JP2000180413A - Auxiliary agent for ionization and method for substance ionization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an auxiliary agent for ionization capable of simply subjecting a substance having a wide range of a mol.wt. to mass analysis with high accuracy and a method for substance ionization using the ionizing auxiliary agent. SOLUTION: An auxiliary agent for ionization comprises a solid, especially, carbon black with an average particle size of 100 nm or less and a PVC blackness of 50 or less and ionizing treatment is performed by adding and dispersing a sample substance in a soln. prepared by dispersing the ionizing auxiliary agent in an org. solvent. An ionizing auxiliary agent can efficiently ionize the molecules of a sample substance for mass analysis continuously and, by a substance ionizing method using the ionizing auxiliary agent, the molecules of the sample substance for mass analysis can be continuously ionized under a relatively gentle condition and a special holder is unnecessary and a sample is simply prepared and the noise originating from the ionizing auxiliary agent at a time of mass analysis is reduced to a large extent to make it possible to enhance analytical accuracy. Therefore, by using this ionizing method, a substance having a wide range of a mol.wt. can be simply subjected to mass analysis with high accuracy and, especially, the partial structural analysis of a low molecular compd. and the measurement of mol distribution and mol.wt. distribution can be simply performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for ionizing a sample for mass spectrometry, which can continuously and efficiently ionize molecules of a sample substance for mass spectrometry, and can perform mass spectrometry easily with high accuracy. And a method of ionizing a substance using the same.

[0002]

2. Description of the Related Art A mass spectrometer ionizes molecules of a sample substance in some way,
An electric or magnetic field is applied to this, and the mass / charge number (m
After the separation according to / z), qualitative analysis and quantitative analysis of the substance can be performed from the mass spectrum detected electrically. In this case, ionization methods include electron impact ionization (EI), chemical ionization (CI), fast atom bombardment (FAB), field desorption (FD),
There are various methods such as laser desorption ionization (LDI). For example, in a laser ionization mass spectrometer, a sample is irradiated with a pulsed laser beam to be ionized, and the ion is guided to an analysis unit such as a time-of-flight type to measure a mass spectrum or the like.

Conventionally, in such a laser ionization mass spectrometer, a solid sample is first dissolved in an organic solvent to prepare a sample solution, and this sample solution is applied to a smooth surface of a metal holder and dried. When a sample is formed in a thin film and this sample thin film is irradiated with laser light, the laser light is absorbed by a metal holder, causing a sharp rise in temperature at the irradiated location.
The ionization of the sample occurs.

[0004] However, in this sample manufacturing method, there is a problem that the sample molecules are not present at the position irradiated with the laser beam several times, and the generation of ions is stopped. This phenomenon is also a problem in SIMS (secondary ion mass spectrometry) and FABMS (fast neutron impact mass spectrometry).

Therefore, as a solution to this problem, FA
In the BMS method and the like, a liquid matrix method is employed. The liquid matrix method is characterized in that a liquid matrix such as glycerin is mixed with a sample solution. Even if the sample molecules are ionized and extracted at the irradiation part such as a line, the sample molecules are sequentially replenished from the surroundings, and the generation of ions can be continued for a long time.

In the MALDI method (matrix assisted laser desorption method) using a matrix employed in laser ionization, 2,5-dihydroxybenzoic acid (DHB), synaptic acid, α-cyano- The use of organic matrices such as hydroxy-cinnamic acid (CHCA) is known. However, according to the studies made by the present inventors, these organic matrices have a problem that the matrix itself is ionized when the sample substance molecules are ionized, which hinders mass spectrometry.

On the other hand, mass spectrometry of low molecular weight compounds requires FA
Although the BMS method is used, mass spectrometry of oligomers and polymers cannot be measured by the FABMS method in many cases. Therefore, even if the operation is troublesome, the relative value to the standard substance can be determined by size exclusion chromatography (SEC). It is currently measuring.

[0008] Therefore, it is desired to develop an ionization technique capable of industrially advantageously ionizing molecules of a sample substance for mass spectrometry and enabling mass spectrometry of substances having a wide range of molecular weights.

The present invention has been made in view of the above circumstances, and it is possible to continuously and efficiently ionize the molecules of a sample substance for mass spectrometry, and to easily mass analyze substances with a wide range of molecular weights with high accuracy. It is an object of the present invention to provide an ionization aid which can be converted into a substance and a method for ionizing a substance using the same.

[0010]

Means for Solving the Problems and Embodiments of the Invention The present inventors have made intensive studies to achieve the above object, and as a result, the average particle diameter is 100 nm or less, the PVC blackness is 50 or less, More preferably, the PVC blackness is 20 to 40.
That solids, especially carbon black, can continuously and efficiently ionize molecules of a mass spectrometry sample substance, are effective as an ionization aid, and can be effectively used for ionization treatment of a mass spectrometry sample. I found it.

In this case, the solid easily absorbs an irradiation source such as laser energy used for the ionization treatment, and uniformly disperses the sample substance in the organic solvent without using a special holder. Thus, ions can be continuously generated to increase the efficiency of the ionization process.

Further, the ionization aid is added and dispersed in a solution in which the ionization aid is dispersed in an organic solvent,
By performing the ionization treatment, the substance molecules can be easily ionized under relatively mild conditions, and a normal sample stage may be used, and the preparation of the sample is simple. Moreover, by ionizing by this method, the noise derived from the ionization aid during mass spectrometry can be significantly reduced, and the analysis can be performed with high accuracy. Therefore, a substance having a wide range of molecular weights, that is,
The present invention has been found that mass spectrometry of monomers, oligomers, and polymers, particularly low-molecular compounds, can be easily performed with high accuracy, and partial structure analysis and molar distribution of substances can be industrially advantageously measured. Reached.

Therefore, according to the present invention, the average particle diameter is 100 n.
m or less and a solid having a PVC blackness of 50 or less, and a sample substance is added and dispersed in a solution in which the ionization aid is dispersed in an organic solvent, and ionization treatment is performed. A method for ionizing a substance is provided.

Now, the present invention will be described in further detail. The ionization aid of the present invention is used as a so-called matrix when ionizing molecules of a sample substance for mass spectrometry, and has an average particle diameter of 100 nm or less. Yes,
And it consists of a solid having a PVC blackness of 50 or less.

Here, the average particle diameter of the solid is 100
nm or less, preferably 50 nm or less, more preferably 2 nm or less.
0 nm or less, if the above value is greater than the above, poor dispersibility,
The object of the present invention cannot be achieved. The average particle size is a value measured by an electron microscope.

The blackness of the solid is 50 or less, preferably 20 to 40, in terms of PVC (polyvinyl chloride) blackness. If the blackness is larger than the above value, the object of the present invention cannot be achieved. .

The solid is not particularly limited in other physical properties as long as it has an average particle diameter and blackness within the above ranges. Carbon black has the above specific average particle diameter and blackness, and has a specific surface area. Is preferably 100 to 400 m ² / g and the DBP oil absorption is 50 to 100 ml / 100 g. Specific examples of such carbon black include Mitsubishi Carbon Black # 2350, # 230
Although 0 and the like are exemplified, Ketjen Black (manufactured by Lion Corporation) is preferably used.

In the method of ionizing a sample substance according to the present invention, the sample substance is added and dispersed in a solution in which the above-described ionization aid of the present invention is dispersed in an organic solvent, and the sample is ionized.

The organic solvent in which the ionization aid is dispersed is preferably a lower alcohol or a polyhydric alcohol. As the lower alcohol, one having 1 to 6 carbon atoms is preferable, and examples thereof include methanol, ethanol, propanol, and butanol. Among them, methanol and ethanol having 1 or 2 carbon atoms are more preferable. As the polyhydric alcohol, a dihydric or trihydric alcohol having viscosity is preferable, and specific examples thereof include glycerin, ethylene glycol, and propylene glycol, and propylene glycol is particularly preferable.

As the organic solvent, the above-mentioned lower alcohols,
Although each of the polyhydric alcohols may be used alone or in combination, a combination of a lower alcohol and a polyhydric alcohol, particularly, a combination of methanol and propylene glycol is preferable. in this case,
The combination ratio of the lower alcohol and the polyhydric alcohol is 1000: 1 to 10: 1 by volume, particularly 200: 1 to 50:
A range of 1 is desirable.

In the present invention, first, the above-mentioned specific ionization aid is dispersed in the above-mentioned organic solvent. In this case, the amount of the organic solvent used can be appropriately adjusted, but is preferably such that the concentration of the ionization aid is 0.5 to 5% by weight. If the ionization aid concentration is less than the above value, the effect of adding the ionization aid may not be obtained.

In the present invention, other matrices, for example, organic matrices such as DHB, synaptic acid, CHCA, etc., are added, if necessary, in addition to the above-mentioned specific ionizing aid within a range not to impair the effects of the present invention. be able to.

The sample substance used in the method of the present invention is not particularly limited, and various substances can be used, and various monomers, oligomers, polymers and the like can be used. In the method of the present invention, among these sample substances, particularly low-molecular-weight compounds, which are usually difficult to perform mass spectrometry, can be suitably used.

As the low molecular weight compound, those having a molecular weight of 500 or less, particularly 200 or less are preferably used. Specifically, mass spectrometry can be performed on various components used in household cleaning agents, cosmetics, and the like. Specific examples of such low-molecular compounds include polyoxyethylene-based nonionic surfactants, various surfactants such as sodium lauryl sulfate, trimethyllauryl ammonium bromide, and triethanolamine laurate, and polyethylene glycol. However, it is needless to say that the present invention is not limited to these.

The amount of the sample substance added to the solution in which the ionization aid is dispersed is 0.1 to 10 mg / sample.
A desirable range is ml.

As a means for dispersing the ionization aid and the sample substance in the organic solvent, a usual method can be adopted.
For example, it is preferable to disperse using an ultrasonic generator or the like.

In the present invention, various methods can be employed for ionizing a sample, and among them, a laser ionization method by laser irradiation is preferable.

Further, at the time of the ionization treatment, it is not necessary to use a special holder, and an ordinary sample stage can be used. The ionization aid of the present invention and the organic solvent solution in which the sample substance is dispersed are placed on the sample stage. It can be processed by drying.

The ionization method of the present invention can be applied to various types of mass spectrometry. Specifically, a time-of-flight mass spectrometer, a magnetic field single focusing mass spectrometer, a double focusing mass spectrometer,
It can be used for mass spectrometry using a mass spectrometer such as an ion-cyclotron resonance mass spectrometer. Of these, a time-of-flight mass spectrometer is preferred.

[0030]

The ionization aid of the present invention can continuously and efficiently ionize molecules of a sample substance for mass spectrometry. According to the method for ionizing the substance of the present invention using this ionization aid, the molecules of the sample substance for mass spectrometry can be continuously ionized under relatively mild conditions, no special holder is required, and the sample preparation is not required. In addition to the simplicity, noise derived from the ionization aid during mass spectrometry can be significantly reduced, and the analysis accuracy can be improved. Therefore, by using this ionization method, mass spectrometry of substances with a wide range of molecular weights can be easily performed with high accuracy, and in particular, partial structure analysis, molar distribution, molecular weight distribution, etc. of low molecular weight compounds can be easily performed. it can.

[0031]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Examples 1 to 7 As shown in Table 1, the following carbon black was used as an ionization aid, methanol / propylene glycol was used as an organic solvent, and the following samples were prepared according to the operation flowchart shown in FIG.
Mass spectrometry was performed by the TOFMS method, and the analysis result was evaluated by the following method. Table 1 shows the results. In addition, charts of mass spectra are shown in FIGS. Sample A: NRE5 (polyoxyethylene lauryl ether EO average addition mole number 5) B: Commercially available kitchen detergent Composition polyoxyethylene lauryl ether 3.0% by weight (EO average addition mole number 15) Sodium α-olefin sulfonate 7. 6 n-dodecyldimethylamine oxide 5.8 para-toluenesulfonic acid aqueous solution 4.0 purified water balance 100.0 wt% C: commercial dentifrice composition sorbitol solution (70%) 35.0 wt% sodium lauryl sulfate 1.6 Abrasives, binders, water, etc. Balance : 100.0% by weight D: Polyethylene glycol # 1000 E: Trimethyl lauryl ammonium bromide F: Triethanolamine laurate

Evaluation of analysis results: (1) Persistence of ionization (stability of ion generation) ：: Continuous ionization was possible under mild conditions. ×: Sudden heat generation or lack of sustained ionization. (2) Analysis results ：: High analysis accuracy. Δ: Inferior in analysis accuracy. ×: Noise is generated and analysis accuracy is poor.

[0034]

[Table 1]

[Comparative Examples 1 to 8] As shown in Table 2, 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxy-cinnamic acid (CHCA) were used as ionizing aids. Using the same organic solvent as in the above example, the same sample as in the above example was subjected to mass spectrometry by MALDI-TOFMS according to the above operation flowchart except that the pretreatment conditions were as follows,
The analysis results were similarly evaluated. Table 2 shows the results. Also,
The chart of the mass spectrum is also shown in FIGS. Pretreatment conditions: sample concentration 10 mg / ml ionization aid concentration 10 mg / ml mixing ratio of sample solution to ionization aid-containing solution 1: 1
0

[0036]

[Table 2]

From the results shown in Tables 1 and 2, it was found that the ionization aid of the present invention can continuously and efficiently ionize the molecules of the sample substance for mass spectrometry. Further, according to the method for ionizing a substance of the present invention using the ionization aid, molecules of the sample substance for mass spectrometry can be continuously ionized under relatively mild conditions, and the sample preparation is simple.
It was confirmed that the noise derived from the ionization aid during mass spectrometry can be significantly reduced, and the analysis accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a flowchart of an analysis operation procedure.

2A is a mass spectrometry spectrum of the sample of Example 1, and FIG. 2B is a mass spectrometry spectrum of the sample of Comparative Example 1.

FIG. 3 is a mass spectrometry spectrum of the samples of Example 2 and Comparative Examples 2 and 3.

FIG. 4 is a mass spectrometry spectrum of the samples of Example 3, Comparative Examples 4 and 5.

FIG. 5 is a mass spectrometry spectrum of the samples of Example 4, Comparative Examples 6 and 7.

FIG. 6 is a mass spectrometry spectrum of the sample of Example 5.

FIG. 7 is a mass spectrometry spectrum of the samples of Example 5 and Comparative Example 8.

FIG. 8 is a mass spectrometry spectrum of the sample of Example 7.

Claims (2)

[Claims] 1. An ionization aid comprising a solid having an average particle diameter of 100 nm or less and a PVC blackness of 50 or less. 2. A method for ionizing a substance, comprising adding and dispersing a sample substance in a solution in which the ionization aid according to claim 1 is dispersed in an organic solvent, followed by ionization.