JP4186290B2 - Sample introduction device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a suitable gas chromatograph using a analysis of particular volatile organic compounds in water.
[0002]
[Prior art]
In recent years, there is an increasing demand for analysis of organic chlorinated solvents such as dichloromethane in groundwater, river water, or factory effluent. Conventionally, gas chromatography is generally used as an analytical method to measure the concentration of these trace volatile organic compounds in water, but the headspace method is known as a method for introducing a sample into this. In the headspace method, sample water is sealed in a sample bottle with a septum lid while leaving some space at the top, and this is kept at a predetermined temperature for a predetermined time, and then the gas in the upper space (headspace) is syringed. It is a method of collecting and analyzing with. Using the difference in vapor pressure between the target component of analysis and water, the target component is extracted from the liquid phase (in water) to the gas phase (headspace), enabling sampling in the gas phase suitable for gas chromatography. To do.
[0003]
[Problems to be solved by the invention]
As described above, the headspace method can sample volatile components in water by a relatively simple method. However, it takes a long time to equilibrate the concentration in the gas phase and the concentration in the liquid phase of the analysis target component. . Further, since the target component remains in water to some extent, gas-liquid equilibrium is established, so that the total amount of the target component in water cannot be extracted. Furthermore, there are some problems that sufficient quantitativeness cannot be ensured unless the temperature and temperature are strictly controlled. The present invention has been made in view of such circumstances, provide a gas chromatograph can be more quickly in water of trace volatile organic compounds, yet be introduced taking out almost all in the vapor phase The purpose is to do.
[0004]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a vaporizer that heats and vaporizes sample water containing a volatile organic compound that is fed by a pump, and a vapor flow that vaporizes the sample water on the outlet side thereof. wherein a gas supply portion for mixing the inert gas at a constant flow rate, a condenser to cool the mixed gas stream to condense water, the condensed water and a separator for separating from the gas, introducing said gas component It is a gas chromatograph .
[0005]
The gas chromatograph according to the present invention is a method for extracting a trace amount of a target component for analysis as a gas phase by vaporizing the whole sample water to form water vapor, mixing it with an inert gas, and cooling to condense and remove the water. Therefore, almost all of the target component remains in the gas phase, so the quantitative property is high. Also, the time required for processing is greatly reduced.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention is shown in FIG. In the figure, reference numeral 1 denotes a pump (for example, a syringe pump) having a characteristic of feeding at a constant flow rate, and feeds sample water from the sample container 2 toward the vaporizer 10 at a flow rate of several ml per minute.
[0007]
The vaporizer 10 is a kind of heat exchanger, and the heating coil 11 in the vaporizer 10 is heated by an electric heater (not shown) or by a heat medium such as steam. Vaporizes into the pressure adjustment chamber 12 as water vapor. The pressure adjustment chamber 12 is a container that alleviates a sudden rise in pressure caused by vaporization and absorbs pressure fluctuations due to non-uniform vaporization, thereby smoothing the pressure. Heated in the same manner as 11. Water droplets remaining without being sufficiently vaporized in the heating coil 11 are also separated here. Inert gas (helium, nitrogen, etc.) supplied from the gas cylinder 3 is adjusted to a constant flow rate by the flow rate regulator 4 and merged with the flow of water vapor that has exited the pressure regulating chamber 12, and then enters the condenser 20. .
[0008]
The condenser 20 is also a heat exchanger, in which the cooling water 23 is forcedly circulated by a pump (not shown), so that the gas passing through the cooling coil 21 is cooled, the water vapor is condensed and returned to the water, It falls on the separator 22. Since the drain valve 24 provided at the outlet 22b at the bottom of the separator 22 is closed at this point, the condensed water accumulates at the bottom of the separator 22 and the remaining gas components (inert gas and volatile organic substances in the sample water). Flows out from the outlet 22 a at the top of the separator 22 and enters the gas chromatograph 30. That is, after passing through the sample pipe 25 of the gas chromatograph 30 (heated so that the slight remaining water vapor does not condense), it passes through the flow path indicated by the solid line of the 6-port gas sampling valve 32 and flows through the measuring pipe 33. The gas is discharged from the vent 36.
[0009]
The carrier gas of the gas chromatograph 30 is adjusted from the gas cylinder 3 of the inert gas by the flow rate regulator 31 and flows to the column 34 and the detector 35 through the gas sampling valve 32. When the gas sampling valve 32 is rotated 60 degrees in the clockwise direction, the flow path is switched from the state shown by the solid line to the state shown by the dotted line, and the flow of the carrier gas changes so as to pass through the measuring pipe 33. A certain amount of the gas component (inert gas and volatile organic substance in the sample water) determined by the inner volume of the measuring tube 33 remaining in the sample is transported toward the column 34 by the carrier gas, whereby sampling in the gas chromatograph 30 is performed. Is done.
[0010]
Among the gas components sampled here, the inert gas is the same substance as the carrier gas, so it is not subject to analysis, and only a small amount of volatile organic substances derived from the sample water are included in each component in the column 34. After being separated, the amount is converted into an electrical signal by the detector 35 and recorded by a recording device (not shown) or processed as analysis data. In this type of analysis, a flame ionization detector or an electron capture detector is often used as the detector 35, but these detectors are selectively sensitive to organic substances and halogen compounds, respectively. Therefore, even if a slight amount of water vapor remaining in the gas component reaches the detector, it is not output as data due to the selectivity of the detector 35. Quantification is possible by introducing an aqueous solution of a known concentration of a standard substance and performing calibration.
[0011]
After the sampling, while the analysis by the gas chromatograph 30 is being performed, the drain valve 24 is opened to discharge the water accumulated in the separator 22, and the sample container 2 becomes a sample container for the sample water to be analyzed next. Replaced. The replacement of the sample container 2 can be automated by using an automatic device such as a liquid handler, and the above-described series of analysis operations can be automatically performed by the program control device.
[0012]
In the above example, the amount of sample actually analyzed by the gas chromatograph 30 is only an amount equivalent to the internal volume of the measuring tube 33 (generally several ml), but instead of the measuring tube, a known trap packed with an adsorbent is used. When a collecting tube is used, a larger amount of an organic substance can be taken in and used for analysis, so that detection sensitivity can be further increased and even a trace amount of components can be quantified.
[0013]
As described above, according to the present invention, an analysis target component having a boiling point lower than that of water is eliminated by mixing and cooling an inert gas after sample water is continuously flowed and then cooling to remove moisture. Since it is essential to take it out into the active gas, introduce it into the gas chromatograph and analyze it, the details of the device configuration are not limited to those illustrated in FIG. 1, and various modifications are conceivable. Such variations are encompassed by the present invention within the scope of claim 1.
[0014]
【The invention's effect】
Since the present invention is configured as described above, the pretreatment process in the analysis of volatile organic compounds in water, which required 15 to 60 minutes in the conventional headspace method, can be completed in 2 to 3 minutes. Thus, the total analysis time including pre-processing can be greatly shortened. In addition, since the entire amount of the sample water is vaporized once, almost the entire amount of the analysis target component in the sample water can be taken out into the gas phase, which is superior in quantitative performance as compared with the conventional method.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Pump 2 ... Sample container 3 ... Gas cylinder 4 ... Flow regulator 10 ... Vaporizer 11 ... Heating coil 12 ... Pressure regulation chamber 20 ... Condenser 21. ..Cooling coil 22 ... Separator 30 ... Gas chromatograph

Claims (1)

“A vaporizer that heats and vaporizes sample water containing volatile organic compounds being pumped and a gas supply that mixes a constant flow of inert gas into the vapor stream vaporized from the sample water at its outlet side. And a condenser for cooling the mixed airflow to condense water, and a separator for separating the gas component containing the condensed water and the volatile organic compound, and introducing the gas component. Graph .

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