Method for rapidly screening odor substances in water

Abstract

The invention belongs to the field of environment detection, and discloses a rapid screening method for odor substances in water, which comprises the following steps: (1) constructing a screening database for the odor substances in water for common odor substances in any region by using an MRM mode of GC-MS / MS (Gas Chromatography-Mass Spectrometry / Mass Spectrometry); wherein the parameters comprise the name and / or the CAS number of the odor substance, the m / z of the characteristic ion pair and the collision voltage; (2) carrying out pretreatment on the water sample, and extracting odor substances in water by utilizing an online solid-phase microextraction method; and (3) creating an MRM screening method by using the constructed screening database, screening the odor substances in the water sample to be detected by using the method, and judging that the water sample contains the odor substances in the MRM screening database when the characteristic ion pairs exist in the retention time range and are identified. According to the invention, the rapid and broad-spectrum screening of dozens of odor substances can be realized at the same time, the screening work cost is reduced, and the efficiency is improved.

Description

TECHNICAL FIELD

[0001] The application relates to a gas chromatography-triple quadrupole mass spectrometry (GC-MS / MS) screening and quantitative analysis method for odorants in water, and belongs to the field of environmental detection. BACKGROUND

[0002] At present, the emission standards for odorants in China have obvious limitations: only a few substances such as hydrogen sulfide and ammonia are clearly regulated, and a large number of new odorants (such as complex volatile organic compounds and algal metabolites) still lack limit standards. At the same time, the "subjectivity" of odor perception, and the significant difference in sensitivity to odors among different people, make it difficult to develop a unified evaluation standard, which directly hinders law enforcement work.

[0003] In terms of detection technology, although the traditional method (such as gas chromatography-mass spectrometry) has high accuracy, it takes a long time and cannot meet the rapid screening needs of sudden odor events; the sensitivity of portable detection equipment is limited, and the recognition accuracy of low-concentration odorants is insufficient; emerging technologies such as biosensors and electronic noses are not yet fully mature and are easily affected by interfering substances. However, with the deep application of "Internet + monitoring" and "big data" technologies, the rapid screening database and online monitoring network for odorants are gradually improving, which is conducive to real-time early warning and accurate tracing of odor events.

[0004] It is worth noting that the distribution of odorants in water shows distinct regional differences, which are rooted in nature and shaped by human activities. Natural environment is the basis for the formation of differences. The geographical characteristics such as topography, vegetation and hydrology in different regions directly determine the types and distribution of natural odorants. From the refreshing smell of mountain streams due to the dissolution of rock minerals to the unique fishy smell of wetland water due to the decomposition of humus, the diversity of natural geography "endows" water with different original odor marks. Human activities, especially industrial and agricultural production, are the key drivers of the intensification of differences: the water around the chemical industry park may contain pungent odorants due to sulfide, and the water in the main agricultural production areas may be contaminated by chemical fertilizers, pesticides or livestock breeding, and thus emit complex chemical or biological fermentation odors. The regional differentiation of industrial structure thus translates into distinct separation of water odor. In view of the existing technical defects, a rapid screening and analysis method suitable for a variety of common odorants in Zhongshan City is urgently needed. SUMMARY

[0005] The application aims to provide a screening and quantification method of odor substances in water based on a gas chromatography triple quadrupole mass spectrometer, which is aimed at odor substances in water in any region, establishes a screening database, uses corresponding standard samples to draw a standard curve for quantitative analysis of positive samples, and provides a quantitative method of odor substances, and has the advantages of high sensitivity, good accuracy, good reproducibility, simple and fast operation, etc.

[0006] The application aims to provide a screening and quantification method of odor substances in water based on a gas chromatography triple quadrupole mass spectrometer, which is aimed at odor substances in water in any region, establishes a screening database, uses corresponding standard samples to draw a standard curve for quantitative analysis of positive samples, and provides a quantitative method of odor substances, and has the advantages of high sensitivity, good accuracy, good reproducibility, simple and fast operation, etc. A rapid screening method of odor substances in water comprises the following steps: (1) Constructing an MRM intelligent screening database: using the MRM mode of GC-MS / MS to construct an intelligent screening database of odor substances in water samples in any region; the intelligent screening database includes the name and / or CAS number, retention time, m / z and collision voltage of the characteristic ion pair of the odor substances; (2) Using an online solid-phase microextraction method to pretreat the water sample; (3) Using the intelligent screening database constructed in step (1), if there is a characteristic ion pair in the retention time range and it is identified, it can be judged that the target substance exists in the sample, and the screening is positive.

[0007] Preferably, the odor substance intelligent screening database in step (1) is obtained by importing the name and / or CAS number, retention time, m / z and collision voltage of the characteristic ion pair of the odor substances into the MRM optimization tool.

[0008] Preferably, the odor substance intelligent screening database in step (1) is obtained by importing the name and / or CAS number, retention time, m / z and collision voltage of the characteristic ion pair of the odor substances into the MRM optimization tool. a) According to the odor substances in the local reservoir, river water, drinking water, etc., and the name and CAS number obtained, an odor substance mixed standard solution is prepared with an organic solvent; b) The mixed standard solution in a) is injected into the GC-MS / MS to obtain the precursor ions and retention time of a plurality of odor substances, and the precursor ion-product ion pair of each substance is obtained by using the product ion scanning function of the mass spectrometer to establish a product ion scanning method; c) The ion pairs generated in b) are scanned by using the MRM function of the detection software, and the collision voltage range is 5-40 ev, and the collision voltage at the maximum ion pair abundance is taken as the optimal collision voltage of the ion pair.

[0009] d) The product ion data file in c) is imported into the odor substance database to obtain parameter information containing the name, CAS number, characteristic ion pair and collision voltage of the odor substance; e) Injecting the mixed standard solution of the odorant into the GC-MS / MS, and obtaining the retention time of the corresponding odorant under the same instrument conditions as b); f) Importing the retention time into the odorant database in d), and completing the construction of the screening database of the odorants in water.

[0010] Preferably, the sample screened positive in step (3) can be quantified by the internal standard method through the gradient standard curve drawn by the standard.

[0011] Preferably, the mixed standard solution of the local odorant in a) includes the details shown in Table 1, and the concentration of each substance is 10 mg / L.

[0012] Preferably, the instrument conditions in b), c) and e) are as follows: the injection port temperature is 200-280 DEG C; the injection mode is splitless injection; the chromatographic column is DB-5MS (30 m x 0.25 mm x 0.25 um); the column flow rate is 1.0-2.0 mL / min (30-55 cm / sec); the temperature rising program is as follows: the initial column temperature is 50-110 DEG C, and is kept for 0-5 min, and is raised to 120-220 DEG C at a rate of 3-20 DEG C / min, and is kept for 0-5 min, and is raised to 300 DEG C at a rate of 5-25 DEG C / min, and is kept for 0-20 min; the mass spectrometry conditions are as follows: the ionization mode is EI; the ionization voltage is 70 eV; the interface temperature is 230 DEG C; the ion source temperature is 230 DEG C; the scanning mode is MRM; the scanning mass number range (m / z) is 45-700; and the detection voltage is the tuning voltage.

[0013] Preferably, the voltage range in c) is 5-40 V, and the voltage interval is 5 V.

[0014] Preferably, the three-phase solid-phase microextraction material used in the pretreatment in step (2) is DVB / CWR / PDMS. The online solid-phase microextraction conditions are as follows: the extraction temperature is 70 DEG C; the extraction time is 30 min; the desorption temperature is 270 DEG C; and the desorption time is 6 min.

[0015] The present application constructs a screening database of common odorants in water in any region by using the MRM mode of the gas chromatography triple quadrupole mass spectrometer. In the actual preliminary screening process, the odorants in water samples of different sources are screened, and the characteristic pollutants possibly existing in the odorants are speculated. In the absence of standard products, the screening database can be used for wide-spectrum and accurate screening. In addition, the present application also provides a quantitative analysis method with good reproducibility and high sensitivity for the samples screened positive.

[0016] Compared with the prior art, the present application has the following beneficial effects: 1. The application builds an intelligent screening database for common taste and odor substances in local water in any region, which includes the name and / or CAS number, retention time, m / z and collision voltage of characteristic ion pairs of the taste and odor substances.

[0017] When encountering the initial screening of taste and odor substances in the region water quality emergency odor complaint, the screening database can be used to simultaneously achieve rapid and broad-spectrum screening of up to dozens of local common taste and odor substances, reducing screening work costs and improving efficiency, and each water sample screening time is not more than 1 h.

[0018] 2. The screening of the application is based on the analysis of the multiple reaction monitoring mode (MRM) of the gas chromatography-triple quadrupole mass spectrometer, which has higher anti-interference ability than the conventional gas chromatography-mass spectrometer selection ion monitoring mode (SIM), is more suitable for water source samples with complex matrix, has better accuracy and higher sensitivity.

[0019] 3. The application provides a high-sensitivity and high-reproducibility quantitative method by purchasing related standard substances to quantify the taste and odor substances in the positive sample after screening by the internal standard method. DETAILED DESCRIPTION

[0020] Figure 1 is the total ion chromatogram of 34 taste and odor substances in the intelligent screening database.

[0021] Figure 2 is the superimposed graph of each ion pair of the water sample in Example 2 after MRM screening. DETAILED DESCRIPTION

[0022] The terms used in the application have the meanings generally understood by those of ordinary skill in the art, unless otherwise specified.

[0023] The application will be further described in detail below with reference to specific examples and data. It should be understood that the examples are only intended to illustrate the application, and not to limit the scope of the application in any way.

[0024] In the following examples, various processes and methods not described in detail are conventional methods known in the art. The materials, reagents, devices, instruments, equipment, etc. used in the examples below can be obtained from commercial sources unless otherwise specified.

[0025] The terms used in the application have the meanings generally understood by those of ordinary skill in the art, unless otherwise specified.

[0026] The application will be further described in detail below with reference to specific examples and data. It should be understood that the examples are only intended to illustrate the application, and not to limit the scope of the application in any way.

[0027] In the following embodiments, the various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, apparatus, instruments, equipment, etc., used in the following examples are commercially available.

[0028] The instrument, reagent, and solvent information in the following examples is as follows: Instruments: Agilent 7890B-7000D gas chromatograph-triple quadrupole system; Zhida RTC three-in-one fully automated sampler solid-phase microextraction module (DVB / CAR / PDMS model arrow extraction head); chromatographic column: VF-624ms (60 m x 320 μm x 1.8 μm); DVB / CAR / PDMS model solid-phase microextraction head; experimental water was Grade I water conforming to GB / T 6682.

[0029] Software: GC / QQQ Enhanced Masshunter; Agilent Qualitative Analysis; Agilent Quantitative Analysis; Inlab solution.

[0030] Reagents: Sodium chloride (NaCl) analytical grade; sodium thiosulfate (NaS2O3); Standard stock solutions: 100 mg / L-1000 mg / L, see the table below for each substance; Standard working solution: 0.1 mg / L - 1 mg / L; Internal standard stock solution: Certified standard solutions 1,2-dichlorobenzene-d4 and acenaphthene-d10 can be purchased; Internal standard solution: 0.1 mg / L of 1,2-dichlorobenzene-d4, acenaphthene-d10.

[0031] Consumables: Needle filter: The filter membrane is made of 0.45um polyvinylidene fluoride and polypropylene; Injection syringe: 2ml; Mass spectrometry collision gas: nitrogen, 99,999%; Mass spectrometer carrier gas: Helium, 99,999%.

[0032] Example 1: An odor and taste substance screening database constructed based on the multiple reaction monitoring mode of a gas chromatography-triple quadrupole mass spectrometer, comprising the following steps: This embodiment uses local odor substances in Zhongshan as an example. Table 1 lists the specific substances and internal standard substances in Zhongshan. Using acetone as the solvent, stock solutions were prepared for each of the above substances. The 36 standard (including internal standard) stock solutions from Table 1 were placed in 10mL volumetric flasks and diluted to the mark with acetone. The target concentration of the mixed standard working solution was 10mg / L. 1μL of the target mixture was injected into GC-MS / MS, and scanned using the scan mode in Masshunter software to obtain the full scan data files of the target substances. The instrument conditions are as follows: Column: VF-624MS (60 m x 320 μm x 1.8 μm); Injector: 270 ℃; Splitless carrier gas flow rate: 1 mL / min; Temperature program: Heat to 40 ℃ and hold for 2 min, ramp to 110 ℃ at 8 ℃ / min and hold for 10 min, ramp to 260 ℃ at 10 ℃ / min and hold for 15 min. Mass spectrometry conditions: Ionization mode: EI; Ionization voltage: 70 eV; Interface temperature: 230 ℃; Ion source temperature: 230 ℃; Scan mode: Q3 full scan; Scan mass range: 45~700; Detection voltage: Tuned voltage.

[0033] By using the full scan data file of odor substances, the retention time of each target analyte and at least one precursor ion m / z are obtained. The product ion scanning method in Masshunter software is then used to obtain at least two product ions (paired with the precursor ions to form ion pairs). Using the MRM scanning function in Masshunter software, ion pairs of various substances were scanned within a collision voltage range of 5-40 eV. The collision voltage at which the abundance of the ion pair was maximized was taken as the optimal collision voltage for that ion pair. The names, CAS numbers, characteristic ion pairs, collision voltages, and retention times of the odor-containing substances were obtained, thus completing the construction of an intelligent screening database for odor-containing substances. The specific parameters of the database are shown in Table 1.

[0034] Table 1. Intelligent Screening Database for Odor and Flavor Substances

[0035] Standard curves for each odor substance in the odor library were established using the following method: Preparation of standard curve water samples: Certified standards for the odor substances were diluted to 0.1 mg / L-1 mg / L to obtain a mixed standard solution. 50 μL of internal standard solution was added to five 10 mL aliquots of pure water, and 5 μL, 10 μL, 20 μL, 50 μL, and 100 μL of mixed standard solution were added to the same five aliquots of pure water, respectively, to obtain five water samples with odor substance concentrations from low to high. Each substance was detected in these five water samples, and standard curves for each substance were plotted using Agilent Quantitative Analysis software. The lowest point of the standard curve for each substance was prepared (using 5 μL of mixed standard solution). The above method was used to perform eight consecutive tests to verify the detection limits and quantification limits of each odor substance. The correlation coefficients and detection limits of each curve are shown in Table 2.

[0036]

[0037] Example 2: Qualitative and quantitative analysis of common odor substances in local water samples from Zhongshan using a rapid screening library. (1) Sample pretreatment Insoluble solids in the water sample were filtered using a 0.45 μm aqueous filter membrane. 1 g of sodium thiosulfate was added per 100 ml of water sample to remove residual chlorine and other oxidizing substances, followed by 3.5 g of sodium chloride. Odor and taste substances in the water were extracted using a three-phase solid-phase microextraction (SPE) column. The online headspace SPE method was programmed using Inlab Solution software with the following settings: extraction temperature: 70 ℃; extraction time: 30 min; desorption temperature: 270 ℃; desorption time: 6 min. The blank, standard curve, and sample were pretreated using this method.

[0038] (2) Screening test The sample was a river water sample collected from a sudden odor incident in a town in Zhongshan City. The purpose of the screening was to determine whether the water sample contained odor substances from the odor screening database.

[0039] The samples in step (1) were screened using the screening database constructed in Example 1. If characteristic ion pairs were found and identified within the retention time range (0-50 min), the sample was determined to contain the target analyte, and the screening result was positive. Figure 2 As shown, 2-methylisoborneol has quantitative and qualitative characteristic ion pairs within its retention time range, and its abundance ratio is identifiable within the range. Based on the screening results, the sample is a positive sample containing 2-methylisoborneol.

[0040] Of course, the present invention is not limited to the above-described embodiments. Those skilled in the art can make equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications and substitutions are all included within the scope defined by the claims of this application.

Claims

1. A rapid screening method for odor substances in water, characterized in that, Includes the following steps: (1) Constructing an MRM screening database: Using the MRM mode of GC-MS / MS, a screening database of odor substances in water samples from any region is constructed; the screening database includes the name and / or CAS number of the odor substance, retention time, m / z of characteristic ion pairs and collision voltage; (2) The water sample was pretreated and the odor substances in the water were extracted by online solid phase microextraction. The specific extraction conditions were: extraction temperature: 70℃; extraction time: 30 min; desorption temperature: 270℃; desorption time: 6 min. (3) Using the odor and odor substance screening database and the corresponding MRM screening method constructed in step (1), the water sample is screened for odor and odor substances. If characteristic ion pairs are found and identified within the retention time range, it is determined that the water sample contains odor and odor substances from the MRM screening database. The establishment process of the water odor substance screening database mentioned in step (1) includes the following steps: a) Based on the odorous substances found in the reservoirs, rivers, and drinking water in the region, obtain their names and CAS numbers, and prepare a mixed standard solution of the odorous substances using organic solvents. b) Inject the mixed standard solution from a) into GC-MS / MS to obtain the precursor ions and retention times of various odor substances. Utilize the product ion scanning function of mass spectrometry to obtain the precursor ion-product ion pairs of each substance and establish a product ion scanning method. c) Scan the ion pairs generated in b) using the MRM detection software with a collision voltage range of 5-40 eV. Take the collision voltage at which the abundance of the ion pair is the highest as the optimal collision voltage for that ion pair. Obtain parameter information such as the name, CAS number, characteristic ion pairs and collision voltage of the semi-volatile organic compounds, and complete the construction of the intelligent screening database for odor substances. The GC-MS / MS described in steps b) and c) is a gas chromatography-triple quadrupole mass spectrometer; the gas chromatography conditions are as follows: column: VF-624MS (60 m x 320 μm x 1.8 μm); injection port: 270 ℃; splitless carrier gas flow rate: 1 mL / min; temperature program: heat to 40 ℃ and hold for 2 min, increase to 110 ℃ at a rate of 8 ℃ / min and hold for 10 min, increase to 260 ℃ at a rate of 10 ℃ / min and hold for 15 min. The mass spectrometry conditions are as follows: ionization mode: EI; ionization voltage: 70 eV; interface temperature: 230 ℃; ion source temperature: 230 ℃; scan mode: MRM; scan mass number range: 45~700; detection voltage: tuned voltage.

2. The rapid screening method for odor substances in water according to claim 1, characterized in that, The odor substance screening database in step (1) is obtained by importing the names and / or CAS numbers of odor substances, the m / z of characteristic ion pairs and the collision voltages of the odor substances obtained by the MRM optimization tool.

3. The water sample pretreatment method according to claim 1 or 2, characterized in that, Sample pretreatment was performed using a three-phase solid-phase microextraction method.

4. The rapid screening method for odor substances in water according to claim 3, characterized in that, After screening positive samples in step (3), a gradient standard curve can be plotted using standard products, and the odor substances in the positive samples can be quantified by internal standard method.

5. The rapid screening method for odor substances in water according to claim 1, characterized in that, In step (2), the water sample is pretreated by filtering it through a 0.45 μm aqueous filter membrane, adding 1 g of sodium thiosulfate to remove residual chlorine and other oxidizing substances, adding 3.5 g of sodium chloride, and then extracting it using a solid phase microextraction column.

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