Method for detecting volatile organic compounds on human body surface by combining SPME-Arrow with GC-MS / MS

Abstract

The invention relates to a method for detecting volatile organic compounds on the body surface of a human body by combining SPME-Arrow with GC-MS / MS. The method comprises the following steps: (1) sample collection: ultrasonically cleaning a medical gauze piece with ethanol, cleaning and drying, folding and putting the medical gauze piece under the armpit of a sample collector to collect odor, and then transferring the medical gauze piece into a headspace sample injection bottle; (2) arrow-shaped solid-phase microextraction: inserting the activated extraction head into the hatched headspace sample injection bottle, and transferring the extraction head to a sample injection port for desorption after extraction; and (3) GC-MS / MS analysis: carrying out qualitative and quantitative detection on the volatile organic compounds in the sample by using a gas chromatography-triple quadrupole mass spectrometry technology. According to the detection method, 93 VOCs in the human body surface can be detected at the same time, the detection method is high in stability, accuracy and precision, environmentally friendly and high in automation degree, and the detection requirement for large-batch VOCs on the human body surface in actual work can be met.

Description

Technical Field

[0001] The invention relates to the technical field of methods for detecting volatile organic compounds on the human body surface, and in particular to a method for detecting volatile organic compounds on the human body surface by combining SPME-Arrow with GC-MS / MS. Background Art

[0002] Volatile Organic Compounds (VOCs) on the human body surface mainly come from the apocrine glands, eccrine glands and sebaceous glands on the surface of the human skin. The compounds secreted by these glands undergo metabolic activities of the microbial flora on the skin and oxidative reactions with oxygen in the air, ultimately forming a unique human odor. The composition and content of VOCs on the human body surface are affected by many factors, such as the individual's health status, eating habits, age, gender and living environment. In the field of disease diagnosis, VOCs on the human body surface can reflect the individual's health status. By analyzing the composition of VOCs on the body surface, medical workers can be assisted in disease diagnosis or disease monitoring. In the field of forensic science, individual identification and feature characterization (such as gender, age, region, etc.) can be performed by analyzing VOCs on the human body surface. In addition, understanding the composition of VOCs on the human body surface can also guide the development and use of beauty products. Therefore, analyzing VOCs on the human body surface has important research significance.

[0003] However, the composition of VOCs on the human body surface is complex, and many VOCs have low content (ppt level), so the enrichment effect of odor samples and the sensitivity of detection methods are required to be high. At present, the common sample pretreatment methods for detecting VOCs on the body surface include liquid-liquid extraction, solid phase microextraction (SPME), stir bar sorptive extraction (SBSE) and thermal desorption. Among them, SPME is widely used in the analysis and determination of VOCs on the human body surface because of its simple and fast operation, convenient injection, small sample amount, and selective adsorption membrane. However, when using SPME for sample pretreatment in the detection of VOCs on the body surface, there are still problems such as low sensitivity, low extraction efficiency, and low stability, and further research on sample pretreatment methods is still needed.

[0004] Solid phase microextraction arrow (SPME-Arrow) is an improved solid phase microextraction technology, which is similar to the traditional SPME technology, but uses an arrow-shaped extraction device with a larger diameter and longer needle. Compared with traditional SPME, the SPME-Arrow device has a larger adsorption phase volume and higher sampling efficiency, and has advantages in improving sensitivity and extraction efficiency. At the same time, when analyzing the surface odor characteristics of different populations, it is usually necessary to detect a large number of samples. Compared with traditional SPME, SPME-Arrow is more durable and has better stability during long-term continuous analysis. However, at present, there are reports on the use of SPME-Arrow technology to detect VOCs in matrices such as sewage and food at home and abroad, but there are still no reports on its application in the analysis of VOCs on the body surface. The types of human VOCs are different from the main components of VOCs in sewage and food. Sewage / food detection focuses on multi-target screening and anti-interference ability, while human VOCs detection emphasizes ultra-high sensitivity. Therefore, specific research is still needed on the pretreatment method of SPME-Arrow suitable for human surface samples.

[0005] At the same time, in terms of human odor detection technology, most of the current detection is done by gas chromatography-single quadrupole mass spectrometry, but its sensitivity is low, some human VOCs components cannot be detected, and there is still matrix interference in the detection of targets in complex matrices. How to improve the sensitivity of detection, effectively eliminate the false positive problem that often occurs in the GC-MS selected ion scanning mode (Selected Ion Monitoring, SIM), and improve its anti-interference ability for complex matrices still requires further research. Summary of the invention

[0006] In view of the deficiencies of the prior art, the technical problem to be solved by the present invention is how to reduce the detection limit of volatile organic compounds on the human body surface while improving the stability and accuracy of the detection. To this end, the present invention provides a method for detecting volatile organic compounds on the human body surface by combining SPME-Arrow with GC-MS / MS. The combination of SPME-Arrow-gas chromatography / triple quadrupole mass spectrometry is suitable for sensitive, efficient, stable, and fully automatic analysis of a variety of volatile substances on the human body surface, and can meet the analysis requirements when used for the determination of VOCs on the human body surface.

[0007] Among them, the present invention takes 93 common VOCs on the human body surface as target objects, optimizes the key parameters that have a significant impact on the extraction efficiency during the extraction process (such as extraction head, extraction temperature, extraction time), and uses gas chromatography-triple quadrupole mass spectrometry in multiple reaction monitoring mode (Multiple Reaction Monitoring, MRM) to detect human volatile substances, effectively eliminating the false positive problem that often occurs in the ion scanning mode, and improving the method's anti-interference ability for complex matrices. The resulting detection method has high stability and accuracy.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] The present invention provides a method for detecting volatile organic compounds on the human body surface by combining SPME-Arrow with GC-MS / MS, comprising the following steps:

[0010] (1) Sample collection:

[0011] (1-1) Pretreatment of medical gauze: ultrasonically clean the medical gauze with ethanol, dry it after cleaning, and set it aside;

[0012] (1-2) Fold the pretreated medical gauze piece in half and place it under the armpit of the sample collector to collect the odor; after collection, put the medical gauze piece adsorbed with human body odor into a headspace sampling bottle and store it for future use;

[0013] (2) Arrow-shaped solid phase microextraction:

[0014] Incubate the headspace injection bottle with the sample collected, and activate the extraction head at the same time; insert the activated extraction head into the incubated headspace injection bottle to perform extraction; after extraction, transfer the extraction head to the injection port of the gas chromatography-mass spectrometer to perform desorption for GC-MS / MS analysis;

[0015] (3) GC-MS / MS analysis:

[0016] Gas chromatography-triple quadrupole mass spectrometry was used to qualitatively and quantitatively detect volatile organic compounds in samples.

[0017] Preferably, the volatile organic compounds on the human body surface include: 2,3-butanedione, methyl butyrate, α-pinene, toluene, hexanal, undecane, p-xylene, m-xylene, 3-carene, pyridine, o-xylene, heptaldehyde, limonene, dodecane, 2-n-pentylfuran, amyl alcohol, styrene, 3-hydroxy-2-butanone, octanal, tridecane, (E)-2-heptenal, methyl heptenone, methyl octanoate, 2-nonanone, nonanal, tetradecane, 1,3-di-tert-butylbenzene, 1-octen-3-ol, 2-ethylhexanol, 2-decanone, methyl nonanoate, pentadecane, dimethyl malonate, decanal, benzaldehyde, (E)-2-nonenal, linalool, octanol, fenchol, methyl decanoate, hexadecane, 2-undecanone, undecanal, L-menthol, Nonanol, heptadecane, dodecanal, (E)-citral, naphthalene, trans-2-undecenal, decanol, N,N-dibutylformamide, methyl salicylate, octadecane, dimethyl adipate, henoxyacetone, hexanoic acid, geranylacetone, undecanol, guaiacol, benzyl alcohol, methyl tridecanoate, phenylethyl alcohol, tetradecal, dodecanol, benzothiazole, eicosane, phenol, 2-pentadecanone, pentadecanal, isopropyl myristate, lilyral, octanoic acid, heneicosane, cedrol, hexadecanal, nonanoic acid, tetradecanol, methyl palmitate, pentadecanol, decanoic acid, galaxol, octadecane, diethyl phthalate, α-hexylcinnamaldehyde, hexadecanol, p-tert-amylphenol, lauric acid, stearyl alcohol, benzyl benzoate, benzamide, dibutyl phthalate, and trans-squalene.

[0018] Preferably, in step (1), the medical gauze piece is sterile and has a size of 5 cm×5 cm;

[0019] Preferably, in step (1), the temperature of ultrasonic cleaning is 55-65°C, and the time is 0.5-1.5h; the temperature of drying is 60-100°C, and the time is 30-60min;

[0020] More preferably, in step (1), the ultrasonic cleaning temperature is 60°C for 1 hour; the drying temperature is 80°C for 45 minutes;

[0021] Preferably, in step (1), the collection time is 20-40 min; the storage temperature is -80°C;

[0022] More preferably, in step (1), the collection time is 30 min; the storage temperature is -80°C;

[0023] Preferably, in step (1), the sample collector keeps his arms clamped against his body during collection to prevent the gauze from falling off;

[0024] Preferably, in step (2), the incubation temperature is 55-65°C, the time is 10-20 min; the activation temperature is 200-300°C, the time is 2-4 min; the extraction temperature is 40-80°C, the extraction time is 20-40 min; the desorption temperature is 200-300°C, the time is 2-6 min;

[0025] More preferably, in step (2), the incubation temperature is 60°C, the incubation time is 15 min; the activation temperature is 250°C, the activation time is 3 min; the extraction temperature is 60°C, the extraction time is 30 min; the desorption temperature is 250°C, the desorption time is 4 min;

[0026] Preferably, in step (2), the extraction head is a DVB / CWR / PDMS extraction head;

[0027] Preferably, in step (3), the chromatographic conditions are: 30m×0.25mm×0.25μm DB-WAX capillary column; carrier gas is high-purity helium with a flow rate of 1.0mL / min; temperature program: initial column temperature is 40°C, maintained for 4min, then heated to 245°C at 5°C / min and maintained for 5min, with a total analysis time of 50min; injection port temperature is 250°C; splitless injection is used;

[0028] Preferably, in step (3), the mass spectrometry conditions are: ion source temperature 230°C, transfer line temperature 250°C, ionization mode is electron impact ion source (EI source), electron energy 70eV, data scanning mode is multiple reaction monitoring mode (MRM), and collision voltage is 3-45eV.

[0029] The technical solution of the present invention achieves the following beneficial technical effects:

[0030] The present invention establishes a method for simultaneously detecting 93 VOCs on the human body surface by combining SPME-Arrow with GC-MS / MS. By optimizing the sample collection, arrow-shaped solid phase microextraction and GC-MS / MS analysis steps, such as gauze cleaning solvent, drying conditions, extraction head, extraction temperature, extraction time and mass spectrometry conditions, 93 VOCs on the human body surface can be detected simultaneously. The detection method has good sensitivity, high stability, accuracy and precision. Among them, the detection limit of the detection method of the present invention is 0.05-0.5 ng, the recovery rate is 75.15%-118.87%, the intra-day precision is 1.27%-11.79%, and the inter-day precision is 2.88%-12.95%.

[0031] The present invention uses a novel arrow-shaped solid phase microextraction head to extract VOCs from the body surface, and uses the multiple reaction monitoring mode of triple quadrupole tandem mass spectrometry to perform high-throughput screening of body surface VOCs. The extraction head used is made of metal material, which enhances the mechanical properties and prolongs the service life. The method is stable, accurate, green and environmentally friendly, and has a high degree of automation. It can meet the needs of large-scale detection of human body surface VOCs in actual work, and lays a foundation for individual identification and characterization using human odor. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Total ion current chromatogram of the mixed standard solution of VOCs on human body surface in Example 2 of the present invention;

[0033] Figure 2 Chromatograms of gauze after ultrasonic treatment with ethanol and blank gauze in Comparative Example 1 of the present invention;

[0034] Figure 3 Chromatogram after baseline alignment of gauze after being treated with different solvents in Comparative Example 1 of the present invention;

[0035] Figure 4 Chromatograms of different blank control groups in Comparative Example 2 of the present invention;

[0036] Figure 5 Chromatograms of different sample experimental groups in Comparative Example 2 of the present invention;

[0037] Figure 6 The average recovery rates of various substances extracted by the five extraction heads in Comparative Example 3 of the present invention;

[0038] Figure 7 Effects of different extraction temperatures on extraction efficiency in Comparative Example 4 of the present invention;

[0039] Figure 8 Effects of different extraction times on extraction efficiency in Comparative Example 5 of the present invention. DETAILED DESCRIPTION

[0040] 1. The apparatus used in the following embodiments of the present invention:

[0041] VE400 electronic temperature-controlled oven (Jiangsu Taichuang Machinery Equipment Co., Ltd.); KQ3200DE CNC ultrasonic cleaner (Kunshan Ultrasonic Instrument Co., Ltd.); GC2030-TQ8050NX triple quadrupole gas chromatograph-mass spectrometer (Shimadzu Corporation, Japan); AOC-6000Plus automatic sampler (Shimadzu Corporation, Japan); 20 mL headspace injection bottle (Beijing Sypures Technology Co., Ltd.).

[0042] 2. the reagents used in the following embodiments of the present invention:

[0043] Five types of SPME-Arrow fibers were purchased from Swiss Analytical Instruments Co., Ltd., including 100 μm polydimethylsiloxane (PDMS), 85 μm polyamide (PA), 75 μm carbon molecular sieve / polydimethylsiloxane (CAR / PDMS), 65 μm divinylbenzene / polydimethylsiloxane (DVB / PDMS), and 50 / 30 μm divinylbenzene / epoxy resin / polydimethylsiloxane (DVB / CWR / PDMS);

[0044] Among them, 50μm in "50 / 30μm" refers to the thickness of the DVB coating; 30μm refers to the thickness of the CWR coating; PDMS is used as a supporting layer and its thickness is not marked.

[0045] Medical gauze (Zhende Medical Supplies Co., Ltd., sterile 5 cm × 5 cm-8p);

[0046] 93 kinds of human body surface VOCs mixed standard solutions (Tianjin Alta Technology Co., Ltd.), the names of the 93 substances in the mixed standard solution are shown in Table 1. Dilute with methanol to a suitable concentration when used, such as the mixed standard solution of 10 μg / mL in the embodiment: the concentration of each substance in the mixed standard solution is 10 μg / mL;

[0047] C9-C40 normal alkane mixed standard solution (Tianjin Alta Technology Co., Ltd.) was diluted with methanol to an appropriate concentration when used.

[0048] Example 1

[0049] This embodiment provides a method for detecting volatile organic compounds on the human body surface by combining SPME-Arrow with GC-MS / MS, comprising the following steps:

[0050] (1) Sample collection:

[0051] Take a piece of medical gauze (size 5 cm×5 cm) out of the package and put it into a 100 mL beaker. Add an appropriate amount of ethanol. After ultrasonic cleaning at 60°C for 1 hour, put it into an oven at 80°C and dry it for 45 minutes.

[0052] Fold the cleaned and dried gauze in half and place it under the volunteer's armpit to collect the odor. The volunteer should try to keep his arm clamped to the body within 30 minutes of sampling to prevent the gauze from falling off and to help the gauze absorb the odor better.

[0053] After 30 minutes, the gauze adsorbed with human odor was placed in a 20 mL headspace injection bottle and stored in a -80 °C refrigerator for testing.

[0054] (2) Arrow-shaped solid phase microextraction:

[0055] Using fully automatic HS-SPME-Arrow conditions and AOC-6000Plus autosampler, the headspace injection bottle containing the odor sample was placed in the injection tray, and the headspace injection bottle with the sample was incubated (the incubation temperature was 60°C and the time was 15 minutes), and the extraction head was activated at the same time (the activation temperature was 250°C and the time was 3 minutes);

[0056] The activated extraction head (DVB / CWR / PDMS extraction head) was inserted into the headspace injection bottle after incubation for extraction (extraction temperature was 60°C and extraction time was 30 min); after extraction, the extraction head was transferred to the injection port of the gas chromatography-mass spectrometer for desorption (desorption temperature was 250°C and time was 4 min) for GC-MS / MS analysis;

[0057] (3) GC-MS / MS analysis:

[0058] Gas chromatography-triple quadrupole mass spectrometry was used to qualitatively and quantitatively detect 93 volatile organic compounds (see Table 1 for specific compound types) in the samples;

[0059] The chromatographic conditions were as follows: 30m×0.25mm×0.25μm DB-WAX capillary column; carrier gas was high-purity helium with a flow rate of 1.0mL / min; temperature program: initial column temperature was 40°C, maintained for 4min, then heated to 245°C at 5°C / min and maintained for 5min, with a total analysis time of 50min; injection port temperature was 250°C; splitless injection was used;

[0060] The mass spectrometry conditions were as follows: ion source temperature 230°C, transfer line temperature 250°C, ionization mode electron impact ion source (EI source), electron energy 70 eV, data scanning mode multiple reaction monitoring mode (MRM), collision voltage 3-45 eV.

[0061] Example 2 Optimization of mass spectrometry conditions

[0062] 1) Determine the precursor ion

[0063] A mixed standard solution of 93 human body surface VOCs with a mass concentration of 10 μg / mL was prepared by diluting with methanol, and the Q3Scan acquisition mode was selected, and the m / z range was set to 20-400 for detection. A mixed standard solution of C9-C40 normal alkanes with a mass concentration of 10 μg / mL was prepared by diluting with methanol, and the detection was carried out under the same conditions. The retention time of each normal alkane under the conditions was obtained, and the retention index of each VOCs was calculated according to the retention time of the 93 VOCs.

[0064] The detected chromatographic peaks in the collected VOCs data file are integrated and qualitatively characterized, the retention index of each target compound is corrected using the collected normal alkane data, the retention time is automatically calculated, and the characteristic ions with high abundance are selected as precursor ions.

[0065] Among them, the retention index (RI) is a relative parameter calibrated based on the retention behavior of homologues (usually normal alkanes), which has higher stability and comparability. By correlating the retention time of the target compound with the retention time of the adjacent normal alkanes, the RI value is calculated to reduce the impact of fluctuations in chromatographic conditions on the results.

[0066] 2) Set product ions

[0067] The collision energy (CE) range was set to 3-45 eV, and the product ion scanning method was used to collect the mixed standard solution of 93 VOCs with a mass concentration of 10 μg / mL. The optimal collision voltage of each target (93 VOCs) was further obtained, and the MRM analysis method was established to obtain the product ion scanning data.

[0068] 3) Optimize collision voltage

[0069] Use the MRM optimization tool software to select the product ion scan data obtained in the previous step, set the MRM Transition number (i.e., the number of quantitative ion and qualitative ion pairs), set the product ion mass number range, start optimization, and select the CE value when the response intensity is optimal. The retention index and mass spectrometry parameters of 93 surface VOCs are shown in Table 1.

[0070] The 1 μg / mL body surface VOCs mixed standard solution was used to verify the MRM method ion pair optimization results. The total ion current chromatogram is shown in Figure 1 As can be seen from the figure, the established method can be successfully used for the detection of 93 substances.

[0071] Table 1 Retention index and mass spectrometry parameters of 93 VOCs

[0072]

[0073]

[0074]

[0075]

[0076]

[0077] Comparative Example 1 Optimization of matrix conditions

[0078] Some impurities in gauze may affect the determination of human body surface VOCs. When directly determining human body surface VOCs in gauze, the recovery rate of 14 VOCs such as hexanal is less than 70%, while the recovery rate of 22 VOCs such as toluene is higher than 120%. The ultrasonic cleaning method can remove the impurities of the gauze itself, which is conducive to improving the extraction efficiency.

[0079] ① Referring to the ultrasonic cleaning method of gauze in step (1) of Example 1, the gauze treated with ethanol ultrasonic cleaning was compared with the gauze not treated with ethanol ultrasonic cleaning. The two groups of gauze were directly sampled according to the method in step (3) of Example 1 (i.e., the gauze was not sampled). The chromatogram of the gauze after ethanol ultrasonic treatment was compared with the chromatogram of the untreated gauze. Figure 2 shown.

[0080] Depend on Figure 2 It can be seen that the impurities in the gauze after ultrasonic cleaning are significantly reduced, which shows that the cleaning operation is necessary. At the same time, in order to achieve a better cleaning effect, three cleaning schemes were further designed, namely, ultrasonic treatment of gauze with ethanol, acetone and n-hexane. Similarly, the gauze was not sampled, and the sample was directly injected according to the method in step (3) of Example 1. Figure 3 Shown are the chromatograms of gauze after treatment with three solvents without sampling.

[0081] Through the integration of all peaks, under the same integration conditions, the number of chromatographic peaks detected in the gauze samples after the three schemes were investigated. Results: 151 peaks were detected in the gauze of the ethanol scheme, and 102 substances were obtained after searching in the NIST library; 189 peaks were detected in the gauze of the acetone scheme, and 116 substances were obtained after searching in the NIST library; 235 peaks were detected in the gauze of the n-hexane scheme, and 121 substances were obtained after searching in the NIST library. From the data results, it can be seen that the cleaning effects of the three solvents are ethanol>acetone>n-hexane from best to worst.

[0082] ② The cleaning solution used in ultrasonic cleaning in step (1) of Example 1 was changed. In this comparative example, ethanol, acetone and n-hexane were used as cleaning solutions respectively. The gauze was ultrasonically cleaned and dried according to the method of step (1) of Example 1, and the armpit odor of volunteers was collected. The other steps and parameters were the same as those in Example 1 to detect volatile organic compounds on the human body surface.

[0083] The results showed that when ethanol was used as the cleaning solution, the recovery rate of each VOCs (i.e. the percentage of actual concentration to theoretical concentration) was the best, and the recovery rates of 93 VOCs were all between 70% and 120%. Therefore, the method of the present invention selected ethanol to perform ultrasonic cleaning on gauze and then perform extraction and detection.

[0084] Comparative Example 2 Oven Condition Optimization

[0085] The main conditions of the oven are the drying temperature and drying time. The drying of gauze requires that the gauze is completely dry while saving experimental time. Therefore, the drying time of the oven depends on the oven temperature. According to different oven temperatures, the corresponding optimal drying time is obtained, see Table 2.

[0086] Table 2 Oven conditions under three schemes

[0087] plan Oven temperature (℃) Drying time (min) one 60 60 two 80 45 three 100 30

[0088] It is necessary to consider not introducing too many impurities during treatment, and not reducing the adsorption capacity of the treated gauze. Therefore, referring to the ultrasonic cleaning method of gauze in step (1) of Example 1, the gauze is dried according to the conditions of Table 2, and the treated gauze is directly injected with the method in step (3) of Example 1, and the strength of the background interference of the three is compared (i.e., the blank control group). The chromatogram results are as follows: Figure 4 As shown;

[0089] In addition, another group of experimental gauze was taken, and the ultrasonic cleaning method of the gauze in step (1) of Example 1 was referred to. The gauze was dried according to the conditions in Table 2, and the treated gauze was used to collect the armpit odor of volunteers according to the method in step (1) of Example 1, and the sample injection test was carried out according to the method in steps (2) and (3) of Example 1 to compare the adsorption capacity of the three (i.e., the sample experimental group). The chromatogram results are as follows: Figure 5 shown.

[0090] The chromatograms show the differences in the overall odor content of the gauze under the three treatments. Figure 4 In the case where the profiles of the three chromatograms are basically the same, the ordinates (peak areas) are 100°C, 80°C, and 60°C from low to high, and the overall average peak areas of the three are calculated by Excel, as shown in Table 3; Figure 5 When the profiles of the three chromatograms are basically the same, the ordinates (peak areas) are 100°C, 80°C, and 60°C from low to high, and the overall average peak areas of the three are calculated by Excel, as shown in Table 3.

[0091] Table 3 Average peak area of ​​gauze

[0092] plan Average peak area of ​​blank Average peak area of ​​samples one 399094 924372 two 429463 806661 three 481197 766200

[0093] Among them, the higher the average peak area of ​​the blank gauze, the higher the number and content of its impurities, and the greater the impact on the experimental results. The possible reason is that the longer drying time makes the gauze adsorb more impurities in the oven, so the drying time should be reduced as much as possible to reduce the impurities on the gauze; the smaller the average peak area of ​​the sample gauze, the worse the adsorption capacity of the gauze, the lower the number and content of odors adsorbed from the human body, and the more unfavorable to the experimental results. The possible reason is that the higher temperature destroys the surface structure of the gauze, resulting in a decrease in its adsorption capacity. Therefore, higher temperatures should be avoided as much as possible to protect the gauze and avoid a decrease in its adsorption capacity. In summary, too high or too low temperatures will affect the experimental results, so option 2 is selected as the best oven condition.

[0094] Comparative Example 3 Optimization of Extraction Fiber

[0095] The extraction efficiency of SPME-Arrow depends largely on the size of the distribution constant between the target component and the fiber coating material. Therefore, five commercially available SPME-Arrow extraction heads were selected to investigate the extraction efficiency of different extraction heads for VOCs on the human body surface. They are 100μm PDMS, 85μm PA, 75μm CAR / PDMS, 65μm DVB / PDMS and 50 / 30μm DVB / CWR / PDMS extraction heads.

[0096] Among them, PDMS is a non-polar siloxane compound that has a good affinity for non-polar volatile organic compounds such as oils and alkanes. PA has good selectivity relative to polar compounds and is suitable for extracting polar compounds such as alcohols and acids. CAR / PDMS and DVB / PDMS are both two-phase extraction heads. Combining the two materials, they have good extraction capabilities for both polar and non-polar compounds. DVB / CWR / PDMS adopts a composite structure that combines the selectivity of DVB, the special affinity of CWR, and the versatility of PDMS, so that it can take into account the needs of multiple compounds during the extraction process, and is particularly suitable for the analysis of complex samples, such as food and environmental samples.

[0097] The armpit odor of volunteers was collected according to the method of Example 1, and the selection of the extraction head during extraction in step (2) of Example 1 was changed. This comparative example was experimented with the above five extraction heads respectively. The other steps and parameters were the same as those of Example 1 to detect volatile organic compounds on the human body surface.

[0098] After the mixed standard sample was extracted by 5 extraction heads, the average recovery rate of each substance (i.e. 93 kinds of human body surface VOCs were divided into 6 categories: alcohols, aldehydes, hydrocarbons, esters, acids, and ketones) was shown in Figure 2. Figure 6 .Depend on Figure 6It can be seen that PDMS and PA have a small selection range when extracting VOCs on the human body surface. The recovery rate of PDMS for extracting alcohols and acids is less than 50%, and the recovery rate of PA for extracting hydrocarbons is less than 30%. Unlike the first two single fiber extraction heads, CAR / PDMS, DVB / PDMS and DVB / CWR / PDMS can select targets in a wider range and have better extraction efficiency for most VOCs on the human body surface. Among them, DVB / CWR / PDMS has the highest recovery rate when extracting aldehydes, esters and acids, and the recovery rate of extracting other types of substances is also good. Finally, the DVB / CWR / PDMS extraction head was selected to extract VOCs on the human body surface.

[0099] Comparative Example 4 Optimization of extraction temperature

[0100] In the SPME process, the extraction temperature refers to the ambient temperature of the sample during extraction. The effect of extraction temperature on SPME extraction efficiency is mainly reflected in two aspects: as the temperature increases, the volatility of many compounds increases, which accelerates the diffusion of target analytes in the sample and promotes the interaction with the SPME coating, resulting in an increase in its concentration in the gas phase, thereby improving the extraction efficiency. However, too high an extraction temperature may cause thermal degradation or chemical changes of thermally unstable compounds at high temperatures, which may lead to the loss of target components and thus reduce the extraction efficiency.

[0101] The armpit odor of volunteers was collected according to the method of Example 1, and the extraction temperature in step (2) of Example 1 was changed. This comparative example was experimented with five extraction temperatures of 40°C, 50°C, 60°C, 70°C, and 80°C. The other steps and parameters were the same as those of Example 1 to detect volatile organic compounds on the human body surface.

[0102] The effect of extraction temperature on the extraction effect (i.e. the peak area of ​​the chromatogram) is shown in Figure 7 .Depend on Figure 7 It can be seen that with the increase of extraction temperature, the total response value of 93 targets first increases and then decreases, and the total response value reaches the maximum value when the extraction temperature is 60° C. Therefore, 60° C. is selected as the extraction temperature of the method of the present invention.

[0103] Comparative Example 5 Optimization of extraction time

[0104] The extraction time is the time required for the extraction to reach equilibrium. It is determined by factors such as the distribution coefficient of the analyte, the diffusion rate of the substance, the sample matrix, and the membrane thickness of the extraction head. It is also a key factor affecting the SPME extraction efficiency.

[0105] The armpit odor of volunteers was collected according to the method of Example 1, and the extraction time in step (2) of Example 1 was changed. This comparative example was experimented with five extraction times of 20 min, 25 min, 30 min, 35 min, and 40 min, respectively. The other steps and parameters were the same as those of Example 1, and volatile organic compounds on the human body surface were detected.

[0106] The effect of extraction time on the extraction effect (i.e. the peak area of ​​the chromatogram) is shown in Figure 8 .Depend on Figure 8 It can be seen that the best extraction effect can be achieved when the extraction time is 30 minutes. After 30 minutes, as the extraction time gradually increases, the extraction efficiency slowly increases. In actual work, an extraction time with a large extraction amount and not too long is usually selected as the actual extraction time, so 30 minutes is finally selected as the extraction time of the method of the present invention.

[0107] Application Example 1 Methodology Validation

[0108] ① Using blank gauze as the substrate, after ultrasonic cleaning the gauze according to the method of step (1) of Example 1, 1 μL, 2 μL, 5 μL, 10 μL, 20 μL, 50 μL of 93 kinds of human body surface VOCs mixed standard solutions (10 ng / mL) and 1 μL, 2 μL, 5 μL, 10 μL, 50 μL, 100 μL of 93 kinds of human body surface VOCs mixed standard solutions (1 μg / mL) were added to the blank gauze for extraction and detection. The determination method refers to steps (2) and (3) of Example 1.

[0109] The standard curve was drawn with the mass x (ng) of each target (93 species) as the horizontal axis and the quantitative ion chromatographic peak area y as the vertical axis. The detection limit (LOD) of each target was calculated with the mass of the component to be tested corresponding to 3 times the baseline noise. The results are shown in Table 4. Each VOCs has a good linear relationship within the linear range, and the correlation coefficient (r 2 ) are all greater than 0.99. The detection limit is between 0.05 and 0.5 ng. It can be seen that the detection method in this paper has good sensitivity.

[0110] ②Using blank gauze as the matrix, ultrasonically clean the gauze according to the method of step (1) of Example 1, and then adding 1 μL, 10 μL, and 100 μL of 93 kinds of human body surface VOCs mixed standard solutions (1 μg / mL) for extraction and detection, that is, the spiked content of each target object is set to 1, 10, and 100 ng, respectively. The determination method refers to step (2) and step (3) of Example 1. The recovery rate of each target object is calculated. The results are shown in Table 4. The recovery rate of 93 VOCs is between 75.15% and 118.87%. It can be seen that the detection method in this paper has good accuracy.

[0111] ③ Using blank gauze as the matrix, ultrasonically clean the gauze according to the method of step (1) of Example 1, and then add 10 μL of 93 kinds of human body surface VOCs standard mixed solution (1 μg / mL) for extraction and detection, that is, set the spiked content of each target to 10 ng, repeat the measurement 6 times, and measure continuously for 5 days. Calculate the intra-day precision and inter-day precision. The results are shown in Table 4. The intra-day precision is between 1.27% and 11.79%, and the inter-day precision is between 2.88% and 12.95%. It can be seen that the detection method in this paper has good stability.

[0112] Table 4 Linear range, correlation coefficient, detection limit, recovery rate and precision of 93 VOCs

[0113]

[0114]

[0115]

[0116] Application Example 2 Actual Sample Testing

[0117] According to the detection method of Example 1 and the mass spectrometry conditions optimized in Example 2, the body surface odor of 5 healthy people was detected. The results showed that the target objects of different human bodies were different, which laid a foundation for individual identification and characterization using human body odor. The results are shown in Table 5. The mass unit of the corresponding target object is ng. The results show that this method can be applied to the detection of VOCs in actual samples with high sensitivity and good accuracy.

[0118] Table 5 Mass of 93 VOCs in 5 body odor samples (unit: ng)

[0119]

[0120]

[0121] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for detecting volatile organic compounds on the human body surface by combining SPME-Arrow with GC-MS / MS, characterized in that: The following steps are involved: (1) Sample collection: (1-1) Pretreatment of the medical gauze piece: ultrasonically clean the medical gauze piece with ethanol, dry it after cleaning, and set it aside; (1-2) Fold the pretreated medical gauze piece in half and place it under the armpit of the sample collector to collect the odor; after collection, put the medical gauze piece adsorbed with human body odor into a headspace sampling bottle and store it for future use; (2) Arrow-shaped solid phase microextraction: Incubate the headspace injection bottle with the sample collected, and activate the extraction head at the same time; insert the activated extraction head into the incubated headspace injection bottle to perform extraction; after extraction, transfer the extraction head to the injection port of the gas chromatography-mass spectrometer to perform desorption for GC-MS / MS analysis; (3) GC-MS / MS analysis: Gas chromatography-triple quadrupole mass spectrometry was used to qualitatively and quantitatively detect volatile organic compounds in samples.

2. The method according to claim 1, characterized in that In the step (1), the medical gauze piece is sterilized and has a size of 5 cm×5 cm.

3. The method according to claim 1, characterized in that In the step (1), the temperature of ultrasonic cleaning is 55-65°C, and the time is 0.5-1.5h; the temperature of drying is 60-100°C, and the time is 30-60min.

4. The method according to claim 1, characterized in that In the step (1), the collection time is 20-40 minutes; the storage temperature is -80°C; during collection, the sample collector keeps his arms clamped to the body to prevent the gauze from falling off.

5. The method according to claim 1, characterized in that The volatile organic compounds on the human body surface include: 2,3-butanedione, methyl butyrate, α-pinene, toluene, hexanal, undecane, p-xylene, m-xylene, 3-carene, pyridine, o-xylene, heptaldehyde, limonene, dodecane, 2-n-pentylfuran, amyl alcohol, styrene, 3-hydroxy-2-butanone, octanal, tridecane, (E)-2-heptenal, methyl heptenone, methyl octanoate, 2-nonanone, nonanal, tetradecane, 1,3-di-tert-butylbenzene, 1-octen-3-ol, 2-ethylhexanol, 2-decanone, methyl nonanoate, pentadecane, dimethyl malonate, decanal, benzaldehyde, (E)-2-nonenal, linalool, octanol, fenchol, methyl decanoate, hexadecane, 2-undecanone, undecanal, L-menthol, nonanol , heptadecane, dodecanal, (E)-citral, naphthalene, trans-2-undecenal, decanol, N,N-dibutylformamide, methyl salicylate, octadecane, dimethyl adipate, henoxyacetone, caproic acid, geranylacetone, undecanol, guaiacol, benzyl alcohol, methyl tridecanoate, phenylethyl alcohol, tetradecal, dodecanol, benzothiazole, eicosane, phenol, 2-pentadecanone, pentadecanal, isopropyl myristate, lilyral, octanoic acid, heneicosane, cedrol, hexadecanal, nonanoic acid, tetradecanol, methyl palmitate, pentadecanol, capric acid, galaxol, octadecane, diethyl phthalate, α-hexylcinnamaldehyde, hexadecanol, p-tert-amylphenol, lauric acid, stearyl alcohol, benzyl benzoate, benzamide, dibutyl phthalate and trans-squalene.

6. The method according to claim 1, characterized in that In the step (2), the incubation temperature is 55-65°C for 10-20 minutes; the activation temperature is 200-300°C for 2-4 minutes.

7. The method according to claim 1, characterized in that In the step (2), the extraction temperature is 40-80°C, and the extraction time is 20-40 minutes; the desorption temperature is 200-300°C, and the time is 2-6 minutes.

8. The method according to claim 1, characterized in that In the step (2), the extraction head is a DVB / CWR / PDMS extraction head.

9. The method according to claim 1, characterized in that In the step (3), the chromatographic conditions are: 30m×0.25mm×0.25μm capillary column; carrier gas is high-purity helium with a flow rate of 1.0mL / min; temperature program: initial column temperature is 40°C, maintained for 4min, then heated to 245°C at 5°C / min and maintained for 5min; injection port temperature is 250°C; splitless injection is used; The mass spectrometry conditions were as follows: ion source temperature 230°C, transfer line temperature 250°C, ionization mode electron bombardment ion source, electron energy 70 eV, data scanning mode multiple reaction detection mode, collision voltage 3-45 eV.

10. The method according to claim 5, characterized in that The retention index, quantitative ion pair and collision voltage, qualitative ion pair and collision voltage in the mass spectrometry conditions of volatile organic compounds on the human body surface are shown in the following table:

Images