Method for detecting acrylonitrile and pyridine in soil
阅读说明：本技术 一种土壤中丙烯腈和吡啶的检测方法 (Method for detecting acrylonitrile and pyridine in soil ) 是由 安彩秀 杨利娟 王磊 刘爱琴 秦冲 刘安 徐麟 宋娟娟 王芸 孙连伟 郭晓阳 于 2020-12-25 设计创作，主要内容包括：本发明公开了一种土壤中丙烯腈和吡啶的检测方法,包括以下方法：采用吹扫捕集的富集方法,使用高纯氦气或氮气吹扫将丙烯腈和吡啶富集于捕集管中,将捕集管加热并以高纯氦气反吹,被热脱附出来的组分进入气相色谱并分离后,用质谱仪进行检测；根据保留时间、碎片离子质荷比及不同离子丰度比定性,内标法定量。通过大批量企业用地污染状况详查项目土壤样品的应用,此方法有以下优点。样品前处理方式简单,无需提取,直接进样。提取稳定,平行性好,精密度高。仪器操作简单,大多实验室都可以实现,可用于大批量检测工作。样品加标和替代物回收率均能在70％～130％之间。(The invention discloses a method for detecting acrylonitrile and pyridine in soil, which comprises the following steps: adopting a purging and trapping enrichment method, purging and enriching acrylonitrile and pyridine in a trapping pipe by using high-purity helium or nitrogen, heating the trapping pipe, performing back flushing by using the high-purity helium, introducing the thermally desorbed components into a gas chromatograph, separating, and detecting by using a mass spectrometer; and (4) according to retention time, fragment ion mass-to-charge ratio and different ion abundance ratios, determining the nature and quantifying by an internal standard method. By using the method for detailed examination of project soil samples according to the pollution condition of land used by large-scale enterprises, the method has the following advantages. The sample pretreatment mode is simple, extraction is not needed, and direct sample introduction is realized. Stable extraction, good parallelism and high precision. The instrument is simple to operate, can be realized in most laboratories, and can be used for large-batch detection. The recovery rate of the sample addition and the substitution can be between 70 and 130 percent.)
1. A method for detecting acrylonitrile and pyridine in soil is characterized by comprising the following steps: adopting a purging and trapping enrichment method, purging and enriching acrylonitrile and pyridine in a trapping pipe by using high-purity helium or nitrogen, heating the trapping pipe, performing back flushing by using the high-purity helium, introducing the thermally desorbed components into a gas chromatograph, separating, and detecting by using a mass spectrometer; and (4) according to retention time, fragment ion mass-to-charge ratio and different ion abundance ratios, determining the nature and quantifying by an internal standard method.
2. The method for detecting acrylonitrile and pyridine in soil according to claim 1, further comprising: sample collection and preservation
Samples should be collected in brown glass sample bottles, all samples were taken in triplicate,
(1) directly sampling about 5.0g of soil sample by using a sampler, quickly transferring the soil sample into a 40mL sample bottle added with a rotor, and screwing a bottle cap; storing at low temperature in dark place, and transporting to a laboratory for analysis as soon as possible;
(2) taking a soil sample of about 5.0g, quickly transferring the soil sample into a 40mL sample bottle added with 10mL methanol, and screwing a bottle cap; storing at low temperature in dark place, and transporting to a laboratory for analysis as soon as possible;
(3) another sample is collected by a 60mL sample bottle (or a sample bottle with other specifications) and is used for measuring the volatile organic compounds in the high-content sample and the water content in the sample;
storing at 4 deg.C in dark place, and detecting within 14 d;
(4) preparation of a blank
The sample was replaced with 5.0g of quartz sand as a blank and measured according to the instrument reference conditions.
3. The method for detecting acrylonitrile and pyridine in soil according to claim 1, further comprising: analysis of samples
(1) Reference conditions of the apparatus
a sweeping and trapping conditions
Purging flow rate: 40 mL/min; purging temperature: 20 ℃; preheating time: 2 min; purging time: 11 min; dry blowing time: 2 min; pre-desorption temperature: 180 ℃; desorption temperature: 190 ℃; desorption time: 2 min; baking temperature: 260 ℃; baking time: 8 min; transmission line temperature: 180 ℃;
b gas chromatography conditions
Temperature programming:and (3) sample introduction mode: split-flow sample introduction, split-flow ratio: 30: 1; (ii) a Sample inlet temperature: at 210 ℃; transmission line temperature: 235 ℃; column flow rate: 1.0 mL/min;
c reference conditions for mass spectrometry
Ion source temperature: 230 ℃; ionization energy: 70 eV;
full Scan (Scan) mass range: 45-300 amu;
(2) calibration
a instrument Performance inspection
Before the instrument is used, the perfluorotributylamine is used for tuning a mass spectrometer; before sample analysis and every 12 hours of operation, 2 mu L of 4-bromofluorobenzene (BFB) solution is removed by a micro-injector and added into 5mL of blank reagent water and injected into a gas chromatograph through a purging and trapping device;
(3) plotting of calibration curves
Respectively transferring acrylonitrile standard use liquid, pyridine standard use liquid and substitute use liquid with different volumes to prepare acrylonitrile and substitute with mass concentrations of 0.40, 1.00, 4.00, 10.0, 20.0 and 40.0 mu g/kg; the mass concentrations of the pyridine are respectively 20.0, 40.0, 200, 400, 1000 and 2000 mug/kg; analyzing according to instrument reference conditions to obtain mass spectrograms of different target compounds; drawing a calibration curve by taking the ratio of the concentration of the target compound to the concentration of the internal standard compound as a horizontal coordinate and the ratio of the response value of the quantitative ions of the target compound to the response value of the quantitative ions of the internal standard compound as a vertical coordinate;
(4) sample assay
Taking a sample to be tested and determining according to the same instrument analysis conditions as the calibration curve;
(5) laboratory blank test
While analyzing the sample, the blank sample was measured under the same instrumental analysis conditions as the calibration curve was drawn.
4. The method for detecting the acrylonitrile and the pyridine in the soil according to claim 1, wherein the qualitative and quantitative method comprises the following steps:
(1) qualitative analysis
Collecting data in a full Scan mode (Scan), and characterizing the Relative Retention Time (RRT) of a target compound in a sample, the abundance ratio (Q) of auxiliary qualitative ions and target ions and the variation range in a standard solution; the difference between the relative retention time of the compound of interest in the sample and the average relative retention time of that compound of the calibration curve should be within ± 0.06; controlling the relative deviation of the area ratio of the auxiliary qualitative ion peak to the quantitative ion peak (Qsample) of the target compound in the sample and the area ratio of the auxiliary qualitative ion peak to the quantitative ion peak (Qstandard) of the target compound in the standard curve within +/-30%;
calculating the relative retention time RRT according to equation (1)
In the formula:
RTc-Retention time of target compound, min;
RTis — retention time of internal standard, min;
mean Relative Retention Time (RRT) the mean relative retention time of the same target compound in a standard series;
calculating the area ratio (Q) of the auxiliary qualitative ion peak to the auxiliary quantitative ion peak according to the formula (2)
In the formula:
At-quantifying the ion peak area;
Aq-auxiliary qualitative ion peak area;
(2) quantitative analysis
Calculating according to the response values of the first characteristic ions of the target object and the internal standard; when a first characteristic ion of the target in the sample is interfered, quantifying by using a second characteristic ion;
when the target object is calibrated by adopting a linear or nonlinear calibration curve, calculating the mass concentration rho ex of the target object in the sample through the corresponding calibration curve;
the content ω (μ g/kg) of the target in the sample was calculated by the following formula;
a for low content samples, the content of the target in the sample (. mu.g/kg) is calculated according to formula (1):
in the formula:
omega is the content of the target object in the sample, mu g/kg;
5-volume of sample, ml;
ρex-mass concentration of target in sample, μ g/L;
w-water content of sample,%;
m is the sample amount;
b for high content samples, the content of the target in the sample (. mu.g/kg) is calculated according to equation (2):
in the formula:
omega is the content of the target object in the sample, mu g/kg;
5-volume of sample, ml;
ρex-mass concentration of target in sample, μ g/L;
Vc-volume of extract, ml;
m is sample amount, g;
Vs-volume of extract used for purging, ml;
w-water content of sample,%;
k is the dilution multiple of the extracting solution.
5. The method for detecting acrylonitrile and pyridine in soil according to claim 4, further comprising: if the water content of the sample is more than 10%, the volume Vc of the extracting solution is the sum of the volume of the methanol and the volume of the water in the sample; if the water content of the sample is less than or equal to 10 percent, the volume Vc of the extracting solution is 10 mL.
Technical Field
The invention relates to the technical field of soil detection, in particular to a method for detecting acrylonitrile and pyridine in soil.
Background
Acrylonitrile (AN), a conjugated unsaturated nitrile, is one of the important raw materials of three major synthetic materials, and occupies a significant position in polymer materials such as synthetic resins, synthetic fibers, synthetic rubbers and the like, and has a wide application prospect. In addition, acrylonitrile polymers and acrylonitrile derivatives are also widely used in building materials and daily necessities.
Pyridine is a six-membered heterocyclic organic compound containing one nitrogen heteroatom, which can be regarded as a compound in which one (CH) of benzene molecules is substituted by N, and is also called nitrobenzene, colorless or yellowish liquid, and has malodor. Pyridine and its homologues are present in bone tar, coal gas, shale oil, petroleum. Pyridine is industrially useful as a denaturant, a dye assistant, and a raw material for synthesizing a series of products including medicines, disinfectants, dyes, etc.
Acrylonitrile and pyridine belong to high toxicity, and can cause acute poisoning and chronic poisoning after entering a human body, anaesthetize the central nervous system, cause symptoms such as neurasthenia, contact dermatitis, digestive tract dysfunction and the like, and have high teratogenicity and carcinogenicity. On 27.10.2017, the list of carcinogens published by the world health organization international agency for research on cancer, acrylonitrile and pyridine were listed in the list of 2B carcinogens.
At present, the determination standard of acrylonitrile in soil in China is only 'determination headspace-gas chromatography for acrolein, acrylonitrile and acetonitrile in soil and sediment' (HJ 679-. The evaluation requirements of acrylonitrile and pyridine in the enterprise land survey project except 85 items listed in GB36600-2018 and other pollutant lists needing attention cannot be met.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a method for detecting acrylonitrile and pyridine in soil, which adopts a sweeping trapping/gas chromatography-mass spectrometry method to detect the acrylonitrile and the pyridine in the soil, does not need to extract a sample before pretreatment, directly sweeps and samples for determination, and meets the evaluation requirements of 85 items listed in GB36600-2018 and other pollutant lists needing attention in enterprise land survey projects. The method can be used for measuring the acrylonitrile and the pyridine in the soil and the sediment, the method can be used for investigating and evaluating the acrylonitrile and the pyridine in the soil, the establishment of the method has great significance for investigating and evaluating the volatile organic compounds acrylonitrile and the pyridine in soil samples in China, and the method is applied to the detection of soil samples for the important enterprise industry in Hebei province at present.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for detecting acrylonitrile and pyridine in soil comprises the following steps: adopting a purging and trapping enrichment method, purging and enriching acrylonitrile and pyridine in a trapping pipe by using high-purity helium or nitrogen, heating the trapping pipe, performing back flushing by using the high-purity helium, introducing the thermally desorbed components into a gas chromatograph, separating, and detecting by using a mass spectrometer; and (4) according to retention time, fragment ion mass-to-charge ratio and different ion abundance ratios, determining the nature and quantifying by an internal standard method.
The method further comprises the following steps: sample collection and preservation
Samples should be collected in brown glass sample bottles, all samples were taken in triplicate,
(1) a soil sample of about 5.0g is directly sampled by a sampler, quickly transferred to a 40mL sample bottle with a rotor, and the bottle cap is screwed. Storing at low temperature in dark place, and transporting to laboratory for analysis as soon as possible.
(2) A soil sample of about 5.0g was collected, quickly transferred to a 40mL sample bottle containing 10mL of methanol, and the bottle cap was closed. Storing at low temperature in dark place, and transporting to laboratory for analysis as soon as possible.
(3) Another sample is taken from a 60mL sample bottle (or other standard sample bottle) and used to determine the content of volatile organic compounds in the high-content sample and the water content in the sample.
The sample was stored at 4 ℃ in the dark and the detection was completed within 14 days.
(4) Preparation of a blank
The sample was replaced with 5.0g of quartz sand as a blank and measured according to the instrument reference conditions.
The method further comprises the following steps: analysis of samples
(1) Reference conditions of the apparatus
a sweeping and trapping conditions
Purging flow rate: 40 mL/min; purging temperature: 20 ℃; preheating time: 2 min; purging time: 11 min; dry blowing time: 2 min; pre-desorption temperature: 180 ℃; desorption temperature: 190 ℃; desorption time: 2 min; baking temperature: 260 ℃; baking time: 8 min; transmission line temperature: 180 ℃ is carried out.
b gas chromatography conditions
Temperature programming:and (3) sample introduction mode: split-flow sample introduction, split-flow ratio: 30: 1; (ii) a Sample inlet temperature: at 210 ℃; transmission line temperature: 235 ℃; column flow rate: 1.0 mL/min.
c reference conditions for mass spectrometry
Ion source temperature: 230 ℃; ionization energy: 70 eV;
full Scan (Scan) mass range: 45-300 amu;
(2) calibration
a instrument Performance inspection
The mass spectrometer was tuned with perfluorotributylamine before use of the instrument. Before sample analysis and every 12h of operation, 2 mu L of 4-bromofluorobenzene (BFB) solution is removed by a micro-syringe and added into 5mL of blank reagent water to be injected into a gas chromatograph through a purging and trapping device.
(3) Plotting of calibration curves
Respectively transferring acrylonitrile standard use liquid, pyridine standard use liquid and substitute use liquid with different volumes to prepare acrylonitrile and substitute with mass concentrations of 0.40, 1.00, 4.00, 10.0, 20.0 and 40.0 mu g/kg; the mass concentrations of pyridine are respectively 20.0, 40.0, 200, 400, 1000 and 2000 mug/kg standard series. And analyzing according to instrument reference conditions to obtain different target compound mass spectrograms. And drawing a calibration curve by taking the ratio of the concentration of the target compound to the concentration of the internal standard compound as a horizontal coordinate and the ratio of the response value of the quantitative ions of the target compound to the response value of the quantitative ions of the internal standard compound as a vertical coordinate.
(4) Sample assay
And (4) taking a sample to be tested and determining according to the same instrument analysis conditions as the calibration curve drawing.
(5) Laboratory blank test
While analyzing the sample, the blank sample was measured under the same instrumental analysis conditions as the calibration curve was drawn.
The method further comprises the following steps: result calculation and representation
(1) Qualitative analysis
Data were collected in a full Scan mode (Scan) and characterized by the Relative Retention Time (RRT) of the target compound in the sample, the auxiliary qualitative ion and target ion abundance ratio (Q) versus the range of variation in the standard solution. The relative retention time of the compound of interest in the sample should be within ± 0.06 of the average relative retention time of that compound of the calibration curve. The relative deviation of the auxiliary qualitative ion and quantitative ion peak area ratio (Qsample) of the target compound in the sample and the auxiliary qualitative ion and quantitative ion peak area ratio (QStandard) of the target compound in the standard curve is controlled within +/-30%.
Calculating the relative retention time RRT according to equation (1)
In the formula:
RTc-Retention time of target compound, min;
RTis-retention time of internal standard, min.
Mean Relative Retention Time (RRT) relative Retention time average of the same target Compound in a Standard series
Calculating the area ratio (Q) of the auxiliary qualitative ion peak to the auxiliary quantitative ion peak according to the formula (2)
In the formula:
At-quantifying the ion peak area;
Aqauxiliary qualitative ion peak area.
A total ion flow graph of a selective ion scan of acrylonitrile and pyridine standards, see figure 1.
(2) Quantitative analysis
And calculating according to the response values of the first characteristic ions of the target substance and the internal standard. Second signature ion quantification may be used when a first signature ion of a target in a sample is perturbed.
When the target is calibrated by using a linear or nonlinear calibration curve, the mass concentration ρ ex of the target in the sample is calculated from the corresponding calibration curve.
The content ω (. mu.g/kg) of the target in the sample was calculated by the following formula.
a for low content samples, the content of the target in the sample (. mu.g/kg) is calculated according to formula (1):
in the formula:
omega is the content of the target object in the sample, mu g/kg;
5-volume of sample, ml;
ρex-mass concentration of target in sample, μ g/L;
w-water content of sample,%;
m is the sample amount.
b for high content samples, the content of the target in the sample (. mu.g/kg) is calculated according to equation (2):
in the formula:
omega is the content of the target object in the sample, mu g/kg;
5-volume of sample, ml;
ρex-mass concentration of target in sample, μ g/L;
Vc-volume of extract, ml;
m is sample amount, g;
Vs-volume of extract used for purging, ml;
w-water content of sample,%;
k is the dilution multiple of the extracting solution.
Note: if the water content of the sample is more than 10%, the volume Vc of the extracting solution is the sum of the volume of the methanol and the volume of the water in the sample; if the water content of the sample is less than or equal to 10 percent, the volume Vc of the extracting solution is 10 mL.
The invention has the technical effects and advantages that: compared with the prior art, the method has the following advantages by using the method for detailed examination of project soil samples according to the pollution condition of large-scale enterprises.
(1) The sample pretreatment mode is simple, extraction is not needed, and direct sample introduction is realized.
(2) Stable extraction, good parallelism and high precision.
(3) The instrument is simple to operate, can be realized in most laboratories, and can be used for large-batch detection.
(4) The recovery rate of the sample addition and the substitution can be between 70 and 130 percent.
Drawings
FIG. 1 is a total ion flow diagram of acrylonitrile and pyridine standard materials.
The compounds in the figure are, in order of retention time: 1. acrylonitrile; 2. dibromofluoromethane; 3. toluene-d 8; 4. pyridine.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
The method is characterized in that a sweeping and trapping enrichment method is adopted, high-purity helium (or nitrogen) is used for sweeping and enriching acrylonitrile and pyridine in a trapping pipe, the trapping pipe is heated and is subjected to back blowing by the high-purity helium, components desorbed thermally enter a gas chromatograph and are separated, and a mass spectrometer is used for detecting. And (4) according to retention time, fragment ion mass-to-charge ratio and different ion abundance ratios, determining the nature and quantifying by an internal standard method.
When the sample size was 5.0g, the detection limits of the method are specified in Table 1.
TABLE 1 name of target Compound and detection and lower determination limits
Example two
Firstly, collecting and storing samples
Samples should be collected in brown glass sample bottles, all samples were taken in triplicate,
(1) a soil sample of about 5.0g is directly sampled by a sampler, quickly transferred to a 40mL sample bottle with a rotor, and the bottle cap is screwed. Storing at low temperature in dark place, and transporting to laboratory for analysis as soon as possible.
(2) A soil sample of about 5.0g was collected, quickly transferred to a 40mL sample bottle containing 10mL of methanol, and the bottle cap was closed. Storing at low temperature in dark place, and transporting to laboratory for analysis as soon as possible.
(3) Another sample is taken from a 60mL sample bottle (or other standard sample bottle) and used to determine the content of volatile organic compounds in the high-content sample and the water content in the sample.
The sample was stored at 4 ℃ in the dark and the detection was completed within 14 days.
(4) Preparation of a blank
The sample was replaced with 5.0g of quartz sand as a blank and measured according to the instrument reference conditions.
Second, analyze the sample
(1) Reference conditions of the apparatus
a sweeping and trapping conditions
Purging flow rate: 40 mL/min; purging temperature: 20 ℃; preheating time: 2 min; purging time: 11 min; dry blowing time: 2 min; pre-desorption temperature: 180 ℃; desorption temperature: 190 ℃; desorption time: 2 min; baking temperature: 260 ℃; baking time: 8 min; transmission line temperature: 180 ℃ is carried out.
b gas chromatography conditions
Temperature programming:and (3) sample introduction mode: split-flow sample introduction, split-flow ratio: 30: 1; (ii) a Sample inlet temperature: at 210 ℃; transmission line temperature: 235 ℃; column flow rate: 1.0 mL/min.
c reference conditions for mass spectrometry
Ion source temperature: 230 ℃; ionization energy: 70 eV;
full Scan (Scan) mass range: 45-300 amu;
selected Ion (SIM) scans, target compound scan ions are shown in table 2.
TABLE 2 scanning ions corresponding to target compounds
(2) Calibration
a instrument Performance inspection
The mass spectrometer was tuned with perfluorotributylamine before use of the instrument. Before sample analysis and every 12h of operation, 2 mu L of 4-bromofluorobenzene (BFB) solution is removed by a micro-syringe and added into 5mL of blank reagent water to be injected into a gas chromatograph through a purging and trapping device. The instrument system was examined and the mass ion abundances obtained should all meet the requirements in table 3.
TABLE 34 bromofluorobenzene (BFB) Key ion and abundance criteria
Mass ion
Abundance standard
Mass ion
Abundance standard
50
8 to 40 percent of the mass of the product
174
More than 50 percent of the mass 95 percent
75
Mass 95 is 30% >. E
175
Mass 174 of 5% >, E
95
Basal peak, 100% relative abundance
176
93%. E of mass 174
96
5 to 9 percent of the mass of the product
177
Mass 176%
173
Less than 2 percent of the mass
－
－
(3) Plotting of calibration curves
Respectively transferring acrylonitrile standard use liquid, pyridine standard use liquid and substitute use liquid with different volumes to prepare acrylonitrile and substitute with mass concentrations of 0.40, 1.00, 4.00, 10.0, 20.0 and 40.0 mu g/kg; the mass concentrations of pyridine are respectively 20.0, 40.0, 200, 400, 1000 and 2000 mug/kg standard series. And analyzing according to instrument reference conditions to obtain different target compound mass spectrograms. And drawing a calibration curve by taking the ratio of the concentration of the target compound to the concentration of the internal standard compound as a horizontal coordinate and the ratio of the response value of the quantitative ions of the target compound to the response value of the quantitative ions of the internal standard compound as a vertical coordinate.
(4) Sample assay
And (4) taking a sample to be tested and determining according to the same instrument analysis conditions as the calibration curve drawing.
(5) Laboratory blank test
While analyzing the sample, the blank sample was measured under the same instrumental analysis conditions as the calibration curve was drawn.
Thirdly, calculating and representing the result
(1) Qualitative analysis
Data were collected in a full Scan mode (Scan) and characterized by the Relative Retention Time (RRT) of the target compound in the sample, the auxiliary qualitative ion and target ion abundance ratio (Q) versus the range of variation in the standard solution. The relative retention time of the compound of interest in the sample should be within ± 0.06 of the average relative retention time of that compound of the calibration curve. The relative deviation of the auxiliary qualitative ion and quantitative ion peak area ratio (Qsample) of the target compound in the sample and the auxiliary qualitative ion and quantitative ion peak area ratio (QStandard) of the target compound in the standard curve is controlled within +/-30%.
Calculating the relative retention time RRT according to equation (1)
In the formula:
RTc-Retention time of target compound, min;
RTis-retention time of internal standard, min.
Mean Relative Retention Time (RRT) relative Retention time average of the same target Compound in a Standard series
Calculating the area ratio (Q) of the auxiliary qualitative ion peak to the auxiliary quantitative ion peak according to the formula (2)
In the formula:
At-quantifying the ion peak area;
Aqauxiliary qualitative ion peak area.
A total ion flow graph of a selective ion scan of acrylonitrile and pyridine standards, see figure 1.
(2) Quantitative analysis
And calculating according to the response values of the first characteristic ions of the target substance and the internal standard. Second signature ion quantification may be used when a first signature ion of a target in a sample is perturbed.
When the target is calibrated by using a linear or nonlinear calibration curve, the mass concentration ρ ex of the target in the sample is calculated from the corresponding calibration curve.
The content ω (. mu.g/kg) of the target in the sample was calculated by the following formula.
a for low content samples, the content of the target in the sample (. mu.g/kg) is calculated according to formula (1):
in the formula:
omega is the content of the target object in the sample, mu g/kg;
5-volume of sample, ml;
ρex-mass concentration of target in sample, μ g/L;
w-water content of sample,%;
m is the sample amount.
b for high content samples, the content of the target in the sample (. mu.g/kg) is calculated according to equation (2):
in the formula:
omega is the content of the target object in the sample, mu g/kg;
5-volume of sample, ml;
ρex-mass concentration of target in sample, μ g/L;
Vc-volume of extract, ml;
m is sample amount, g;
Vs-volume of extract used for purging, ml;
w-water content of sample,%;
k is the dilution multiple of the extracting solution.
Note: if the water content of the sample is more than 10%, the volume Vc of the extracting solution is the sum of the volume of the methanol and the volume of the water in the sample; if the water content of the sample is less than or equal to 10 percent, the volume Vc of the extracting solution is 10 mL.
The points to be finally explained are: first, in the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "mounted," "connected," and "connected" should be understood broadly, and may be a mechanical connection or an electrical connection, or a communication between two elements, and may be a direct connection, and "upper," "lower," "left," and "right" are only used to indicate a relative positional relationship, and when the absolute position of the object to be described is changed, the relative positional relationship may be changed;
the above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that are within the spirit and principle of the present invention are intended to be included in the scope of the present invention.