

7. The detection method according to claim 1, characterized in that: The stationary phase of the medium polar capillary chromatographic column is 5% phenyl-95% methyl polysiloxane.

8. The detection method according to claim 1, characterized in that: The chromatographic column comprises at least one of DB-5HT 20m×0.18mm×0.18μm and DB-5 30m×0.25mm×0.25μm.

9. The detection method according to claim 1, characterized in that: In the programmed temperature rise of the chromatographic column, the heating rate is 5-25°C / min.

10. The detection method according to claim 1, characterized in that: The gas chromatography analysis conditions include an injection split ratio of (5-20):1.

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