CN112881573A - Method and equipment for measuring methanol, ethanol and n-butanol in soil and underground water - Google Patents
Method and equipment for measuring methanol, ethanol and n-butanol in soil and underground water Download PDFInfo
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Abstract
The invention belongs to the technical field of soil determination, and discloses a method and equipment for determining methanol, ethanol and n-butanol in soil and underground water, wherein volatile components in a sample in a headspace bottle volatilize to the headspace of liquid at the temperature of 130 ℃ to generate vapor pressure, and after a gas-liquid two-phase reaches thermodynamic dynamic balance, volatile organic compounds in the gas phase are separated by gas chromatography and are detected by a mass spectrum detector; and qualitative by chromatographic retention time and quantitative by external standard method; obtaining the detection limit and the determination lower limit of the methanol, the ethanol and the n-butanol in the soil and the underground water. Specifically, the method comprises the steps of collecting a soil sample; sample preservation; preparing a sample; preparing a blank sample; and (5) measuring soil moisture. Collecting and storing underground water: sample preservation; preparing a sample; and preparing a blank sample. And establishing a working curve. The headspace-gas chromatography-mass spectrometry method for determining the methanol, the ethanol and the n-butanol in the soil and the underground water has high accuracy of determination data.
Description
Technical Field
The invention belongs to the technical field of soil determination, particularly relates to a method and equipment for determining methanol, ethanol and n-butanol in soil and underground water, and particularly relates to a method for determining methanol, ethanol and n-butanol in soil and underground water by headspace-gas chromatography-mass spectrometry.
Background
At present, methanol, ethanol and n-butanol belong to water-soluble volatile organic compounds, in the prior art, HJ 895-2017 is adopted as methanol in underground water, and EPA 8015c is adopted as n-butanol in soil, but no method capable of simultaneously measuring methanol, ethanol and n-butanol in soil and underground water exists.
Through the above analysis, the problems and defects of the prior art are as follows:
(1) in the prior art, methanol, ethanol and n-butanol in soil and underground water are not simultaneously measured by adopting a headspace-gas chromatography-mass spectrometry method, so that the accuracy of the measured data in the prior art is poor.
(2) The boiling points of the n-butanol are different and higher, and the existing headspace-gas chromatography cannot simultaneously measure
(3) The chromatographic peak of moisture has a large influence on the degree of separation of the components to be measured at a headspace heating temperature of 100 ℃ or higher.
The difficulty in solving the above problems and defects is:
the boiling points of ethanol and n-butanol are relatively high.
The significance of solving the problems and the defects is as follows:
the method can simultaneously determine the water-soluble methanol, ethanol and n-butanol in the soil and underground water samples, has simple operation steps and improves the analysis efficiency.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method and equipment for measuring methanol, ethanol and n-butanol in soil and underground water.
The invention is realized in such a way that a headspace-gas chromatography-mass spectrometry method for determining methanol, ethanol and n-butanol in soil and underground water comprises the following steps:
volatilizing volatile components in a sample in the headspace bottle to the headspace at the temperature of 130 ℃ to generate vapor pressure, separating volatile organic compounds in a gas phase through gas chromatography after the gas phase and the liquid phase reach thermodynamic dynamic equilibrium, and detecting by using a mass spectrometer; and qualitative by chromatographic retention time and quantitative by external standard method; obtaining the detection limit and the determination lower limit of the methanol, the ethanol and the n-butanol in the soil and the underground water.
Further, the sample is soil, and the collection and preservation of the soil sample comprise:
(1) collecting a soil sample;
(2) sample preservation;
(3) preparing a sample;
(4) preparing a blank sample;
(5) and (5) measuring soil moisture.
Further, the step (1) of sampling the soil comprises:
primarily screening the sample in the sampling site according to the concentration; at least 3 replicates of all samples were collected; collecting a sample and placing the sample in a refrigerating box;
the step (2) of sample preservation comprises the following steps:
sealed at below 4 deg.C for no more than 7 days.
Further, the preparation of the sample of the step (3) comprises:
(3.1) Low content sample: after the sample is recovered to the room temperature, weighing 2g of sample, placing the sample in a headspace bottle, adding a stirrer, quickly adding 10mL of matrix modifier into the headspace bottle, sealing, oscillating on a magnetic oscillator at the frequency of 150 times/min for 10min to be measured;
(3.2) high content sample:
primarily screening the volatile organic compounds on site to obtain high-content samples when the measurement result is more than 1000 mug/kg; high content sample preparation included:
weighing 2g of sample, placing in a headspace bottle, adding a stirrer, rapidly adding 10ml of matrix modifier, sealing, and oscillating on a magnetic oscillator at 150 times/min for 10 min. Standing and settling. If necessary, the extract can be centrifugally separated; the extractive solution can be stored in a refrigerator at 4 deg.C with a shelf life of 14 d;
adding 2g of quartz sand, 10mL of matrix modifier and 1mL of extracting solution into another headspace bottle, sealing, oscillating on a magnetic oscillator at the frequency of 150 times/min for 10min, and standing for testing.
The step (4) of preparing the blank sample comprises the following steps:
(4.1) low content blank: replacing a sample with 2g of quartz sand to prepare a low-content blank sample;
(4.2) high content blank: a high-content blank sample was prepared by replacing the high-content sample with 2g of quartz sand.
Further, the sample is groundwater, and the collecting and storing of groundwater comprises:
1) and (3) sample preservation: after the sample is collected, adding a hydrochloric acid solution to ensure that the pH value of the sample is less than or equal to 2, refrigerating and transporting the sample below 4 ℃, keeping the sample in a dark place and sealing the sample, and completing analysis and determination within 14 days;
2) sample preparation: after the groundwater sample is restored to the room temperature, transferring 10.0mL of the groundwater sample into a headspace bottle which is added with 3.0g of sodium chloride in advance, sealing, and shaking up to be tested; when the actual sample concentration exceeds the working curve range, reducing the sample sampling amount, and determining after the constant volume is 10.0 mL;
3) and preparing a blank sample.
Furthermore, when multiple underground water samples are collected, swinging washing is not required, and all samples are collected into parallel double samples; if the sample contains residual chlorine, adding 25mg of ascorbic acid into the sampling bottle before sampling; if the residual chlorine content in the sample exceeds 5mg/L, increasing the addition of ascorbic acid according to a proportion, and adding 25mg more ascorbic acid when the residual chlorine content is increased by 5 mg/L; and meanwhile, filling water for the laboratory into a closed glass bottle, bringing the bottle to a sampling site, and collecting blank samples of the whole process according to the steps, wherein each batch of samples is provided with a blank of the whole process.
Further, in the step 1), the sample storage area has no interference of volatile organic compounds; if bubbles are generated after the sample is added into the hydrochloric acid solution, re-sampling, preserving the re-collected sample without adding the hydrochloric acid solution, and completing analysis and determination within 24 hours;
further, the detecting with the mass spectrometer detector comprises:
taking 7 headspace bottles, respectively adding 3.0g of sodium chloride, accurately transferring 10.00ml of experimental water to each headspace bottle, respectively adding a certain amount of mixed standard storage solution I and standard use solution II to prepare mixed standard series of concentrations of methanol, ethanol and n-butanol of 0 mug/L, 1.6 mug/L, 4.0 mug/L, 8.0 mug/L, 16.0 mug/L, 40.0 mug/L and 80.0 mug/L respectively, and shaking uniformly; sequentially measuring from low concentration to high concentration; and establishing a working curve by taking the mass concentration (mg/L) of the target object as a horizontal coordinate and taking the peak area or the peak height as a vertical coordinate.
Further, the preparation of the mixed standard stock solution I comprises:
transferring a proper amount of experimental water into a 100ml volumetric flask, and weighing the volumetric flask on a balance; sequentially dripping methanol, ethanol and n-butanol until the weight of each component is increased by 3.0g, fixing the volume, shaking up, and calculating the accurate concentration of the methanol, the ethanol and the n-butanol;
the preparation of the standard use solution II comprises the following steps: transferring 1.00mL of the mixed stock solution into a 100mL volumetric flask, adding experimental water to a constant volume, and shaking up.
Another object of the present invention is to provide an apparatus for measuring methanol, ethanol and n-butanol in soil and groundwater, comprising:
gas chromatography mass spectrometer: the column box is provided with a shunt/non-shunt sample inlet and is subjected to temperature programming;
automatic headspace sampler: the heating temperature is between room temperature and 250 ℃, and the temperature control precision is as follows: 1 ℃ C;
the chromatographic column is a quartz capillary chromatographic column, and the stationary phase is polyethylene glycol or other equivalent capillary columns;
analytical balance: the sensory quantity is 0.0001 g;
a headspace bottle: a 22ml glass headspace bottle with a sealing gasket and a sealing cover, or a glass headspace bottle matched with an automatic headspace sample injector;
micro injector 5 μ L, 10 μ L, 25 μ L, 100 μ L, 250 μ L, 1.0 mL;
sampling bottle: screw cap with silicon rubber-polytetrafluoroethylene lining
By combining all the technical schemes, the invention has the advantages and positive effects that:
volatile components in a sample in a headspace bottle volatilize to the headspace of liquid at the temperature of 130 ℃ to generate vapor pressure, and volatile organic compounds in a gas phase are separated by gas chromatography and detected by a mass spectrometer after the gas phase and the liquid phase reach thermodynamic dynamic equilibrium. Qualitative by chromatographic retention time and quantitative by external standard method.
The headspace-gas chromatography-mass spectrometry method for determining the methanol, the ethanol and the n-butanol in the soil and the underground water has high accuracy of determination data.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained from the drawings without creative efforts.
FIG. 1 is a flow chart of a method for measuring methanol, ethanol and n-butanol in soil and groundwater by headspace-gas chromatography mass spectrometry as provided in an embodiment of the invention.
FIG. 2 is a TIC graph of a 15.0mg/L standard solution provided by an embodiment of the present invention.
FIG. 3 is a graph showing the operation of methanol according to an embodiment of the present invention.
FIG. 4 is a graph of the operation of ethanol provided by an embodiment of the present invention.
FIG. 5 is a graph of the working curve of n-butanol provided in the examples of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In view of the problems of the prior art, the present invention provides a method and apparatus for measuring methanol, ethanol and n-butanol in soil and groundwater, which is described in detail below with reference to the accompanying drawings.
The invention provides a method for determining methanol, ethanol and n-butanol in soil and underground water by headspace-gas chromatography-mass spectrometry, which comprises the following steps:
volatilizing volatile components in a sample in the headspace bottle to the headspace at the temperature of 130 ℃ to generate vapor pressure, separating volatile organic compounds in a gas phase through gas chromatography after the gas phase and the liquid phase reach thermodynamic dynamic equilibrium, and detecting by using a mass spectrometer; and qualitative by chromatographic retention time and quantitative by external standard method; obtaining the detection limit and the determination lower limit of the methanol, the ethanol and the n-butanol in the soil and the underground water.
As shown in fig. 1, the method specifically includes:
s101, collecting and storing a soil sample: collecting a soil sample; sample preservation; preparing a sample; preparing a blank sample; and (5) measuring soil moisture.
S102, collecting and storing underground water: sample preservation; preparing a sample; and preparing a blank sample.
S103, establishing a working curve: taking 7 headspace bottles, respectively adding 3.0g of sodium chloride, accurately transferring 10.00ml of experimental water to each headspace bottle, respectively adding a certain amount of mixed standard storage solution I and standard use solution II to prepare mixed standard series of concentrations of methanol, ethanol and n-butanol of 0 mug/L, 1.6 mug/L, 4.0 mug/L, 8.0 mug/L, 16.0 mug/L, 40.0 mug/L and 80.0 mug/L respectively, and shaking uniformly; sequentially measuring from low concentration to high concentration; and establishing a working curve by taking the mass concentration (mu g/L) of the target object as a horizontal coordinate and taking the peak area or the peak height as a vertical coordinate.
The technical solution of the present invention is further described with reference to the following specific examples.
Examples
1. The principle of the measuring method of the invention is as follows: volatile components in a sample in the headspace bottle volatilize to the headspace to generate vapor pressure at the temperature of 130 ℃, and after the gas-liquid two phases reach thermodynamic dynamic equilibrium, volatile organic compounds in the gas phase are separated by gas chromatography and detected by a mass spectrometer. Qualitative by chromatographic retention time and quantitative by external standard method.
2. Apparatus and device
2.1 gas chromatograph mass spectrometer: the column box can be heated by program with split/non-split injection port.
2.2 automatic headspace sampler: the heating temperature range is controlled between room temperature and 250 ℃, and the temperature control precision is as follows: and 2, and 1C.
2.3 chromatographic column, quartz capillary chromatographic column, 30m (length) x530 μm (inner diameter) x3.0 μm (film thickness), and polyethylene glycol or other equivalent capillary column as stationary phase.
2.4 analytical balance: the sensory was 0.0001 g.
2.5 headspace bottle: a22 ml glass headspace bottle with a gasket (PTFE/Silicone rubber or PTFE/butyl rubber), a sealing cap (screw cap or disposable cap), or a glass headspace bottle with an automatic headspace sampler.
2.6 micro-syringes 5. mu.L, 10. mu.L, 25. mu.L, 100. mu.L, 250. mu.L, 1.0 mL.
2.7 sampling bottle: a40 mL brown glass bottle with a silicone rubber-polytetrafluoroethylene liner screw cap.
2.8. Common laboratory instruments and equipment are used.
3. Reagents and materials
3.1 Experimental water, namely minister secondary distilled water. A blank test is carried out before use, and the condition that no interference chromatographic peak appears in a retention time interval of the target or the concentration of the target in the retention time interval is lower than the detection limit of the method is confirmed.
3.3 sodium chloride: and 4, high-grade purity.
Igniting the mixture for 4 hours at 400 ℃ in a muffle furnace, placing the mixture in a dryer to cool to room temperature, and transferring the mixture to a ground glass bottle for storage.
3.4 phosphoric acid: and 4, high-grade purity.
3.5 matrix modifier.
Measuring 500ml of experimental water, dropwise adding a few drops of phosphoric acid to adjust the pH value to be less than or equal to 2, adding 180g of sodium chloride, dissolving and uniformly mixing. Can be stored at 4 deg.C for 6 months.
3.6 hydrochloric acid/. rho.1.19 g/mL.
3.7 hydrochloric acid solution 1+ 1.
100mL of hydrochloric acid was measured and added to 100mL of test water and mixed well.
3.8 sodium chloride, super pure.
Heating at 400 deg.C for 2h to remove organic substances possibly adsorbed on the surface, cooling, and storing in clean reagent bottle.
3.9 ascorbic acid
3.10 methanol, pesticide residue grade.
3.11 ethanol: pesticide residue grade.
3.12 n-butanol: pesticide residue grade.
3.13 Standard Mixed stock solution of methanol, ethanol and n-butanol, 3X 103mg/L。
An appropriate amount of experimental water was removed to a 100mL volumetric flask and weighed on a balance. And carefully and sequentially dripping a plurality of drops of methanol, ethanol and n-butanol until the weight of each component is increased by about 3.0g (to be accurate to 0.1mg), fixing the volume, shaking up, and calculating the accurate concentration (to be accurate to 1mg/L) of the methanol, the ethanol and the n-butanol. Prepared immediately after use.
3.14 mixing standard use solution II: 300 mg/L.
Accurately transferring 1.00mL of mixed stock solution into a 100mL volumetric flask, metering the volume with experimental water, and shaking up.
3.15 the quartz sand is 20-50 meshes. Before use, the target compound is checked to confirm that the target compound is not available or the concentration of the target compound is lower than the detection limit of the method.
4 collecting and preserving soil samples
4.1 soil sample collection:
the soil samples were collected and stored according to the relevant regulations for HJ/T166. The tool for collecting the sample is a metal product which is subjected to purification treatment before use. The portable instrument for volatile organic compound determination can be used for primary screening of the sample with high and low concentration on the sampling site. All samples should be taken in at least 3 replicates. Samples were collected as soon as possible into sample bottles with a spatula or spatula and filled as full as possible. And quickly removing the sample adhered to the thread and the outer surface of the sample bottle, and sealing the sample bottle. Placed in a portable refrigerator and brought back to the laboratory. With one full process blank and transport blank per batch of samples.
4.2 sample preservation.
Samples should be analyzed as soon as possible after they are sent to the laboratory. If the analysis cannot be carried out immediately, the product is stored at a temperature below 4 ℃ in a sealed manner, and the storage life is not more than 7 days. The sample storage area should be free of organic interference.
4.3 preparation of the samples
4.3.1 Low content sample
Taking out the sample bottle in the laboratory, after the sample bottle is restored to the room temperature, weighing 2g of the sample, placing the sample in a headspace bottle, adding a stirrer, quickly adding 10mL of matrix modifier into the headspace bottle, immediately sealing, oscillating on a magnetic oscillator for 10min at the frequency of 150 times/min, and waiting to be measured.
4.3.2 high content sample.
If the primary screening of the volatile organic compounds on site is carried out to obtain a high-content or low-content determination result which is more than 1000 mug/kg, the volatile organic compounds are regarded as high-content samples. High-content specimens were prepared by taking out the specimen bottles for high-content specimen testing and returning them to room temperature.
Weighing 2g of sample, placing in a headspace bottle, adding a stirrer, rapidly adding 10mL of matrix modifier, sealing, and oscillating on a magnetic oscillator at 150 times/min for 10 min. Standing and settling. If necessary, the extract may be subjected to centrifugal separation. The extractive solution can be stored in a refrigerator at 4 deg.C, with a shelf life of 14 days.
Adding 2g of quartz sand, 10mL of matrix modifier and 1mL of extracting solution into another headspace bottle, sealing, oscillating on a magnetic oscillator at the frequency of 150 times/min for 10min, and standing for testing.
4.4 preparation of a blank.
4.4.1 Low content blank.
A low content blank was prepared by replacing the sample with 2g of quartz sand.
4.4.2 high content blank.
High content blanks were prepared by replacing the high content samples with 2g of quartz sand (5.11).
4.5 determination of moisture
The determination of the water content of the soil sample was performed according to HJ 613.
And 5, collecting and storing a groundwater sample.
When the sample is collected, the sample must not be washed by shaking, the sample can overflow in the sampling bottle without leaving space, and the exposure of the sample in the air can be avoided or reduced as much as possible during sampling. All samples were collected in duplicate. If the sample contains residual chlorine, 25mg (to the nearest 0.001g) of ascorbic acid should be added to the sampling bottle before sampling. If the residual chlorine content in the sample exceeds 5mg/L, the addition amount of ascorbic acid should be increased proportionally, and 25mg (to the accuracy of 0.001g) more ascorbic acid should be added for every 5mg/L increase in the residual chlorine content. And meanwhile, filling water for the laboratory into a closed glass bottle, bringing the bottle to a sampling site, and collecting blank samples of the whole process according to the steps, wherein each batch of samples is required to be provided with a blank of the whole process.
5.1 sample preservation.
After the sample is collected, a proper amount of hydrochloric acid solution is immediately added to ensure that the pH value of the sample is less than or equal to 2, the bottle stopper is screwed down, the label is stuck, and the sample is immediately placed into a refrigerator for refrigeration transportation at the temperature of below 4 ℃. After the sample is transported back to the laboratory, the sample should be refrigerated below 4 ℃, protected from light and sealed for storage, and the analytical determination is completed within 14 d. The sample storage area should be free of interference of volatile organic compounds. If bubbles are generated after the hydrochloric acid solution is added into the sample, resampling is needed, the re-collected sample is not added with the hydrochloric acid solution for storage, and the sample is labeled and is not acidified, so that the analysis and the determination are completed within 24 hours.
5.2 sample preparation.
After the sample is returned to room temperature, 10.0mL of the sample is accurately transferred to a headspace bottle in which 3.0g of sodium chloride is added in advance, immediately capped and sealed, and shaken up to be measured. When the actual sample concentration exceeds the working curve range, the sample sampling amount can be properly reduced, and the volume is determined to 10.0 mL.
5.3 blank preparation.
The sample was replaced with experimental water and the sample preparation was followed (same procedure, laboratory blank was prepared).
6 apparatus conditions.
6.1 headspace sample injection reference conditions.
The heating balance temperature is 130 ℃; the heating balance time is 30 min; the temperature of the sampling needle is 140 ℃; the temperature of the transmission line is 150 ℃; the injection volume is 1.0 mL.
6.2 gas chromatography reference analysis conditions.
Temperature programming: keeping the initial column temperature at 80 ℃ for 1min, and raising the temperature to 150 ℃ at 10 ℃/min for 5 min; the temperature of a sample inlet is 200 ℃; the split ratio is 10: 1; carrying gas; high purity helium gas, flow: 1.0 mL/min.
Mass spectrum conditions:
the ion source is an EI source; the temperature of the ion source is 250 ℃; ionization energy is 70 eV; the scanning mode is as follows: the selective ion Scanning (SIM) and the FULL scanning (FULL SCAN) are performed in an alternating mode. Full scan range: 29-150, the selected ions are: 32. 45, 74, solvent delay 1.0 min; electron multiplication voltage: consistent with the tuning voltage; interface temperature: at 250 ℃ to obtain a mixture. The remaining parameters were set with reference to the instrument instructions.
7. Experiment (experiments)
TIC chart of 7.1, 16.0. mu.g/L standard solution, as shown in FIG. 2.
7.2 preparation of working curve:
taking 7 headspace bottles, respectively adding 3.0g of sodium chloride, accurately transferring 10.00ml of experimental water to each headspace bottle, respectively adding a certain amount of mixed standard storage solution I and standard use solution II to prepare mixed standard series concentrations of methanol, ethanol and n-butanol of 0 mug/L, 1.6 mug/L, 4.0 mug/L, 8.0 mug/L, 16.0 mug/L, 40.0 mug/L and 80.0 mug/L respectively, and uniformly pressing and shaking. The measurement was performed sequentially from low concentration to high concentration according to the instrument reference conditions. A working curve is established by taking the mass concentration (mu g/L) of the target substance as the abscissa and the peak area or peak height as the ordinate, as shown in the working curve of methanol in FIG. 3. As shown in the working curve for 4 ethanol. As shown in the working curve for n-butanol in fig. 5.
7.3 determination method performance of methanol, ethanol and n-butanol in soil.
7.3.1 detection limit and lower determination limit of the method for determining methanol, ethanol and n-butanol in soil, unit: μ g/Kg, as shown in Table 1 below:
TABLE 1
7.3.2 the accuracy, precision and linear range units of the method for measuring methanol, ethanol and n-butanol in soil are as follows: μ g/Kg, as in Table 2.
TABLE 2
7.4 determination method performance of methanol, ethanol and n-butanol in the groundwater.
7.4.1 determination method detection limit and determination lower limit unit of methanol, ethanol and n-butanol in groundwater: μ g/L, as in Table 3.
TABLE 3
4.2 the accuracy, precision and linear range unit of the method for measuring the methanol, the ethanol and the n-butanol in the groundwater are as follows: μ g/L, as in Table 4.
TABLE 4
In the description of the present invention, "a plurality" means two or more unless otherwise specified; the terms "upper", "lower", "left", "right", "inner", "outer", "front", "rear", "head", "tail", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the invention. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A method for measuring methanol, ethanol and n-butanol in soil and underground water by headspace-gas chromatography-mass spectrometry, which is characterized in that the method for measuring the methanol, the ethanol and the n-butanol in the soil and underground water by headspace-gas chromatography-mass spectrometry comprises the following steps:
volatile components in a sample in the headspace bottle volatilize to the headspace to generate vapor pressure, and after a gas-liquid two phase reaches thermodynamic dynamic balance, volatile organic compounds in the gas phase are separated by gas chromatography and detected by a mass spectrometry detector; and qualitative by chromatographic retention time and quantitative by external standard method; obtaining the detection limit and the determination lower limit of the methanol, the ethanol and the n-butanol in the soil and the underground water.
2. The headspace-gas chromatography-mass spectrometry method for the determination of methanol, ethanol and n-butanol in soil and groundwater according to claim 1, wherein the temperature condition at which the volatile component in the sample in the headspace bottle volatilizes to the headspace above the liquid and the vapor pressure is generated is 130 ℃.
3. The headspace-gas chromatography mass spectrometry method for the determination of methanol, ethanol and n-butanol in soil and groundwater according to claim 1, wherein said sample is soil and the collection and preservation of said soil sample comprises:
(1) collecting a soil sample;
(2) sample preservation;
(3) preparing a sample;
(4) preparing a blank sample;
(5) and (5) measuring soil moisture.
4. The method for determining methanol, ethanol and n-butanol in soil and groundwater by headspace-gas chromatography mass spectrometry as claimed in claim 2, wherein the step (1) of sampling the soil comprises:
primarily screening the sample in the sampling site according to the concentration; at least 3 replicates of all samples were collected; collecting a sample and placing the sample in a refrigerating box;
the step (2) of sample preservation comprises the following steps:
sealing and storing at below 4 deg.C for no more than 14 days;
the preparation of the sample in the step (3) comprises the following steps:
(3.1) Low content sample: after the sample is recovered to the room temperature, weighing 2g of sample, placing the sample in a headspace bottle, adding a stirrer, quickly adding 10mL of matrix modifier into the headspace bottle, sealing, oscillating on a magnetic oscillator at the frequency of 150 times/min for 10min to be measured;
(3.2) high content sample:
primarily screening the volatile organic compounds on site to obtain high-content samples when the measurement result is more than 1000 mug/kg; high content sample preparation included:
weighing 2g of sample, placing in a headspace bottle, adding a stirrer, rapidly adding 10mL of matrix modifier, sealing, and oscillating on a magnetic oscillator at 150 times/min for 10 min. Standing and settling. If necessary, the extract can be centrifugally separated; the extractive solution can be stored in a refrigerator at 4 deg.C with a shelf life of 14 d;
adding 2g of quartz sand, 10mL of matrix modifier and 1mL of extracting solution into another headspace bottle, sealing, oscillating on a magnetic oscillator at the frequency of 150 times/min for 10min, and standing for testing.
The step (4) of preparing the blank sample comprises the following steps:
(4.1) low content blank: replacing a sample with 2g of quartz sand to prepare a low-content blank sample;
(4.2) high content blank: a high-content blank sample was prepared by replacing the high-content sample with 2g of quartz sand.
5. The headspace-gas chromatography mass spectrometry method for the determination of methanol, ethanol and n-butanol in soil and groundwater according to claim 1, wherein the sample is groundwater and the collection and preservation of groundwater comprises:
1) and (3) sample preservation: after the sample is collected, adding a hydrochloric acid solution to ensure that the pH value of the sample is less than or equal to 2, refrigerating and transporting the sample at the temperature of below 4 ℃, keeping the sample in the dark and hermetically, and completing analysis and determination within 14 days;
2) sample preparation: after the groundwater sample is restored to the room temperature, transferring 10.0mL of the groundwater sample into a headspace bottle which is added with 3.0g of sodium chloride in advance, sealing, and shaking up to be tested; when the actual sample concentration exceeds the working curve range, reducing the sample sampling amount, and determining after the constant volume is 10.0 mL;
3) and preparing a blank sample.
6. The method for determining methanol, ethanol and n-butanol in soil and groundwater by headspace-gas chromatography mass spectrometry as claimed in claim 5, wherein multiple samples of groundwater are collected without washing, and all samples are collected in parallel; if the sample contains residual chlorine, adding 25mg of ascorbic acid into the sampling bottle before sampling; if the residual chlorine content in the sample exceeds 5mg/L, increasing the addition of ascorbic acid according to a proportion, and adding 25mg more ascorbic acid when the residual chlorine content is increased by 5 mg/L; and meanwhile, filling water for the laboratory into a closed glass bottle, bringing the bottle to a sampling site, and collecting blank samples of the whole process according to the steps, wherein each batch of samples is provided with a blank of the whole process.
7. The method for determining methanol, ethanol and n-butanol in soil and groundwater according to claim 5, wherein in step (1), the sample storage area is free of interference of volatile organic compounds; and if bubbles are generated after the hydrochloric acid solution is added into the sample, re-sampling, preserving the re-collected sample without adding the hydrochloric acid solution, and completing analysis and determination within 24 hours.
8. The method of headspace-gas chromatography mass spectrometry for the determination of methanol, ethanol and n-butanol in soil and groundwater according to claim 5, wherein said detecting with a mass spectrometry detector comprises:
taking 7 headspace bottles, respectively adding 3.0g of sodium chloride, accurately transferring 10.00mL of experimental water to each headspace bottle, respectively adding a certain amount of mixed standard storage solution I and standard use solution II to prepare mixed standard series of methanol, ethanol and n-butanol with the concentrations of 0 mug/L, 1.6 mug/L, 4 mug/L, 8 mug/L, 16.0 mug/L, 40.0 mug/L and 80.0 mug/L respectively, and shaking uniformly; sequentially measuring from low concentration to high concentration; and establishing a working curve by taking the mass concentration (mu g/L) of the target object as a horizontal coordinate and taking the peak area or the peak height as a vertical coordinate.
9. The method for determining methanol, ethanol and n-butanol in soil and groundwater by headspace-gas chromatography mass spectrometry as claimed in claim 8, wherein the preparation of mixed standard stock solution I comprises:
transferring a proper amount of experimental water into a 100ml volumetric flask, and weighing the volumetric flask on a balance; sequentially dripping methanol, ethanol and n-butanol until the weight of each component is increased by 3.0g, fixing the volume, shaking up, and calculating the accurate concentration of the methanol, the ethanol and the n-butanol;
the preparation of the standard use solution II comprises the following steps: transferring 1.00mL of the mixed stock solution into a 100mL volumetric flask, adding experimental water to a constant volume, and shaking up.
10. The device for measuring the methanol, the ethanol and the n-butanol in the soil and the underground water is characterized by comprising:
gas chromatography mass spectrometer: the column box is provided with a shunt/non-shunt sample inlet and is subjected to temperature programming;
automatic headspace sampler: the heating temperature is between room temperature and 250 ℃, and the temperature control precision is as follows: 1 ℃ C;
the chromatographic column is a quartz capillary chromatographic column, and the stationary phase is polyethylene glycol or other equivalent capillary columns;
analytical balance: the induction is 0.001 g;
a headspace bottle: a 22mL glass headspace bottle with a sealing gasket and a sealing cover, or a glass headspace bottle matched with an automatic headspace sample injector;
micro injector 5 μ L, 10 μ L, 25 μ L, 100 μ L, 250 μ L, 1.0 mL;
sampling bottle: the screw cap with silicon rubber-polytetrafluoroethylene lining.
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