Application of quantitative nuclear magnetic resonance method for determining purity of synthetic flavor

Abstract

The application belongs to the technical field of synthetic flavor quality control, and particularly relates to application of quantitative nuclear magnetic resonance method in determination of purity of synthetic flavor. The purity of five synthetic flavors, including malic acid, ascorbic acid, lactic acid, L-valine and L-proline, is detected by the quantitative nuclear magnetic resonance method. The purity of the synthetic flavor is detected by the quantitative nuclear magnetic resonance method, and no special standard product is needed. The method is simple, efficient, accurate, stable, and good in universality, and can provide reliable technical support for quality control of cigarette raw materials, flavor blending and quality control of tobacco industrialization.

Description

Technical Field

[0001] This invention belongs to the field of synthetic fragrance quality control technology, specifically involving the application of quantitative nuclear magnetic resonance method for determining the purity of synthetic fragrances. Background Technology

[0002] The purity of synthetic fragrances directly determines the aroma quality, safety, and compliance level of the fragrance, making it a core testing indicator for fragrance quality control. Currently, national and industry standards for testing the purity of synthetic fragrances employ chromatographic normalization, which results in cumbersome work due to the "one method per product" approach and a lack of more universal testing methods.

[0003] Synthetic fragrances are chemically very similar to pharmaceutical raw materials in terms of structure and properties. Therefore, the purity identification methods used in pharmaceutical raw materials are of great reference value to synthetic fragrances. Quantitative nuclear magnetic resonance (qNMR) technology is based on the principle that the area of ​​the NMR spectrum signal is proportional to the number of excited atoms in the sample. It can calculate the corresponding number of excited atoms without introducing correction factors, thus achieving quantitative analysis and eliminating the need for drug-specific standards. Currently, the legal status of qNMR is clearly defined in the 2020 edition of the Pharmacopoeia of the People's Republic of China, Volume IV, the United States Pharmacopeia 40th edition, the European Pharmacopoeia 9.0 edition, and the Japanese Pharmacopoeia 17th edition, and its application in drug research is becoming increasingly widespread. Zhao Hengjun et al., based on the principle of qNMR, established a qNMR method for dichloromethane in industrial wastewater, achieving the same quantitative results as the standard method. Ruslan et al. ingeniously utilized the residual CHCl3 signal in deuterated chloroform, the cheapest NMR solvent, as a quantitative internal standard to establish a quantitative method for the purity of chemical drugs in organic synthesis laboratories, achieving ideal results in terms of linearity, lower limit of quantitation, and reproducibility. Some scholars have also conducted sporadic research on the quantification of fragrances using quantitative nuclear magnetic resonance (qNMR). Xian Yunxia, ​​Wang Zhaoping, and others optimized and established an absolute quantitative method for raspberry ketone and ethyl maltol using DMSO as solvent and benzoic acid as an internal standard. A comparison with the HPLC normalization method showed that the qNMR method was slightly slower than the HPLC method, and that the qNMR method eliminated moisture interference, thus better reflecting the true purity of the sample. Zhang Shaofeng et al., to reduce the cumbersome purity determination procedures of the mass balance method, investigated and compared the feasibility of the mass balance method (MBA) and quantitative nuclear magnetic resonance (qNMR) in the purity determination of n-propyl acetate, using n-propyl acetate as an example, laying a technical foundation for the development of national first-class standard materials for ester-based tobacco additives. In December 2022, the International Organization for Standardization (ISO) issued and implemented ISO 24583-2022, officially recognizing the qNMR method as the official method for purity testing.

[0004] The mainstream detection methods for synthetic fragrances currently available are gas chromatography (GC) and high-performance liquid chromatography (HPLC). These methods offer high sensitivity and good separation, but they also have significant drawbacks: First, simultaneous detection of multiple components requires optimization of complex chromatographic gradient programs, resulting in long detection cycles. Second, they rely on individual fragrance monomer standards, and high-purity standards for niche fragrances are scarce and costly to procure. Third, they cannot accurately identify isomers and structurally similar impurities, which can easily lead to deviations in purity detection results. Fourth, the efficiency of batch sample detection is low, making it difficult to meet the needs of large-scale fragrance sample screening and value determination.

[0005] There are currently no reports on the use of quantitative nuclear magnetic resonance (qNMR) for the determination of purity in synthetic fragrances. Summary of the Invention

[0006] The purpose of this invention is to provide an application of quantitative nuclear magnetic resonance method for determining the purity of synthetic fragrances, in order to overcome the shortcomings of existing detection methods.

[0007] To achieve the above objectives, this application employs the following technical solution:

[0008] The application of quantitative nuclear magnetic resonance (NMR) method for determining the purity of synthetic fragrances: The purity of five synthetic fragrances, namely malic acid, ascorbic acid, lactic acid, L-valine and L-proline, was determined by quantitative NMR method.

[0009] Furthermore, 1,3,5-trimethoxybenzene was used as an internal standard for the three synthetic fragrances malic acid, ascorbic acid, and lactic acid, while acrylic acid was used as an internal standard for L-valine and L-proline.

[0010] Furthermore, the solvent used in the test was DMSO-d6.

[0011] Furthermore, the parameters for quantitative nuclear magnetic resonance (NMR) were as follows: relaxation delay time: 20.00 s; pulse sequence: zg30; sampling time: 4.00 s; number of samplings: 16 t; test temperature: 300 K.

[0012] Furthermore, the data obtained from nuclear magnetic resonance spectroscopy were analyzed and calculated, whereby the purity Pt of the sample was calculated using the following formula:

[0013] Pt=It×Ns×Mt×ms×Ps / Is×Nt×Ms×mt,

[0014] Where: Pt—purity of the target substance in the sample, %; Ps—purity of the internal standard, %; It—integral value of hydrogen atoms used for quantification in the target molecule of the sample; Is—integral value of hydrogen atoms used for quantification in the internal standard molecule; Nt—number of hydrogen atoms used for quantification in the target molecule of the sample; Ns—number of hydrogen atoms used for quantification in the internal standard molecule; Mt—molar mass of the target molecule of the sample, in grams per mole; Ms—molar mass of the internal standard molecule, in grams per mole; ms—mass of the sample, in milligrams; mt—mass of the internal standard, in milligrams.

[0015] Furthermore, this includes comparing the results of quantitative nuclear magnetic resonance purity testing of five synthetic fragrances with the results of existing national standard methods.

[0016] The beneficial effects of this invention are:

[0017] This invention uses quantitative nuclear magnetic resonance (NMR) to detect the purity of synthetic flavorings. It does not require specialized standards and is simple, efficient, accurate, stable, and versatile. This provides reliable technical support for quality control of cigarette raw materials, flavoring formulation, and industrial-scale quality management in the tobacco industry. Attached Figure Description

[0018] Figure 1a A schematic diagram of the quantitative atomic structure of malic acid;

[0019] Figure 1b The original spectrum of malic acid;

[0020] Figure 1c The superimposed spectra of six malic acid samples;

[0021] Figure 2a This is a schematic diagram of the quantitative atomic structure of ascorbic acid;

[0022] Figure 2b Ascorbic acid spectrum;

[0023] Figure 3a This is a schematic diagram of the quantitative atomic structure of lactic acid;

[0024] Figure 3b This is the original spectrum of lactic acid;

[0025] Figure 3c The image shows the overlay of the spectra of seven lactic acid samples.

[0026] Figure 4a A schematic diagram of the quantitative atomic structure of L-valine;

[0027] Figure 4b The original spectrum of L-valine;

[0028] Figure 4c This is a superimposed spectrum of five L-valine samples;

[0029] Figure 5a Schematic diagram of the quantitative atomic structure of L-proline;

[0030] Figure 5b The original spectrum of L-proline;

[0031] Figure 5c This is a superimposed spectrum of five L-proline samples. Detailed Implementation

[0032] The technical solutions of the present invention will be described in detail below through embodiments. The following embodiments are merely exemplary and can only be used to explain and illustrate the technical solutions of the present invention, and should not be construed as limiting the technical solutions of the present invention.

[0033] In the various embodiments of this application, unless otherwise specified, the technology or conditions are based on the prior art or conditions. The materials or equipment used, unless otherwise specified, are all conventional products that can be purchased.

[0034] Unless otherwise stated, in this invention, the percentage sign refers to volume percentage, and the ratio refers to volume ratio.

[0035] Example 1

[0036] This embodiment mainly utilizes existing national standard methods to detect the purity of six synthetic fragrances, which are briefly described below.

[0037] Six samples of malic acid were tested for purity according to the national standard method GB 1886.40—2025.

[0038] One sample of ascorbic acid was tested for purity according to the national standard method GB 14754—2010;

[0039] Seven lactic acid samples were tested for purity according to the national standard method GB 1886.173—2016;

[0040] Five samples each of L-valine and L-proline were tested for purity according to the national standard GB 29938-2020, General Rules for Food Flavorings.

[0041] The specific test results are shown in Table 1.

[0042] Table 1. Results of testing 24 samples of 5 synthetic fragrances using national standard methods.

[0043]

[0044] Example 2

[0045] This embodiment mainly describes the process of quantitative nuclear magnetic resonance (NMR) detection of the purity of synthetic fragrances, which is briefly introduced below.

[0046] The purity of malic acid in six samples was determined using quantitative nuclear magnetic resonance (NMR).

[0047] Weigh 10 mg - 30 mg (accurate to 0.01 mg) of sample and 10 mg - 30 mg (accurate to 0.01 mg) of internal standard 1,3,5-trimethoxybenzene using an analytical balance. Place them in a chromatographic vial, add 0.5 - 0.6 mL of DMSO-d6, tighten the cap and seal the vial. Shake the solution well to ensure complete dissolution (there should be no insoluble matter or air bubbles). Then transfer the solution to an NMR tube and perform analysis.

[0048] The parameters are as follows: relaxation delay time: 20.00 s; pulse sequence: zg 30; sampling time: 4.00 s; number of samples: 16 t; test temperature: 300 K.

[0049] Data obtained from nuclear magnetic resonance spectroscopy analysis were used for calculations. The purity Pt of the sample was calculated using the following formula.

[0050] Pt=It×Ns×Mt×ms×Ps / Is×Nt×Ms×mt,

[0051] Where: Pt—purity of the target substance in the sample, %; Ps—purity of the internal standard, %; It—integral value of hydrogen atoms used for quantification in the target molecule of the sample; Is—integral value of hydrogen atoms used for quantification in the internal standard molecule; Nt—number of hydrogen atoms used for quantification in the target molecule of the sample; Ns—number of hydrogen atoms used for quantification in the internal standard molecule; Mt—molar mass of the target molecule of the sample, in grams per mole (g / mol); Ms—molar mass of the internal standard molecule, in grams per mole (g / mol); ms—mass of the sample, in milligrams (mg); mt—mass of the internal standard, in milligrams (mg).

[0052] The final result is the arithmetic mean of two parallel measurements, rounded to one decimal place. The relative standard error of the parallel measurements should be less than 1%.

[0053] The results of quantitative nuclear magnetic resonance detection of malic acid in 6 samples are shown in the following spectral images. Figures 1a to 1c As shown.

[0054] Example 3

[0055] Using the method described in Example 2, the purity of one ascorbic acid sample and seven lactic acid samples was determined (results are shown below). Figure 2a , Figure 2b , Figure 3a , Figure 3b , Figure 3c (As shown).

[0056] Example 4

[0057] The purity of five samples each of L-valine and L-proline was determined using quantitative nuclear magnetic resonance (NMR).

[0058] Weigh 10 mg - 30 mg (accurate to 0.01 mg) of sample and 10 mg - 30 mg (accurate to 0.01 mg) of internal standard acrylic acid using an analytical balance. Place them in a chromatographic vial, add 0.5 - 0.6 mL of DMSO-d6, tighten the cap and seal the vial. Shake the solution well to ensure complete dissolution (there should be no insoluble matter or air bubbles). Then transfer the solution to an NMR tube and perform analysis.

[0059] The instrument parameters were selected in the same manner as in Example 2, and the detection results are as follows: Figure 4a , Figure 4b , Figure 4c , Figure 5a , Figure 5b , Figure 5c As shown.

[0060] Example 5

[0061] The results of quantitative nuclear magnetic resonance (NMR) testing of the purity of five synthetic fragrances were compared with those obtained using the national standard method. Except for lactic acid, the results for the other four synthetic fragrances were largely consistent between the two methods. The trend for lactic acid was also relatively consistent. This may be because: firstly, lactic acid reagents with a concentration of 60% or higher are highly hygroscopic, and moisture absorption during weighing and use can lead to inaccurate measurements; secondly, the acid-base volumetric titration method accurately detects the content of high-purity lactic acid reagent, allowing for the introduction of organic and inorganic acids during lactic acid processing and purification, whose hydrogen ions may react chemically with the titrant sodium hydroxide, as shown in Table 2.

[0062] Table 2. Comparison of detection results of 24 samples of 5 synthetic fragrances using two methods.

[0063]

[0064] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. An application of quantitative nuclear magnetic resonance (NMR) method for determining the purity of synthetic fragrances, characterized in that, The purity of five synthetic flavorings—malic acid, ascorbic acid, lactic acid, L-valine, and L-proline—was determined by quantitative nuclear magnetic resonance (NMR).

2. The application of the quantitative nuclear magnetic resonance method for determining the purity of synthetic fragrances according to claim 1, characterized in that, 1,3,5-trimethoxybenzene was used as an internal standard for the three synthetic fragrances malic acid, ascorbic acid and lactic acid, while acrylic acid was used as an internal standard for L-valine and L-proline.

3. The application of the quantitative nuclear magnetic resonance method for determining the purity of synthetic fragrances according to claim 2, characterized in that, The solvent used in the test was DMSO-d6.

4. The application of the quantitative nuclear magnetic resonance method for determining the purity of synthetic fragrances according to claim 1, characterized in that, The parameters for quantitative nuclear magnetic resonance (NMR) were as follows: relaxation delay time: 20.00 s; pulse sequence: zg 30; sampling time: 4.00 s; number of samplings: 16 t; test temperature: 300 K.

5. The application of the quantitative nuclear magnetic resonance method for determining the purity of synthetic fragrances according to claim 4, characterized in that, Data obtained from nuclear magnetic resonance spectroscopy analysis were used for calculations, where the sample purity Pt was calculated using the following formula: Pt=It×Ns×Mt×ms×Ps / Is×Nt×Ms×mt, Where: Pt—purity of the target substance in the sample, %; Ps—purity of the internal standard, %; It—integral value of hydrogen atoms used for quantification in the target molecule of the sample; Is—integral value of hydrogen atoms used for quantification in the internal standard molecule; Nt—number of hydrogen atoms used for quantification in the target molecule of the sample; Ns—number of hydrogen atoms used for quantification in the internal standard molecule; Mt—molar mass of the target molecule of the sample, in grams per mole; Ms—molar mass of the internal standard molecule, in grams per mole; ms—mass of the sample, in milligrams; mt—mass of the internal standard, in milligrams.

6. The application of the quantitative nuclear magnetic resonance method for determining the purity of synthetic fragrances according to claim 1, characterized in that, This includes comparing the purity test results of five synthetic fragrances using quantitative nuclear magnetic resonance with the test results of existing national standard methods.

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