A rapid detection method for butyric acid and its isomers in baijiu

Abstract

The application discloses a method for rapidly detecting butyric acid and isomers thereof in liquor, which does not need any pretreatment process and a large amount of organic solvents, directly takes 0.5-3ml of a liquor sample and adds the sample into a sample bottle of a rapid gas chromatography-PTR photochemical ionization source-time of flight mass spectrometer, selects appropriate rapid gas chromatography mass spectrometry conditions, and utilizes the rapid gas chromatography-PTR photochemical ionization source-time of flight mass spectrometer to rapidly complete detection of butyric acid and isomers thereof in the liquor. The method established by the application does not need any pretreatment process and a large amount of organic solvents, can rapidly detect butyric acid and isomers thereof in the liquor within five minutes, and provides a strong means for acidity and taste adjustment of the liquor.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of analytical chemistry instruments, and particularly relates to a rapid detection method of butyric acid and its isomers in liquor. BACKGROUND

[0002] Butyric acid is a colorless transparent liquid with certain irritating odor and taste. It is an organic acid commonly used in food, medicine, cosmetics and industrial fields. In the light-flavor liquor, the role of butyric acid is to increase the acidity and taste of the liquor. Under normal circumstances, the acidity of the light-flavor liquor is usually between 0.2% and 0.5%, and butyric acid can keep the acidity within the appropriate range and improve the taste of the liquor. Butyric acid is an important acidity regulator. In the light-flavor liquor, it can control the acidity of the liquor, adjust the taste of the liquor, improve the balance and smoothness of the taste, make the liquor more lubricating, and make the entry feeling more comfortable. Butyric acid is usually detected by GC-MS, but in actual regulation, because the liquor contains various complex organic and inorganic substrates, including alcohol, acid, ester, aldehyde, ketone, furan, pyrazine, aromatic and phenol, etc., it is necessary to carry out pretreatment such as purification and enrichment, and the complex pretreatment takes a long time and affects the repeatability of the quantitative results. Therefore, it is necessary to develop a high-sensitivity, rapid and efficient detection method for the detection of butyric acid and its isomers.

[0003] Soft ionization mass spectrometry can obtain the molecular ion or quasi-molecular ion of the analyte, has the advantages of simple spectrum and easy analysis, and can realize rapid analysis of complex gas without or only with simple sample pretreatment. The core of soft ionization mass spectrometry is a soft ionization source. The mainstream soft ionization sources are high-pressure photoionization (HPPI) and proton transfer reaction ionization (PTRCI). The working pressure (102Pa) of the two is higher than that of the EI source (10-3Pa) used in GC-MS, and has a higher source molecular density, and the detection sensitivity can reach ppt-ppb level. Among them, HPPI is suitable for the analysis of aromatic, furan, pyrazine, phenol and other compounds with high photoionization cross section, and PTRCI has good ionization effect on alcohol, acid, aldehyde, ketone, ester and other compounds with high proton affinity.

[0004] In view of this, the present application discloses a rapid detection method of butyric acid and its isomers in liquor. The method does not need pretreatment process, directly takes a certain amount of liquor sample into a sample bottle, and uses rapid gas chromatography-PTR photochemical ionization source-time-of-flight mass spectrometry to quickly complete the detection of butyric acid and its isomers in liquor. The butyric acid isomers are not limited to isobutyric acid, isoamyl alcohol, ethyl acetate, 3-hydroxy-2-butanone, etc., which provides a powerful means for the acidity and taste adjustment of liquor. SUMMARY

[0005] In view of the problems existing in the prior art, the present application provides a rapid detection method for butyric acid and its isomers in liquor, which utilizes rapid gas chromatography-PTR photochemical ionization source-time of flight mass spectrometry, sets appropriate detection conditions, and completes the detection of butyric acid and its isomers in liquor within five minutes. The rapid detection method for butyric acid and its isomers in liquor of the present application does not require any pretreatment process and a large amount of organic solvent, directly takes a certain amount of liquor sample into a sample bottle, selects appropriate rapid gas chromatography mass spectrometry conditions, utilizes rapid gas chromatography-PTR photochemical ionization source-time of flight mass spectrometry, and completes the detection of butyric acid and its isomers in liquor within five minutes. The butyric acid isomers are not limited to isobutyric acid, acetic acid, isoamyl alcohol, ethyl acetate, 3-hydroxy-2-butanone, acetaldehyde, etc., and provide a powerful means for the acidity and taste adjustment of liquor.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A rapid detection method for butyric acid and its isomers in liquor directly takes 0.5-3ml of liquor sample into a sample bottle of rapid gas chromatography-PTR photochemical ionization source-time of flight mass spectrometer, selects appropriate detection conditions, utilizes rapid gas chromatography-PTR photochemical ionization source-time of flight mass spectrometry, and completes the detection of butyric acid and its isomers in liquor.

[0008] When the rapid gas chromatography-PTR photochemical ionization source-time of flight mass spectrometer is used for testing, the rapid gas chromatography injection port temperature is 150-240℃, the carrier gas is high-purity helium (He), the flow rate is 0.8-5mL / min, the split ratio is 10:1, the polar chromatographic column is a DB-WAX chromatographic column, the rapid gas chromatography adopts a rapid programmed temperature rising mode, the temperature rising program is that the initial temperature is 100-140℃, and the temperature is maintained for 0.5-2.5min, then the temperature is raised to 140-200℃ at a rate of 10-30℃ / min, and the temperature is maintained for 0.2-5min. The headspace sampling device equilibrium temperature is 40-80℃; the sampling needle temperature is 60-100℃, the cleaning time is 0.5-1.0min; the quantitative ring temperature is 80-150℃, the volume is 1-5mL, the injection time is 0.3-1.0min, the equilibrium time is 0.01-0.1min; the transmission pipe temperature is 80-180℃; the PTR photochemical ionization source-time of flight mass spectrometer conditions are that the proton transfer reaction photochemical ionization source is used, the vacuum ultraviolet lamp voltage is 1000-2000V, the high-purity helium water bubbling flow rate is 50-200mL / min, the ionization zone gas pressure is 2.0x10 2 ~ 5.00x10 2 Pa, the ion source temperature is 150-180℃, the MCP voltage is 3700-4800V, and the detection zone gas pressure is 7.00x10 -6 ~ 3.00x10-4 Pa;

[0009] Qualitative analysis of butyric acid and its isomers: the characteristic peaks and mass numbers of each component in the detected liquor sample are compared with those of the standard sample to determine butyric acid and its isomers in the liquor sample.

[0010] The isomers of butyric acid include, but are not limited to, isobutyric acid, acetic acid, isoamyl alcohol, ethyl acetate, 3-hydroxy-2-butanone, acetaldehyde, etc.

[0011] The rapid PTR photochemical ionization source-time of flight mass spectrometer used includes a headspace sampling device, a photoelectron-induced H3O + reagent ion chemical ionization source, ion transmission system and time of flight mass analyzer.

[0012] Compared with the prior art, the advantages of the present application are that: the detection method provided by the present application does not require any pretreatment process and a large amount of organic solvent, a certain amount of liquor sample is directly taken into a sampling bottle, specific rapid gas chromatography-mass spectrometry conditions are selected, and rapid gas chromatography-PTR photochemical ionization source-time of flight mass spectrometry is used for detection of butyric acid and its isomers in liquor. The method established by the present application can rapidly detect butyric acid and its isomers in liquor within five minutes, and provides a powerful means for acidity and taste adjustment of liquor. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 . Butyric acid and its isomer ion flow change tracking diagram. DETAILED DESCRIPTION

[0014] Example 1

[0015] The rapid gas chromatography-PTR photochemical ionization source-time of flight mass spectrometer is used for testing, the rapid gas chromatography adopts a rapid temperature programming mode, the polar chromatographic column DB-WAX chromatographic column (30m x 0.53mm x 0.1um) temperature programming is 100℃ initial temperature, 1min holding, then 10℃ / min to 200℃, 2min holding. The injection port temperature is 150-240℃, the carrier gas is high-purity helium (He), the flow rate is 3mL / min, and the split ratio is 10:1.

[0016] The PTR photochemical ionization source-time of flight mass spectrometer conditions are proton transfer reaction photochemical ionization source, vacuum ultraviolet lamp voltage is 1400V, high-purity helium water bubble flow is 50mL / min, ionization zone gas pressure is 3.00x10 2 Pa, ion source temperature is 160℃, MCP voltage is 4300V, detection zone gas pressure is 7.00x10 -5 Pa;

[0017] Directly take 1ml baijiu sample to be tested and place it in the sample bottle of the fast gas chromatography-PTR photochemical ionization source-time of flight mass spectrometer. After sampling, the butyric acid and its isomers in the baijiu sample to be tested are detected by the fast gas chromatography-PTR photochemical ionization source-time of flight mass spectrometer. The ion flow change tracking diagram of butyric acid and its isomers in baijiu is shown as Figure 1 , wherein, 1 # is butyric acid, 2 # is isobutyric acid, 3 is acetic acid, 4 # is 3-hydroxy-2-butanone, 5 # is isoamyl alcohol, 6 # is ethyl acetate, 7 # is acetaldehyde; the mass number of butyric acid and its isomers in baijiu is shown in Table 1. According to the standard qualitative analysis, the corresponding components are butyric acid, isobutyric acid, acetic acid, isoamyl alcohol, ethyl acetate, 3-hydroxy-2-butanone and acetaldehyde.

[0018] Table 1 Mass number corresponding to butyric acid and its isomers tested by fast gas chromatography-PTR photochemical ionization time of flight mass spectrometer

[0019] Serial number Component name Characteristic peak Mass number 1 Butyric acid 13 C-C3H8O2)H + ]]> ​ 90.064 2 Isobutyric acid 13 C-C3H8O2)H + ]]> ​ 90.064 3 Acetic acid (C2H4O2)NO + ]] 90.019 4 3-hydroxy-2-butanone 13 C-C3H8O2)H + ]]> ​ 90.064 5 Isopentanol <![CDATA[( 13 C-C4H 12 O)H + ]]> 90.100 6 Ethyl acetate 13 C-C3H8O2)H + ]]> ​ 90.064 7 Acetaldehyde 13 C-CH4O·C2H4O)H + ]]> ​ 90.064

Claims

1. A rapid detection method for butyric acid and its isomers in baijiu (Chinese liquor), characterized in that, Add 0.5-3 ml of baijiu sample directly to the injection vial of the rapid gas chromatography-PTR photochemical ionization source-time-of-flight mass spectrometer. Select appropriate detection conditions and use rapid gas chromatography-PTR photochemical ionization source-time-of-flight mass spectrometry to detect butyric acid and its isomers in baijiu. The specific detection method is as follows: (1) Detection conditions: The test was performed using a rapid gas chromatography-PTR photochemical ionization source-time-of-flight mass spectrometer. The rapid gas chromatography was performed in rapid temperature program mode. The polar chromatographic column was a DB-WAX column. The temperature program was as follows: initial temperature 100-140℃, hold for 0.5-2.5 min, then increase to 140-200℃ at 10-30℃ / min and hold for 0.2-5.0 min. The PTR photochemical ionization source-time-of-flight mass spectrometer conditions are as follows: proton transfer reaction photochemical ionization source, vacuum UV lamp voltage of 1000–2000 V, high-purity helium-water bubbling flow rate of 50–200 mL / min, and ionization region pressure of 2.0 × 10⁻⁶. 2 ~5.00×10 2 Pa, ion source temperature 150–180℃, MCP voltage 3700–4800V, detection zone gas pressure 7.00 × 10⁻⁶. -6 ~3.00×10 -4 Pa; (2) Qualitative analysis of butyric acid and its isomers: The characteristic peaks and mass numbers of each component in the detected liquor sample are compared with the characteristic peaks and mass numbers of the standard to determine the butyric acid and its isomers in the liquor sample.

2. The rapid detection method for butyric acid and its isomers in baijiu according to claim 1, characterized in that: Isomers of butyric acid include isobutyric acid, ethyl acetate, 3-hydroxy-2-butanone, and acetaldehyde.

3. The rapid detection method for butyric acid and its isomers in baijiu according to claim 1, characterized in that: In step (1), the injection port temperature of the rapid gas chromatograph is 150-240℃, the carrier gas is high-purity helium (He), the flow rate is 0.8-5 mL / min, and the split ratio is 10:

1.

4. The rapid detection method for butyric acid and its isomers in baijiu according to claim 1, characterized in that: The fast PTR photochemical ionization source-time-of-flight mass spectrometer used includes a headspace sampler and a photoelectron-induced H3O sampler. + Reagent ion chemical ionization source, ion transport system and time-of-flight mass analyzer.

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