JP2001108663A - Method for analyzing low molecular compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To analyze a low molecular compound without necessity of complicated pretreatment by off-line. SOLUTION: First, switching valves V1, V2 are set to a solid line state, and a sample is filled from a sample filling unit 3. The sample is separated in a GPC column 4, and introduced into a loop 7 for a trap. When a predetermined substance component flows to a UV detector 5, the valves V1, V2 are switched from a solid line to a dotted line after a predetermined time from this time point, and an eluate in the loop 7 is filled in a PTV injector 17. When the filling is finished, the valves V1, V2 are switched from the dotted line to the solid line, the predetermined component is vaporized, and sent to a GC column 17 with carrier gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for analyzing low molecular compounds such as pesticides, additives, and environmental hormones contained in foods such as agricultural products.

[0002]

2. Description of the Related Art If pesticides remain in agricultural products such as vegetables, there is a possibility that human health may be impaired gradually.
Consumer interest in pesticide residues is growing. In response, the Ministry of Health and Welfare has set pesticide residue standards. Against this background, in order to supply crops that are guaranteed to be safe, it is necessary to determine whether the concentration of pesticide residues is below an acceptable level within a limited time from when the crop is harvested until it is shipped. Accurate determination is required.

Conventionally, when analyzing pesticides and the like contained in foods such as agricultural products, extraction and concentration with a solvent or gel permeation chromatography (GPC) are performed as pretreatment.
After separation by the cleanup method and off-line concentration, a liquid chromatograph (LC), a gas chromatograph (GC), a gas chromatograph-mass spectrometer (GC
-MS).

[0004]

However, in the conventional analysis method, since the pre-processing is off-line, the operation is complicated and time-consuming, and the low-concentration target component may be lost during the pre-processing. In particular, in the pretreatment of extraction and concentration with a solvent, impurities such as lipids and dyes cannot be removed when food is used, so that chromatography columns and detectors used for analysis are damaged.

Accordingly, the present invention provides a novel analytical method which eliminates the complexity of the pretreatment operation when analyzing low molecular compounds such as pesticides, additives, and environmental hormones contained in foods such as agricultural products. Aim.

[0006]

In order to solve the above-mentioned problems, the present invention separates a low-molecular compound in a sample from contaminants using a column for liquid chromatography (LC), and then elutes the low-molecular compound containing the low-molecular compound. This is a method for analyzing low molecular weight compounds, in which a part or all of a liquid fraction is introduced into a sample vaporization chamber for gas chromatography (GC), vaporized, and then analyzed by a GC column.

Here, the low-molecular compound is, for example, a pesticide,
It refers to additives, environmental hormones, etc., and is a concept that is contrary to the general term of high molecular compounds such as polymers. The pesticide is a concept including not only the pesticide itself before spraying but also the residual pesticide contained in foods such as agricultural products. Also, the additive
For example, it refers to additives such as various dyes contained in food, preservatives such as benzoic acid and sorbic acid, and antioxidants such as BHT and BHA. Environmental hormones are called endocrine disrupting substances, and dioxins and the like are typical.

As an LC column, for example, GP filled with polystyrene gel, polyvinyl alcohol gel or the like is used.
A column for C, a column for reverse phase chromatography having an octadecyl group, a column for normal phase chromatography filled with silica gel, and the like can be used, but are not limited thereto. The eluent (mobile phase) is selected according to the column and the substance to be analyzed. For example, when analyzing pesticide residues in food, a shodex CLNpak EV filled with polystyrene hard gel is used as a column, and a mixed solution of acetone and cyclohexane is used as an eluent. Also, BHT and B
When analyzing additives in foods such as HA, use a column
Shim-pack GPC is used, and tetrahydrofuran is used as an eluent. Furthermore, when analyzing environmental hormones such as phthalate esters, shodex CLNpak PAE packed with polyvinyl alcohol gel is used as a column, and acetone or acetonitrile is used as an eluent.
In addition, as a detector for LC, a differential refractometer, an ultraviolet-visible absorptiometer, etc. can be used.

The eluate fraction containing the low-molecular compound from the LC column is introduced into the sample vaporization chamber for GC. At this time, the eluate fraction containing the low-molecular compound is split to obtain an arbitrary width and amount. It is preferable to adjust to. Here, "width" means
The horizontal axis of the chromatogram, that is, the elution time.
Therefore, the eluate from the LC column is introduced into the GC sample vaporization chamber for an arbitrary time or an arbitrary amount by splitting. The splitting is performed by providing a resistance tube branched from the outlet channel to the LC column outlet and adjusting the resistance ratio.

The GC sample vaporization chamber holds and evaporates the eluate from the LC column, and is provided with a PTV (Programmed
Temperature Vaporizer) injectors are preferred. P
TV is a method in which a sample is introduced into a sample vaporization chamber in a liquid state, and the sample is not instantaneously vaporized in the vaporization chamber as in the case of split / splitless injection. This is an injection method that allows the injection amount to be much larger than the split / splitless injection. In the PTV injector, a filler or silica wool is stored in the insert in order to hold the sample in the glass insert in the vaporization chamber. T as filler
ENAX GC or the like is used.

As the GC column, any of a capillary column and a packed column may be used, and the liquid phase is appropriately selected depending on the component to be analyzed. For example, when analyzing a phthalate, methyl silicon is used. Also, GC
As the detector for use, any detector such as a thermal conductivity detector, a flame ionization detector, and an electron capture detector can be used.

[0012]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of the apparatus of the present invention. Reference numeral 4 denotes a GPC column, which is adjusted to a constant temperature in a column thermostat 41. A sample injector 3 is connected to one end of the GPC column 4, and the injected sample is introduced into the GPC column 4 by the liquid sending pump 2 together with the mobile phase in the mobile phase reservoir 1. Note that a deaerator 6 is provided between the mobile phase reservoir 1 and the liquid sending pump 2 to remove bubbles in the mobile phase. GPC
The UV detector 5 is connected to the elution end of the column 4, and the outlet side flow path 10 of the UV detector 5 is connected to the flow path switching valve V1. Further, a part of the flow path 10 is branched, and a resistance pipe R1 whose one end is open to the atmosphere is connected to the branched flow path 11.

The above-described flow path 10, trap loop 7, resistance tube R2, sample injection flow path 12, and GC connection flow path 13 are connected to each port of the flow path switching valve V1, respectively. A first loop composed of a trap loop 7 and a resistance tube R2
The flow path and the second flow path including the sample injection flow path 12 and the GC connection flow path 13 can be switched. Note that the resistance of the resistance tube R2 is determined in relation to the resistance tube R1.
The width and amount of the eluate entering the trap loop 7 can be adjusted by the resistance ratio (split ratio) between the resistance tubes R1 and R2. The sample injection flow path 12 is provided with a sample injection liquid reservoir 8, a deaerator 14, a sample injection pump 9, and a resistance tube R3. 8 and is sent to the GC connection channel 13. The extrusion speed of the sample can be controlled by adjusting the flow rate of the sample injection pump.

Reference numeral 17 denotes a PTV injector, and a glass insert (not shown) for holding a sample therein.
And a heater (not shown) is provided on the outer periphery of the PTV injector 17. PTV
The temperature inside the injector 17 is controlled to a predetermined program temperature by controlling the heater using a controller (not shown). Further, reference numeral 16 denotes a septum, through which the sample introduction channel 15 is inserted. The tip of the sample introduction channel 15 is located in the glass insert.

The PTV injector 17 is provided with a carrier gas supply port 22 to which a carrier gas flow path 20 is connected. This carrier gas flow path 20
The sample switching channel 15 and the carrier gas introducing channel 21 are switched and connected by the channel switching valve V2.

Reference numeral 18 denotes a GC column (capillary column) connected to the PTV injector 17, and a GC detector (for example, FPD) 19 is connected to the elution end of the capillary column 18. The capillary column 18
It is housed in a thermostat (not shown) and controlled according to a predetermined temperature program.

With the above configuration, the analysis of the sample is performed as follows. First, the sample is injected from the sample injector 3 by setting the flow path switching valves V1 and V2 to the solid line state in the figure. The sample is
For example, it is a food extract and is injected with a manual or auto injector. The sample flows into the GPC column 4 together with the mobile phase supplied from the mobile phase reservoir 1, and is separated based on the molecular weight and the adsorption action on the packing material,
For example, it enters the UV detector 5 as a group of a pesticide and a lipid / dye.

The eluate eluted from the GPC column 4 flows into the trapping loop 7 at a ratio (split ratio) determined by the flow path resistance of the resistance tube R1 and the flow path resistance of the resistance tube R2, and the remainder is the resistance tube. It is discharged out of the system via R1.

When the eluate passes through the UV detector 5 and a predetermined component (for example, a pesticide component) flows into the UV detector 5, a predetermined time from this time, that is, until the pesticide component flows into the trapping loop 7, After the time elapses, the flow path switching valve V1 is switched from the solid line to the dotted line. For example, when the concentration of the pesticide is sufficiently high, a part is split by the action of the resistance tubes R1 and R2.
One end may be covered with a black plug and the whole amount may be trapped in the trap loop 7 and injected.

When the flow path switching valve V1 is switched from the solid line to the dotted line, the flow path switching valve V2 is also switched from the solid line to the dotted line, and the eluate in the trap loop 7 is injected into the glass insert of the PTV injector 17 by the sample injection liquid. I do. The temperature inside the PTV injector 17 before the injection is set near the boiling point of the solvent used as the GPC mobile phase.

At the end of the injection, the flow path switching valve V
1 and V2 are switched from the dotted line to the solid line, and the PTV
The temperature in the injector 17 is increased according to a predetermined program, and is vaporized for each pesticide component, for example, and sent to the capillary column 18 by a carrier gas. Capillary column 18
The pesticide components that have entered are separated and used for GC detectors (FP
D) Detected at 19. Here, the capillary column 18
Is increased in accordance with a predetermined temperature program in the same manner as the temperature control in the PTV injector 16.

In the above description, the switching control of the flow path switching valves V1 and V2 is automatically switched while monitoring signals from the UV detector 5 and the like.

[0023]

EXAMPLES Corn oil, .beta.-carotene and phosphorus-based pesticides were analyzed under the analysis conditions shown in Table 1. In this analysis, GPC
After separating corn oil, β-carotene and phosphorus-based pesticides by a column, the pesticide fraction is introduced into a PTV injector to analyze the pesticide components. The pesticide fraction was split at 1/6
And those introduced into the PTV injector without splitting and those introduced into the PTV injector without splitting were analyzed.

[0024]

[Table 1]

The analysis results are shown in FIGS. FIG.
This is a chromatogram detected by a UV detector (SPD-10Avp) after separation by a PC column. In the figure, the horizontal axis indicates elution time, and the vertical axis indicates signal intensity. As is clear from this chromatogram, the phosphorus-based pesticide, corn oil and β-carotene are separated on the GPC column. FIG.
Split the pesticide fraction from the eluate of the PC column to P
The chromatogram when injected into the TV injector (the horizontal axis is the elution time, the vertical axis is the signal intensity in the figure), and FIG. 4 is the chromatogram when the whole amount was injected into the PTV injector without splitting the pesticide fraction (in the figure , The horizontal axis is the elution time, and the vertical axis is the signal intensity). It can be seen that the pesticide components can be analyzed by any means.

[0026]

According to the present invention, troublesome off-line pretreatment operations are not required, and for example, pesticides and other components can be analyzed by one sample injection.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of the apparatus of the present invention.

FIG. 2 Chromatogram after separation by GPC column

FIG. 3 is a chromatogram obtained when the pesticide fraction of the eluate of the GPC column is split and injected into the PTV injector

FIG. 4 is a chromatogram obtained when the entire amount of the eluate of the GPC column was injected into the PTV injector without splitting the pesticide fraction.

[Explanation of symbols]

 3: Sample injector 4: GPC column 7: Loop for trap V1, V2: Channel switching valve 17: PTV injector 18: Capillary column

Claims (3)

[Claims] After separating a low-molecular compound and a contaminant in a sample by a liquid chromatography column, a part or all of an eluate fraction containing the low-molecular compound is introduced into a gas chromatography sample vaporization chamber. A method for analyzing low molecular weight compounds, wherein the analysis is performed by a gas chromatography column after vaporization. 2. The method for analyzing low molecular compounds according to claim 1, wherein the low molecular compounds are pesticides, additives and environmental hormones. 3. The method according to claim 1, wherein the eluate fraction containing the low-molecular compound to be introduced into the sample vaporization chamber for gas chromatography is split and introduced into the gas vaporization sample vaporization chamber in an arbitrary width and quantity. 3. The method for analyzing a low-molecular compound according to 1 or 2.