Method for detecting and analyzing smelly substances in water through in-situ purge and trap-gas chromatography-mass spectrometry

Abstract

According to the invention, qualitative and quantitative analysis of the smelly substances in water is realized based on a pretreatment method of a soil sample, and a method for sensitively, rapidly and simply analyzing the smelly substances in water by using an in-situ purge and trap-gas chromatograph-mass spectrometer combined method is established for detection and analysis of the smelly substances in water. The method comprises the steps of sample pretreatment, qualitative analysis, quantitative analysis and adsorption model fitting. The method can be fully automatically carried out, salt addition is not needed, operation is easy and convenient, the sample detection speed is three times that of a national standard method, the detection limit is low, reproducibility is good, the high standard addition recovery rate can be achieved in various water bodies, and the degree of fitting of the smell substance experiment detection result and an activated carbon adsorption model is high. The method is beneficial to large-scale scientific research related to the odor substances in the water, and continuous detection of the odor substances in the polluted water can be realized.

Description

Technical Field

[0001] The present invention belongs to the field of water pollution detection and treatment, and specifically relates to a method for detecting and analyzing odorous substances in water by in-situ purge and trapping-gas chromatography-mass spectrometry. Background Art

[0002] With the destruction of the water environment, eutrophication of water bodies has become frequent worldwide, leading to the appearance of taste and odor compounds in water. 2-Methylisoborneol (2-MIB) and geosmin (GSM) are two typical odorous substances that can cause unpleasant odors in water but are difficult to remove during water treatment. The newly revised "Standard for Drinking Water Quality" (GB 5749-2022) has imposed additional restrictions on 2-MIB and GSM, indicating that people are increasingly concerned about the odor in water. However, due to the extremely low odor threshold concentrations of these substances, the perception concentration of 2-MIB is 1–10 ng / L, and the perception concentration of GSM is 4–10 ng / L, making it difficult to detect odors in water quickly and accurately.

[0003] The national standard (GB / T 32470-2016) headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry is widely used to monitor odorants in water. While this method offers low detection limits and high precision, it is fragile and expensive. A single sample requires more than an hour to measure and manual injection, and a maximum of 10 samples can be measured per day. Research on odorant treatment requires measuring a large number of samples at once, and the limited storage time of odorant water samples (less than 24 hours) severely limits large-scale research on odorant treatment.

[0004] The traditional purge-and-trap-gas chromatography-mass spectrometry method can also be used to detect substances in water and has the advantage of fully automatic operation. However, the measurement process requires the addition of salt to increase the response intensity. Salt has the risk of corroding instrument components and shortening the instrument life. In addition, because the purge work is carried out in a purge tube, the purge tube is easily contaminated by high-concentration pollutants and easily residual components, resulting in poor anti-pollution ability (this invention does not require the use of salt and a purge tube). It cannot effectively detect odorous substances in highly eutrophic water bodies, which limits its development in the detection of odorous substances in natural water. Therefore, there is an urgent need for a sensitive, rapid, and simple detection and analysis method that not only facilitates odor research in water treatment but also enables the continuous detection of odorous substances in polluted water bodies while ensuring the safety of the instrument.

[0005] The U.S. Environmental Protection Agency (EPA) standard methods recommend two different gas purge and trap methods (5030C and 5030A in SW-846). Method 5030C is used for pretreatment of water samples to detect volatile organic compounds (VOCs) in water, while method 5030A is used for pretreatment of soil samples to detect VOCs. To date, researchers have used method 5030C as a reference, using a purge tube to collect gaseous compounds and establishing a purge and trap-gas chromatography-mass spectrometry (GC-MS) method to detect odorants in water. However, no one has attempted to use the in-situ purge technique described in method 5030A to detect odorants or VOCs, such as 2-MIB and GSM, in water samples.

[0006] In the soil pretreatment purge method of 5030A, a certain amount of water needs to be added to the soil sample, and the sample in the suspension state needs to be purged and captured in situ. The design concept of the present invention is to regard water samples as more special soil samples, breaking through the traditional thinking limitation that water samples can only be treated with water sample pretreatment methods. This method avoids the use of purge tubes that are easily contaminated, and instead directly performs in-situ purge and capture in the purge bottle, thereby achieving a detection effect that is superior to the traditional purge and capture method. The low detection limit of the method can be achieved without the use of salt, extending the life of the instrument. Since the invention is based on the purge method of soil pretreatment, even highly eutrophic water samples usually have less component concentration and complexity than soil samples, which gives the method a unique anti-pollution ability, successfully solving the anti-pollution problem that has long plagued the traditional purge and capture-gas chromatography-mass spectrometry technology, and can also solve the problem that the headspace solid phase microextraction method in the national standard is time-consuming and labor-intensive and difficult to achieve large-scale odor substance processing research. Summary of the Invention

[0007] A method for detecting and analyzing odorous substances in water by in-situ purge and trap-gas chromatography-mass spectrometry, characterized by comprising the following steps:

[0008] (1) Sample pretreatment:

[0009] Take a water sample containing odorous substances, filter it through a filter membrane, take a volume of V mL and place it in a purge bottle, add a certain concentration of internal standard and a magnetic rotor into the bottle, and place the purge bottle on the sample table.

[0010] (2) Purge and capture:

[0011] Insert a sample needle into the purge bottle, and purge the odorous substances in the water for t minutes at a purge temperature of T℃, a purge flow rate of QmL / min, and a stirring speed of vr / min. The purge gas is captured by a trap and desorbed at a temperature of T 吸 ℃, desorption t 吸After 10 minutes, the sample was sent to the gas chromatography mass spectrometer injection port, and then the trap was baked at temperature T 烘烤 ℃ with flow rate Q 烘烤 mL / min for baking 烘烤 minute.

[0012] (3) Qualitative analysis:

[0013] The pre-treated samples were tested using a gas chromatography-mass spectrometer, which began to operate according to the following parameters: injection port temperature T 进样口-1 ℃, the initial temperature of the column heating program T 0-1 ℃, holding time t 0- 1min, with a heating rate v 1-1 ℃ / min heating to T 1-1 ℃, and finally the heating rate v 2-1 ℃ / min heating to T 2-1 ℃; injection method: split injection, split ratio R1; flow rate Q 色谱-1 mL / min, mass spectrometry conditions, transfer line temperature T 传输-1 ℃, ion source temperature T 离子源-1 ℃, acquisition mode: SCAN. The odorant was tested as a standard under the same conditions. The obtained standard was a real-time mass spectrum. By comparing the retention time and characteristic ions of the chromatographic peaks of the standard and sample in the spectrum, the presence of the analyte in the sample was determined.

[0014] Furthermore, after sample pretreatment and purging and trapping, in addition to qualitative analysis of odorous substances, quantitative analysis of odorous substances can also be performed.

[0015] Quantitative analysis:

[0016] After the sample is pre-treated and purged at a constant temperature, the sample is tested using a gas chromatography-mass spectrometer. The gas chromatography-mass spectrometer starts running according to the following parameters: injection port temperature T 进样口-2 ℃, the initial temperature of the column heating program T 0-2 ℃, holding time t 0-2 min, with heating rate v 1-2 ℃ / min heating to T 1-2 ℃, and finally the heating rate v 2-2 ℃ / min heating to T 2-2 ℃; injection method: split injection, split ratio R2; flow rate Q 色谱-2 mL / min, mass spectrometry conditions, transfer line temperature T 传输-2 ℃, ion source temperature T 离子源-2℃, acquisition mode: SIM. Next, weigh the standard sample and dilute it with ultrapure water to prepare a standard solution. Add the internal standard to the solution to a specific concentration. After sample pretreatment and purge-and-trap, test under equivalent gas chromatography-mass spectrometry conditions. Place the sample on a sample tray and analyze on the instrument. A standard curve for standard internal standard quantification is generated. The corresponding concentration is then determined on the standard curve by comparing the response values ​​of the sample to the internal standard. The content of the odorant in the sample is determined.

[0017] Furthermore, the odorous substance in step (1) is at least one of 2-methylisoborneol (2-MIB) and geosmin (GSM), and the V is 1-30 mL.

[0018] Furthermore, a magnetic rotor may be added to the purge bottle described in step (2) to improve the stability of the detection results. The specification of the magnetic rotor is 0.05mm*0.1mm-0.1mm*mm.

[0019] Furthermore, in step (2), the t is 5-15 min, the T is 10° C.-70° C., the Q is 10 mL / min-80 mL / min, and the v is 0 r / min-300 r / min.

[0020] Furthermore, the desorption and baking conditions in step (2) are as follows: desorption time t 吸 1-5min, desorption temperature T 吸 10-300℃, trap baking temperature T 烘烤 10-300℃, baking time t 烘烤 1-10min, baking gas flow Q 烘烤 10-300mL / min.

[0021] Furthermore, the T 进样口-1 is 100-250°C; the T 0-1 is 10-50°C, the t 0-1 For 1-5min, the v 1-1 is 10-30℃ / min; the T 1-1 is 100-250°C, the v 2-1 is 10-50℃ / min, the T 2-1 is 100-350℃; the R1 is 1:3-1:100; the Q 色谱-1 is 1-10mL / min; the T 传输-1 is 100-380°C, the T 离子源-1 100-380℃.

[0022] Furthermore, the parameters of the gas chromatography-mass spectrometry instrument in step (3) are: 进样口-2 is 100-250°C; the T 0-2 is 10-50°C, the t 0-2 For 1-5min, the v 1-2 is 10-30℃ / min; the T 1-2 is 100-250°C, the v 2-2 is 10-50℃ / min, the T 2-2 is 100-350℃; the R2 is 1:3-1:100; the Q 色谱-2 is 1-10mL / min; the T 传输-2 is 100-380°C, the T 离子源-2 100-380℃.

[0023] Furthermore, the standard substance described in step (1) and the quantitative analysis is an odorant; the odorant is at least one of 2-methylisoborneol (2-MIB) and geosmin (GSM).

[0024] Furthermore, an internal standard substance 2-methoxy-3-isobutylpyrazine (IBMP) is added as described in step (1) and quantitative analysis, and IBMP is added to a concentration of 10-2000 ng / L.

[0025] The beneficial effects achieved by the present invention are:

[0026] (1) The in-situ purge and trap-gas chromatography-mass spectrometry method of the present invention is a sensitive, rapid and simple method for analyzing odorous substances in water. It is fully automatic, does not require the addition of salt, and is easy to operate. Since the in-situ purge and trap pretreatment can be run simultaneously with the gas chromatography-mass spectrometry detection, it only takes 20 minutes to detect a single sample. The sampling speed is three times that of the national standard method. It has a low detection limit and good reproducibility. It achieves a high recovery rate in a variety of water bodies, which facilitates large-scale scientific research related to odorous substances in water.

[0027] (2) Compared with the traditional purge and trap method, the in-situ purge and trap method of the present invention avoids the erosion and damage of salt to the instrument, has stronger anti-pollution ability, can realize the rapid determination of odor substances in highly eutrophic water bodies, and can realize the continuous detection of odor substances in highly polluted water bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of a method for detecting and analyzing odorous substances in water using in-situ purge and trap-gas chromatography-mass spectrometry.

[0029] Figure 2 Detail of the in-situ purge process.

[0030] Figure 3 The graphs are the mass spectra and matching results of 2-MIB and GSM.

[0031] Figure 4 This is a 2-MIB and GSM line diagram.

[0032] Figure 5 This is the adsorption isotherm diagram of 2-MIB and GSM on activated carbon. DETAILED DESCRIPTION

[0033] The following describes preferred embodiments of the present invention. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0034] The experimental samples were spiked water samples with varying water quality backgrounds: ultrapure water, tap water, and natural water. The tap water and natural water were filtered through a 10µm filter membrane. The internal standard, 2-MIB, and GSM were added to the ultrapure water and filtered water at specific concentrations to obtain the desired test samples. Specific implementation method 1

[0036] A method for qualitatively detecting odorous substances in water by in-situ purge and trap-gas chromatography-mass spectrometry, the steps of which are as follows:

[0037] (1) Sample pretreatment: Take a water sample, filter it through a membrane according to the type of water sample, add 20 mL of sample and 0.5 mL of IBMP with a concentration of 8 μg / L into a purge bottle (with a polytetrafluoroethylene-surfaced silicone diaphragm), then add a magnetic rotor (0.5 mm*1 mm) and place it on the sample table.

[0038] Purge and trap:

[0039] The purge time was 12 min, the purge temperature was 60 °C, the purge flow rate was 40 mL / min, the stirring speed was 120 r / min, the solution volume was 20 mL, and the additional water amount was 0 mL. The desorption conditions were as follows: time 2.5 min, desorption temperature 250 °C, trap baking at 280 °C for 2 min, baking gas flow rate 200 mL / min. The details of the in-situ purge process are as follows: Figure 1 shown.

[0040] (2) Qualitative analysis:

[0041] The odorous substances collected by in-situ purge are injected into the gas chromatography-mass spectrometry instrument for testing. At the same time, the standard water sample is tested under the same conditions to obtain the chromatogram and mass spectrum of the odorous substances, such as Figure 2 As shown in FIG, by comparing the retention time and characteristic ions of the chromatographic peaks of the standard and sample, it is determined that the sample contains the analyte.

[0042] The GC-MS parameters were as follows: purge time 12 min, temperature 60°C, flow rate 40 mL / min, stirring speed 120 rpm, solution volume 20 mL, and additional water volume 0 mL. Desorption conditions were 2.5 min, desorption temperature 250°C, trap bakeout at 280°C for 2 min, and bakeout gas flow rate 200 mL / min. GC-MS parameters included an inlet temperature of 250°C, constant carrier gas flow rate 1.3 mL / min, and a column temperature program of 40°C, hold time 2 min, ramp to 180°C at a rate of 30°C / min, and finally to 270°C at a rate of 10°C / min. Injection mode: split injection, split ratio 1:5, flow rate 3 mL / min. The GC-MS column was an Elite-5MS, 60 mm × 0.25 mm × 0.25 μm. The mass spectrometry conditions were as follows: transfer line temperature: 280°C, ion source temperature: 230°C, acquisition mode: Scan; scan range: 50–300 m / z; Specific implementation method 2

[0044] After qualitative analysis of the specific implementation method, the sample was purged and captured in situ, and quantitative analysis was performed using a gas chromatography-mass spectrometer.

[0045] (1) Sample pretreatment:

[0046] Take a water sample, filter it through a membrane according to the type of water sample, add 20 mL of sample and 0.5 mL of IBMP with a concentration of 8 μg / L into a purge bottle (with a polytetrafluoroethylene-surfaced silicone diaphragm), then add a magnetic rotor (0.5 mm*1 mm) and place it on the sample table.

[0047] (2) Purge and capture:

[0048] Insert a sample needle into the purge bottle, and purge the odorous substances in the water in the bottle according to the set parameters. The in-situ purge and capture parameters are: purge time 12 min, purge temperature 60 ° C, purge flow 40 mL / min, stirring speed 120 r / min, solution volume 20 mL, additional water amount 0 mL, desorption conditions are time 2.5 min, desorption temperature 250 ° C, trap baking 280 ° C, 2 min, baking gas flow 200 mL / min.

[0049] (3) Qualitative analysis:

[0050] The odorous substances collected by in-situ purge are injected into the gas chromatography-mass spectrometry instrument for testing. At the same time, the standard water sample is tested under the same conditions to obtain the chromatogram and mass spectrum of the odorous substances, such as Figure 2 As shown in FIG, by comparing the retention time and characteristic ions of the chromatographic peaks of the standard and sample, it is determined that the sample contains the analyte.

[0051] The GC-MS parameters were as follows: purge time 12 min, temperature 60°C, flow rate 40 mL / min, stirring speed 120 rpm, solution volume 20 mL, and additional water volume 0 mL. Desorption conditions were 2.5 min, desorption temperature 250°C, trap bakeout at 280°C for 2 min, and bakeout gas flow rate 200 mL / min. GC-MS parameters included an inlet temperature of 250°C, constant carrier gas flow rate 1.3 mL / min, and a column temperature program of 40°C, hold time 2 min, ramp to 180°C at a rate of 30°C / min, and finally to 270°C at a rate of 10°C / min. Injection mode: split injection, split ratio 1:5, flow rate 3 mL / min. The GC-MS column was an Elite-5MS, 60 mm × 0.25 mm × 0.25 μm. The mass spectrometry conditions were as follows: transfer line temperature: 280°C, ion source temperature: 230°C, acquisition mode: Scan; scan range: 50–300 m / z;

[0052] (4) Quantitative analysis:

[0053] Standard curve configuration: Mix the standards (2-MIB and GSM) with various concentrations of IBMP and dilute them to 5, 10, 20, 40, 60, 80, 100, 160, and 400 ng / L, with the IBMP concentration fixed at 200 ng / L. Place 20 mL of the solution in a 40 mL purge vial. Place the vial in the injection tray and analyze on the gas chromatography-mass spectrometer. The purge parameters were: purge time 12 min, temperature 60°C, flow rate 40 mL / min, stirring speed 120 rpm, solution volume 20 mL, and additional water addition 0 mL. Desorption conditions were: desorption time 2.5 min, desorption temperature 250°C, trap bakeout at 280°C for 2 min, and bakeout gas flow rate 200 mL / min. GC-MS parameters included: inlet temperature of 250°C; carrier gas constant flow mode, flow rate of 1.3 mL / min; column temperature program: initial temperature 40°C, hold time 2 min, ramp to 180°C at a rate of 30°C / min, and finally to 270°C at a rate of 10°C / min; injection method: split injection, split ratio 1:5; flow rate 3 mL / min. GC-MS column model: Elite-5ms, 60 mm × 0.25 mm × 0.25 μm. The mass spectrometry conditions were as follows: transfer line temperature: 280°C, ion source temperature: 230°C, acquisition mode: Sim; IBMP detection ions m / z 94, 124, 151; 2-MIB detection ions m / z 95, 107, 135; GSM detection ions m / z 112, 125; the obtained standard curves for 2-MIB and GSM internal standard quantification were as follows: Figure 4 The samples were tested under the same conditions, and the corresponding concentrations were found in the standard curve using the detected response values ​​to determine the contents of 2-MIB and GSM in the samples.

[0054] (5) Determination of method detection limit

[0055] According to the National Ecological Environment Standard of the People's Republic of China (HJ 168-2020), follow all the steps of sample analysis, repeat the blank test n times (n ≥ 7), convert each measurement result into the concentration or content in the sample, calculate the standard deviation of n parallel measurements, and calculate the method detection limit according to the following formula.

[0056] MDL=t (n-1,0.99) ×S

[0057] Where: MDL is the method detection limit; n is the number of replicate measurements of the sample; t is the t distribution value (one-sided) when the degree of freedom is n-1 and the confidence level is 99%; S is the standard deviation of n replicate measurements.

[0058] After repeated experiments, the detection limit of 2-MIB and GSM was 0.41 ng / L, which were far lower than the limit of 10 ng / L specified in the national standard (GB 5749-2022).

[0059] (4) Actual sample testing

[0060] The actual water sample from the odor outbreak was taken and tested according to this method. The test results were: 2-MIB concentration was 29.4 ng / L, and GSM was not detected. Specific implementation method three

[0062] (1) Sample pretreatment:

[0063] Take a water sample, filter it through a membrane according to the type of water sample, add 20 mL of sample and 0.5 mL of IBMP with a concentration of 8 μg / L into a purge bottle (with a polytetrafluoroethylene-surfaced silicone diaphragm), then add a magnetic rotor (0.5 mm*1 mm) and place it on the sample table.

[0064] (2) Purge and capture:

[0065] Insert a sample needle into the purge bottle, and purge the odorous substances in the water in the bottle according to the set parameters. The in-situ purge and capture parameters are: purge time 12 min, purge temperature 60 ° C, purge flow 40 mL / min, stirring speed 120 r / min, solution volume 20 mL, additional water amount 0 mL, desorption conditions are time 2.5 min, desorption temperature 250 ° C, trap baking 280 ° C, 2 min, baking gas flow 200 mL / min.

[0066] (3) Qualitative analysis:

[0067] The odorous substances collected by in-situ purge are injected into the gas chromatography-mass spectrometry instrument for testing. At the same time, the standard water sample is tested under the same conditions to obtain the chromatogram and mass spectrum of the odorous substances, such as Figure 2 As shown in FIG, by comparing the retention time and characteristic ions of the chromatographic peaks of the standard and sample, it is determined that the sample contains the analyte.

[0068] The GC-MS parameters were as follows: purge time 12 min, temperature 60°C, flow rate 40 mL / min, stirring speed 120 rpm, solution volume 20 mL, and additional water volume 0 mL. Desorption conditions were 2.5 min, desorption temperature 250°C, trap bakeout at 280°C for 2 min, and bakeout gas flow rate 200 mL / min. GC-MS parameters included an inlet temperature of 250°C, constant carrier gas flow rate 1.3 mL / min, and a column temperature program of 40°C, hold time 2 min, ramp to 180°C at a rate of 30°C / min, and finally to 270°C at a rate of 10°C / min. Injection mode: split injection, split ratio 1:5, flow rate 3 mL / min. The GC-MS column was an Elite-5MS, 60 mm × 0.25 mm × 0.25 μm. The mass spectrometry conditions were as follows: transfer line temperature: 280°C, ion source temperature: 230°C, acquisition mode: Scan; scan range: 50–300 m / z;

[0069] (4) Quantitative analysis:

[0070] 20 mL of the solution was placed in a 40 mL purge bottle. The sample was placed on the injection tray and analyzed using the following gas chromatography-mass spectrometry parameters: purge time 12 min, temperature 60°C, flow rate 40 mL / min, stirring speed 120 rpm, solution volume 20 mL, and additional water volume 0 mL. Desorption conditions were: time 2.5 min, desorption temperature 250°C, trap bakeout at 280°C for 2 min, and bakeout gas flow rate 200 mL / min. Gas chromatography-mass spectrometry parameters included: inlet temperature 250°C; carrier gas constant flow mode, flow rate 1.3 mL / min; column temperature program: initial temperature 40°C, hold time 2 min, ramp to 180°C at a rate of 30°C / min, and finally to 270°C at a rate of 10°C / min. Injection mode: split injection, split ratio 1:5, flow rate 3 mL / min. The gas chromatography-mass spectrometry column model was Elite-5ms, 60 mm × 0.25 mm × 0.25 μm. The mass spectrometry conditions were: transfer line temperature: 280°C, ion source temperature: 230°C, acquisition mode: Sim; IBMP detection ions were m / z 94, 124, and 151; 2-MIB detection ions were m / z 95, 107, and 135; and GSM detection ions were m / z 112 and 125. The resulting standard curve for quantification using the internal standard method for 2-MIB and GSM was as follows: Figure 3 The samples were tested under the same conditions, and the corresponding concentrations were found in the standard curve using the detected response values ​​to determine the contents of 2-MIB and GSM in the samples.

[0071] (5) Precision analysis

[0072] 2-MIB and GSM standard solutions were added to ultrapure water at concentrations of 5 ng / L, 10 ng / L, 20 ng / L, and 400 ng / L. Multiple measurements were performed. Samples at fixed concentration levels were subjected to eight replicate measurements, and the relative standard deviation (RSD) was tested. The results are shown in Table 1. This method demonstrates high precision and stability across a wide range of concentrations.

[0073] Table 1 Precision analysis

[0074] (6) Spike recovery analysis

[0075] 2-MIB and GSM standard solutions were spiked into water samples with different water quality backgrounds (ultrapure water, tap water, and natural water) at concentrations of 20, 100, and 400 ng / L, respectively. Eleven replicates were performed to calculate the spiked recoveries (R%), as shown in Table 2. As can be seen from the table, the method achieved high recoveries at various concentrations across a variety of water types.

[0076] The recovery rate is calculated as follows:

[0077] R% = (measured value - sample background value) / spiked amount * 100%

[0078] Relative standard deviation formula: RSD (%) = standard deviation value / average value

[0079] Table 2 Analysis of spike recovery Specific implementation method four

[0081] (1) Sample pretreatment:

[0082] Take a water sample, filter it through a membrane according to the type of water sample, add 20 mL of sample and 0.5 mL of IBMP with a concentration of 8 μg / L into a purge bottle (with a polytetrafluoroethylene-surfaced silicone diaphragm), then add a magnetic rotor (0.5 mm*1 mm) and place it on the sample table.

[0083] (2) Purge and capture:

[0084] Insert a sample needle into the purge bottle, and purge the odorous substances in the water in the bottle according to the set parameters. The in-situ purge and capture parameters are: purge time 12 min, purge temperature 60 ° C, purge flow 40 mL / min, stirring speed 120 r / min, solution volume 20 mL, additional water amount 0 mL, desorption conditions are time 2.5 min, desorption temperature 250 ° C, trap baking 280 ° C, 2 min, baking gas flow 200 mL / min.

[0085] (3) Quantitative analysis:

[0086] 20 mL of the solution was placed in a 40 mL purge bottle. The sample was placed on the injection tray and analyzed using the following gas chromatography-mass spectrometry parameters: purge time 12 min, temperature 60°C, flow rate 40 mL / min, stirring speed 120 rpm, solution volume 20 mL, and additional water volume 0 mL. Desorption conditions were: time 2.5 min, desorption temperature 250°C, trap bakeout at 280°C for 2 min, and bakeout gas flow rate 200 mL / min. Gas chromatography-mass spectrometry parameters included: inlet temperature 250°C; carrier gas constant flow mode, flow rate 1.3 mL / min; column temperature program: initial temperature 40°C, hold time 2 min, ramp to 180°C at a rate of 30°C / min, and finally to 270°C at a rate of 10°C / min. Injection mode: split injection, split ratio 1:5, flow rate 3 mL / min. The gas chromatography-mass spectrometry column model was Elite-5ms, 60 mm × 0.25 mm × 0.25 μm. The mass spectrometry conditions were: transfer line temperature: 280°C, ion source temperature: 230°C, acquisition mode: Sim; IBMP detection ions were m / z 94, 124, and 151; 2-MIB detection ions were m / z 95, 107, and 135; and GSM detection ions were m / z 112 and 125. The resulting standard curve for quantification using the internal standard method for 2-MIB and GSM was as follows: Figure 3 The samples were tested under the same conditions, and the corresponding concentrations were found in the standard curve using the detected response values ​​to determine the contents of 2-MIB and GSM in the samples.

[0087] (4) Adsorption model fitting

[0088] Commercially available activated carbon was used to adsorb a certain concentration of odorous substances in water. The prepared water sample was placed in a sealed wide-mouth bottle, a magnetic rotor was added, and the adsorption experiment was carried out in a constant temperature water bath at multiple temperatures. The experiment lasted for 24 hours until the activated carbon adsorption equilibrium was reached. Three parallel experiments were performed for each group of samples. The initial concentration of the odorous substance and the equilibrium concentration of the activated carbon adsorption were determined by the method of the present invention, the adsorption capacity of the activated carbon for the odorous substance was calculated, and the adsorption isotherm of the activated carbon for the odorous substance was drawn. The origin drawing software was used to fit the adsorption model of the activated carbon adsorption of odorous substances according to the Langmuir isotherm and the Freundlich isotherm. After the iterative convergence was calculated, the model fitting correlation R2 was obtained. The experimental practicality and measurement accuracy of the method were evaluated. The formulas of the Langmuir isotherm and the Freundlich isotherm are as follows:

[0089] Langmuir isotherm

[0090]

[0091] Freundlich isotherm

[0092] q=kc 1 / n

[0093] Where q is the equilibrium adsorption capacity in mg / g; c is the equilibrium concentration in mg / L; qe is the saturated adsorption capacity in mg / g, and b, k, and n are parameters.

[0094] Correlation analysis was performed using the orgin software to fit the curve. The closer R2 is to 1, the higher the fitting degree of the adsorption model. Figure 5 As shown in Table 3, the 2-MIB adsorption isotherm closely matches the Langmuir isotherm, indicating that the adsorption of 2-MIB by activated carbon in water conforms to the Langmuir adsorption model and that the adsorption of 2-MIB by activated carbon in water is monolayer adsorption. The GSM adsorption isotherm closely matches the Freundlich isotherm, indicating that the adsorption of 2-MIB by activated carbon in water conforms to the Freundlich adsorption model. As shown in Table 3, the detection results of this method have a high degree of fit with the adsorption model, reaching over 99%. This further demonstrates the practicality of this method for detecting odor and taste substances in experimental research.

[0095] Table 3 Adsorption model fitting analysis

[0096] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for detecting and analyzing odorous substances in water by in-situ purge and trap-gas chromatography-mass spectrometry, characterized in that: The following steps are involved: (1) Sample pretreatment: Take a water sample containing odorous substances, filter it through a filter membrane, take a volume of VmL and place it in a purge bottle, add a certain concentration of internal standard and a magnetic rotor into the bottle, and place the purge bottle on the sample table. (2) Purge and capture: Insert a sample needle into the purge bottle, and purge the odorous substances in the water for t minutes at a purge temperature of T℃, a purge flow rate of QmL / min, and a stirring speed of vr / min. The purge gas is captured by a trap and desorbed at a temperature of T 吸 ℃, desorption t 吸 After 10 minutes, the sample was sent to the injection port of the gas chromatography-mass spectrometer, and then the trap was baked at the temperature T 烘烤 ℃ at flow rate Q 烘烤 mL / min for baking 烘烤 minute. (3) Qualitative analysis: The pre-treated samples were tested using a gas chromatography-mass spectrometer, which started running according to the following parameters: injection port temperature T 进样口-1 ℃, the initial temperature of the column heating program T 0-1 ℃, holding time t 0-1 min, with heating rate v 1-1 ℃ / min heating to T 1-1 ℃, and finally the heating rate v 2-1 ℃ / min heating to T 2-1 ℃; injection method: split injection, split ratio R1; flow rate Q 色谱-1 mL / min, mass spectrometry conditions, transfer line temperature T 传输-1 ℃, ion source temperature T 离子源-1 ℃, acquisition mode: SCAN. At the same time, the odor substances are tested as standard products under the same conditions, and the standard products are obtained as real-time mass spectrometers. By comparing the retention time and characteristic ions of the chromatographic peaks of the standard products and samples in the spectrum, it is determined that the sample contains the analyte.

2. The method for detecting and analyzing odorous substances in water by in-situ purge and trap-gas chromatography-mass spectrometry according to claim 1, characterized in that: After sample pretreatment, purge and trap, and qualitative analysis, the following steps are also included: (1) Quantitative analysis: The pre-treated samples were tested using a gas chromatography-mass spectrometer, which started running according to the following parameters: injection port temperature T 进样口-2 ℃, the initial temperature of the column heating program T 0-2 ℃, holding time t 0-2 min, with heating rate v 1-2 ℃ / min heating to T 1-2 ℃, and finally the heating rate v 2-2 ℃ / min heating to T 2-2 ℃; injection method: split injection, split ratio R2; flow rate Q 色谱-2 mL / min, mass spectrometry conditions, transfer line temperature T 传输-2 ℃, ion source temperature T 离子源-2 ℃, acquisition mode: SIM. Then weigh the standard sample and dilute it with ultrapure water to prepare a standard solution, add the internal standard substance to the solution to a certain concentration, test it under the same gas chromatography-mass spectrometry conditions after sample pretreatment and purge trapping, place it in the sample tray, analyze it on the machine, and obtain the standard curve of the standard internal standard method quantification, then find the corresponding concentration in the standard curve chart by the ratio of the response value detected by the sample and the internal standard substance, and determine the content of the odor substance in the sample.

3. The method for detecting and analyzing odorous substances in water by in-situ purge and trap-gas chromatography-mass spectrometry according to claim 1, characterized in that: The odor substance described in step (1) is at least one of 2-methylisoborneol (2-MIB) and geosmin (GSM), and the V is 1-30 mL.

4. The method for detecting and analyzing odorous substances in water by in-situ purge and trap-gas chromatography-mass spectrometry according to claim 1, characterized in that: A magnetic rotor may be added to the purge bottle described in step (2) to improve the stability of the test results. The specification of the magnetic rotor is 0.05m*0.1mm-1mm*2mm.

5. The method according to claim 1, characterized in that In step (2), t is 5-15 min, T is 10° C.-70° C., Q is 10 mL / min-80 mL / min, and v is 0 r / min-300 r / min.

6. The method according to claim 1, characterized in that The desorption and baking conditions described in step (2) are: desorption time t 吸 1-5min, desorption temperature T 吸 20-300℃, trap baking temperature T 烘烤 20-300℃, baking time t 烘烤 1-10min, baking gas flow Q 烘烤 50-300mL / min.

7. The method according to claim 1, characterized in that T in step (3) 进样口-1 is 100-250°C; the T 0-1 is 10-50°C, the t 0-1 For 1-5min, the v 1-1 is 10-30℃ / min; the T 1-1 is 100-250°C, the v 2-1 is 10-50℃ / min, the T 2-1 is 100-350℃; R1 is 1:3-1:100; Q 色谱-1 is 1-10mL / min; the T 传输-1 is 100-380°C, the T 离子源-1 It is 100-380℃.

8. The method according to claim 1, characterized in that Parameters of the gas chromatography-mass spectrometry instrument in step (3): 进样口-2 is 100-250°C; the T 0-2 is 10-50°C, the t 0-2 For 1-5min, the v 1-2 is 10-30℃ / min; the T 1-2 is 100-250°C, the v 2-2 is 10-50℃ / min, the T 2-2 is 100-350℃; the R2 is 1:3-1:100; the Q 色谱-2 is 1-10mL / min; the T 传输-2 is 100-380°C, the T 离子源-2 It is 100-380℃.

9. The method according to claim 1 or 2, characterized in that: The standard substance described in step (3) of claim 1 and step (1) of claim 2 is an odor substance; the odor substance is at least one of 2-methylisoborneol (2-MIB) and geosmin (GSM).

10. The method according to claim 1, characterized in that The internal standard substance described in step (1) of claim 1 and step (1) of claim 2 is 2-methoxy-3-isobutylpyrazine (IBMP), and the added concentration range of the internal standard substance is 10-2000 ng / L.

Images