CN112964795B - Method for analyzing semi-volatile organic compounds in soil - Google Patents
Method for analyzing semi-volatile organic compounds in soil Download PDFInfo
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Abstract
The invention discloses a method for analyzing semi-volatile organic compounds in soil, which comprises the following steps: pressurized fluid extraction-concentration under reduced pressure-column purification-GC/MS analysis. The invention can complete the analysis method of 56 or more semi-volatile organic compounds (including polycyclic aromatic hydrocarbon, nitrosamine, phthalate ester, halogenated ether, nitro aromatic hydrocarbon, cyclic ketone, chlorohydrocarbon, phenols, aniline and other semi-volatile organic compounds) in the soil through one process (extraction, purification, concentration and instrumental analysis). The phenolic compound and the aniline compound can be analyzed together with other semi-volatile organic compounds; meanwhile, the recovery rate of the aniline target substance meets the requirements of relevant standards.
Description
Technical Field
The invention belongs to the field of organic chemical analysis, and relates to an analysis method of semi-volatile organic compounds, in particular to an analysis method of semi-volatile organic compounds in soil.
Background
The semi-volatile organic compounds are a large class of organic compounds with slower volatility than volatile organic compounds, are easier to migrate and convert in media such as water, soil, air, organisms and the like, exist in the water and the soil for a long time, and are harmful to human health through biological enrichment. The environmental fate is usually soil and sediment. The organic matters have the common property of being fat-soluble and easy to dissolve in organic solvents, but have strong polarity and are slightly soluble in water (such as aniline, esters, aldehydes and ketones and the like). In general, organic chlorine pesticides, organophosphorus pesticides, other herbicides, polycyclic aromatic hydrocarbons, phthalates, polychlorinated biphenyls, anilines, phenols, nitrobenzenes and the like can be included in the range of such organic compounds.
In the prior art, the analysis methods of semi-volatile Organic Compounds include standard analysis methods such as "gas chromatography-mass spectrometry for measuring semi-volatile Organic Compounds in soil and sediments" HJ834 and 2017, "gas chromatography for measuring phenolic Compounds in soil and sediments (HJ703-2014)," EPA Method 8270E discrete Organic Compounds by GC-MS, "EPA Method 3545A Presurized Flex Emission (PFE)" and "EPA Method 3630C SILICA GEL clean". In the above standards, the U.S. EPA standard method only describes partial contents of a complete analysis method, such as extraction method, purification method, instrumental analysis method, etc., and different extraction and purification methods are required for different kinds of targets.
In the process of implementing the invention, the inventor finds that at least one of the following problems exists in the prior art:
1. in the domestic analysis standard, the HJ834 content is relatively comprehensive, but analysis of different indexes needs to be carried out respectively by different pretreatment steps, for example, phenolic compounds need to be subjected to derivatization and then analyzed, semi-volatile organic compound chromatographic column purification methods need to be subjected to treatment respectively, anilines cannot be subjected to GPC purification operation, the GPC purification method is small in flux, time-consuming, labor-consuming, large in solvent consumption, poor in environmental friendliness and the like.
2. HJ703 is only suitable for the measurement of phenolic compounds, and cannot be used for the simultaneous measurement of other semi-volatile organic compounds.
3. In the existing 'soil environmental quality construction land soil pollution risk control standard (trial) GB 36600-2018', the standard 1 basic 45 items in the standard require the determination and evaluation of 11 semi-volatile organic compounds, and the above standards for the target substances cannot be analyzed at one time.
4. Other methods for analyzing semi-volatile organic compounds are disclosed in the prior art, but all of them have certain limitations, such as large target loss during sample processing; the purification is carried out by adopting a silica gel column, and has certain limitation aiming at the purification of target objects of phthalate esters, nitrosamines and anilines; the solvent used for purification is high, and the environmental friendliness is poor; the separation difficulty of the sample and the extracting solution is high; the analysis of 56 semi-volatile organic compounds (including polycyclic aromatic hydrocarbon, nitrosamine, phthalate ester, halogenated ether, nitroaromatic hydrocarbon, cyclic ketone, chlorohydrocarbon, phenol, aniline and other semi-volatile organic compounds) in the soil can not be completed through one process (extraction, purification, concentration and instrumental analysis).
5. The problems of great influence on the quantitative accuracy, instrument pollution and the like caused by the interference of the sample matrix due to incomplete purification are easy to occur.
6. The method aims at the problem of dehydration of the fresh sample extracting solution, and easily causes the problems of incomplete dehydration, influence on subsequent purification effect, quantitative accuracy and the like.
Disclosure of Invention
In view of this, the present invention aims to provide a method for determining 56 semi-volatile targets by a set of analysis procedures.
The inventor provides a method for analyzing semi-volatile organic compounds in soil by continuous innovation and innovation through long-term exploration and trial and multiple experiments and endeavors, and in order to solve the technical problems, the technical scheme provided by the invention comprises the following steps:
1) taking a fresh soil sample with impurities removed, adding diatomite, grinding uniformly, and filling into an extraction tank;
2) adding a 1:1 acetone/n-hexane mixed solvent into the extraction tank, and performing pressure extraction to obtain a first extracting solution;
3) adding anhydrous sodium sulfate and sodium chloride into the first extracting solution respectively for dehydration to obtain a second extracting solution;
4) evaporating and concentrating the second extracting solution to obtain a first concentrated solution;
5) a purification process: the purification filler is florisil magnesium silicate, the purification filler is filled into a chromatographic column by a dry method, anhydrous sodium sulfate is filled at the bottom and the upper part of the chromatographic column, the chromatographic column is activated by adding a 1:9 acetone/n-hexane mixed solvent after being washed by n-hexane, and a knob is closed after gravity automatically flows out until the anhydrous sodium sulfate is just immersed in the solvent; completely transferring the first concentrated solution obtained in the step 4) to a purification column; opening a knob, adding a 1:9 acetone/n-hexane mixed solvent for elution before the anhydrous sodium sulfate at the upper layer is exposed to air, collecting a sample and an eluent, evaporating and concentrating to obtain a second concentrated solution, converting the solvent n-hexane into the second concentrated solution, adding a sample injection internal standard, and fixing the volume to a scale container to obtain a fixed solution;
6) and (3) a part of the fixed solution is divided and transferred into a sample injection vial, and is subjected to gas chromatography-mass spectrometry.
According to one embodiment of the method for analyzing the semi-volatile organic compounds in the soil, in the step 2), the extraction is circulated and carried out for 3 times, the extraction temperature is 100 ℃, the extraction pressure is 1600psi, and the equilibrium time is 6 min.
According to one embodiment of the method for analyzing semi-volatile organic compounds in soil, in the step 4), the evaporation concentration is parallel evaporation or rotary evaporation concentration, and the concentration conditions are as follows: concentrating under gradient reduced pressure at 40 deg.C in water bath.
According to one embodiment of the method for analyzing the semi-volatile organic compounds in the soil, the gradient concentration at reduced pressure is 450mbar for 10min, and the uniform speed of 30mbar/min is reduced to 240mbar for about 5 min.
According to one embodiment of the method for analyzing the semi-volatile organic compounds in the soil, the florisil magnesium silicate is pesticide residue grade, and is baked for 4 hours at 450 ℃ before use and is placed into a ground glass bottle for storage in a dryer.
According to one embodiment of the method for analyzing semi-volatile organic compounds in soil, the gas chromatography-mass spectrometry conditions are as follows: the sample inlet temperature is 280 ℃, the chromatographic column DB-5, the sample volume is 1 mu L, the column flow is 1ml/min, the column temperature is kept at 40 ℃ for 3min-15 ℃/min, the temperature is increased to 160 ℃ -10 ℃/min, the temperature is increased to 300 ℃ for 5min, the EI ion source temperature is 230 ℃, the transmission line temperature is 280 ℃, and the ion scanning mode is selected.
According to one embodiment of the method for analyzing semi-volatile organic compounds in soil, the standard size of the chromatographic column DB-5 is 30m multiplied by 0.25mm multiplied by 0.25 μm.
According to one embodiment of the method for analyzing the semi-volatile organic compounds in the soil, the semi-volatile organic compounds include polycyclic aromatic hydrocarbons, nitrosamines, phthalate esters, halogenated ethers, nitroaromatics and cyclic ketones, chlorinated hydrocarbons, phenols and aniline organic compounds in the soil.
According to one embodiment of the method for analyzing semi-volatile organic compounds in soil of the present invention, the semi-volatile organic compounds include aniline, phenol, bis (2-chloroethyl) ether, 2-chlorophenol, 1, 3-dichlorobenzene, 1, 4-dichlorobenzene, 1, 2-dichlorobenzene, 2-methylphenol, bis (2-chloroisopropyl) ether, 4-methylphenol, N-nitrosodi-N-propane, hexachloroethane, nitrobenzene, isophorone, bis (2-chloroethoxy) methane-ane, 2, 4-dichlorophenol, 1,2, 4-trichlorobenzene, naphthalene, 4-chloroaniline, hexachlorobutadiene, 4-chloro-3-methylphenol, 2-methylnaphthalene, hexachlorocyclopentadiene, 2-chloronaphthalene, 2-nitroaniline, acenaphthylene, dimethyl phthalate, 2, 6-dinitrotoluene, acenaphthene, 3-nitroaniline, dibenzofuran, 2, 4-dinitrotoluene, fluorene, 4-chlorophenyl phenyl ether, diethyl phthalate, azobenzene, 4-bromodiphenyl ether, hexachlorobenzene, atrazine, phenanthrene, anthracene, carbazole, fluoranthene, pyrene, butylbenzyl phthalate, benzo [ a]Anthracene, 3-dichlorobenzidine,
Di- (2-diethylhexyl) phthalate, di-n-octyl phthalate, benzo [ b ]]Fluoranthene, benzo [ k ]]Fluoranthene, benzo [ a ]]Pyrene, indeno [1,2,3-cd]Pyrene, dibenzo [ a, h ]]Anthracene, benzo [ g, h, i ]]A perylene.
According to one embodiment of the method for analyzing the semi-volatile organic compounds in the soil, the method comprises the following steps:
1) taking 10.00g of fresh soil sample without impurities, adding 10g of diatomite, grinding uniformly, and filling into an extraction tank; the addition amount of the diatomite is flexibly adjusted according to the dry matter content;
2) adding 1:1 acetone/n-hexane mixed solvent into the extraction tank, and performing pressure extraction for 3 times, wherein the extraction temperature is 100 ℃, the extraction pressure is 1600psi, and the balance time is 6 min; obtaining a first extracting solution;
3) adding 5g of anhydrous sodium sulfate and 5g of sodium chloride into the first extracting solution respectively for dehydration to obtain a second extracting solution; the addition amount of the anhydrous sodium sulfate and the sodium chloride can be properly adjusted according to the water content;
4) concentrating the second extractive solution to 1ml by parallel evaporation or rotary evaporation to obtain first concentrated solution;
5) a purification process: the purification filler is 2.00g of florisil magnesium silicate, the purification filler is filled into a chromatographic column by a dry method, 1g of anhydrous sodium sulfate is filled at the bottom and the upper part of the chromatographic column, the chromatographic column is washed by 10ml of n-hexane and then activated by adding 10ml of a 1:9 acetone/n-hexane mixed solvent, and the knob is closed when the solvent just submerges the anhydrous sodium sulfate after gravity automatically flows out; completely transferring the first concentrated solution obtained in the step 4) to a purification column; opening a knob, adding 10ml of a 1:9 acetone/n-hexane mixed solvent for elution before the anhydrous sodium sulfate at the upper layer is exposed to air, collecting a sample and 13ml of eluent, evaporating and concentrating to obtain about 3ml of second concentrated solution, completely transferring the second concentrated solution into a 10ml graduated test tube, adding an internal sample injection standard, and fixing the volume to 10 ml;
6) 1ml of the fixed solution is dispensed into a sample injection vial for gas chromatography-mass spectrometry.
Compared with the prior art, one of the technical solutions has the following advantages:
a) the invention can complete the analysis method of 56 or more semi-volatile organic compounds (including polycyclic aromatic hydrocarbon, nitrosamine, phthalate ester, halogenated ether, nitro aromatic hydrocarbon, cyclic ketone, chlorohydrocarbon, phenols, aniline and other semi-volatile organic compounds) in the soil through one process (extraction, purification, concentration and instrumental analysis). The phenolic compound and the aniline compound can be analyzed together with other semi-volatile organic compounds; meanwhile, the recovery rate of the aniline target substance meets the requirements of relevant standards.
b) The method for analyzing the soil semi-volatile organic compounds can simultaneously analyze the anilines, the phenols and other semi-volatile organic compounds, and greatly improves the analysis efficiency. The method comprises the steps that 56 target objects cover 11 semi-volatile organic matters required by the current GB36600 limit value standard in site pollution investigation as a necessary measurement item, 2 sets of analysis processes of the 11 semi-volatile organic matters in the current standard can be integrated into 1, 2-chlorophenol and other phenolic compounds are integrated with other target objects by adjusting a purification mode, and aniline without the national standard is integrated into the method, the recovery rate of the target objects with strong volatility such as aniline is guaranteed by a concentration mode of rotary evaporation instead of nitrogen blowing, the recovery rate is increased to more than 50% from below 30%, the analysis efficiency is greatly improved, the cost is saved, and the practicability is greatly improved.
c) The method can be simultaneously suitable for measuring other semi-volatile organic compounds such as organochlorine pesticides, polychlorinated biphenyl and the like after fine adjustment of the constant volume and the instrumental analysis method, and has good universality.
d) The sodium chloride is added in the dehydration process to reduce the intersolubility of water and the organic solvent, so that the water in the sample solution can be removed more thoroughly, and the subsequent purification analysis is facilitated.
e) The invention innovatively improves the sensitivity by selecting an ion scanning mode, increases the constant volume, can effectively reduce the interference of a sample matrix and reduce the pollution of a sample solution to an instrument, ensures more accurate quantification and greatly reduces the use and maintenance cost of the instrument. Meanwhile, the loss of volatile targets such as aniline and the like caused by the solution concentration process can be effectively reduced by increasing the volume fixing volume.
f) The invention can effectively reduce the loss of volatile target substances such as aniline and the like caused by the concentration process by replacing the mode of normal-pressure nitrogen blowing concentration with reduced-pressure concentration.
g) The invention can purify 56 semi-volatile organic compounds, 24 organochlorine pesticides, 18 polychlorinated biphenyls and other target objects at one time by innovatively adjusting and purifying the filler and the elution solution, and has the advantages of high purification speed, good effect and very strong practicability.
Detailed Description
The following description will be given with reference to specific examples.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention will be described in detail and completely with reference to the accompanying drawings. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. Thus, the following detailed description of embodiments of the invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention.
Example 1
The method for analyzing semi-volatile organic compounds in soil described in this embodiment can analyze and determine 56 semi-volatile organic compounds in a single process. The 56 semi-volatile organic compounds are respectively aniline, phenol, bis (2-chloroethyl) ether, 2-chlorophenol, 1, 3-dichlorobenzene, 1, 4-dichlorobenzene, 1, 2-dichlorobenzene, 2-methylphenol, bis (2-chloroisopropyl) ether, 4-methylphenol, N-nitrosodi-N-propane, hexachloroethane, nitrobenzene, isophorone, bis (2-chloroethoxy) methane-ane, 2, 4-dichlorophenol, 1,2, 4-trichlorobenzene, naphthalene, 4-chloroaniline, hexachlorobutadiene, 4-chloro-3-methylphenol, 2-methylnaphthalene, hexachlorocyclopentadiene, 2-chloronaphthalene, 2-nitro, acenaphthylene, dimethyl phthalate, 2, 6-dinitrotoluene, acenaphthylene, 3-nitroaniline, Dibenzofuran, 2, 4-dinitrotoluene, fluorene, 4-chlorophenyl phenyl ether, diethyl phthalate, azobenzene, 4-bromodiphenyl ether, hexachlorobenzene, atrazine, phenanthrene, anthracene, carbazole, fluoranthene, pyrene, butylbenzyl phthalate, benzo [ a]Anthracene, 3-dichlorobenzidine,
Di- (2-diethylhexyl) phthalate, di-n-octyl phthalate, benzo [ b ]]Fluoranthene, benzo [ k ]]Fluoranthene, benzo [ a ]]Pyrene, indeno [1,2,3-cd]Pyrene, dibenzo [ a, h ]]Anthracene, benzo [ g, h, i ]]A perylene. The general flow is pressurized fluid extraction-reduced pressure concentration-chromatographic column purification-GC/MS analysis.
1. Sample preparation
Weighing 10.00g of fresh soil sample, adding 10g of diatomite, grinding uniformly, filling into an extraction tank, adding the substitute, and extracting by a pressurized fluid extractor. The soil sample is taken from the land used by a certain enterprise. The addition amount of the diatomite is flexibly adjusted according to the dry matter content.
2. Pressurized fluid extraction
In this example, the extraction conditions were: extracting with acetone/n-hexane mixed solvent at volume ratio of 1:1 for 3 times at 100 deg.C under 1600psi for 6min to obtain first extractive solution.
The extraction conditions have very obvious influence on the extraction effect of the analytes, and whether the extraction of the organic matters in the soil sample is sufficient and complete is a basic guarantee of the analysis method, and the analysis quantity of the semi-volatile organic matters in the soil sample and the accuracy of the analysis result are directly influenced by the whole analysis method.
Through repeated research and exploration, the inventor determines the extraction conditions of semi-volatile organic compounds in the soil sample, namely extraction is carried out by using an acetone/n-hexane mixed solvent with the volume ratio of 1:1, the cycle times are 3 times, the extraction temperature is 100 ℃, the extraction pressure is 1600psi, and the balance time is 6 min. In carrying out the present invention, the inventors repeatedly tried different extraction conditions, and by performing a single comparison on the pressurized fluid extraction conditions, part of the experimental procedures and results are shown in table 1 below.
Table 1 "GB 36600-2018 soil environmental quality construction land soil pollution risk control standard (trial) in table 1 (hereinafter referred to as" standard table 1 ") in item 45 of basis 45, the extraction effects of nitrobenzene, aniline, 2-chlorophenol and 8 polycyclic aromatic hydrocarbon semi-volatile organic compounds are compared
As can be seen from table 1 above, when extracting semi-volatile organic compounds in a soil sample, the solvent system, the extraction temperature, and the cycle number in the extraction conditions have a significant effect on the recovery rate of the target compound.
GB36600-2018 soil environmental quality construction land soil pollution risk management and control standard (trial) is used as an enterprise land survey basic file, 45 items in a standard table 1 (basic item) are required to be tested necessarily, and information acquisition and stationing judgment are carried out to determine characteristic pollutants as additional testing items. In the basic 45 items of the standard table 1, nitrobenzene, aniline, 2-chlorophenol and 8 polycyclic aromatic hydrocarbon semi-volatile organic compounds are involved. For the extraction of the 11 semi-volatile organic compounds with large polarity difference, dichloromethane: the n-hexane system has lower recovery rate when extracting 2-chlorophenol, probably because the system has weaker polarity and incompletely extracts strong polar objects. Acetone: the dichloromethane system yields lower yields when extracting aniline, probably due to the higher volatility of aniline and the lower boiling points of dichloromethane and acetone, which results in process losses. N-hexane: the acetone system can better extract the 11 target substances, the recovery rate can meet the standard requirement, and the method is suitable for extracting SVOC samples.
When the extraction temperature is 80 ℃, the extraction effect on the difficultly volatile polycyclic aromatic hydrocarbon is not ideal; when the extraction temperature is 120 ℃, the extraction effect of volatile organic compounds such as aniline is poor, and the extraction temperature is 100 ℃ and the target substances can be considered.
For the cycle times, aiming at the extraction of semi-volatile organic compounds, most target objects can be extracted by 2 cycles, but considering that a single-channel ASE system is easy to generate mutual interference, 3 cycles of extraction are finally selected to eliminate the mutual interference.
And adding 5g of anhydrous sodium sulfate and 5g of sodium chloride into the first extracting solution respectively for dehydration to obtain a second extracting solution. The addition amounts of the anhydrous sodium sulfate and sodium chloride may be appropriately adjusted depending on the dehydration conditions.
3. Concentrating under reduced pressure
And transferring the second extracting solution to parallel evaporation or rotary evaporation for concentration to obtain a first concentrated solution. The parallel evaporation concentration condition is gradient decompression, water bath temperature is 40 ℃, concentration time is 20min, and a condensing device is provided. The rotary evaporation concentration condition is that the pressure is reduced in a gradient way, the water bath temperature is 40 ℃, and the concentration time is 40 min.
The following table 2 shows the recovery effect of aniline as the target in different concentration modes and under different concentration conditions.
TABLE 2 recovery of semi-volatile organic compounds (aniline) with relatively low boiling point in different concentration modes and conditions
The inventor researches and compares the recovery rates under different concentration modes and concentration conditions, and particularly, the concentration mode and the concentration conditions directly determine whether the standard addition recovery rate meets the requirement aiming at semi-volatile organic matters with relatively low boiling points such as aniline, nitrobenzene and 2-chlorophenol. Experiments prove that different concentration modes have great difference in the recovery rate of the target substances.
Through the research on the conditions of water bath temperature, air flow speed and concentration time applicability of a nitrogen blowing instrument, the recovery rate of low-boiling targets such as aniline, nitrobenzene and 2-chlorophenol is unstable even in a very slow condition when the nitrogen blowing type concentration is carried out, and the reason is summarized that the low-boiling targets such as aniline, nitrobenzene and 2-chlorophenol are too volatile, the concentration speed at normal pressure is slow and cannot be easily controlled.
Through the experimental exploration of the concentration conditions of the rotary evaporator, data show that the rotary evaporator adopting a decompression mode in the whole process is concentrated to improve the recovery rate of the target object by more than 40%, the automation conditions are easy to control, and the defects that the capacity of a single channel is limited and the progress cannot meet the requirement are overcome.
Adopt the parallel concentrator of multichannel decompression to concentrate, compared and taken condensing reflux unit and the rate of recovery that does not take, found when concentrated to about 1ml, condensing reflux unit can improve the target object rate of recovery more than 40%, can be fine reach relevant standard requirement.
Finally, the inventor determines that the optimal concentration scheme is to adopt a multi-channel reduced pressure parallel concentrator for concentration, and the concentration conditions are as follows: the water bath temperature is 40 ℃, the gradient reduced pressure concentration is carried out to about 1ml, then the purification is carried out, the gradient reduced pressure concentration condition is that 450mbar is kept for 10min, 30mbar/min is uniformly reduced to 240mbar and kept for 5min, the recovery rate of the target is greatly improved by setting the concentration mode, and meanwhile, the multi-channel simultaneous concentration saves several times of concentration time.
4. Purification with chromatographic column
A purification process: the purification filler is 2.00g of florisil magnesium silicate (flexibly adjusted according to the polluted condition of the sample), the purity of the florisil magnesium silicate is equal to or more than that of a chromatographic grade, and the florisil magnesium silicate is baked for 4 hours at 450 ℃ before use and put into a ground glass bottle for storage in a dryer. Filling a purification filler into a chromatographic column by a dry method, filling 1g of anhydrous sodium sulfate at the bottom and the upper part of the chromatographic column respectively for blocking, tapping and uniformly filling, washing the chromatographic column by 10ml of n-hexane, adding 10ml of acetone/n-hexane mixed solvent with the volume ratio of 1:9 for activation, automatically flowing out by gravity until the solvent just submerges the anhydrous sodium sulfate, closing a knob, transferring the concentrated first concentrated solution to a purification column, washing by using 2ml of acetone/n-hexane mixed solvent with the volume ratio of 1:9, transferring to the purification column, opening the knob, adding 10ml of acetone/n-hexane mixed solvent with the volume ratio of 1:1 for elution before the anhydrous sodium sulfate is exposed to air, collecting 13ml of upper sample and eluent, and concentrating to about 3ml by parallel evaporation or rotary evaporation to obtain a second concentrated solution. And transferring the second concentrated solution to a 10ml graduated test tube, adding an internal injection standard, and fixing the volume to 10 ml. About 1ml of the solution was dispensed into a sample vial for gas chromatography-mass spectrometry.
In the process of the invention, the inventor finds that: the full-automatic solid phase extraction method is only suitable for a mode of an SPE small column, and cannot be used for analysis by adopting a chromatographic column, while in a strict sense, HJ834 should be purified by adopting the chromatographic column or a GPC mode, and the GPC mode flux is too small to meet the analysis requirement of a large number of samples; meanwhile, the analysis efficiency is seriously influenced by the fact that 2-chlorophenol and other target substances cannot be purified simultaneously.
The inventor researches and analyzes and compares various purification modes (part of test process data are shown in table 3), and gives consideration to both the elution effect and the purification effect, and finally selects florisil magnesium silicate as a purification filler and acetone/normal hexane as an eluent. The chromatographic column is adopted for purification, the activating and eluting solvent is acetone-n-hexane mixed solvent, the eluting volume is 10ml, and the purifying effect and the purifying efficiency can be considered while the target object can be well eluted.
TABLE 3 comparison of cleaning mode effects
5. GC-MS analysis
Gas chromatography-mass spectrometry conditions: the sample inlet temperature is 280 ℃, the chromatographic column DB-5(30m multiplied by 0.25mm multiplied by 0.25 mu m), the sample volume is 1 mu L, the column flow is 1ml/min, the column temperature is kept at 40 ℃ for 3min-15 ℃/min, the temperature is increased to 160 ℃ -10 ℃/min, the temperature is increased to 300 ℃ for 5min, the EI ion source temperature is 230 ℃, the transmission line temperature is 280 ℃, and the ion scanning mode is selected. The selective ion scanning mode with higher sensitivity is adopted, and compared with the full scanning mode, the volume of the sample pre-treatment constant volume can be increased, so that the sample introduction concentration is reduced, the instrument pollution and the sample interference are reduced, and the detection limit of the method can be ensured to meet the requirements of the related method standard and the limit value standard; meanwhile, the pretreatment concentration time can be effectively saved by increasing the concentration volume, and the analysis efficiency is greatly improved.
The results of testing for each semi-volatile organic compound in the soil sample are shown in table 4 below.
TABLE 4 detection results of semi-volatile organic compounds in 56 in soil samples
The above is only a preferred embodiment of the present invention, and it should be noted that the above preferred embodiment should not be considered as limiting the present invention, and the protection scope of the present invention should be subject to the scope defined by the claims. It will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the spirit and scope of the invention, and these modifications and adaptations should be considered within the scope of the invention.
Claims (8)
1. A method for analyzing semi-volatile organic compounds in soil is characterized by comprising the following steps:
1) taking a fresh soil sample with impurities removed, adding diatomite, grinding uniformly, and filling into an extraction tank;
2) adding a 1:1 acetone/n-hexane mixed solvent into the extraction tank, and carrying out pressurized fluid extraction to obtain a first extracting solution;
3) adding anhydrous sodium sulfate and sodium chloride into the first extracting solution respectively for dehydration to obtain a second extracting solution;
4) evaporating and concentrating the second extracting solution under reduced pressure to obtain a first concentrated solution;
5) a purification process: the purification filler is magnesium silicate, the purification filler is filled into a chromatographic column by a dry method, anhydrous sodium sulfate is filled at the bottom and the upper part of the chromatographic column, the chromatographic column is washed by n-hexane and then activated by adding a 1:9 acetone/n-hexane mixed solvent, and the knob is closed after gravity automatically flows out until the solvent just submerges the anhydrous sodium sulfate; completely transferring the first concentrated solution obtained in the step 4) to a purification column; opening a knob, adding a 1:9 acetone/n-hexane mixed solvent for elution before the anhydrous sodium sulfate at the upper layer is exposed to air, collecting a sample and an eluent, performing reduced pressure evaporation and concentration to obtain a second concentrated solution, converting the solvent n-hexane into the second concentrated solution, adding an injection internal standard, and fixing the volume to a scale container to obtain a fixed solution;
6) a part of the fixed solution is taken and transferred into a sample injection vial, and is subjected to gas chromatography-mass spectrometry;
the semi-volatile organic compounds include aniline, phenol, bis (2-chloroethyl) ether, 2-chlorophenol, 1, 3-dichlorobenzene, 1, 4-dichlorobenzene, 1, 2-dichlorobenzene, 2-methylphenol, bis (2-chloroisopropyl) ether, 4-methylphenol, N-nitroso-di-N-propane, hexachloroethane, nitrobenzene, isophorone, bis (2-chloroethoxy) methane, 2, 4-dichlorophenol, 1,2, 4-trichlorobenzene, naphthalene, 4-chloroaniline, hexachlorobutadiene, 4-chloro-3-methylphenol, 2-methylnaphthalene, hexachlorocyclopentadiene, 2-chloronaphthalene, 2-nitroaniline, acenaphthylene, dimethyl phthalate, 2, 6-dinitrotoluene, acenaphthene, 3-nitroaniline, Dibenzofuran, 2, 4-dinitrotoluene, fluorene, 4-chlorophenyl phenyl ether, diethyl phthalate, azobenzene, 4-bromodiphenyl ether, hexachlorobenzene, atrazine, phenanthrene, anthracene, carbazole, fluoranthene, pyrene, butylbenzyl phthalate, benzo [ a ] anthracene, 3-dichlorobenzidine, chrysene, di (2-diethylhexyl) phthalate, di-n-octyl phthalate, benzo [ b ] fluoranthene, benzo [ k ] fluoranthene, benzo [ a ] pyrene, indeno [1,2,3-cd ] pyrene, dibenzo [ a, h ] anthracene and benzo [ g, h, i ] perylene.
2. The method for analyzing semi-volatile organic compounds in soil according to claim 1, wherein the step 2) comprises 3 times of cyclic extraction, wherein the extraction temperature is 100 ℃, the extraction pressure is 1600psi, and the equilibrium time is 6 min.
3. The method for analyzing semi-volatile organic compounds in soil according to claim 1, wherein in the step 4), the evaporation concentration is parallel evaporation or rotary evaporation concentration, and the concentration conditions are as follows: concentrating under gradient reduced pressure at 40 deg.C in water bath.
4. The method for analyzing semi-volatile organic compounds in soil according to claim 3, wherein the gradient decompression concentration is 450mbar for 10min, and the average speed of 30mbar/min is reduced to 240mbar for about 5 min.
5. The method for analyzing semi-volatile organic compounds in soil according to claim 1, wherein the magnesium silicate is florisil magnesium silicate, and the florisil magnesium silicate is baked at 450 ℃ for 4 hours before use and put into a ground glass bottle for storage in a dryer.
6. The method for analyzing semi-volatile organic compounds in soil according to claim 1, wherein the gas chromatography-mass spectrometry conditions are as follows: the sample inlet temperature is 280 ℃, the chromatographic column DB-5, the sample volume is 1 mu L, the column flow is 1ml/min, the column temperature is kept for 3min at 40 ℃, the temperature is increased to 160 ℃ at 15 ℃/min, the temperature is increased to 300 ℃ at 10 ℃/min and kept for 5min, the EI ion source temperature is 230 ℃, the transmission line temperature is 280 ℃, and the ion scanning mode is selected.
7. The method for analyzing semi-volatile organic compounds in soil according to claim 6, wherein the size of the chromatographic column DB-5 is 30m x 0.25mm x 0.25 μm.
8. The method for analyzing semi-volatile organic compounds in soil according to claim 1, comprising the steps of:
1) taking 10.00g of fresh soil sample without impurities, adding 10g of diatomite, grinding uniformly, and filling into an extraction tank;
2) adding 1:1 acetone/n-hexane mixed solvent into the extraction tank, and performing pressure extraction for 3 times, wherein the extraction temperature is 100 ℃, the extraction pressure is 1600psi, and the balance time is 6 min; obtaining a first extracting solution;
3) adding 5g of anhydrous sodium sulfate and 5g of sodium chloride into the first extracting solution respectively for dehydration to obtain a second extracting solution;
4) concentrating the second extractive solution to 1ml by parallel evaporation or rotary evaporation to obtain first concentrated solution;
5) a purification process: the purification filler is 2.00g of florisil magnesium silicate, the purification filler is filled into a chromatographic column by a dry method, 1g of anhydrous sodium sulfate is filled at the bottom and the upper part of the chromatographic column, the chromatographic column is washed by 10ml of n-hexane and then activated by adding 10ml of a 1:9 acetone/n-hexane mixed solvent, and the knob is closed when the solvent just submerges the anhydrous sodium sulfate after gravity automatically flows out; completely transferring the first concentrated solution obtained in the step 4) to a purification column; opening a knob, adding 10ml of a 1:9 acetone/n-hexane mixed solvent for elution before the anhydrous sodium sulfate on the upper layer is exposed to air, collecting a sample and 13ml of an eluent, evaporating and concentrating to obtain 3-5ml of a second concentrated solution, adding a conversion solvent n-hexane into the second concentrated solution, adding an internal sample injection standard, and fixing the volume to a 10ml graduated container to obtain a fixed solution;
6) 1ml of the fixed solution is dispensed into a sample injection vial for gas chromatography-mass spectrometry.
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