JPH11108833A - Method for spectroscopic analysis of substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an analyzed value before variation of a substance which varies with time by applying a mixed system containing a substance to be measured which varies with time and a volatile substance which interferes with spectrum analysis onto a plate-shaped body, vaporizing a volatile substance, and performing analysis before variation with time develops. SOLUTION: A substance to be measured has a -OH group and a group capable of reacting with a -OH group and condensing, and a siloxane compound expressed by a general formula [SiOa (OH)b (OR<1> )c (OR<2> )d ] in the formula, 0.8<=a<=1.6, 0.3<=b<=1.3, 0.2<=c+d<=1.9, b=4-(2a+c+d), R<1> is a methyl group or a ethyl group, R<2> is an organic group different from R<1> } becomes an object. An infrared spectroscopic method is used as an analyzing method. Variations with time include changes in the amount of functional groups, gelation, etc., as well as, for example, chemical changes, physical changes such as liquefaction from a solid, sublimation, etc. Here, a mixed system containing a substance to be measured is applied onto a plate-shaped body, and spectroscopic analysis is performed after vaporizing a volatile substance in the mixed system while the mixed substance is present on the plate-shaped body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a spectroscopic analysis method. In particular, the present invention relates to a spectroscopic analysis method suitable for measurement of a substance that can change over time.

[0002]

2. Description of the Related Art Spectroscopic analysis is an analytical method in which the spectrum of light emitted from a substance or the spectrum of light transmitted through a substance is measured to determine the type and amount of a substance present. In the spectroscopic analysis method, in the method of measuring the light passing through by irradiating a light beam from a light source onto a substance to be measured, the transmitted light is compared with the incident light and evaluated, and the intensity of the transmitted light is determined as the light transmittance or absorbance. It is common to determine and plot changes in wavelength or wavenumber of these intensities. Typical analysis methods are an infrared spectroscopic analysis method in which the light to be measured is in the infrared region and an ultraviolet-visible spectroscopic method in which the light is measured in the ultraviolet-visible region. In these analyses, the substance to be measured is measured in a sample holder or cell. The sample holder is placed as it is or diluted with an inorganic salt or the like according to the form of the substance to be measured. Liquid analytes as such or dissolved in solvents can also be analyzed using sealed cells.

[0003] When a substance to be measured in a solvent is measured by a cell, a method is used in which the spectrum of the solvent is subtracted from the spectrum of the substance to be measured in the solvent by a difference spectrum method. However, particularly in infrared spectroscopy, many solvents also have a considerably strong absorption band, and it is impossible to detect an infrared spectrum in a wavelength region where the solvent has a strong absorption band. In this case, conventionally, only the substance to be measured is measured by removing the solution by means such as drying. Specifically, for example, a method has been proposed in which a solution containing the substance to be measured is coated on a polytetrafluoroethylene film, dried, and the obtained thin film is peeled off from polytetrafluoroethylene and analyzed. (See Japanese Unexamined Patent Publication No. 7-500180).

[0004]

However, depending on the substance to be analyzed, a volatile substance such as a solvent that coexists may evaporate over time, and such a substance may be a solvent or the like. Of the substance to be measured may not be able to measure the original spectrum of the substance to be measured. On the other hand, when the measurement is performed quickly to prevent the change over time, the coexisting substance such as a solvent is insufficiently dried to leave a substantial amount, and the remaining volatile substance such as a solvent affects the spectrum, and the substance to be measured is In many cases, it is not possible to measure only the spectrum, and there has been a demand for a method capable of analyzing a substance which causes such a change with time.

An object of the present invention is to provide a spectroscopic analysis method capable of measuring even a substance which cannot be measured by such a conventional method.

[0006]

Means for Solving the Problems In view of the above-mentioned problems of the prior art, the present inventors have made various investigations and, by adopting a specific analysis method, it has become possible to carry out spectroscopic analysis of a substance to be measured which changes with time. Having found this, the present invention has been reached.
Further, the progress of the temporal change can be continuously measured by the specifying means of the present invention. In addition, quantitative analysis was made possible by comparison with the absorbance derived from a functional group having a known abundance contained in the substance to be measured or the absorbance derived from the added internal standard substance.

That is, the present invention relates to a method for spectroscopic analysis of a mixed system containing a substance to be measured which causes a change with time and a volatile substance which interferes with spectroscopic analysis. Is characterized by performing an analysis after evaporating and before a change with time progresses.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
In the present invention, a mixed system containing a substance to be measured is subjected to spectroscopic analysis. The applicable spectroscopic analysis method is not particularly limited, and a method known as a spectroscopic analysis method can be appropriately used. Typical analysis methods include infrared spectroscopy, which measures infrared light as a light source, and ultraviolet-visible spectroscopy, which measures the ultraviolet-visible region.

The use of infrared spectroscopy makes it possible to determine the characteristics of the substance to be measured.
Functional group information can be obtained depending on the position of the sexual absorption band.
Wear. Normally wave number 4000cm^-1(2.5 μm) and 450
cm ^-1(22 μm), but broadly 1
6666cm^-1(0.6μm) and 200cm^-1(50μ
m), the near-infrared region and the far-infrared region are also included. Spec
If you plot the torr in absorbance, the absorbance is
It is used for quantitative analysis using examples. Absorbance is-
It is expressed by log (transmittance (percent) / 100).

[0010] UV-visible spectroscopy is a method of measuring the energy absorbed when electrons in a molecule are raised from a ground state to an excited state, and the absorption wavelength is determined by the electronic structure of the molecule. The measurement area is between 0.18 μm and 0.78 μm. As in the case of infrared spectroscopy, plotting by absorbance is used for quantitative analysis. As the substance to be measured,
The substance is not particularly limited as long as it is a substance that can be detected by spectroscopic analysis. However, in the present invention, a substance whose measured value of spectroscopic analysis changes due to some change with time is targeted. Changes over time include chemical changes that change to other compounds due to chemical reactions,
Examples include physical changes such as liquefaction from a solid, vaporization from a liquid, and sublimation from a solid to a gas, as well as changes over time such as changes in the amount of functional groups, high molecular weight, and gelation. In particular, a substance which changes with time when a coexisting volatile substance evaporates, for example, a compound having an -OH group and a group capable of undergoing a condensation reaction with the -OH group, for example, a polycondensation obtained by hydrolyzing and condensing an alkoxysilane Suitable for siloxane compounds, especially siloxane compounds in which it is difficult to use a solvent other than an alcohol that has an OH group and interferes with spectroscopic analysis as a solvent that is a volatile substance, and thus it is difficult to determine silanol groups. Can be used.

[0011] Such siloxane compounds are typically represented by the general formula [I]

[0012]

Embedded image SiO _a (OH) _b (OR ¹ ) _c (OR ² ) d... [I] (where 0.8 ≦ a ≦ 1.6, 0.3 ≦ b ≦ 1. 3,
0.2 ≦ c + d ≦ 1.9, b = 4- (2a + c + d),
R ¹ is a methyl group or an ethyl group, and R ² is an organic group different from R ¹ . ) Alternatively, the general formula [II]

[0013]

Embedded image SiO _a (OH) _b (OR ¹ ) _c (OR ² ) _d ... [II] (where 1.0 ≦ a ≦ 1.6, 0 ≦ b ≦ 0.3, 0.2
≤c≤2.0, 0≤d≤1.4, b = 4- (2a + c
+ D), R ¹ is a methyl group or an ethyl group, and R ² is R ¹
Are different organic groups. ).

As described above, these siloxane compounds, particularly the compounds represented by the general formula [I], undergo a time-dependent change, in particular, a change such as increase in molecular weight and thickening due to the presence of a silanol group which influences the time-dependent change. Cheap. For this reason, if the measurement was performed after simply removing the solvent according to the conventional technique, the change with time was large, and it was difficult to perform an accurate measurement. According to the present invention, if spectroscopic analysis is performed after the removal of the solvent and before the change with time progresses, not only the control of the physical properties of the siloxane compound, but also it can greatly contribute to the investigation of the reaction mechanism, and industrial, The technical significance is great.

[0015] In addition to the siloxane compounds described above, polymerization of epoxy resin paint, polyurethane resin paint, etc.,
The present invention can also be suitably applied to a substance that causes a change such as gelation and changes the measured value of spectroscopic analysis. Substances that cause a change such as polymerization, gelling, etc., and change the measured value of spectroscopic analysis, such as siloxane compounds, epoxy resin paints, polyurethane resin paints, etc., which are represented by the following formulas, are suitable.

The mixed system in the present invention contains the above-mentioned substance to be measured and a specific volatile substance. Volatile substances are substances that interfere with the spectroscopic analysis, but are substances that can interfere with the spectroscopic analysis of the analyte by being present in a mixed system, typically overlapping the measurement wavelength range of the analyte. Substances having a strong absorption band.
Further, it is a substance that can evaporate in a state where the mixed system is applied to the plate-like body, and in such a state, is a substance having a relatively high evaporation (volatilization) rate at least with respect to the substance to be measured.

Typically, the liquid (solvent) is capable of dissolving or dispersing, preferably dissolving, the substance to be measured in the volatile substance, but may further contain impurities, stabilizers and the like. 1
It may contain one or more components. Examples of volatile substances used as solvents include, in addition to water, hydrocarbons such as hexane and heptane, alcohols such as methanol and ethanol, and aliphatic carboxylic acid alkyl esters such as ethyl acetate and propyl acetate. Organic solvents. Volatile substances include substances which can be evaporated by forced evaporation with a heater or the like, in addition to substances which can be naturally evaporated at normal temperature and normal pressure. Alternatively, a substance which can be evaporated by connecting an exhaust device and forcibly evaporating under reduced pressure is also included. In some cases, evaporation may be performed under cooling or under pressure in order to suppress evaporation of the substance to be measured. At this time, if the evaporation rate of the volatile substance is too slow, it is not desirable because the substance to be measured may change with time during the evaporation.

The sample to be analyzed in the present invention is a mixed system containing the above-mentioned substance to be measured and a volatile substance. The concentration of the substance to be measured in the mixed system is preferably closer to the saturated concentration for volatile substances, and depends on the substance used.
About 0% by weight is preferable. The mixed system may contain other substances, for example, impurities obtained when synthesizing the substance to be measured, substances decomposed from the substance to be measured, and the like within a range that does not substantially inhibit the spectroscopic analysis.

It is preferable to mix an internal standard substance according to the type of spectroscopic analysis in the mixed system. As described below, the analysis method of the present invention is a method of applying an appropriate amount of a substance to be measured, and thus it is difficult to quantitatively handle a sample amount.
The use of the internal standard material enables a quantitative measurement of the substance to be measured. The internal reference material used may be different because the substance to be measured does not affect the wavelength range to be measured, or even if it does, it exhibits specific absorption in the wavelength range different from the absorption of the substance to be measured. Substances whose effects can be excluded by a technique such as a spectral method are preferred. In addition, the characteristics suitable for the internal standard substance are that it has a sufficiently high boiling point so that it does not evaporate when evaporating or removing volatile substances, does not react with the substance to be measured and volatile substances, and dissolves in volatile substances. When the volatile substance evaporates, it does not separate from the substance to be measured, and stability that does not change over time. Examples of suitable internal standard materials include dibutyl phthalate, diphenylamine, and polyacrylonitrile in infrared spectroscopy, and dibutyl phthalate and diphenylamine in ultraviolet spectroscopy.

In the present invention, a mixed system containing the substance to be measured is applied on a plate-shaped body, and after volatile substances in the mixed system are evaporated, spectroscopic analysis is performed while the mixture is still on the plate-shaped body. The plate-like body includes what is called a film such as a thin film and a plate. In general, the plate-shaped body should be made of an appropriate material and thickness that does not interfere with the wavelength range of the analyte, if the analyte and the internal standard are used, and that the analyte is retained. When the internal standard is used, the material and the shape are made of a material that can hold the internal standard. Furthermore, this material is a substance to be measured, an internal standard substance,
Select a substance that does not dissolve or react with any of the volatile substances. For example, polyolefin resin, fluororesin,
Inorganic salts, quartz and the like may be mentioned, and may be set in a holder. It is preferable to increase the surface area by making the surface to which the mixed system is applied porous so that the evaporation rate of the volatile substance is increased.

In particular, when the substance to be measured is a substance which has a high molecular weight and / or gels after evaporation of volatile substances or changes with time, it is desirable to use a resin film and dispose it. Examples of such a resin film include:
Microporosity (for example, pore size 0.1
-50 μm) of polyethylene or polytetrafluoroethylene, particularly those supported on a support such as cardboard. These resin films are limited to infrared spectroscopy.
It is excellent in retention of the substance to be measured, evaporation of volatile substances, and infrared light transmission. This type of film is known in
No. 0180, the trade name "Dispo"
A product commercially available from Minnesota Mining Company as "sable IR Card" can also be used.

The method of applying the mixed system containing the substance to be measured on the plate-like body can be appropriately selected. However, in order to quickly evaporate the volatile substance, 0.01 to 0.5 g of the mixed system droplets are applied. Generally, a method of dripping onto a plate-like body is used. The volatiles are then evaporated. Evaporation can be appropriately selected depending on the mixed system to be measured, such as natural drying at room temperature, evaporation under heating, and evaporation under cooling.Especially suitable means are the type of volatile substance, It changes greatly depending on the concentration of the analyte in the mixed system. Also, the time required for the evaporation of the volatile substance varies greatly, but when the amount of application of the mixed system is extremely small as described above, the evaporation of the volatile substance is one time.
It occurs in a short time of about 10 seconds. In general, the time required for evaporation is determined by continuously measuring the absorbance derived from a volatile substance using a spectrophotometer after applying the substance to be measured containing the volatile substance. That is, it refers to the time at which the absorbance derived from volatile substances suddenly decreases and then starts to stabilize.

In the present invention, the measurement of the substance to be measured is
This is performed after the volatile substance is evaporated and before the change with time of the substance to be measured progresses. The term “before the time-dependent change” refers to a time before the substantial time-dependent change of the substance to be measured progresses, and the progress of the time-dependent change is a mixed plate-like body containing a volatile substance and the substance to be measured. After the application, the absorbance can be determined by measuring the absorbance continuously or at a specific time by a spectrophotometer.

After the volatile substance volatilizes and the absorbance derived from the volatile substance sharply decreases, the change in the absorbance after the point at which the absorbance starts to stabilize is considered to be substantially due to the change with time of the substance to be measured. Therefore, by measuring and extrapolating the absorbance thereafter, it is possible to infer the state in which the absorbance of the substance to be measured itself changes from the beginning of the measurement (at the time of application to the plate-like body). .

In the present invention, judging from the absorbance of the substance to be measured at the start of the measurement (at the time of application to the plate-like body) determined by extrapolation, the substance to be measured is measured before the change with time substantially progresses. Perform spectroscopic analysis. By doing so, the original analysis value of the substance to be measured can be obtained without being affected by the volatile substance. It is substantially before the change over time progresses that the absorbance of the analyte is
This can be confirmed by being within a certain ratio of the absorbance of the substance to be measured at the start of measurement determined by extrapolation. In particular, it is desirable to perform the spectroscopic analysis of the substance to be measured at a time when the change in the absorbance of the substance to be measured at the start of measurement is within 5%.

In the analysis method of the present invention, the volatile substance such as a solvent is evaporated in a very short time by applying a mixed system containing the substance to be measured on a plate and evaporating a volatile substance such as a solvent. Since the substance can be removed, spectroscopic analysis can be performed even before a substantial change occurs even for a substance that changes over time. For example, the general formula SiO _a (OH) _b (OR ¹ ) _c (OR ² ) d (where 0.8 ≦ a ≦ 1.6, 0.3 ≦ b ≦ 1.3,
0.2 ≦ c + d ≦ 1.9, b = 4- (2a + c + d),
R ¹ is a methyl group or an ethyl group, and R ² is an organic group different from R ¹ . In the siloxane compound represented by the formula (1), the average structure is important in discussing its performance.
The quantitative determination of the silanol group in the siloxane compound is suitably measured by an infrared spectrophotometer. However, in the case of an alcohol solution of a siloxane compound, the alcohol is the same O
As the H group, a broad absorption was shown at a position close to the absorption of the silanol group in the siloxane compound, so that the absorptions overlapped and could not be quantified. This solution changes over time when the alcohol solvent is evaporated. Therefore, when the alcohol solvent is evaporated and only the siloxane compound is separated and subjected to infrared spectroscopy, accurate determination of the silanol group cannot be performed. Other groups could be measured by NMR or the like, but the amount of silanol groups could not be directly measured.
The value of b was calculated and estimated from the amount and the values of a, c, and d. On the other hand, according to the analysis method of the present invention, the change with time of the siloxane compound can be traced, and therefore, the actual amount of the silanol group at the stage before the change with time can be quantified.

Further, a mixed system containing a substance to be measured which undergoes a temporal change according to the present invention and a volatile substance which hinders spectroscopic analysis is applied on a plate-like body, and after the volatile substance is volatilized,
By performing the spectroscopic analysis, by measuring the progress of the change with time of the substance to be measured, it is possible to grasp the state of the change with time such as the amount of the functional group of the substance to be measured which is easily changed with time as described above.

[0028]

The present invention will be described in more detail with reference to the following examples. A 10 wt / vol% methanol solution of dibutyl phthalate (boiling point: 341 ° C.) in methanol (10 g of dibutyl phthalate is contained in 100 cc of the solution) was prepared in advance as an internal standard substance. The general formula [I] as the substance to be measured
A siloxane compound represented by the formula was selected, and a 50% methanol solution was prepared, and 1 ml of the internal standard substance solution was mixed with 1 g of the substance to be measured.

One drop of the obtained mixed solution was dropped on a sample holder (trade name “Disposable IR Card”, manufactured by Minnesota Mining Co., Ltd.) using a pipette, and a microporous polyethylene film was sandwiched between cardboards. The holder was set on an infrared spectrophotometer, and the evaporation of methanol as a solvent and the change over time of the siloxane compound were observed by an IR spectrum about every 5 seconds.

As a result, the absorption of OH of 3400 cm
The absorbance at ^-1 was 2.98 immediately after installation, but decreased to 0.299 in about 40 seconds. Thereafter, the rate of decrease decreased sharply, and the absorbance was 0.293 after 9 minutes and 0.272 after 21 minutes. These absorbance changes are:
This means that 2 minutes after 9 minutes and 9% after 21 minutes compared to about 40 seconds later. In parallel, the change with time of the silanol group was confirmed by an increase in the absorbance of 1100 cm ^-1 derived from the SiOSi bond. As a result, it was found that the alcohol solvent evaporated until 40 seconds, and thereafter the silanol group changed with time and decreased.

Next, in order to quantify the silanol group, a 10% by weight / volume methanol solution of triphenylsilanol (triphenylsilanol 10
g is contained in 100 cc of the solution. ) Was prepared. The calibration curve test solution was prepared by mixing 1, 2 and 5 parts by volume of a methanol solution of triphenylsilanol with 1 part by volume of the internal standard solution, and dissolving each solution in the same manner as the siloxane compound in "Disposable IR Card". 1 in
The measurement was performed by applying a drop.

A plot of the ratio of the absorbance (3400 cm ^-1 ) derived from the silanol groups of triphenylsilanol to the absorbance (1728 cm ^-1 ) derived from the ester groups of dibutyl phthalate was plotted against the concentration ratio of the charge. did. From this calibration curve, the silanol groups of the siloxane compound could be quantified.

[0033]

According to the analysis method of the present invention, it is easy to obtain an analytical value before the change for a substance which undergoes a change with time, which has been extremely difficult to analyze in the past, and is extremely useful industrially. is there.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshihiro Komura 1-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu City Inside Kurosaki Plant of Mitsubishi Chemical Corporation

Claims (7)

[Claims] In a spectroscopic analysis method of a mixed system containing a substance to be measured causing a change with time and a volatile substance which hinders spectroscopic analysis, the mixed system is applied on a plate-like body to evaporate the volatile substance. After that, the spectroscopic analysis method is characterized in that the analysis is performed before the time-dependent change progresses. 2. The spectroscopic analysis method according to claim 1, wherein the plate-like body is a porous body. 3. The spectroscopic method according to claim 1, wherein an internal standard substance is contained in the mixed system containing the substance to be measured. 4. The spectroscopic method according to claim 1, wherein the substance to be measured is a substance which produces at least one of a high molecular weight and a gelation with the lapse of time. 5. The spectroscopic method according to claim 1, wherein the substance to be measured is a compound having an —OH group and a group capable of undergoing a condensation reaction with the —OH group. 6. The substance to be measured is represented by the general formula [I]:_a(OH)_b(OR¹)_c(OR^Two) D... [I] (where, 0.8 ≦ a ≦ 1.6, 0.3 ≦ b ≦ 1.3,
0.2 ≦ c + d ≦ 1.9, b = 4- (2a + c + d)
Yes, R¹Is a methyl group or an ethyl group;^TwoIs R ¹When
Different organic groups. The siloxane compound represented by
Characterized in that infrared spectroscopy is used as an analytical method.
The spectroscopic method according to any one of claims 1 to 4. 7. A method comprising applying a mixed system containing a substance to be measured which undergoes a change with time and a volatile substance which hinders spectroscopic analysis to a plate-like body, volatilizing the volatile substance, and performing analysis. A spectroscopic method characterized by measuring the progress of a change with time of a substance to be measured.