JP2002148239A - Method and apparatus for measurement of concentration of halogenide molecule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus wherein the time and a loss can be reduced and the concentration of a halogenide molecule can be measured easily and quickly by a method wherein an ultrashort pulsed laser beam is used, the halogenide molecule can be ionized irrespective of the kind of the halogenide molecule as a measuring object, the adjustment of the pulsed laser beam is not required according to the kind of the halogenide molecule and the halogenide molecule is set to a condition under which the measuring object can be gasified. SOLUTION: The halogenide molecule 1 is irradiated with the ultrashort pulsed laser beam. Product ions derived from the halogenide molecule are generated by its irradiation. The parent ions are accelerated toward a first accelerating electrode 2 due to a potential difference applied to an entrance port. They are accelerated to their advance direction by the electrode 2, and an acceleration is applied to the parent ions in a direction perpendicular to the advance direction by a second accelerating electrode 3. An acceleration is applied to the parent ions in a direction opposite to the advance direction by a reflectron 4, and the ions collide with an MCP 5. Electrons are generated by their collision, and the electrons are observed by an oscilloscope 6. Their ionic strength is measured by using a mass spectrometer, and the concentration of the halogenide molecule is found on the basis of the ionic strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for measuring the concentration of a halogenated molecule.

[0002]

2. Description of the Related Art Conventionally, methods for analyzing trace components of halogenated molecules represented by dioxins include an extraction separation method,
Resonant multiphoton ionization, laser-induced fluorescence, and the like are known.

The extraction separation method is a method in which a target sample is sampled and extracted by the Soxhlet method, then treated with concentrated sulfuric acid, separated using a column, and analyzed by a gas chromatography / mass spectrometer. The resonance multiphoton ionization method and the laser-induced fluorescence method are methods of irradiating a target sample with light of a specific wavelength to excite electrons to ionize or emit fluorescence to measure.

[0004]

However, the above extraction and separation method has a problem that it takes time and costs. In the above-described resonance multiphoton ionization method and laser-induced fluorescence method, it is necessary to irradiate light of a specific wavelength in accordance with an object to be measured. Need to be measured. Further, the polysubstituted halogenated molecule has a problem that the sensitivity is remarkably reduced.

Therefore, an object of the present invention is to easily and quickly measure the concentration of a halogenated molecule.

[0006]

According to the present invention, a halogenated molecule is irradiated with an ultra-short pulse laser beam, and a product ion derived from the halogenated molecule generated by the irradiation is applied to the ion by using a mass spectrometer. The above problem was solved by measuring the intensity and obtaining the concentration of the halogenated molecule from the ionic intensity.

Since an ultrashort pulsed laser beam is used, the halogenated molecule can be ionized regardless of the type of the halogenated molecule to be measured, and the pulse laser beam is adjusted according to the type of the halogenated molecule. You don't have to. In addition, if the measurement sample is set under a condition that can be gasified, the sample can be analyzed, so that time and cost can be reduced.

[0008]

Embodiments of the present invention will be described below.

In the method for measuring the concentration of a halogenated molecule according to the present invention, an ultrashort pulsed laser beam is applied to the halogenated molecule, and a product ion derived from the halogenated molecule generated by the irradiation is analyzed using a mass spectrometer. Then, the ionic strength is measured, and the concentration of the halogenated molecule is determined from the ionic strength.

The above-mentioned halogenated molecule means a halogen-substituted substance which is a substance to be measured. The halogen-substituted substance is not particularly limited, but can be more preferably used for a polyhalogen-substituted aromatic which is difficult to measure by a conventional laser method.
Further, the number of halogens to be substituted is not particularly limited.

Examples of the halogenated molecule include 2,2
3,7,8-tetrachlorodibenzoparadioxane,
1,2,3,7,8-pentachlorodibenzoparadioxane, 2,3,7,8-tetrachlorodibenzoparafuran, PCB, pentachlorobenzene and the like.

The ultra-short pulse laser beam has a light condensing intensity of 10 ¹² to 10 ¹⁶ Wcm ⁻² and a pulse width of 1 to 1000 f.
s laser light. Further, the wavelength of the laser beam is not particularly limited, but it is preferable to use 350 to 2500 nm (near infrared ray). By using such a laser beam, a halogenated molecule which is a substance to be irradiated can be ionized while minimizing molecular destruction. That is, a parent ion of the irradiation target substance can be obtained.

The luminous intensity and pulse width of the laser light are as follows:
Although there is an optimum value depending on the halogenated molecule, an exact value is not required. For this reason, the fine adjustment for each halogenated molecule is not required, and a plurality of halogenated molecules can be ionized at the same time.

As the above ultrashort pulse laser beam, a high-power femtosecond titanium sapphire laser (maximum output 0.1 J / pulse, pulse width 100 fs) marketed by Continium (US), BMI (France) and others. , Center wavelength 800 nm, 10 Hz).

The above-mentioned mass spectrometer means a device which separates product ions derived from the above-mentioned halogenated molecules according to a mass-to-charge ratio (m / z). As an example of such a mass spectrometer, there is a time-of-flight mass spectrometer which is easy to handle.

At this time, the product ions separated by the mass spectrometer are transferred to a microchannel plate (hereinafter referred to as “MC”).
P ”. ) To generate electrons. By measuring the generated electrons with an oscilloscope or the like, the ionic strength of the product ions can be measured.
By this measurement, the concentration of the halogenated molecule can be determined.

The above-described measuring method can be performed, for example, using a laser device that emits ultrashort pulse laser light and a measuring device for measuring the concentration of halogenated molecules having a time-of-flight mass spectrometer. Next, this measuring method will be described in more detail using examples.

[0018]

EXAMPLE An experiment was conducted using pentachlorobenzene as the sample molecule 1.

First, each condition of the time-of-flight mass spectrometer used is shown in FIG. At the inlet, pentachlorobenzene vapor at room temperature is introduced. Then, a high-power femtosecond titanium sapphire laser (maximum output 0.1 J / pulse, pulse width 100 f) from Continium (US)
s, center wavelength 800 nm, 10 Hz) (not shown), light-collecting intensity 1.9 × 10 ¹⁵ Wcm ⁻² , pulse width 10
The vapor of pentachlorobenzene was irradiated with an ultrashort laser beam of 0 fs. As a result, a parent ion (monovalent cation) of pentachlorobenzene was generated. The parent ions are accelerated toward the first accelerating electrode 2 by the potential difference applied to the entrance. And the first acceleration electrode 2
, And is accelerated by the second acceleration electrode 3 in a direction perpendicular to the traveling direction. Then, acceleration is applied in a direction opposite to the traveling direction by the reflectron 4, and the collision with the MCP 5 occurs. Electrons are generated by the collision, and the electrons are observed by the oscilloscope 6. The observation results are shown in FIGS.

FIG. 2 is a graph showing the relationship between the mass-to-charge ratio (m / z) and the ionic strength. FIG.
Shows the peak of the product ion of FIG.
This shows that the product ion is (C ₆ HCl ₅ ) ⁺ .

FIG. 3 shows a plurality of graphs, which indicate that the condensing intensity of the ultrashort laser beam is 1.3 ×
The figure shows the product ions when irradiation is performed at 10 ¹⁴ Wcm ^-2 and 6.3 × 10 ¹³ Wcm ^-2 . The relationship between the condensing intensity of the ultrashort laser beam and the ion intensity of the parent peak (54 μs) indicating (C ₆ HCl ₅ ) ⁺ has a relationship of a straight line bent in the middle as shown in FIG. Thus, when the intensity of the condensing intensity of the ultrashort laser beam is kept constant, the concentration of the pentachlorobenzene vapor provided for the measurement can be calculated by measuring the ion intensity.

[0022]

According to the present invention, since an ultrashort pulse laser beam is used, the halogenated molecule can be ionized regardless of the type of the halogenated molecule to be measured. There is no need to adjust the pulse laser beam depending on the type of the laser beam.

In addition, if the measurement sample is set to a condition that can be gasified, the sample can be analyzed, so that the time and cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing conditions of a time-of-flight mass spectrometer used in the present invention.

FIG. 2 is a graph showing the relationship between mass-to-charge ratio (m / z) and ionic strength in Examples.

FIG. 3 shows peaks indicating product ions at each laser intensity.

FIG. 4 shows the focusing intensity of the ultra-short laser beam and (C ₆ HC
l ₅ ) Graph showing the relationship between the amount of parent peak (54 μs) indicating ⁺

[Explanation of symbols]

 Reference Signs List 1 sample molecule 2 first accelerator 3 second accelerator 4 reflectron 5 MCP 6 oscilloscope

Claims (4)

[Claims] 1. A method for irradiating a halogenated molecule with an ultrashort pulse laser beam, measuring the ion intensity of a product ion derived from the halogenated molecule generated by the irradiation using a mass spectrometer, and measuring the ion intensity. A method for measuring the concentration of a halogenated molecule from the above. 2. The light intensity of the ultrashort pulse laser beam is 10 ¹² to 10 ¹⁶ Wcm ⁻² , and the pulse width is 1 to 10 Wcm ^−2.
The method for measuring the concentration of a halogenated molecule according to claim 1, which is 00 fs. 3. The method according to claim 1, wherein the mass spectrometer is a time-of-flight mass spectrometer. 4. A measuring device for measuring the concentration of a halogenated molecule, comprising a laser device for emitting an ultrashort pulse laser beam and a mass spectrometer.