JPH0666693A - Desorption of organic chlorine based solvent and sampling tube therefor - Google Patents

Abstract

PURPOSE:To obtain accurate results of analysis while preventing a target substance from scattering or decomposing by employing a tube having one end coupled with a nitrogen gas introducing part and the other end coupled with a stop valve, adding distilled water to sampled soil, and then heating the soil as it is thereby desorbing organic chlorine based solvent. CONSTITUTION:A tube body 1 and a nitrogen introducing pipe 3 are coupled previously and total weight thereof is measured. Sampled soil is placed in the tube 1 and added with distilled water. A stop valve 5 is then coupled with the tube 1 which is then carried back to a laboratory where the weight of the soil is measured. The distilled water prevents target substance from scattering or decomposing. In order to enhance recovery of the target substance, the sampling tube is subjected to ultrasonic processing and then placed in an oven 16 and coupled with the injection port 3C of gas chromatography. Furthermore, a valve 5 is coupled through a thin pipe 13 with a dehydrating pipe 9 which is then coupled through a thin pipe 14 with a 'Tedlar(R)' bag 15. Nitrogen gas is then fed while varying the heating conditions thus sampling the target substance into the 'Tedlar(R)' bag while thermally desorbing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for desorbing an organic chlorine solvent contained in soil and a sampling container for the organic chlorine solvent used in the desorption method.

[0002]

2. Description of the Related Art As a conventional desorption analysis method for organic chlorine-based solvents, one is to use an organic solvent such as ethyl alcohol or acetone, and mix it with soil and shake it to remove a trace amount of organic chlorine-based solvent. There is a method of eluting into these organic solvent layers. Although there are many methods for elution with this organic solvent, the one proposed as the best method is
Using ethyl alcohol as an organic solvent, shaking for a long time, adding water, further dissolving in hexane, an organic solvent that is insoluble in water, and performing an operation to remove interfering substances, then a method for quantitative determination by gas chromatography Is. However, with this method, it takes a long time to elute the organic chlorine solvent from the soil, the operation is rather complicated, and attention should be paid to the scattering of the target substance into the atmosphere during the test operation and the mixture of interfering substances from the outside. I had to. It was also difficult to judge whether all the target substances were eluted from the soil.

As another conventional desorption analysis method for organic chlorine-based solvents, there is a method in which nitrogen gas or the like is passed through the soil at room temperature or while heating to expel the organic chlorine-based solvent from the soil. It is a simple desorption analysis method compared to the elution method using a solvent.

[0004]

However, in the conventional method of expelling the organic chlorine-based solvent from the soil with nitrogen gas or the like, the target substance is not so much desorbed from the soil when it is carried out at room temperature. Had challenges. On the other hand, the method of passing nitrogen gas or the like while heating the soil has a problem that the target substance is decomposed by the heating and correct measurement cannot be performed. In any case, since the organic chlorine solvent has a low boiling point and easily scatters into the atmosphere, even if the soil is collected on site and sealed, the target substance will not be released into the atmosphere from the gap between the stoppers while being brought back to the laboratory. There was a problem that there is a very high possibility of scattering inside.

Therefore, the present invention is a desorption analysis method that is simpler than the elution method using an organic solvent, and in the method of desorbing an organochlorine solvent through nitrogen gas, a desorption method that allows accurate analysis of the organochlorine solvent. The purpose is to provide a method. Specifically, the purpose is to prevent the target substance from scattering into the atmosphere before desorption. Also,
The purpose is to prevent the target substance from decomposing during desorption.

[0006]

Therefore, in order to achieve the above-mentioned object, the method for desorbing an organic chlorine-based solvent according to the present invention is an organic method for desorbing an organic chlorine-based solvent by passing nitrogen gas through the soil while heating it. In the method for desorbing a chlorine-based solvent, distilled water is added to the sampled soil, and the soil is heated as it is. It is preferable that the soil to which the distilled water is added is ultrasonically treated using the distilled water contained before heating. In addition, the method for desorbing the organic chlorine-based solvent is preferably desorption by selecting heating conditions according to the decomposability of the target component in the soil by heating and heating in multiple times under different heating conditions. . Moreover, when the target component in the soil is 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene, the desorption method of the organic chlorine-based solvent is 1,1,1 under heating conditions of 120 ° C. and 80 minutes. -Trichloroethane, trichloroethylene, and tetrachloroethylene are desorbed, and further 2
It is preferable to desorb tetrachloroethylene under heating conditions of 00 ° C. and 60 minutes. Furthermore, the present invention provides a sampling container for an organic chlorine solvent suitable for use in the method for desorbing an organic chlorine solvent, wherein an openable and closable nitrogen gas inlet is provided at one end of the container body and the other end is stopped. It is characterized by having a valve.

[0007]

According to the method for desorbing an organic chlorine solvent of the present invention,
It is possible to prevent the target substance from scattering into the atmosphere by adding distilled water after collecting the soil. Further, by adding distilled water, it is possible to prevent the decomposition of the target substance which has been decomposed by heating. In addition, if distilled water added to the soil is used for ultrasonic treatment before heating, the recovery rate of the target substance from the soil can be further increased. Further, by selecting the heating temperature and the heating time and desorbing under a plurality of heating conditions, it is possible to prevent the decomposition of the target substance and further improve the recovery rate.

Further, according to the sampling container of the organic chlorine-based solvent of the present invention, by attaching a stop valve for atmospheric analysis to the container body, it is possible to perform thermal desorption in the same state even if it is returned to the laboratory. Therefore, it is almost unnecessary to consider the loss due to scattering in the atmosphere.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 is an exploded perspective view of the sampling container of the present invention, FIG.
Is an exploded perspective view showing a dehydration pipe part connected to a sampling container, and FIG. 3 is an overall configuration diagram of an organic chlorine solvent desorption device using the sampling container.

As shown in FIG. 1, the sampling container has a container body 1 made of a stainless steel tube for containing soil, and the container body 1 is provided with screw portions 1a and 1b at both ends. Reference numerals 2a and 2b denote joints made of stainless steel, which have thread grooves corresponding to the threaded portions 1a and 1b of the container body 1 at one end, and are attached to both ends of the container body 1. The other end of the joint 2a is threaded so that the nitrogen gas introducing pipe 3 can be connected. The nitrogen gas introducing pipe 3 is made of stainless steel, is bent into an L-shape, and has an upper end portion which is a nitrogen gas introduction portion 3a and a lower end portion which is a connecting portion 3b with the joint 2a. The nitrogen gas introducing part 3a is a blind plug (not shown) at the time of sampling.
However, at the time of thermal desorption, the nitrogen gas inlet 3c can be connected as shown in FIG. Joint 2b
The other end of is threaded so that the joint 4 can be connected. The joint 4 is made of stainless steel, and is further configured to be connectable with the stop valve 5. The stop valve 5 is also made of stainless steel and has an outlet 5a on the side.
And an operating rod 5b at the upper end. Between the container body 1 and the joint 2a, a stainless plate 6 having pores and a filter 7 made of glass fiber are provided on the stainless plate 6. Further, a glass wool 8 is provided between the stainless pipe 1 and the joint 2b so that the soil does not scatter during the heat desorption. In the above embodiment, the nitrogen gas introduction part 3a is provided in the nitrogen gas introduction pipe 3, but it may be provided directly at the bottom of the container body 1.

Dewatering pipe 9 connected to the sampling container
Is a stainless steel tube with a bottom, and has a threaded portion 9a on the upper open end side. The stainless cap 10 is provided with a thread groove corresponding to the threaded portion 9a on the inner circumference, and seals the opening end of the dehydration pipe 9. Further, the stainless cap 10 has two holes, and the connection pipe 11 on the gas inflow side and the connection pipe 12 on the gas outflow side are inserted into the holes, respectively. In addition, to prevent water from flowing out from the dehydration pipe 9,
The lower end of the connecting pipe 12 is located above the lower end of the connecting pipe 11. The upper ends of the connecting pipes 11 and 12 are connecting portions 11a and 12a connectable to the stainless pipes 13 and 14, respectively.
Has become. Further, regarding the screw portion for connecting the respective parts, a Teflon seal is wound around each of them when screwing in in order to make the sealing more complete.

Next, a method of using the desorption device for the organic chlorine solvent will be described. First, a method of collecting soil on site will be described. In the sampling container shown in FIG. 1, the container body 1, the joint 2a, and the nitrogen gas introducing pipe 3 are connected in advance. At this time, the stainless plate 6
The filter 7 is attached when the container body 1 and the joint 2a are connected. Also, the nitrogen gas introduction pipe 3
The nitrogen gas introduction part 3a of 1 is blindly capped. On the other hand, the joint 2b, the joint 4 and the stop valve 5 are also connected in advance. Then, the total weight of these is measured. The soil collected at the site is immediately put in the container body 1, 10 ml of distilled water prepared in advance is added, and the joint 2b is connected to the container body 1. At this time, make sure that the stop valve 5 is always closed.

Next, the sampling container was directly brought back to the laboratory and weighed, and the weight of the collected soil was calculated from the difference between the empty weight of the entire sampling container and the weight of 10 ml of distilled water, which had been measured in advance. Ask. Then, this sample container is subjected to ultrasonic treatment for a predetermined time as it is, and then placed in a temperature control device. In addition,
In this example, a gas chromatograph oven was used as the temperature control device.

Next, as shown in FIG. 3, the sampling container is put in the oven 16 and the outlet portion 5 of the stop valve 5 is placed.
The stainless thin tube 13 is connected to a. Further, the nitrogen gas introducing portion 3a of the nitrogen gas introducing pipe 3 is connected to the inlet 3c of the gas chromatograph by removing the blind plug. Stainless thin tube 1
3, one end is connected to the outlet portion 5a of the stop valve 5 and the other end is connected to the connecting portion 11a of the connecting pipe 11, and the dehydrating pipe 9 side is connected downward at least at a portion exiting from the oven 16. This is because the stainless thin tube 13 is at room temperature when it comes out of the oven 16, so that water does not flow back. The stainless thin tube 14 has one end connected to the connecting portion 12a of the connecting pipe 12 and the other end connected to the gas collecting Tedlar bag 15, and is connected so that the connecting portion 12a is lower than the connecting portion with the Tedlar bag 15. . Further, the dehydration pipe 9 is immersed in a cooling container 17 containing, for example, ice water in order to completely remove water. After assembling the entire apparatus as described above, the stop valve 5 is opened, nitrogen gas is caused to flow from the nitrogen gas inlet 3c, and the Tedlar bag 15 is sampled.

Next, the method for desorbing the organic chlorine solvent according to the present invention will be described. FIG. 4 shows a process diagram of the desorption method. First, distilled water is added to the collected soil and ultrasonic treatment is performed for a predetermined time. After that, heat desorption is performed and the sample is collected in a Tedlar bag. The heat desorption is performed multiple times by changing heating conditions. The nitrogen gas is passed at a rate of 30 to 50 ml / min.

Next, concrete experimental results concerning the analysis method will be shown. First, the results of studies on the soil used are shown.
As standard gas, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene each 2500 pp
m was prepared in a vacuum bottle. As the target soil, two types of soil were examined, that is, the soil of the C factory, which is heavily contaminated with tetrachlorethylene, and the soil of the D factory, which is heavily contaminated with trichlorethylene. It was found that when 5 ml of standard gas was injected into these soils, almost all of them were desorbed at room temperature without being adsorbed to the soil, so the soil was put in a sampling tube at 240 ° C for about half a day with nitrogen gas. Desorption was carried out to prepare a soil from which the contained water and target substance were completely removed. When standard gas is injected into this soil at room temperature,
Even after desorption for 20 minutes, all three substances were not detected in the Tedlar bag, and it was considered that they were completely adsorbed in the soil. Therefore, in order to make an accurate evaluation, decomposition experiments were conducted using this soil.

Next, the examination results of the decomposition experiment by heating will be shown. After injecting standard gas at a constant temperature, desorption with nitrogen gas for 20 minutes was collected in a Tedlar bag, 0.2 ml in the Tedlar bag was injected into a gas chromatograph-mass spectrometer (GC-MS), and the obtained TIC was obtained. The comparison was performed by the peak height on the chromatogram. Table 1 shows the decomposition products of the three substances and their generation ratios when the soil temperature was changed.

[0018]

[Table 1]

The measurement of 1,1,1-trichloroethane was carried out from 40 ° C to 200 ° C. At 40 ° C., a trace amount of 1,1,1-trichloroethane was confirmed, but in all other cases, only dichloroethylene was produced. In this case, in desorption at 40 ° C, 1,1,1-trichloroethane is adsorbed on the soil in a large amount, so
About 0% was collected in the Tedlar bag as dichloroethylene. In Table 1, 100% means a state in which only dichloroethylene was observed on the TIC chromatogram.

Trichloroethylene was measured from 120 ° C to 240 ° C. A slight amount of dichloroethylene was observed at 200 ° C and 5-6% at 240 ° C, but no decomposition products were observed at temperatures below that.

200 ° C. for tetrachlorethylene
6 to 8%, and at 240 ° C., 11 to 13% were decomposed into trichlorethylene. Also, the presence of a small amount of dichloroethylene was observed at this temperature. However, no decomposition products were found at other temperatures.

Next, the results of studies on the effect of water content on the decomposition of 1,1,1-trichloroethane will be shown. As described above, most of 1,1,1-trichloroethane collected through soil even at 40 ° C. was changed to dichloroethylene. Therefore, the influence of water content was investigated in order to suppress the decomposition.

For the above-mentioned dry soil, 1,1,
2500 ml of 1-trichloroethane standard gas was injected in an amount of 5 ml, and distilled water was further injected from the injection port in different amounts of 1 ml, 3 ml, 5 ml, 8 ml, and 10 ml. These hydrous soils were heated to 120 ° C., desorbed with nitrogen gas for 20 minutes, and collected in a Tedlar bag. Inject 0.2 ml of gas in Tedlar bag into GC-MS,
The peak was confirmed on the chromatogram. as a result,
The presence of a trace amount of dichloroethylene was confirmed only when 1 ml of distilled water was added, but when the amount of water was other than that, all of the injected 1,1,1-trichloroethane was collected in the Tedlar bag.

Also, 1,1,1-trichloroethane and dichloroethylene were not detected in the Tedlar bag collected at 200 ° C. after desorption of the soil at 120 ° C. for a further 60 minutes. From these results, 1,1,1-
For desorption of trichloroethane from soil, 10 ml of distilled water was added to the soil in order to obtain as much water content as possible.
It was found that the desorption at 120 ° C. together with the desorption of 1,1-trichloroethane allows desorption from the soil without decomposition.

Next, the examination results of the change in the amount of desorption due to the difference in the pretreatment method are shown. Targeting the soil of the C factory, we examined tetrachloroethylene, which is contained in a large amount in this soil and is said to be difficult to desorb. As an experimental method, 10 ml of distilled water was added to the soil and changes in the desorption amount were observed when ultrasonic waves were not applied for 5 minutes, 10 minutes, and 30 minutes. Moreover, the case where distilled water was not added was also performed.

Regarding the desorption temperature, a high condition was set in order to find the point where the desorption of tetrachloroethylene from the soil was almost completed. Heating temperature 1 for the first 20 minutes
Desorption was carried out at 20 ° C., then the temperature was raised to 240 ° C., desorption was carried out for 20 minutes each for 100 minutes and then desorption was carried out at 270 ° C. for 20 minutes. However, even if the heating temperature is 240 ° C, it is considered that the temperature of the soil is kept at about 100 ° C for about 60 minutes until the water content in the stainless steel tube disappears. The obtained results are shown in FIG.

The amount of tetrachloroethylene desorbed was the lowest when distilled water was not added. Further, when distilled water was added, the value was slightly lower when ultrasonic waves were not applied, but when ultrasonic waves were applied, the values were almost the same. However, when the ultrasonic wave is applied for a long time, the inside of the sampling tube is warmed, and loss may occur especially in the case of a low boiling point substance, so the ultrasonic treatment time was set to 10 minutes. In addition, in the present experimental method, the amount of desorbed tetrachlorethylene did not increase even when the temperature was raised from 240 ° C to 270 ° C, and it was considered that desorption from soil was almost completed at a temperature lower than 240 ° C.

Finally, experimental results on changes in the amount of desorption due to differences in desorption time and desorption temperature are shown. As the soil, the soils of plants D and C were targeted. The soil of Factory D has a very high content of trichlorethylene and a low content of tetrachlorethylene. Therefore, as mentioned above, the generation of trichlorethylene due to the thermal decomposition of tetrachlorethylene when the desorption temperature was raised was almost negligible, and the end point of the soil content of trichlorethylene was almost understood.

Regarding the soil of the C factory, since the content of tetrachloroethylene was very high and the generation of trichlorethylene by the thermal decomposition of tetrachloroethylene when the desorption temperature was raised cannot be ignored, the 1,1,1-trichloroethane content Since its content is small, it was examined only with tetrachloroethylene. 10 g of the soil was taken in a sampling tube, and 10 ml of distilled water was added thereto, followed by ultrasonic treatment for 10 minutes. Collection was performed at 120 ° C for 20 minutes each for 80 minutes, and then the temperature was raised to 200 ° C.
Collection was carried out for 0 minutes each for 60 minutes, then heated to 240 ° C., 20 minutes for 40 minutes, and finally 270 ° C. for 20 minutes. The obtained results are shown in FIGS.

From FIG. 6, it can be seen that almost all 1,1,1-trichloroethane could be desorbed from the soil at 120 ° C. in the presence of water. Further, it can be seen from FIG. 7 that 88 to 90% of the soil content was collected by desorbing trichlorethylene at 120 ° C. for 80 minutes. At this temperature, since there is no effect from the thermal decomposition of tetrachlorethylene as described above, the collection of trichlorethylene is 1
It was decided to carry out at 20 ° C. for 80 minutes. Further, when the temperature of the sampling tube was increased from 120 ° C to 200 ° C, the desorption amount of trichlorethylene slightly increased, but the desorption amount did not increase at 240 ° C, and the desorption amount was hardly present at 270 ° C. Therefore, it was considered that almost all trichlorethylene in the soil was desorbed at this stage.

As can be seen from FIGS. 8 and 9, the desorption of tetrachloroethylene at 120 ° C. for 80 minutes was 76 to 77% in the soil of the D factory and 65 to 66% in the soil of the C factory. I couldn't. Therefore, at 200 ℃ 6
When the desorption for 0 minutes was performed, 93% of the soil in the factory D, C
90% or more of the soil of the factory was collected even when the loss due to decomposition after the desorption temperature was set to 200 ° C was taken into consideration. Therefore,
For tetrachloroethylene, it was decided to obtain the sum of the amount desorbed at 120 ° C. for 80 minutes and the amount desorbed at 200 ° C. for 60 minutes. Further, even if the temperature of the sampling tube was raised from 200 ° C. to 240 ° C., the amount of desorbed tetrachloroethylene did not increase, and the desorbed amount significantly decreased at a temperature increase up to 270 ° C. Therefore, it was considered that almost all tetrachloroethylene in the soil was completely desorbed at this stage.

[0032]

As is apparent from the above description, according to the method for desorbing an organic chlorine-based solvent of the present invention, the target substance is dispersed in the atmosphere by adding distilled water after the soil is collected and the conventional method by heating. It is possible to prevent decomposition of the decomposed target substance. Further, if ultrasonic treatment is performed before heating, the recovery rate of the target substance from the soil can be further increased. Furthermore, by desorbing under a plurality of heating conditions, the recovery rate can be further increased while preventing the decomposition of the target substance. Further, the sampling container of the present invention does not scatter the target substance into the atmosphere, and is suitable for use in the desorption method.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a sampling container of a desorption device used in the present invention.

FIG. 2 is an exploded perspective view showing a dehydration pipe section of the apparatus.

FIG. 3 is an overall configuration diagram of the device.

FIG. 4 is a process diagram of a desorption method according to the present invention.

FIG. 5 is a characteristic diagram showing changes in the amount of tetrachlorethylene desorbed depending on the pretreatment conditions.

FIG. 6 is a characteristic diagram showing changes in the desorption amount of 1,1,1-trichloroethane in the soil at the D factory site.

[Fig. 7] Characteristic diagram showing changes in the desorption amount of trichlorethylene in the soil on the premises of Factory D

FIG. 8 is a characteristic diagram showing changes in the amount of tetrachlorethylene desorbed in the soil on the premises of Factory D.

[Fig. 9] Characteristic diagram showing changes in the amount of tetrachlorethylene desorbed in the soil at the C factory site

[Explanation of symbols]

 1 Container Main Body 3 Nitrogen Gas Introducing Pipe 3a Nitrogen Gas Introducing Section 5 Stop Valve 9 Dehydrating Pipe 15 Tedlar Bag 16 Oven 17 Cooling Container

Claims (5)

[Claims] 1. A method of desorbing an organic chlorine solvent by heating the soil and passing nitrogen gas through the soil to desorb the organic chlorine solvent, wherein distilled water is added to the sampled soil,
A method for desorbing an organic chlorine-based solvent, which comprises heating the soil as it is. 2. The method for desorbing an organic chlorine solvent according to claim 1, wherein the soil to which the distilled water has been added is subjected to ultrasonic treatment before heating. 3. The method according to claim 1, wherein heating conditions are selected in accordance with the decomposability of the target component in soil by heating, and heating is performed under different heating conditions in a plurality of times for desorption. The method for desorbing an organic chlorine-based solvent as described in 1. 4. A target component in soil is 1,1,1-trichloroethane, trichlorethylene, and tetrachloroethylene, which are heated at 120 ° C. for 80 minutes to give 1,
1,1-trichloroethane and trichlorethylene,
With the elimination of tetrachloroethylene, a further 200
The method for desorbing an organic chlorine-based solvent according to claim 1, wherein tetrachloroethylene is desorbed under heating conditions of 60 ° C. for 60 minutes. 5. A sampling container for an organic chlorine-based solvent, comprising an openable and closable nitrogen gas inlet at one end of a container body and a stop valve at the other end.