Method for rapidly detecting volatile organic components in white spirit in real time

Abstract

The invention discloses a real-time rapid detection method for volatile organic components of white spirit based on combination of dynamic headspace purging and a high-resolution time-of-flight chemical ionization mass spectrometer, and belongs to the technical field of analysis and detection. The method specifically comprises the following steps: carrying out volatile organic components in air above a closed purging bottle filled with white spirit by using carrier gas, diluting the volatile organic components, and performing in-situ ionization and real-time determination on the diluted volatile organic components in a high-resolution flight time chemical ionization mass spectrometer to obtain a component spectrum of the volatile organic components in the white spirit; the quantitative detection of second-level time resolution of the volatile organic components in the white spirit is realized by combining a quantitative model constructed by mass transfer efficiency correction, reaction rate constants and the like. According to the method, the original white spirit sample (1-3mL) is directly analyzed, pretreatment is not needed, and sample loss caused by extraction and concentration in a traditional method is avoided; the adopted quantitative model solves the problem of high-resolution mass spectrum quantification faced by white spirit sample analysis. The method is resistant to water vapor and high-concentration ethanol (gt); the method can be used for rapidly identifying more than 71 volatile organic components (such as ethyl acetate and furfural), and is suitable for white spirit quality control, authenticity identification and flavor database construction.

Description

Technical Field

[0001] The present invention belongs to the field of analysis and relates to a detection method, specifically a method for real-time rapid analysis of dozens of volatile organic compounds in liquor. The method does not require pre-treatment and can simultaneously quantitatively detect more than 70 volatile organic components such as alcohols, acids, esters (ethyl acetate, ethyl butyrate), aldehydes (furfural), ketones (acetylacetone), ethers, etc., to achieve real-time rapid detection of volatile organic components in liquor. Background Art

[0002] The content of volatile organic components in liquor is very rich, mainly oxygen-containing organic compounds, including alcohols, aldehydes, ketones, acids, esters, furans, etc., and they are important factors affecting the quality and flavor of liquor. The liquor industry urgently needs a fast, highly sensitive, and anti-interference online detection method to solve the stability problems of different batches of liquor and support the construction of flavor databases. Existing technologies such as electronic tongue / nose, liquid chromatography-mass spectrometry (LC-MS), and gas chromatography-mass spectrometry (GC-MS) can be used for non-volatile component detection, but their applicability to volatile components is limited. Electronic tongue / nose has low species resolution for volatile components in complex systems. GC-MS or LC-MS is the mainstream detection technology for volatile organic components in liquor, but it needs to be combined with pre-treatment technologies such as sample separation. At present, separation technologies mainly include liquid-liquid extraction, distillation extraction, supercritical fluid extraction, solid phase microextraction, static headspace and dynamic headspace sampling. Existing studies have used stir bar adsorption extraction (CN 101762658 A) and headspace-solid phase microextraction (CN 113237977 A) combined with GC-MS to qualitatively and quantitatively analyze the characteristics of volatile components in liquor. However, this type of method has the disadvantages of complex sample pretreatment process, long processing time, serious loss of some species, low sensitivity and inconvenience in online detection; the non-polar or polar chromatographic columns used in GC-MS or LC-MS methods have selectivity problems for volatile components in liquor, and it is difficult to achieve simultaneous measurement of all volatile components of liquor, and there are complex qualitative and quantitative processes and low time resolution, which makes it impossible to achieve real-time online detection of volatile components in liquor. In addition, the high concentration of ethanol in liquor also limits the selection of pretreatment methods, chromatographic column types and detection methods. There are also studies that use vacuum ultraviolet photoionization mass spectrometry technology (CN 112946057 A) to achieve minute-level online detection of 10 volatile components in fermentation tanks, including gaseous acetic acid, n-propanol, isobutanol, benzaldehyde, ethyl lactate, and ethyl acetate. However, this technology is not sensitive enough to most volatile components in liquor, and the number of detectable components is limited.

[0003] In recent years, with the development of high-resolution chemical ionization time-of-flight mass spectrometry (LToF-CIMS), its mass resolution can reach 10,000, and its time resolution is 1s. The detection limit of trace organic volatile gases can reach ppt level (volume ratio), which can meet the real-time online detection requirements of trace volatile components. The present invention has developed an analytical technology based on dynamic headspace online purge-high-resolution time-of-flight chemical ionization mass spectrometry, which can realize the real-time online detection of more than 70 volatile components in liquor without pretreatment; it solves the problems of long equilibrium time required for traditional headspace sampling, low species and time resolution of traditional detection methods, and difficulty in multi-component quantification in complex matrices, and can be used for the identification of different liquor brands, the identification of liquor flavor substances, and the quality monitoring of liquor production process. Summary of the invention

[0004] In view of the above-mentioned technical problems existing in the existing technology for detecting volatile components in liquor, the purpose of the present invention is to provide a real-time and rapid online detection method for volatile components in liquor, which can simultaneously obtain the composition spectrum of volatile components in liquor and the real-time concentrations of multiple volatile components.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A method for real-time rapid detection of volatile organic components in liquor, characterized by:

[0007] It includes a dynamic headspace purge and dilution device, a proton transfer reaction time-of-flight mass spectrometer (H 3 O + -PTR-LToF-CIMS), high-resolution mass spectrometry analysis methods and quantitative analysis models;

[0008] The dynamic headspace purge and dilution device provides a test gas source for volatile organic components in liquor. The zero gas or high-purity nitrogen is divided into two by a tee. The A2 port of the tee is connected to the inlet of the purge bottle through a mass flow meter, and the A3 port of the tee is connected to the zero gas or high-purity nitrogen controlled by the mass flow meter to provide dilution gas. The outlet of the purge bottle and the outlet of the dilution gas mass flow meter are respectively connected to the B1 and B2 ports of the tee for mixing and dilution.

[0009] The purge bottle is a container for containing liquor and placed in a constant temperature water bath at 25°C, and has an inlet and an outlet on the top.

[0010] The diluted and mixed gas is directly connected to the inlet of the proton transfer time-of-flight mass spectrometer through the B3 port of the three-way, and the excess gas is automatically exhausted from the inlet of the mass spectrometer.

[0011] The gas sampling pipeline 6, pipeline 7 and pipeline 11 are all maintained at a temperature of 80 to 120°C (5).

[0012] The volatile organic components entering the entrance of the proton transfer time-of-flight mass spectrometer are mixed with water vapor charged by the ionization source in the ion molecular reactor (16) at a pressure of 2 mbar (controlled by the Ebara pump (24) and the pressure control valve (26)). After the proton transfer reaction is carried out and the components are charged, they enter the capillary column (17) and the large segmented quadrupole (BSQ) region in the Vocus in sequence. The charged ions are focused to form an ion beam under the action of the radial voltage and are accelerated under the action of the axial voltage. Then, they enter the ion lens (20) for fine adjustment of the spatial distribution of the ion beam. After passing through the flight region (the pressure is controlled by the molecular pump (23)), they finally reach the multi-channel electron multiplier (MCP) for detection. The data acquisition system converts the electrical signal into a numerical signal to obtain and record the mass spectrum. The mass spectrometry detection tail gas is directly discharged through the Ebara pump (27).

[0013] The mass scanning range of the proton transfer time-of-flight mass spectrometer was 1-500 Th, and the time resolution was set to 1 s.

[0014] Using H 3 O + -PTR-LToF-CIMS obtains mass spectrometry signals, and uses the ToFtool toolkit built on MATLAB to average all data to 1 min, and Gaussian normalizes the average mass spectrum peak shape in the range of 30-300Th to obtain the average peak shape within the mass-to-charge ratio range for high-resolution mass spectrometry fitting; then, the average mass spectrum distribution data is mass-corrected using single-peak species to obtain accurate mass spectrum mass distribution; based on the corrected mass spectrum mass distribution, the mass spectrum data in the range of 30-500Th with a mass-to-charge ratio of 30-500Th is fitted with unit mass resolution (UMR) based on the distribution of carbon, hydrogen and oxygen atoms with C12 as the standard mass to obtain UMR data; based on the UMR data, the mass resolution (Mass Resolution, MS) of the mass spectrum data in the range of 30-500Th with a mass-to-charge ratio is calibrated to obtain the optimal mass resolution distribution parameterization scheme within this range; based on the UMR data and MS results obtained above, the UMR data is subjected to high-quality resolution (High The high-mass resolution (HMR) spectrum was used to obtain the spectral library of volatile organic components in liquor. Based on the spectral library, the peaks of the characteristic volatile components of liquor measured in real time were fitted to obtain high-resolution data and real-time characteristics of the volatile components of liquor.

[0015] The mass transfer efficiency in the entire analytical test system is obtained using known compounds, and a curve of the relationship between the transfer efficiency and the mass-to-charge ratio is constructed. Further, a quantitative model such as formula (1) is established based on the detection signal, proton transfer reaction rate and pressure, thereby obtaining the concentration characteristics of the volatile components of liquor.

[0016]

[0017] Where Signal is H 3 O + - Signal intensity of volatile organic matter detected by PTR-LToF-CIMS, k PTR is the reaction rate of the organic matter with water and hydrogen protons, P 0 and P Vocus are the atmospheric pressure and H under standard conditions respectively. 3 O + -PTR-LToF-CIMS injection pressure, Trans is H 3 O + -Mass transfer efficiency of PTR-LToF-CIMS.

[0018] The volatile organic compounds (13) used for calibration include alkanes, alkenes, aromatic hydrocarbons and oxygen-containing organic compounds with known structures and concentrations.

[0019] The present invention adopts dynamic headspace purge to carry out the volatile components of liquor, and directly enters the proton transfer flight time chemical ionization mass spectrometer for detection without complicated pre-treatment operation, and uses the unit of mass spectrum data and high-resolution spectrum analysis technology to identify the characteristic spectrum library of volatile components of liquor, and establishes a quantitative model based on the calibrated mass transfer curve, etc., to achieve the problem of quantitative detection of unknown volatile components in liquor using limited standard substances. The method is simple to operate, fast and efficient, and can simultaneously and quickly quantify more than 70 kinds of volatile components such as alcohols, acids, aldehydes, esters, ethers, etc. in liquor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the method flow of the present invention.

[0021] Figure 2 H 3 O + -Species sensitivity and mass transfer curves of PTR-LToF-CIMS.

[0022] Figure 3 This is the composition spectrum of the volatile organic components of a certain Luzhou-flavor liquor.

[0023] Figure 4 This is a time series diagram of some volatile components of four types of liquor of the same brand. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the implementation of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] See also Figure 1 , is a schematic diagram of the method flow of the present invention.

[0026] The present invention relates to dynamic headspace purging, dilution and H 3 O + -PTR-LToF-CIMS combined method, characterized by:

[0027] Take 1 ml of liquor sample and place it in a dynamic purge glass bottle at a constant temperature of 25°C. Purge it with zero air at a flow rate of 1 mL / min for 10 min to reach equilibrium. Then, mix and dilute it with 5 L / min zero air and then connect it to H 3 O + -Injection port for PTR-LToF-CIMS;

[0028] Using H 3 O + -PTR-LTof-CIMS was used for detection. The detection conditions were as follows: injection flow rate was 100 mL / min, reagent ions were deionized water, reagent ion temperature was 40°C, reagent ion flow rate was 20 mL / min, ion source voltage was 425 V, temperature of ion molecule reaction zone was 60°C, Vocus pressure was 2 mbar, BSQ pressure was 1e-3 mbar, automatic protection threshold pressure of ToF was 5e-6 mbar, Skimmer operating voltage was -4.4 V, BSQ fornt operating voltage was -9.2 V, BSQ back operating voltage was -13.7 V, Skimmer2 operating voltage was -13.2 V, mass-to-charge ratio scanning range was 1-500 Th, data acquisition time resolution was 1 s, and data storage format was h5 file format;

[0029] The h5 file was read using the MATLAB-based TOFtool toolkit, the mass spectrum was averaged for 1 min, Gaussian peak correction was performed in the range of 30-300 Th, and C 3 H 6 OH + , C 2 H 4 O 2 H + and C 8H 16 O 2 H + The standard substance was subjected to dual-parameter equation mass correction. The mass-to-charge ratio range selected for UMR fitting was 1-500 Th, the signal interval was set to 0.5, the noise interval was set to 0.4, the mass-to-charge ratio range for mass resolution correction was set to 30-300 Th, and the correction equation was m / (r 1 ×m+r 2 ), and finally, HR fitting is performed on the measured mass spectrum in the range of 27-250Th, the mass spectrum of the volatile organic components of the liquor is analyzed, and the composition spectrum of the volatile components of the liquor is established;

[0030] The 1ppm mixed VOCs standard gas was diluted to 500mL / min at 2mL / min, and the mass spectrometer signal was stably collected for 15min. The transmission efficiency (detected ions / total ions) was calculated based on the number of ions transmitted from the ion source to the detector versus the total number of ions calculated based on the proton transfer reaction rate constant. The relationship between the transmission efficiency and the mass-to-charge ratio was further plotted to obtain the following: Figure 2 The transmission curve within 1-200Th is shown, and then the concentration of different volatile organic compounds in the liquor is calculated according to formula (1), and the concentration change curve of different compounds over time is obtained.

[0031] The present invention utilizes dynamic headspace purge-H 3 O + -PTR-LToF-CIMS combined technology can quickly measure the concentration of volatile components of liquor at the ppt level with a time resolution of 1s, overcoming the shortcomings of traditional detection methods for volatile components of liquor, such as complex pre-treatment, severe sample loss, large interference from high-concentration ethanol, and difficulty in multi-component quantification. It can also monitor multiple volatile components simultaneously in real time and intuitively identify subtle differences in the content of volatile components in different liquors.

[0032] It should be noted that the monitoring method of the back-end volatile components is not limited to H 3 O + -PTR-LToF-CIMS, other different reagent ions (such as methyl iodide, nitric acid, organic amines, etc.) can also be used to measure the volatile aroma components of liquor.

[0033] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0034] Example 1

[0035] In view of the method and application of real-time rapid monitoring of volatile components of liquor described in the present invention, component spectrum measurement and real-time online monitoring were performed on four series of liquor samples (L1-L4) of a domestic Luzhou-flavor liquor. Figure 3 The composition spectrum of volatile organic components of a certain Luzhou-flavor liquor was shown in Figure 1. Based on high-resolution mass spectrometry fitting, 376 compounds were identified, and 71 compounds such as methanol, acetaldehyde and ketone were identified by GC-MS method as listed in Table 1. Figure 4 To compare the representative alcohols (pentanol, C 5 H 12 O), esters (ethyl acetate, C 4 H 8 O 2 , ethyl butyrate, C 6 H 12 O 2 and ethyl hexanoate, C 8 H 16 O 2 ), aldehydes (acetaldehyde, C 2 H 4 O and furfural, C 5 H 4 O 2 ) and ketones (acetylacetone, C 5 H 8 O 2 ) and other volatile components. Except for furfural, the concentrations of all species reached equilibrium within 3-5 minutes. The zero gas blank used in online monitoring had no significant interference on all monitored species. By comparing and analyzing the changes in the volatile components of L1-L4 liquors, it can be found that there is no significant difference in amyl alcohol and ethyl acetate in L1-L4 liquors (p<0.01), and there is little difference in acetaldehyde and furfural between L1 and L3 liquors and between L2 and L4 liquors. At the same time, there is no significant difference in ethyl butyrate and ethyl hexanoate between L3 and L4 liquors (p<0.01), and there is little difference in ethyl butyrate, ethyl hexanoate and acetylacetone between L1 and L2 liquors. The contents of ethyl butyrate, ethyl hexanoate and acetylacetone in L1 and L2 are significantly different from those in L3 and L4 (p<0.01).

[0036] Table 1 Volatile components of liquor obtained by the method of the present invention

[0037]

[0038]

[0039]

Claims

1. A method for real-time rapid detection of volatile organic components in liquor, characterized in that: The following steps are involved: ① Dynamic headspace purging and dilution (12): 1-3 mL of liquor (9) is placed in a 30 mL purge bottle (8), equilibrated at 25°C (10), and then purged with 1 mL / min of zero gas (3) for 10 min. The purge gas is diluted with 5 L / min (4) of zero gas or high-purity nitrogen (1); ② In-situ online detection: The volatile organic component gas in the sample is connected to the proton transfer reaction time-of-flight mass spectrometer (H3O + -PTR-LTof-CIMS)(28) injection port (11), in H3O + The reagent ions (15) are charged, and are detected by MCP (22) through Vocus focusing (16, pressure 2 mbar), BSQ segmented quadrupole (18, pressure 1e-3 mbar) and time-of-flight mass spectrometry (21, voltage parameters: BSQfront (25) is -9.2 V, Skimmer2 (20) is -13.2 V,) to obtain mass spectrometry signals; ③ High-resolution mass spectrometry interpretation: Use MATLAB and other tools to perform peak shape correction (mass-to-charge ratio 30-300Th), mass correction, mass resolution correction (equation: m / (r1×m+r2)) and UMR / HMR fitting on the mass spectrometry data to establish a spectral library of volatile organic components in liquor; ④ Quantitative model: Based on the proton transfer reaction rate constant (k PTR ), mass transfer efficiency (Trans), ambient pressure (P0) and Vocus operating pressure P Vocus Etc., through the formula Calculate the concentration of volatile components to achieve quantitative analysis.

2. The method according to claim 1, characterized in that Chemical ionization mass spectrometer can be but not limited to H3O + The reagent ions of -PTR-LTof-CIMS are deionized water, the ion source (13) temperature is 40°C, the flow rate is 20mL / min, and the ion source voltage is 425V.

3. The method according to claim 1, characterized in that The dynamic headspace purge with H3O + -The time resolution of the PTR-LToF-CIMS combination technology is 1s, which can monitor the dynamic changes of volatile components in real time.

4. The method according to claim 1, characterized in that The UMR / HMR fitting method can effectively identify 376 molecular formulas in the mass-to-charge ratio range of 27-250Th, and effectively identify 71 volatile components of liquor, including acids, esters (ethyl acetate, ethyl butyrate), aldehydes (furfural), ketones (acetylacetone), ethers and alcohols (pentanol).

5. The method according to claim 1, characterized in that: The method has no interference with the matrix with ethanol concentration>50% in liquor, and the detection sensitivity is at ppt level.

6. Application of the method according to any one of claims 1 to 5 in liquor production quality control, authenticity identification and flavor database construction.

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