JP2022089102A - Method for visualizing cavity of sample - Google Patents

Abstract

To provide a method for visualizing cavities, which can distinguish between water and an organic matter, which have low X-ray absorption rates.SOLUTION: A method for visualizing cavities of a sample using X-ray CT, comprises preparing a target obtained by filling the cavities of the sample with ionic liquid containing a highly X-ray absorptive component, irradiating the prepared target with X-rays, detecting X-rays that have passed through the target, and obtaining an image of the target with emphasized contrast between the cavities area and other areas.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method of visualizing a void in a sample, a method of treating the sample for that purpose, and a composition used for that purpose. The present invention is useful in various fields including microstructure analysis of samples such as strata.

It is important to observe in detail the geological environment in which minerals and organic matter are intricately woven. Therefore, a method for obtaining information on the fine structure of a stratum sample is being studied. For example, Patent Document 1 describes a porosity measuring device and a measuring method using radon as a means for accurately grasping the internal structure of rock in three dimensions. This porosity measuring device changes the concentration of radon gas by filling the voids of the medium with radon gas, and measures the porosity of the medium based on such a change.

In addition, the resin embedding method commonly used in the field of microscopic observation of biological samples is applied to the treatment of soft and water-rich geological samples, and the resin-embedded geological samples are smoothly cut with a microtome and scanned electron microscopes. A method of observing with (SEM) or obtaining a cross-sectional image from a resin-encapsulated sample by microfocus X-ray CT has been carried out (Non-Patent Document 1).

On the other hand, ionic liquids are also called third liquids, and because of their unique properties, they are applied to separation / purification processes, synthesis / catalytic reactions, polymer polymerization / depolymerization, and new electrolytic solutions using ionic liquids as solvents. It is also applied to electrochemical devices such as lithium-based secondary batteries and non-humidified fuel cells. Further, since the ionic liquid has an extremely low vapor pressure, it is applied to electron microscope observation as a solvent that can be handled in a vacuum (Patent Document 2 and Non-Patent Document 2).

There is a report that the ionic liquid was used to investigate the structure inside the seeds that had absorbed water by X-ray micro CT. Here, by treating with a high-concentration ionic liquid after immobilization with osminium tetraoxide, deterioration of image quality due to the presence of water was prevented, and shrinkage of seeds due to drying during imaging was suppressed, and good observation was possible. It has been reported (Non-Patent Document 3).

Japanese Unexamined Patent Publication No. 2015-52580 International Publication WO2007 / 083756 (Patent No. 4581100)

Goichiro Uramoto et al .: Observation of microstructure of seafloor sediments and microbial cells, microscope, vol. 51, No. 2: 108-113 (2016) Susumu Kuwahara: Application of ionic liquids as liquid conductivity-imparting agents to electron microscope observation, Microscope, vol. 48, No. 2: 100-106 (2013) Yamauchi D, et. Al. Use of ionic liquid for X-ray micro-CT specimen preparation of imbibed seeds. Microscopy, Vol. 68, No. 1: 92-97 (2019)

In three-dimensional structural analysis by microfocus X-ray CT, voids and material portions can be distinguished by the difference in the X-ray absorption coefficient of the material constituting the sample. Specifically, in the three-dimensional structure of the sample visualized by the difference in the X-ray absorption coefficient, the portion displayed dark due to the low X-ray absorption coefficient is recognized as a void. However, in the case of a geological sample containing minerals with a low X-ray absorption coefficient, organic matter consisting of carbon, nitrogen, oxygen, hydrogen, etc. has a low X-ray absorption rate like water existing in voids, so X-rays are emitted. In the case of a geological sample containing minerals with a high absorption rate, it cannot be expected that a contrast can be obtained so that the voids and organic substances can be distinguished, and it can be said that there is no method for visualizing the true voids. Both water and organic substances with low X-ray absorption rate can be distinguished, and a method for visualizing voids is desired.

The present inventors have been diligently studying the development and improvement of sample processing techniques related to microstructure analysis of geological samples and the like. Then, he devised to visualize the voids of the stratum sample by infiltrating the ionic liquid containing iodine into the stratum sample and observing it by X-ray CT, and completed the present invention. The present invention provides:

[1] A method of visualizing the voids of a sample using X-ray CT.
A sample was prepared by filling the voids of the sample with an ionic liquid containing a highly X-ray absorptive component.
A method comprising a step of irradiating a prepared target with X-rays, detecting the X-rays transmitted through the target, and obtaining an image of the target in which the contrast between the void portion and the other portion is emphasized.
[2] The method according to 1, wherein the high X-ray absorptive component is a component containing iodine.
[3] The method according to 1 or 2, wherein the X-ray CT is a microfocus X-ray CT or a synchrotron light source X-ray micro CT.
[4] The item according to any one of 1 to 3, wherein the step of producing a sample in which the voids of the sample are filled with an ionic liquid containing a high X-ray absorptive component is carried out by a process including the following steps. the method of:
Embed the sample in an aqueous gel, fill the voids in the sample with an aqueous gel,
A step of immersing a sample embedded in an aqueous gel in an ionic liquid and replacing the water with the ionic liquid to fill the voids of the sample with the ionic liquid.
[5] A method for producing a standard for X-ray CT.
The sample with voids is embedded with an aqueous gel, and the voids of the sample are filled with the aqueous gel.
A production method comprising a step of immersing a sample embedded in an aqueous gel in an ionic liquid and filling the voids of the sample with the ionic liquid by substituting the water with the ionic liquid.
[6] A method of visualizing the voids of a sample using X-ray CT.
The sample with voids is embedded with an aqueous gel, and the voids of the sample are filled with the aqueous gel.
A sample embedded in an aqueous gel is immersed in an ionic liquid, and the voids of the sample are filled with the ionic liquid by substituting the water with the ionic liquid to prepare a standard.
A method comprising a step of irradiating a prepared target with X-rays, detecting the X-rays transmitted through the target, and obtaining an image of the target in which the contrast between the void portion and the other portion is emphasized.
[7] A composition comprising the following for preparing a standard for X-ray CT:
A. Ionic liquids containing iodine, and B. An ionic liquid that can be mixed with A and has lower X-ray absorption than A.
[8] The composition according to 7, wherein the content mass ratio (A / (A + B)) of A is 20 to 40%.

By the method of the present invention using an ionic liquid containing a highly X-ray absorptive component, voids in a sample can be displayed brightly in a CT image. (Contrast is enhanced.)

By using an ionic liquid for dilution that does not contain a high X-ray absorbing component together with an ionic liquid containing a high X-ray absorbing component, the X-ray absorption efficiency of the voids of the sample can be controlled.

Further, in a geological sample in which water is present in the voids, the method of the present invention replaces the water with an ionic liquid, so that it is possible to prevent the vaporization of water by the energy of X-rays and the deformation of the sample due to it. X-ray micro CT scan using a synchrotron light source such as SPring-8 is also possible, and it is possible to analyze the structure of a sample on a multi-scale basis. In addition, in the measurement of the synchrotron light source, iodine-specific contrast enhancement is achieved by taking the difference between the tomography images scanned before and after the K absorption edge energy (33.169 kiloelectronvolts) of iodine whose X-ray absorption coefficient changes sharply. It is possible to visualize voids with higher selectivity.

Micro focus X-ray CT image of a geological sample. (A) When the stratum sample is photographed as it is. (B) When an ionic liquid containing iodine is infiltrated and photographed. In (A), the dark gray portion is a void. When the ionic liquid is not used, X-rays are hardly absorbed in the void portion, so that the CT image becomes dark. In (B), the ionic liquid permeates the voids, so that the X-ray absorption of the voids becomes large, and the voids are displayed brightly (contrast is enhanced) in the CT image. Micro focus X-ray CT image of a simulated stratum sample. When shooting without using ionic liquid. Micro focus X-ray CT image of a simulated stratum sample. When shooting with an ionic liquid that does not contain iodine. Micro focus X-ray CT image of a simulated stratum sample. When an ionic liquid containing iodine is infiltrated and photographed.

The present invention relates to a method of visualizing a sample void using X-ray CT.

[Ionic liquid]
The present invention uses an ionic liquid for processing a sample observed by X-ray CT. An ionic liquid is a salt having a melting point near room temperature, and is a liquid consisting only of ions. The ionic liquid is composed of organic ions in which one or both of the cation and the anion have various structural changes, and the type of the ionic liquid is enormous because the type of the cation × the type of the anion.

It is important that the ionic liquid used in the present invention is a liquid under the conditions for processing the sample. As long as it is a liquid when processing the sample and can fill the voids of the sample, there is no problem even if it is a solid when scanning by X-ray CT. In the present invention, a plurality of ionic liquids can be mixed and used.

<Ionic liquid containing highly X-ray absorptive components>
Further, the ionic liquid used in the present invention can contain at least one kind of highly X-ray absorbing component (anionic component or cationic component). Regarding the present invention, when the ionic liquid or a component thereof is referred to as having high X-ray absorption, it has at least higher X-ray absorption than water, and is preferably contained in a relatively large amount in the target sample, unless otherwise specified. It has higher X-ray absorption than the components, and therefore, when it is filled in the voids of the sample and X-ray CT scan is performed, the voids can be displayed brightly in the image so as to be distinguishable from other parts. ..

An example of a component that is highly X-ray absorptive is a component that contains any of the group consisting of iodine, bromine, and chlorine. Iodine is preferred. Iodine has a large atomic number and a high X-ray absorption rate. Reagents containing iodine are used as contrast media in general-purpose CT imaging, and by infiltrating the sample, the contrast between the iodine infiltrated site and other images can be enhanced. The term "containing" includes the case where the component is contained as an ion or an atom.

An example of an ionic liquid containing a highly X-ray absorbing component used in the present invention is an iodine-based ionic liquid. In this specification, the case where the ionic liquid containing a highly X-ray absorbing component is an iodine-based ionic liquid may be described as an example, but the description thereof includes the case where the ionic liquid containing a high X-ray absorbing component is included. This also applies when using ionic liquids from.

The cationic component of the iodine-based ionic liquid used in the present invention is not particularly limited. Examples of the cation component include ammonium-based, imidazolium-based, phosphonium-based, pyridinium-based, pyridinium-based, pyroridinium-based, and the like.

More specifically, as examples of ammonium-based cations, tributylmethylammonium, ethyldimethylpropylammonium, 2-hydroxyethyl-trimethylammonium, methyltrioctylammonium, tributylammonium, tetraethylammonium, tetraheptylammonium, triethylmethylammonium, Tris (2-hydroxyethyl) methylammonium can be mentioned.
Examples of imidazolium-based cations are 1-methyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-ethyl-3-propylimidazolium, 1-propyl-3-methylimidazolium, 1- Butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-octyl-3-methylimidazolium, 1-methyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium Examples thereof include lium, 1-hexyl-2,3-dimethylimidazolium, and 1-octyl-2,3-dimethylimidazolium.
Examples of phosphonium-based cations are tributylmethylphosphonium, ethyldimethylpropylphosphonium, 2-hydroxyethyl-trimethylphosphonium, methyltrioctylphosphonium, tributylphosphonium, tetraethylphosphonium, tetraheptylphosphonium, triethylmethylphosphonium, tris (2-hydroxyethyl). ) Methylphosphonium can be mentioned.
Examples of pyridinium-based cations include 1-butyl-3-methylpyridinium, 1-butyl-4-methylpyridinium, 1-ethyl-1-methylpyridinium, 1-octyl-4-methylpyridinium, 1-methylpyridinium, Examples thereof include 1-butylpyridinium and 1-hexylpyridinium.
Examples of the pyrrolidinium-based cation include 1-butyl-1-methylpyrrolidinium, 1-butyl-1-methylpyrrolidinium, and 1-ethyl-1-methylpyrrolidinium.
Examples of other cations include 1-butyl-1-methylpiperidinium, choline and triethylsulfonium.

Particularly preferred examples of the ionic liquid containing a highly X-ray absorbing component used in the present invention are ammonium salts such as tetraethylammonium iodide, tetrapropylammonium iodide and tetrabutylammonium iodide, and dimethylpropylimidazolium iodide. , 1-Methyl-3-propylimidazolium iodide, 1-ethyl-3-butylimidazolium iodide and other imidazolium salts, methyltriphenylphosphonium iodide, and isopropyltriphenylphosphonium iodide are ionic liquids. Some of these substances containing iodine are solid at room temperature, but as long as they can be in a liquid state when the sample is processed by mixing with other ionic liquids, they can be used as components of ionic liquids. It can be used in the present invention.

<Other ionic liquids>
Examples of anion components other than iodine contained in other ionic liquids used in the present invention include bisfluorosulfonylimide-based anions, fluorinated sulfonic acid-based anions, fluorinated carboxylic acid-based anions, thiocyanate-based anions, and dicyanamide-based anions. Examples thereof include anions and tetracyanoborate anions.

More specifically, examples of bisfluorosulfonylimide-based anions include bisfluorosulfonylimide, bistrifluoromethylsulfonylimide, and bistrifluorobutanesulfonylimide.
Examples of fluorinated sulfonic acid-based anions include tetrafluoroborate, hexafluoroborate, and trifluoromethylsulfonate.
Examples of fluorinated carboxylic acid-based anions include trifluoroacetic acid. The cationic component of the ionic liquid having such an anionic component used in the present invention is not particularly limited, and may be any of the anionic components listed for iodine-based ionic liquids.

In a preferred embodiment of the present invention, an ionic liquid having high X-ray absorption such as an iodine-based ionic liquid and another ionic liquid are mixed and used. According to the study of the present inventor, when the sample is treated using only iodine-based ionic liquids and X-ray CT is performed, the X-ray absorption in the voids increases too much and the X-ray transmittance of the entire sample decreases remarkably. It may happen. Therefore, by using an ionic liquid having low X-ray absorption as an ionic liquid for dilution, it is possible to control the X-ray absorption in the voids.

From this point of view, in a preferred embodiment of the present invention, examples of the ionic liquid used together with the ionic liquid having high X-ray absorption include alkyl-, hydroxyalkyl-and / or aryl-substituted imidazolium cations and tetrafluoro. Examples thereof include salts with borate anions, specifically 1,3-dimethylimidazolium tetrafluoroborate, 1-benzyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate. , 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-methyl-3-propylimidazolium tetrafluoroborate, 1-methyl-3-octylimidazolium tetra Fluorobolate, 1-Methyl-3-tetradecylimidazolium tetrafluoroborate, 1-methyl-3-phenylimidazolium tetrafluoroborate, 1,2,3-trimethylimidazolium tetrafluoroborate, 1,2-methyl-3 -Octyl imidazolium tetrafluoroborate, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate, 1-hexyl-2,3-methylimidazolium tetrafluoroborate, and 1- (2-hydroxyethyl) -2, Examples thereof include 3-dimethylimidazolium tetrafluoroborate.

Examples of ionic liquids in other preferred embodiments include salts of alkyl-, hydroxyalkyl- and / or aryl-substituted imidazolium cations and bis (trifluoromethylsulfonyl) imide anions, specifically 1, 3-Dimethylimidazolium bis (trifluoromethylsulfonyl) imide, 1-benzyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-Ethyl-3-methylimidazoliumbis (trifluoromethylsulfonyl) imide, 1-ethyl-3-propylimidazoliumbis (trifluoromethylsulfonyl) imide, 1-hexyl-3-methylimidazoliumbis (trifluoromethyl) Sulfonyl) imide, 1-methyl-3-propylimidazolium bis (trifluoromethylsulfonyl) imide, 1-methyl-3-octylimidazoliumbis (trifluoromethylsulfonyl) imide, 1-methyl-3-tetradecylimidazolium Bis (trifluoromethylsulfonyl) imide, 1-methyl-3-phenylimidazolium bis (trifluoromethylsulfonyl) imide, 1,2,3-trimethylimidazolium bis (trifluoromethylsulfonyl) imide, 1,2-methyl -3-octylimidazolium bis (trifluoromethylsulfonyl) imide, 1-butyl-2,3-dimethylimidazoliumbis (trifluoromethylsulfonyl) imide, 1-hexyl-2,3-methylimidazoliumbis (trifluoro) Methylsulfonyl) imide and 1- (2-hydroxyethyl) -2,3-dimethylimidazolium bis (trifluoromethylsulfonyl) imide can be mentioned.

Examples of ionic liquids in other preferred embodiments include salts of alkyl-, hydroxyalkyl- and / or aryl-substituted imidazolium cations and cyanate anions, specifically 1,3-dimethylimidazolium dicyanate. , 1-benzyl-3-methylimidazolium thiocyanate, 1-butyl-3-methylimidazolium tricyanomethane, 1-ethyl-3-methylimidazolium dicyanate, 1-hexyl-3-methylimidazolium thiocyanate, 1- Methyl-3-propylimidazolium tricyanomethane, 1-methyl-3-octylimidazolium dicyanate, 1-methyl-3-tetradecylimidazolium thiocyanate, 1-methyl-3-phenylimidazolium dicyanate, 1, 2 , 3-trimethylimidazolium thiocyanate, 1,2-methyl-3-octylimidazolium tricyanomethane, 1-butyl-2,3-dimethylimidazolium dicyanate, 1-hexyl-2,3-methylimidazolium thiocyanate, And 1- (2-hydroxyethyl) -2,3-dimethylimidazolium tricyanomethane.

Examples of ionic liquids in other preferred embodiments include salts of alkyl-, hydroxyalkyl- and / or aryl-substituted imidazolium cations and tetracyanoborate anions, specifically 1,3-dimethylimidazolium. Tetracyanobolate, 1,3-dimethylimidazolium tetracyanoborate, 1-benzyl-3-methylimidazolium tetracyanoborate, 1-butyl-3-methylimidazolium tetracyanoborate, 1-ethyl-3-methylimidazolium Tetracyanoborate, 1-hexyl-3-methylimidazolium tetracyanoborate, 1-methyl-3-propylimidazolium tetracyanoborate, 1-methyl-3-octylimidazolium tetracyanoborate, 1-methyl-3-tetra Decyl imidazolium tetracyanoborate, 1-methyl-3-phenylimidazolium tetracyanoborate, 1,2,3-trimethyl imidazolium tetracyanoborate, 1,2-methyl-3-octyl imidazolium tetracyanoborate, 1- Butyl-2,3-dimethylimidazolium tetracyanoborate, 1-hexyl-2,3-methylimidazolium tetracyanoborate, and 1- (2-hydroxyethyl) -2,3-dimethylimidazolium tetracyanoborate can be mentioned. Be done.

Examples of ionic liquids in other preferred embodiments are alkyl-, hydroxyalkyl- and / or aryl-substituted imidazolium cations and tetrakis- (p- (dimethyl (1H, 1H, 2H, 2H-perfluorooctyl) silyl) phenyl). ) Salt with borate anion, specifically 1,3-dimethylimidazolium tetrakis- (p- (dimethyl (1H, 1H, 2H, 2H-perfluorooctyl) silyl) phenyl) borate, 1- Benzyl-3-methylimidazolium tetrakis- (p- (dimethyl (1H, 1H, 2H, 2H-perfluorooctyl) silyl) phenyl) borate, 1-butyl-3-methylimidazolium tetrakis- (p- (dimethyl (dimethyl) 1H, 1H, 2H, 2H-Perfluorooctyl) Cyril) Phenyl) Borate, 1-ethyl-3-methylimidazolium tetrakis- (p- (dimethyl (1H, 1H, 2H, 2H-perfluorooctyl) silyl) phenyl) ) Borate, 1-hexyl-3-methylimidazolium tetrakis- (p- (dimethyl (1H, 1H, 2H, 2H-perfluorooctyl) silyl) phenyl) borate, 1-methyl-3-propylimidazolium tetrakis- ( p- (dimethyl (1H, 1H, 2H, 2H-perfluorooctyl) silyl) phenyl) borate, 1-methyl-3-octylimidazolium tetrakis- (p- (dimethyl (1H, 1H, 2H, 2H-perfluoro)) Octyl) Cyril) Phenyl) Borate, 1-Methyl-3-tetradecylimidazolium tetrakis- (p- (dimethyl (1H, 1H, 2H, 2H-perfluorooctyl) Cyril) Phenyl) Bolate, 1-Methyl-3- Phenylimidazolium tetrakis- (p- (dimethyl (1H, 1H, 2H, 2H-perfluorooctyl) silyl) phenyl) borate, 1,2,3-trimethylimidazolium tetrakis- (p- (dimethyl (1H, 1H,)) 2H, 2H-perfluorooctyl) silyl) phenyl) borate, 1,2-methyl-3-octylimidazolium tetrakis- (p- (dimethyl (1H, 1H, 2H, 2H-perfluorooctyl) silyl) phenyl) borate , 1-butyl-2,3-dimethylimidazolium tetrakis- (p- (dimethyl (1H, 1H, 2H, 2H-perfluorooctyl) silyl) phenyl) borate, 1-hexyl-2,3-methylimi Dazolium tetrakis- (p- (dimethyl (1H, 1H, 2H, 2H-perfluorooctyl) silyl) phenyl) borate, and 1- (2-hydroxyethyl) -2,3-dimethylimidazolium tetrakis- (p-) (Dimethyl (1H, 1H, 2H, 2H-perfluorooctyl) silyl) phenyl) borate can be mentioned.

Examples of ionic liquids in other preferred embodiments include salts of alkyl-, hydroxyalkyl- and / or aryl-substituted imidazolium cations and hexafluorophosphate anions, specifically 1,3-dimethylimidazolium. Hexafluorophosphate, 1-benzyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methyl Imidazolium hexafluorophosphate, 1-methyl-3-propyl imidazolium hexafluorophosphate, 1-methyl-3-octyl imidazolium hexafluorophosphate, 1-methyl-3-tetradecyl imidazolium hexafluorophosphate, 1-methyl- 3-Phenylimidazolium hexafluorophosphate, 1,2,3-trimethylimidazolium hexafluorophosphate, 1,2-methyl-3-octylimidazolium hexafluorophosphate, 1-butyl-2,3-dimethylimidazolium hexafluorophosphate Phosphates, 1-hexyl-2,3-methylimidazolium hexafluorophosphate, and 1- (2-hydroxyethyl) -2,3-dimethylimidazolium hexafluorophosphate can be mentioned.

Examples of ionic liquids in other preferred embodiments are 1-ethyl-3-methylimidazolium tetrachloroaluminate, 1-butyl-3-methylimidazolium tetrachloroaluminate, 1-ethyl-3-methylimidazolium acetate, 1-Butyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium ethylsulfate, 1-butyl-3-methylimidazolium methylsulfate, 1-ethyl-3-methylimidazolium thiocyanate, 1- Butyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-ethyl-3-methylimidazolium tetracyanoborate, 1-butyl-1-methyl-pyrrolidi Examples thereof include niumdisyanamide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium trifluoroacetate, and 1-ethyl-3-methylimidazolium bis (fluoromethylsulfonyl) imide.

<Composition for producing a standard for X-ray CT>
In one of the preferred embodiments of the present invention, an ionic liquid having high X-ray absorption such as an iodine-based ionic liquid and another ionic liquid are mixed and used. This makes it possible to control the X-ray absorption efficiency of the voids of the sample. That is, the present invention also provides a composition for processing a sample to be scanned by X-ray CT, including:
A. Highly X-ray absorptive ionic liquids such as iodine-based ionic liquids, and B. An ionic liquid that can be mixed with A and has lower X-ray absorption than A.

The mixing ratio of the ionic liquid having high X-ray absorption and other ionic liquids can be appropriately set depending on the sample. For example, when an iodine-based ionic liquid (A) and another low X-ray-absorbing ionic liquid (B) are mixed, the mass ratio of A (A / (A + B)) is set to 1 to 90%. It may be 5 to 80%, 10 to 60%, or 20 to 40%. When measuring with a general-purpose microfocus X-ray CT scanner, it is preferable to use an ionic liquid having high X-ray absorption at a high concentration from the viewpoint of making the ionic liquid portion have as high contrast as possible compared to the sample composition. .. On the other hand, when measuring with the energy before and after the iodine K absorption edge when measuring with micro CT using synchrotron radiated X-rays, the contrast is lower than that of the sample composition before the K absorption edge, and the sample composition is after the K absorption edge. It is better to mix the ionic liquid so that it has a higher ton last. From this point of view, the content mass ratio (A / (A + B)) is recommended to be 20 to 40%.

When measuring a sample such as a stratum containing water, it is preferable that the iodine-based ionic liquid (A) and the other low X-ray absorbing ionic liquid (B) can be mixed with water.

[Sample processing, preparation of specimen]
In the present invention, a standard is prepared in which the voids of the sample are filled with an ionic liquid having a large X-ray absorption coefficient. The production can be paraphrased as manufacturing or production (Patent Law Article 2, Paragraph 3, Item 3).

The preparation of the sample in the present invention can be carried out by various means so that the voids of the sample are filled with the ionic liquid and the water contained in the sample is replaced with the ionic liquid, but the sample is preferably made of an aqueous gel. After embedding and filling the voids of the sample with an aqueous gel, the sample embedded with the aqueous gel is immersed in an ionic liquid. Immersion in the ionic liquid replaces the water contained in the sample with the ionic liquid, and the voids of the sample are filled with the ionic liquid.

Preferred examples of the aqueous gel used in the present invention are polysaccharide gels or protein gels. This is because these have low X-ray absorption and have little influence on the observation of the sample. Examples of the materials constituting the polysaccharide gel include agar (agarose), carrageenan, pectin, gellan gum, alginic acid or a salt thereof. Examples of the materials constituting the protein gel include gelatin, collagen, elastin, fibronectin, laminin, entactin, heparin or a salt thereof.

In a preferred embodiment, agar, more preferably agar having a lower melting point, is used as the aqueous gel material. Since it is a liquid with low viscosity above a certain temperature, it is easy to fill the fine voids of the sample, and it easily gels and becomes solid by lowering the temperature, and it has relatively high mechanical strength, so it is cut. This is because it is easy to process it with tools and shape it. Regarding the melting point of agar, low means that the melting point of general agar is 85 to 93 ° C, lower than that, specifically 80 ° C or lower, preferably 75 ° C or lower. It means that there is, more preferably 70 ° C. or lower. In the following, the process of processing a sample and preparing a sample may be described by taking as an example the case where an agar gel is used as an aqueous gel, but the description may be given even when another aqueous gel is used. apply.

When a low melting point agar gel is used, the concentration of agar can be appropriately adjusted depending on the sample to be embedded. For example, when embedding a stratum sample, the concentration of low melting point agar can be 0.5 to 3%, preferably 1 to 2%.

The specimen, which is embedded in an aqueous gel and the water is replaced by an ionic liquid, is molded as necessary before scanning by X-ray CT. The molding is performed in consideration of the pixel size of the CT reconstructed image obtained by setting and measuring the device to be used. The CT reconstructed image obtained by many general-purpose microfocus X-ray CT scanners and radiated X-ray micro CT has 1024 pixels in the vertical and horizontal directions. Therefore, for example, when the pixel size is 5 microns, the vertical and horizontal size of the sample is 10 mm or less, preferably 7.5 mm or less, for example, 5 mm or less, and when the pixel size is 1 micron, 5 mm or less, preferably 2 mm or less, for example. When it is 1 mm or less, it is possible to measure the sample within the image.

[Scan by X-ray CT]
The specimen can be mounted on the sample table and X-ray CT scan can be performed. The X-ray CT apparatus used in the present invention is not particularly limited in terms of the X-ray source, scanning method, etc., and various X-ray CT devices can be used. For example, a micro focus X-ray CT device or a synchrotron light source X-ray micro CT device can be used.

In the standard treated and produced according to the present invention, the void portion is filled with an ionic liquid containing a component having high X-ray absorption. In the target body configured in this way, the void portion is brightly displayed and visualized when observed by X-ray.

In the present invention, even in a sample containing water, water is replaced with a non-volatile ionic liquid in the prepared sample. Therefore, deformation due to vaporization during observation can be prevented, and voids close to the natural state can be observed.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to perform an X-ray micro CT scan of a geological sample using a synchrotron light source such as SPring-8, and it is possible to analyze the structure of the sample on a multi-scale basis. In addition, in the measurement of the synchrotron light source, iodine-specific contrast enhancement is achieved by taking the difference between the tomography images scanned before and after the K absorption edge energy (33.169 kiloelectronvolts) of iodine whose X-ray absorption coefficient changes sharply. It is possible to visualize voids with higher selectivity.

〔sample〕
According to the present invention, the voids of various samples can be visualized. As long as the voids are connected to the outside and can introduce ionic liquids, various voids can be clearly observed. Samples with such voids include geological formations, rocks, shells, sediments, coagulum, foams, dried products, pathological tissues, bones, plant tissues, microbial flora, fermented products, foods, molded products, castings, etc. Examples include solidified materials, various materials / materials, and appliances.

Examples of the present invention are shown below. The present invention is not limited to the following examples.

[Ionic liquid impregnation treatment protocol]
[Used equipment]
・ Electronic balance ・ Incubator (constant temperature bath)
・ Rotator / hot stirrer

[Used equipment]
・ Spatula ・ Straw or syringe with cut tip ・ Pipette ・ Plastic rod ・ Plastic tube ・ Beaker ・ Female

[Reagents used]
・ Pure water ・ Low melting point agarose ・ Ionic liquid containing iodine ・ Ionic liquid for dilution (ionic liquid not containing iodine)

[measuring device]
・ Micro focus X-ray CT
・ Synchrotron light source X-ray micro CT

[Processing procedure]
Prior to sampling, an aqueous solution of 1 to 2% by weight of agarose in pure water is prepared and dispensed into a plastic tube. The tube is placed in a constant temperature bath (incubator) whose temperature is set above the gelling temperature of agarose.

Then, a straw or a syringe with a cut tip is pierced into the core sample for subsampling.

Next, make space at both ends of the subsampled straw or syringe cylinder. The space inside the straw is made with a plastic rod with a thickness that matches the inner diameter of the straw, and the space inside the syringe is made by adjusting with a plunger (see the figure below).

Agarose is dropped on one side of the created space and solidified.

Then place the straw or syringe in a plastic tube containing the melted agarose and leave it for at least half a day. For syringes, pull out the plunger when placing the sample in the tube. During this time, the tube may be shaken in the incubator to promote the penetration of the agarose solution. After more than half a day, lower the temperature of the tube to solidify the agarose.

Meanwhile, prepare a plastic tube into which the ionic liquid has been dispensed. Once the agarose has solidified, remove the straw or syringe from the tube. Then, the sample is extruded into a tube into which the ionic liquid is dispensed, and the sample is immersed in the ionic liquid. When extruding, use a straw or a plastic rod with a thickness that matches the inner diameter of the syringe, or use a plunger for the syringe. Place the tube in which the sample is immersed in a shaker (rotator) and leave it for at least half a day.

The sample infiltrated with the ionic liquid is molded and then scanned by X-ray CT. The sample molding is carried out in consideration of the pixel size of the CT reconstructed image obtained by setting and measuring the device. The CT reconstructed image obtained by many general-purpose microfocus X-ray CT scanners and radiated X-ray micro CT has 1024 pixels in the vertical and horizontal directions. Therefore, for example, if the vertical and horizontal size of the sample is about 5 mm or less when the pixel size is 5 microns, and about 1 mm or less when the pixel size is 1 micron, it is possible to measure the sample within the image. The molded sample is mounted on a sample table and a CT scan is performed.

[Experimental example 1: Preparation and visualization of a target from a stratum sample]
According to the above procedure, a standard with a sample diameter of 5 mm was prepared for a stratum sample (quartz sand, Fuji Film Wako Pure Chemical Industries, Ltd.), and observation was performed by microfocus X-ray CT with a pixel size of 5 um / pixel.

[Materials, equipment, etc.]
・ Low melting point agarose: Sea Plaque GTG Agarose (Lonza Japan Co., Ltd.), melting point is 1.5%, about 65 ℃
・ Ionic liquid: 1-propyl-3-methylimidazolium iodide (Kanto Chemical Co., Inc.)
-Device: Xradia Versa 410 Micro Focus X-ray CT Scanner (Carl Zeiss X-ray Microscopy)

FIG. 1 shows a microfocus X-ray CT image of the obtained stratum sample. (A) When the stratum sample is photographed as it is. (B) When an iodine-containing ionic liquid is infiltrated and photographed. In (A), the dark gray portion is a void. When the ionic liquid is not used, X-rays are hardly absorbed in the void portion, so that the CT image becomes dark. In (B), the ionic liquid permeates the voids, so that the X-ray absorption of the voids becomes large, and the voids are displayed brightly (contrast is enhanced) in the CT image.

[Experimental example 2: Visualization of simulated stratum sample]
A simulated stratum sample was prepared by mixing glass beads with voids that do not allow liquid to penetrate with minerals and organic matter. Water and an ionic liquid containing / not containing iodine were infiltrated into the simulated formation sample, and the brightness of the image components was confirmed by CT scanning.

[material]
<Simulated stratum constituent particles>
-Glass beads (beads made of sodium borosilicate glass with a hollow inside): Q-CEL 7014 (registered trademark), Potters Barotini Co., Ltd.-Minerals: Quartz sand (Fuji Film Wako Junyaku Co., Ltd.)
-Organic matter (beads made of polystyrene (specific gravity 1.04-1.09)): Abacus beads approx. 4 mm, Daiso Sangyo Co., Ltd.

<solvent>
・ Ultrapure water (Milli-Q water)
-Iodine-free ionic liquid: 1-methyl-3-propylimidazolium bis (trifluoromethanesulfonyl) imide (Tokyo Kasei Kogyo Co., Ltd.)
・ Ionic liquid containing iodine: 1-propyl-3-methylimidazolium iodide (Kanto Chemical Co., Inc.)

[Method]
Quartz sand and plastic beads were crushed in a mortar and sieved to 250 um and 100 um, and the one remaining on the 100 um sieve was used. A mixture of Q-CEL, quartz sand, and plastic beads was CT-scanned for each solvent using the same equipment as in Experimental Example 1, and the obtained images were compared.

[result]
<Sample using ultrapure water>
In the CT image of the sample mixed with ultrapure water (Fig. 2), the brightness of the image for each element is quartz sand (light gray)> ultrapure water (gray) ≒ plastic beads (gray)> voids inside the glass beads ( It was dark gray). The measurement conditions are shown below.

・ 100kV, 10W
・ Exposure time 3 seconds ・ Number of projections 3201 ・ Pixel size 4.71um / pixel

In this case, since the ultrapure water and the plastic beads could not be distinguished, there was a part that looked like a large void. Therefore, in this method, substances composed of light elements in the formation cannot be distinguished from voids.

<Sample using ionic liquid that does not contain iodine>
In the CT image of the sample using the iodine-free ionic liquid (Fig. 3), the brightness of the image for each element is quartz sand (light gray)> iodine-free ionic liquid (gray)> plastic beads (dark gray). > It was a void (black) inside the glass beads. The measurement conditions are shown below.

・ 40kV, 10W
・ Exposure time 5 seconds,
・ Number of projections 3201 ・ Pixel size 4.984um / pixel

In this case, the high density of iodine-free ionic liquids made it possible to distinguish between plastics and ionic liquids.

<Sample using ionic liquid containing iodine>
In the CT image of the sample using the ionic liquid containing iodine (Fig. 4), the brightness of the image for each element is the ionic liquid containing iodine (light gray)> quartz sand (gray)> plastic beads = voids inside the glass beads. It was (dark gray). The measurement conditions are shown below.

・ 90kV, 10W
・ Exposure time 3 seconds ・ Number of projections 3201 ・ Pixel size 4.984um / pixel

In this case, the voids inside the glass beads remain dark because the ionic liquid does not permeate, but the voids other than the voids of the glass beads in which the ionic liquid permeates have the brightness of the image reversed to that of quartz sand or the like.

According to the present invention, it is possible to analyze minute voids in a stratum sample. In addition to the stratum, it is possible to analyze various samples having voids into which ionic liquids can be introduced.

Claims (8)

It is a method of visualizing the voids of a sample using X-ray CT.
A sample was prepared by filling the voids of the sample with an ionic liquid containing a highly X-ray absorptive component.
A method comprising a step of irradiating a prepared target with X-rays, detecting the X-rays transmitted through the target, and obtaining an image of the target in which the contrast between the void portion and the other portion is emphasized. The method according to claim 1, wherein the high X-ray absorptive component is a component containing any one selected from the group consisting of iodine, bromine, and chlorine. The method according to claim 1 or 2, wherein the X-ray CT is a microfocus X-ray CT or a synchrotron light source X-ray micro CT. The step according to any one of claims 1 to 3, wherein the step of producing a sample in which the voids of the sample are filled with an ionic liquid containing a high X-ray absorptive component is carried out by a process including the following steps. Method:
Embed the sample in an aqueous gel, fill the voids in the sample with an aqueous gel,
A step of immersing a sample embedded in an aqueous gel in an ionic liquid and replacing the water with the ionic liquid to fill the voids of the sample with the ionic liquid. This is a method for producing a standard for X-ray CT.
The sample with voids is embedded with an aqueous gel, and the voids of the sample are filled with the aqueous gel.
A production method comprising a step of immersing a sample embedded in an aqueous gel in an ionic liquid and filling the voids of the sample with the ionic liquid by substituting the water with the ionic liquid. It is a method of visualizing the voids of a sample using X-ray CT.
The sample with voids is embedded with an aqueous gel, and the voids of the sample are filled with the aqueous gel.
A sample embedded in an aqueous gel is immersed in an ionic liquid, and the voids of the sample are filled with the ionic liquid by substituting the water with the ionic liquid to prepare a standard.
A method comprising a step of irradiating a prepared target with X-rays, detecting the X-rays transmitted through the target, and obtaining an image of the target in which the contrast between the void portion and the other portion is emphasized. A composition comprising the following for making a specimen for X-ray CT:
A. Ionic liquids containing iodine, and B. An ionic liquid that can be mixed with A and has lower X-ray absorption than A. The composition according to claim 7, wherein the content mass ratio of A (A / (A + B)) is 20 to 40%.

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