Method for preparing sample for analyzing residual pesticide

Abstract

The preparation of a sample for analyzing residual pesticide in caffeine-containing food such as tea comprises the steps of: extracting residual pesticide from food using an organic water-soluble extraction solvent to obtain an extract; a step of obtaining a mixture of a silica gel containing a powdered ion exchange group-modified carbon-containing material, a treatment agent of the silica gel containing the powdered carbon-containing material, an extract, and an organic purification solvent capable of dissolving a residual pesticide; and a step of separating a part of the liquid component from the mixture. The ion exchange group of the powdery ion exchange group modified silica gel containing the carbon material is an amine functional group with anion exchange capacity, such as 3-(2-aminoethylamino) propyl or 3-aminopropyl.

Description

Technical Field

[0001] This application claims priority based on Japanese Patent Application No. 2022-144699 filed in Japan on September 12, 2022, the contents of which are incorporated herein by reference.

[0002] The present invention relates to a method for preparing a sample for analysis of residual pesticides, and in particular to a method for preparing a sample for simultaneous analysis of residual pesticides in food using a mass spectrometer. Background Art

[0003] In 2006, Japan implemented the so-called Positive List System, which in principle prohibits the sale of foods containing pesticides and other residues exceeding the prescribed amount. Among various pesticides, residual standard values ​​are set for all about 800 pesticides except for some pesticides that are clearly not harmful to human health. Therefore, it is required to simultaneously analyze about 800 pesticides for foods sold, and the Ministry of Health, Labor and Welfare of Japan notified the test method for this purpose (Non-Patent Document 1).

[0004] The simultaneous test method notified by the Ministry of Health, Labor and Welfare of Japan (hereinafter referred to as the "notified method") is basically composed of the following steps: a sample preparation step for homogenizing a food sample by crushing it; an extraction step for extracting residual pesticides from the prepared sample; a purification step for removing impurities from the extract obtained in the extraction step; and a measurement / analysis step for analyzing the test solution obtained in the purification step. In the extraction step, a solvent (acetonitrile) is added to the sample homogenized in the sample preparation step for homogenization, and then suction filtration is performed. Then, the filtrate is subjected to salting out and the solvent is removed, and the residue obtained thereby is dissolved in the solvent (acetonitrile) to prepare an extract. In the purification step, the extract obtained in the extraction step and a mixed solvent of acetonitrile and toluene are sequentially injected into a graphite carbon / aminopropyl silylated silica gel laminated microcolumn to obtain an eluent from the microcolumn. Then, the solvent is removed from the eluent, and the obtained residue is dissolved in a prescribed solvent to prepare a prescribed amount of a test solution. In the measurement / analysis step, the prepared test solution is analyzed by a mass spectrometer, specifically, by GC-MS, GC-MS / MS, LC-MS, or LC-MS / MS, thereby simultaneously evaluating the pesticides contained in the food sample.

[0005] However, the notification method is to prepare a test solution that is compatible with both GC-MS and LC-MS, so the operations in the purification step are many and complicated. For example, since a microcolumn is used, a large amount of organic solvent is required, and the operation of removing the solvent must be repeated. In particular, since the operations in the purification step are complicated, it takes a long time to prepare the required test solution, and the reliability of the test solution varies depending on the proficiency and skills of the operator.

[0006] Therefore, as a method for obtaining an analytical sample for simultaneous testing in a relatively short time by simple operation, an improved method (hereinafter referred to as "improved method") (non-patent document 2) combining the QuEChERS method (キャッチャーズ method) and the dispersed solid phase extraction method has been proposed. The improved method is also adopted in the EU standard (non-patent document 3), and is gradually being adopted by food operators in Japan, etc., as a synchronous testing method for residual pesticides in place of the notification method.

[0007] The improved method comprises the following steps: an extraction step for extracting residual pesticides from a food sample; a purification step for the extract obtained in the extraction step; and a measurement / analysis step for analyzing the extract obtained in the purification step. In the extraction step, acetonitrile is added to the food sample, and residual pesticides are extracted by shaking. A salt is added to the extract obtained by shaking, so that water and acetonitrile are separated, and residual pesticides contained in the extract are transferred to the acetonitrile layer, and highly polar impurities are transferred to the water layer. In the purification step, the extract is added / dispersed to a powdered or granular solid phase containing ethylenediamine-N-propylsilylated silica gel and graphite carbon and magnesium sulfate that can adsorb impurities contained in the extract obtained and treated in the extraction step, and then centrifuged. Then, in the measurement / analysis step, the supernatant obtained by centrifugation in the purification step is analyzed using a mass spectrometer in the same manner as the notification method, and the pesticides contained in the food sample are evaluated simultaneously.

[0008] The improved method removes impurities contained in the extract by adding / dispersing the extract into the solid phase. Therefore, the operation is simpler than the notification method using a microcolumn, and the sample for analysis (test solution) can be prepared in a short time. However, this purification step is a dispersed solid phase extraction, so impurities such as food matrix, especially caffeine or catechins contained in tea, are likely to remain in the test solution, and the obtained test solution may sometimes significantly contaminate the column or detector of the mass spectrometer due to impurities. Therefore, according to the improved method, frequent maintenance operations such as cleaning of the mass spectrometer are required.

[0009] Prior art literature

[0010] Non-patent literature

[0011] Non-patent document 1: Notice of the Director-General of the Food Safety Bureau of the Ministry of Health, Labor and Welfare, Food and Drug Administration, No. 0124001, January 24, 2005, "Testing Methods for Residues of Pesticides, Feed Additives or Substances as Components of Animal Pharmaceuticals in Foods" (Notice of the Director-General of the Food Safety Bureau of the Ministry of Health, Labor and Welfare, Food and Drug Administration, No. 0124001, January 24, 2005, "Testing Methods for Residues of Pesticides, Feed Additives or Substances as Components of Animal Pharmaceuticals in Foods")

[0012] Non-patent document 2: SUNATEC, a general foundation for food analysis and development, "About the QuEChERS method", [searched on August 19, 2022], Index (SUNATEC, a general foundation for food analysis and development, "About the QuEChERS method", [searched on August 19, 2022], website) (URL: http: / / www.mac.or.jp / mail / 140401 / 03.shtml)

[0013] Non-patent document 3: European standard EN 15662, Foods of Plant Origin-Multimethod for the determination of pesticide residues using GC-and LC-based analysis following acetonitrile extraction / partitioning and clean-up by dispersive SPE-Modular QuEChERS-method Summary of the invention

[0014] Problems to be solved by the invention

[0015] The present invention aims to easily prepare an analysis sample that suppresses contamination of a mass spectrometer when performing simultaneous analysis of residual pesticides in food using a mass spectrometer.

[0016] Means for solving problems

[0017] The present invention relates to a method for preparing a sample for simultaneous analysis of residual pesticides in food using a mass spectrometer. The preparation method comprises the following steps: a step of extracting residual pesticides from food using an organic water-soluble extraction solvent and obtaining an extract; a step of obtaining a mixture of a treatment agent containing silica gel of a carbonaceous material modified with a powdered ion exchange group, an extract and an organic purification solvent capable of dissolving the residual pesticides; and a step of separating a portion of the liquid component from the mixture. The ion exchange group of the silica gel of the carbonaceous material modified with a powdered ion exchange group contained in the treatment agent used here is an amine functional group having an anion exchange capacity.

[0018] The amine functional group having anion exchange ability is, for example, 3-(2-aminoethylamino)propyl or 3-aminopropyl.

[0019] The powdered ion exchange group-modified silica gel of carbon-containing material contained in the treatment agent used in the present invention is usually prepared by a method including the step of further treating the silica gel of the carbon-containing material with a silane coupling agent having an amine functional group with anion exchange capacity, and the silica gel of the carbon-containing material is prepared by a method including the steps of adding hydrochloric acid to a sodium silicate aqueous solution to which the carbon material is added to gelate it and further adding hydrochloric acid until the pH of the gelled reaction system is less than 2.

[0020] The powdery ion exchange group-modified carbonaceous material contained in the treatment agent used in the present invention contains, for example, silica gel having a specific surface area of ​​700 to 1,700 m 2 / g of the first carbon material, and the specific surface area is 100 to 300 m 2 / g, and when 1g of it is added to 5mL of pure water, the pH of the pure water is changed to the alkaline region. When the powdery ion exchange group-modified carbonaceous material silica gel is in such a form, the content ratio of the first carbon material in the powdery ion exchange group-modified carbonaceous material silica gel is usually 5 to 50% by mass.

[0021] In one embodiment of the method for preparing a sample for analysis of residual pesticides according to the present invention, the treatment agent may further contain silica gel which is a powdery carbonaceous material.

[0022] The silica gel of the powdered carbon-containing material used in this case is usually prepared by a method comprising the following steps: a step of adding hydrochloric acid to an aqueous sodium silicate solution to which the carbon material is added to gelate it; and a step of further adding hydrochloric acid until the pH of the gelled reaction system is less than 2.

[0023] The powdered carbonaceous material contained in the treatment agent used in this method contains, for example, silica gel having a specific surface area of ​​700 to 1,700 m 2 / g of the second carbon material, and a specific surface area of ​​700 to 900 m 2 / g, and when 1g of it is added to 5mL of pure water, the pH of the pure water is changed to the acidic region. When the silica gel of the powdery carbon-containing material is in such a form, the content ratio of the second carbon material in the silica gel of the powdery carbon-containing material is usually 0.5 to 10% by mass.

[0024] In the method for preparing an analytical sample of the present invention, when the food is a food other than a caffeine-containing food, it is preferred to use acetonitrile as the water-soluble extraction solvent and to use a mixed solvent of toluene and acetonitrile or acetonitrile as the purification solvent.

[0025] In addition, in the method for preparing a sample for analysis of the present invention, when the food is a caffeine-containing food, a processing agent is used that contains silica gel containing powdered carbon-containing material in addition to silica gel containing powdered ion-exchange group-modified carbon-containing material, and acetonitrile is used as a water-soluble extraction solvent, and a mixed solvent of acetone and hexane is used as a purification solvent.

[0026] The present invention according to another aspect is directed to a treatment agent for purifying an organic water-soluble solvent containing residual pesticides extracted from food. The treatment agent comprises silica gel of a carbonaceous material modified with a powdered ion exchange group, wherein the ion exchange group of the silica gel of the carbonaceous material modified with a powdered ion exchange group is an amine functional group having an anion exchange capacity.

[0027] The amine functional group of the ion exchange group of the silica gel as the powdery ion exchange group-modified carbonaceous material is, for example, 3-(2-aminoethylamino)propyl or 3-aminopropyl.

[0028] The powdery ion exchange group-modified carbonaceous material contained in the purification treatment agent of the present invention contains, for example, silica gel having a specific surface area of ​​700 to 1,700 m 2 / g of the first carbon material, and the specific surface area is 100 to 300 m 2 / g, and when 1g of it is added to 5mL of pure water, the pH of the pure water changes to the alkaline region. When the powdery ion exchange group-modified carbonaceous material silica gel is in this form, the content ratio of the first carbon material in the powdery ion exchange group-modified carbonaceous material silica gel is usually 5 to 50% by mass.

[0029] One embodiment of the purification treatment agent of the present invention may further contain silica gel as a powdery carbonaceous material.

[0030] The powdered carbonaceous material contained in the purification treatment agent of this embodiment contains, for example, silica gel having a specific surface area of ​​700 to 1,700 m 2 / g of the second carbon material, and a specific surface area of ​​700 to 900 m 2 When 1 g of the silica gel is added to 5 mL of pure water, the pH of the pure water changes to an acidic region. When the silica gel of the powdery carbon-containing material is in such a form, the content of the second carbon material in the silica gel of the powdery carbon-containing material is usually 0.5 to 10% by mass.

[0031] Effects of the Invention

[0032] The method for preparing a sample for analysis of residual pesticides involved in the present invention is to mix an extract obtained by extracting residual pesticides from food using an organic water-soluble extraction solvent, a treatment agent containing silica gel of a powdered carbonaceous material modified with a specific ion exchange group called an amine functional group having anion exchange capacity, and an organic purification solvent that can dissolve the residual pesticides, thereby making it possible to easily prepare an analytical sample for simultaneous testing of residual pesticides in food, and the analytical sample can suppress contamination of a mass spectrometer.

[0033] The purification treatment agent for the organic solvent containing residual pesticides involved in the present invention comprises silica gel which is a powdered carbonaceous material modified with a specific ion exchange group called an amine functional group having anion exchange capacity. Therefore, if it is used in the method for preparing analytical samples of the present invention, analytical samples for simultaneous testing of residual pesticides in food can be easily prepared, and the analytical samples can suppress contamination of a mass spectrometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] [ Figure 1 ] is a graph showing the removal rate of each inclusion compound when 9 inclusion compounds are mixed in Experimental Example A.

[0035] [ Figure 2 ] is a GC-MS scanning chromatogram when green tea is mixed in Experimental Example A.

[0036] [ Figure 3 ] is the GC-MS scanning chromatogram of Experimental Example B.

[0037] [ Figure 4 ] is a graph showing the removal rate of each inclusion compound when 9 inclusion compounds are added to the silica gel I of the carbon-containing material in Experimental Example E.

[0038] [ Figure 5 ] is a graph showing the removal rate of each inclusion compound when 9 inclusion compounds were added to the silica gel of the carbonaceous material modified with ion exchange groups in Experimental Example E.

[0039] [ Figure 6 ] is a graph showing the removal rate of each inclusion compound regarding Experimental Example G. DETAILED DESCRIPTION

[0040] The method for preparing samples for synchronous analysis of residual pesticides in food is to prepare analytical samples for synchronous evaluation of residual pesticides in food using a mass spectrometer, such as a gas chromatograph-mass spectrometer such as GC-MS or GC-MS / MS or a liquid chromatograph-mass spectrometer such as LC-MS or LC-MS / MS, and mainly includes the following steps 1 to 3.

[0041] (Step 1)

[0042] In this step, residual pesticides are extracted from food using an organic water-soluble extraction solvent to obtain an extract. The food from which residual pesticides are extracted is various crops, edible meat, fish and shellfish, or processed products thereof, and the type is not particularly limited. In order to extract residual pesticides, the required amount is usually crushed or chopped into a fine state and homogenized.

[0043] Extraction of residual pesticides from food can generally be performed according to the method adopted in the Notification Method or the QuEChERS method. That is, in these methods, first, an extraction solvent is added to a required amount of a homogenized food sample for homogenization to prepare a slurry. In the Notification Method or the QuEChERS method, as an extraction solvent, a highly polar water-soluble organic solvent such as acetonitrile, methanol or acetone that can dissolve residual pesticides and is easily soluble in water is generally used. In the present invention, a water-soluble organic solvent can also be used as an extraction solvent, but from the perspective of the small amount of lipids dissolved as an inclusion component in the simultaneous analysis of residual pesticides, it is preferred to select acetonitrile, which is mostly used as an extraction solvent in the simultaneous analysis of residual pesticides.

[0044] Next, in the notification method, the obtained slurry is subjected to suction filtration to obtain a filtrate, i.e., an extract of residual pesticides. The extract is usually adjusted to pH by adding phosphate buffer and sodium chloride, and salting out is performed at the same time to separate it into an organic solvent layer and an aqueous layer. Then, the separated organic solvent layer is used as an extract of residual pesticides. On the other hand, in the QuEChERS method, salt is added to the obtained slurry to separate it into an organic solvent layer and an aqueous layer. The salt used here is sodium chloride, trisodium citrate or its hydrate, disodium hydrogen citrate or its hydrate, anhydrous magnesium sulfate, magnesium sulfate, anhydrous sodium sulfate, sodium sulfate, anhydrous sodium acetate or sodium acetate, etc. These salts can also be used in combination. Then, the separated organic solvent layer is centrifuged to separate it into a solid component and a liquid component, and the liquid component is used as an extract of residual pesticides.

[0045] (Step 2)

[0046] In this step, the extract obtained in step 1 is mixed with a treatment agent and an organic purification solvent capable of dissolving residual pesticides to obtain a mixture. The treatment agent used here comprises powdered silica gel of a carbonaceous material modified with ion exchange groups.

[0047] The silica gel of the carbon-containing material modified with the ion exchange group contained in the treatment agent has an amine functional group having anion exchange ability as an ion exchange group. The amine functional group having anion exchange ability is not particularly limited, and is, for example, 3-(2-aminoethylamino)propyl or 3-aminopropyl. The silica gel of the carbon-containing material modified with the ion exchange group can use two or more silica gels of carbon-containing materials having different amine functional groups having anion exchange ability.

[0048] The silica gel of the carbon-containing material modified with the ion exchange group can be prepared by preparing silica gel of the carbon-containing material in powder form and treating the silica gel of the carbon-containing material with a silane coupling agent having an amine functional group having an anion exchange capacity.

[0049] Specifically, the silica gel of the powdered carbon-containing material is a powdered product prepared by a method including the following steps: step A of adding hydrochloric acid to an aqueous sodium silicate solution to which the carbon material is added to gelate it; and step B of further adding hydrochloric acid until the pH of the gelled reaction system is less than 2. The silica gel of the carbon-containing material prepared by this method is usually preferably the silica gel of the carbon-containing material which is washed with pure water and dried after being left for a predetermined time after the addition of hydrochloric acid in step B, thereby obtaining the silica gel of the powdered carbon-containing material. Then, the silica gel of the powdered carbon-containing material is added to an aqueous solution of a silane coupling agent, stirred, dehydrated, and the residue is dried to obtain the silica gel of the carbon-containing material modified with the target ion exchange group. As the silane coupling agent, for example, 3-(2-aminoethylamino)propyltrimethoxysilane, which can modify the silica gel of the carbon-containing material with a 3-(2-aminoethylamino)propyl group, or 3-aminopropyltriethoxysilane, which can modify the silica gel of the carbon-containing material with a 3-aminopropyl group, can be used.

[0050] The carbon material used in the preparation of the silica gel containing carbon material (hereinafter referred to as the "first carbon material") is in powder form, and it is preferable to select a carbon material with an appropriate specific surface area according to the impurities contained in the food. In the case where it is necessary to suppress the mixing of impurities from foods that easily impose a load on the mass spectrometer, such as caffeine or catechins contained in tea, into the analytical sample, it is preferable to select a carbon material with a larger specific surface area as the first carbon material. On the other hand, in the case where impurities from foods that easily impose a load on the mass spectrometer are not easily mixed into the analytical sample, it is preferable to select a carbon material with a smaller specific surface area as the first carbon material from the perspective of easily improving the recovery rate of residual pesticides. From this point of view, as the first carbon material, a specific surface area of ​​700 to 1,700 m2 is generally preferred. 2 / g of carbon material, especially 1,000 to 1,600 m 2 / g of carbon material.

[0051] The specific surface area is 700 to 1,700 m 2 / g of the first carbon material and the ion exchange group-modified carbon-containing silica gel prepared by the above method as a silica gel containing the first carbon material and having a specific surface area of ​​100 to 300 m 2 / g of powdered material. The powdered ion exchange group-modified carbonaceous material silica gel has the following characteristics: when 1g of the powdered ion exchange group is added to 5mL of pure water, the pH of the pure water changes to the alkaline region, usually to pH 8 to 10. The pure water used to confirm this characteristic is usually distilled water, pure water prepared by reverse osmosis membrane treatment, or ion exchange water, and the pH is generally 5 to 7.

[0052] From the viewpoint of suppressing the mixing of impurities into the analytical sample and improving the recovery rate of residual pesticides, the amount of the first carbon material used is usually preferably set to 5 to 50 mass % of the sodium silicate contained in the sodium silicate aqueous solution, and more preferably set to 5 to 20 mass %.

[0053] The treatment agent generally includes a powdered dehydrating agent in addition to silica gel containing a carbonaceous material modified with powdered ion exchange groups. The dehydrating agent is used to remove the water contained in the extract obtained in step 1, and examples thereof include magnesium sulfate, sodium sulfate, calcium sulfate, potassium carbonate and calcium chloride, preferably magnesium sulfate. It should be noted that if water remains in the extract, the purification effect of the treatment agent on the extract may be reduced, and the analysis in the mass spectrometer may be unstable. In the treatment agent, the content of the dehydrating agent is generally preferably set appropriately according to the amount of water contained in the extract.

[0054] The treating agent may further contain powdered carbonaceous silica gel in addition to the powdered ion exchange group-modified carbonaceous silica gel. When the food is tea containing caffeine as an impurity, the use of such a treating agent can easily suppress the mixing of caffeine into the analytical sample.

[0055] The silica gel of the carbon-containing material used here is a powdered silica gel of the carbon-containing material prepared by a method comprising the following steps: step A of adding hydrochloric acid to a sodium silicate aqueous solution to which the carbon material is added to form a gel; and step B of further adding hydrochloric acid until the pH of the gelled reaction system is less than 2. The silica gel of the carbon-containing material prepared by this method is usually preferably the silica gel of the carbon-containing material which is washed with pure water and dried after leaving it for a predetermined time after adding hydrochloric acid in step B, thereby obtaining the silica gel of the powdered carbon-containing material.

[0056] The carbon material used in the preparation of the silica gel containing carbon material (hereinafter referred to as the "second carbon material") is in powder form, and a carbon material with an appropriate specific surface area is selected from the same viewpoint as the first carbon material. Therefore, as the second carbon material, it is preferred to use a carbon material with the same specific surface area as the first carbon material, that is, a carbon material with a specific surface area of ​​700 to 1,700 m 2 / g of carbon material, especially 1,000 to 1,600 m 2The second carbon material may be a carbon material of another type having a different specific surface area from that of the first carbon material, or may be the same carbon material as the first carbon material.

[0057] The specific surface area is 700 to 1,700 m 2 / g of the second carbon material and the carbon material-containing silica gel prepared by the above method as a silica gel containing the second carbon material and having a specific surface area of ​​700 to 900 m 2 / g of powdered material. The silica gel of the powdered carbonaceous material has the following characteristics: when 1g of the silica gel is added to 5mL of pure water, the pH of the pure water changes to the acidic region, usually to pH 3 to 5.5. The pure water used to confirm this characteristic is usually distilled water, pure water prepared by reverse osmosis membrane treatment, or ion exchange water, and the pH is generally 5 to 7.

[0058] From the viewpoint of suppressing the mixing of impurities into the analytical sample and improving the recovery rate of residual pesticides, the amount of the first carbon material used is usually preferably set to 0.5 to 10 mass % of the sodium silicate contained in the sodium silicate aqueous solution, and more preferably set to 0.5 to 2 mass %.

[0059] In the treatment agent, the blending ratio (A:B) of the powdered carbonaceous material silica gel (A) and the powdered ion exchange group-modified carbonaceous material silica gel (B) is not limited to a specific ratio, but is usually preferably set to 3:2 to 1:1 in terms of mass ratio.

[0060] The purification solvent used in this step can be any organic solvent that can dissolve residual pesticides, and various organic solvents can be used. For example, acetonitrile or acetone can be used, but the purification solvent is preferably used according to the type of food. By distinguishing and using purification solvents, in the analysis sample, the impurities from the food that imposes a contamination load on the mass spectrometer can sometimes be suppressed from mixing without damaging the recovery rate of residual pesticides in the food. For example, when the food is a caffeinated food such as tea and acetonitrile is used as the extraction solvent of step 1, a mixed solvent of acetone and hexane is preferably used as the purification solvent. If this mixed solvent is used, the recovery rate of residual pesticides can be maintained at a necessary level in the analysis sample modulated by the caffeinated food, and the content of caffeine that imposes a contamination load on the mass spectrometer can be suppressed at the same time.

[0061] In the mixed solvent of acetone and hexane, the proportion of acetone is preferably set to 20 to 50% by mass, more preferably to 20 to 30% by mass. When the proportion is less than 20% by mass, residual pesticides are not easy to recover, and when the proportion exceeds 50% by mass, although residual pesticides are easy to recover, caffeine as an impurity is easily mixed into the analytical sample.

[0062] On the other hand, when acetonitrile is used as the extraction solvent of step 1 for foods other than caffeinated foods, acetonitrile is used as the purification solvent as the extraction solvent, or a mixed solvent of toluene and acetonitrile is preferably used. If these solvents are used, it is sometimes easy to suppress the mixing of impurities in the analytical sample. In the mixed solvent of toluene and acetonitrile, the proportion of toluene is preferably set to less than 40% by mass, more preferably set to less than 30% by mass. If the proportion exceeds 40% by mass, it is sometimes difficult to suppress the mixing of impurities in the analytical sample.

[0063] The specific operation in this step is, for example, to add the extract obtained in step 1 to a test tube containing a treatment agent and a purification solvent, and to mix the treatment agent, the purification solvent, and the extract by shaking the test tube by hand. If these are mixed, the impurities contained in the extract are easily captured by the silica gel of the carbon-containing material modified by the ion exchange group in the treatment agent. In addition, when the treatment agent contains silica gel of the carbon-containing material, they are easily captured by the silica gel of the carbon-containing material and the silica gel of the carbon-containing material modified by the ion exchange group, and thus move to the solid phase. On the other hand, the residual pesticides contained in the extract are not easily captured by the treatment agent, and remain in the liquid phase. That is, the residual pesticides and impurities contained in the extract are separated by the treatment agent, and the extract is purified.

[0064] The amount of the treatment agent used is not particularly limited, but is usually preferably set to 300 to 700 mg relative to 1 mL of the extract. In addition, the amount of the purification solvent used is not particularly limited, but, for example, when the food is a food other than a caffeinated food and acetonitrile or a mixed solvent of toluene and acetonitrile is used as the purification solvent, it is preferably set to 4 mL relative to 1 mL of the extract. In addition, when the food is a caffeinated food and a treatment agent containing silica gel of a powdered ion exchange group-modified carbonaceous material and silica gel of a powdered carbonaceous material is used as the treatment agent, and a mixed solvent of acetone and toluene is used as the purification solvent, it is preferably set to about 9 mL relative to 1 mL of the extract.

[0065] (Step 3)

[0066] In this step, a portion of the liquid component is separated from the mixture obtained by mixing the treatment agent, the extract and the purification solvent in step 2. For example, the test tube in which the treatment agent, the extract and the purification solvent are mixed in step 2 is applied to a centrifuge, and the liquid component and the solid component in the test tube are centrifuged to separate a portion of the liquid component. The separated liquid component can be used as a sample for residual pesticide analysis directly or after being appropriately concentrated and applied to a mass spectrometer.

[0067] Since the method for preparing an analytical sample of the present invention includes the above-mentioned steps 1 to 3, an analytical sample of residual pesticides can be simply prepared from an extract of residual pesticides from food in a short time compared to the notification method. In addition, since the prepared analytical sample is separated by trapping impurities in the treatment layer in step 2, it is less likely to contaminate the column or detector of the mass spectrometer than the analytical sample prepared by the improved method, and the maintenance burden of the mass spectrometer can be reduced.

[0068] The method for preparing analytical samples of the present invention can be used to prepare analytical samples for simultaneous testing of residual pesticides in various foods. When a treating agent comprising silica gel containing a carbonaceous material modified with powdered ion exchange groups and a treating agent comprising silica gel containing powdered carbonaceous material are used as treating agents, it is particularly useful in preparing analytical samples for simultaneous testing of residual pesticides in foods containing caffeine or catechins as impurities, typically tea.

[0069] [Experimental example]

[0070] <Preparation of treatment agent>

[0071] The carbonaceous material silica gel and the carbonaceous material silica gel modified with ion exchange groups used in the following experimental examples are shown below.

[0072] Silica gel containing carbon materials:

[0073] A sodium silicate aqueous solution was prepared, and the first carbon material containing 10% by mass of sodium silicate was added thereto and stirred. Hydrochloric acid was added thereto to gelate it, and further hydrochloric acid was added until the pH of the reaction system was less than 2. The reaction formula at this time is shown below.

[0074] Na2SiO3+2HCl→H2SiO3+2NaCl

[0075] After the reaction system was left for a certain period of time, the product was washed with pure water and dried to obtain silica gel of powdered carbon-containing material. Here, six types of silica gels I to VI of carbon-containing materials were obtained by using the second carbon material of six specific surface areas shown in Table 1. The properties of the prepared silica gels I to VI of carbon-containing materials are shown in Table 1.

[0076] [Table 1]

[0077] Table 1

[0078]

[0079]

[0080] * The pH of distilled water when 1g of carbonaceous silica gel is added to 5mL of distilled water

[0081] In addition, for the carbon-containing silica gel I, the addition amount of the second carbon material relative to sodium silicate was changed to prepare four carbon-containing silica gels (Ia, Ib, Ic, Id) having different contents of the second carbon material as shown in Table 2. The properties of the prepared carbon-containing silica gels Ia to Id are shown in Table 2.

[0082] [Table 2]

[0083] Table 2

[0084] Silicone rubber containing carbon materials Ia Ib Ic Id <![CDATA[Specific surface area of the second carbon material (m 2 / g)]]> － 1,680 1,680 1,680 Second carbon material content (mass %) 0 0.5 1 5 <![CDATA[Specific surface area (m 2 / g)]]> 407 － 625 647 pH* 4.96 4.13 5.42 4.08

[0085] * The pH of distilled water when 1g of carbonaceous silica gel is added to 5mL of distilled water

[0086] Silica gel containing carbonaceous materials modified with ion exchange groups:

[0087] A sodium silicate aqueous solution was prepared, and a first carbon material (specific surface area of ​​1,680 m2) containing 10% by mass of sodium silicate was added thereto. 2 / g) and stirred. Hydrochloric acid was added thereto to gelate it, and further hydrochloric acid was added until the pH of the reaction system was less than 2. After the reaction system was left for a certain period of time, the product was washed with pure water and dried to obtain silica gel of powdered carbonaceous material. 10g of the obtained silica gel of carbonaceous material was added to 200mL of 3-(2-aminoethylamino)propyltrimethoxysilane aqueous solution (concentration of 5% by mass), stirred and then dehydrated, and the residue was dried to obtain silica gel of carbonaceous material modified with ion exchange groups (specific surface area of ​​180m 2 When 1 g of the silica gel containing the carbon material modified with the ion exchange group was added to 5 mL of distilled water, the pH of the distilled water became 9.6.

[0088] <Experimental Example A>

[0089] 1 mL of acetonitrile solution containing 10 μg each of 9 impurities (linoleic acid, palmitic acid monoglyceride, β-sitosterol, squalene, caffeine, monomyristic acid glyceride, stigmasterol, phytol and dl-α-tocopherol) considered as impurities in food, 1 mL of acetonitrile solution containing 0.2 μg each of 35 pesticides or 1 mL of acetonitrile solution containing 0.2 g of green tea (caffeine content of 4 mg) and 9 mL of a mixed solvent obtained by mixing 3 parts by mass of hexane with 1 part by mass of acetone were added to 500 mg of powdered carbonaceous silica gel I in a test tube, and the mixture was shaken by hand for 1 minute. Then, the test tube was centrifuged, the supernatant was separated, and analyzed by GC-MS to study the removal rate of each impurity compound in the supernatant and the recovery rate of each pesticide. In addition, the carbonaceous silica gel I was changed to the carbonaceous silica gel modified with ion exchange groups, and the same operation was performed to study the removal rate of each impurity compound and the recovery rate of each pesticide. The results are shown in Table 3 (the results of pesticide recovery rate when 35 pesticides were added and the results of caffeine removal rate when green tea was added) and Figure 1 (Results of removal rate of each impurity compound when 9 impurity compounds were added) In addition, in the case of mixing with green tea, the scanning chromatogram obtained by mass spectrometry shows Figure 2 .

[0090] [Table 3]

[0091] Table 3

[0092]

[0093] According to Table 3, when either the carbonaceous material silica gel I or the carbonaceous material silica gel modified with ion exchange groups was used, almost all the pesticides among the 35 pesticides were recovered at a high recovery rate of 70 to 120%. Figure 1 and Figure 2 It is known that the combined use of carbonaceous silica gel I and carbonaceous silica gel modified with ion exchange groups can remove many impurities. Figure 2 In the case of simultaneous testing of residual pesticides in tea, it is believed that caffeine and catechins, which are characteristic impurities, can be easily removed by using both silica gel I of the carbonaceous material and silica gel of the carbonaceous material modified with ion exchange groups.

[0094] <Experimental Example B>

[0095] 650 mg of powdered carbonaceous silica gel I, 400 mg of powdered ion exchange group-modified carbonaceous silica gel and 800 mg of powdered magnesium sulfate were uniformly mixed and placed in a test tube, and 1 mL of acetonitrile solution containing 0.2 g of green tea (caffeine content was 4 mg), 0.1 mL of acetonitrile solution containing 0.2 μg of each 35 kinds of pesticides and 9 mL of a mixed solvent obtained by mixing 3 parts by mass of hexane with respect to 1 part by mass of acetone were added thereto, and the mixture was shaken by hand for 1 minute. Then, the test tube was centrifuged, and the supernatant was separated and used as a sample for analysis. In addition, two mixed solutions of 1 mL acetonitrile solution containing 0.2 g of green tea (caffeine content was 4 mg) and 0.1 mL acetonitrile solution containing 0.2 μg of each 35 kinds of pesticides were prepared. Then, these mixed solutions were regarded as extracts obtained by extracting residual pesticides from food, and were processed separately according to the notification method and the improvement method, thereby preparing samples for analysis.

[0096] By analyzing each analytical sample using GC-MS, the removal rate of caffeine in each analytical sample and the recovery rate of each pesticide were studied. The results are shown in Table 4. In addition, the scanning chromatogram obtained by GC-MS is shown in Table 4. Figure 3 .

[0097] [Table 4]

[0098] Table 4

[0099]

[0100] * A mixed treatment agent of silica gel I for carbon-containing materials, silica gel for carbon-containing materials modified with ion exchange groups, and magnesium sulfate

[0101] The mixed treatment agent of silica gel I of powdered carbon-containing material and silica gel of powdered ion exchange group-modified carbon-containing material can recover almost all types of pesticides among 35 types of pesticides at a high recovery rate of 70 to 120%. The recovery rate of pesticides is not inferior to the notification method and the improved method. On the other hand, the removal rate of caffeine is higher than that of the notification method and the improved method, and analytical samples that are not easy to contaminate the mass spectrometer can be prepared.

[0102] <Experimental Example C>

[0103] 500 mg of each powdered carbonaceous material silica gel I to VI were placed in test tubes, and 1 mL of acetonitrile solution containing 10 μg of caffeine, 1 μg of each of 6 pesticides (buprofezin, fenamiphos, vinylclothion, tetrachlorophthalide, simazine and cyclazinone) and 9 mL of a mixed solvent obtained by mixing 3 parts by mass of hexane with 1 part by mass of acetone were added to each test tube, and the mixture was shaken by hand for 1 minute. Then, the test tubes were centrifuged, the supernatant was separated, and analyzed by GC-MS to study the removal rate of caffeine in the supernatant and the recovery rate of each pesticide. The results are shown in Table 5.

[0104] [Table 5]

[0105] Table 5

[0106]

[0107] According to Table 5, regarding silica gel containing carbon materials, the following tendency was observed: if the specific surface area of ​​the carbon material used was large, the caffeine removal rate became high, and the recovery rate of some pesticides became low, and the following tendency was observed: if the specific surface area of ​​the carbon material used was small, the caffeine removal rate became low, and the recovery rate of pesticides became high.

[0108] <Experimental Example D>

[0109] 500 mg of silica gel I, Ia, Ib, Ic, and Id containing carbon materials were placed in test tubes, and 1 mL of an acetonitrile solution containing 10 μg of caffeine, 1 μg of tetrachlorophthalide, one of the pesticides that exhibits strong adsorption to carbon materials, and 9 mL of a mixed solvent obtained by mixing 3 parts by mass of hexane with 1 part by mass of acetone were added to each test tube, and the mixture was shaken by hand for 1 minute. Then, the test tubes were centrifuged, the supernatant was separated, and analyzed by GC-MS to study the removal rate of caffeine in the supernatant and the recovery rate of tetrachlorophthalide. The results are shown in Table 6.

[0110] [Table 6]

[0111] Table 6

[0112] Silicone rubber containing carbon materials Ia Ib Ic Id I Caffeine removal rate 55％ 67％ 71％ 86％ 94％ Recovery rate of tetrachlorophthalide 57％ 57％ 26％ 12％ 8％

[0113] <Experimental Example E>

[0114] To 500 mg of silica gel I of powdered carbon-containing material placed in a test tube, add 1 mL of acetonitrile solution containing 10 μg each of 9 impurities considered as impurities in food (the same impurities as used in Experimental Example A) or 1 mL of acetonitrile solution containing 0.2 μg each of 35 pesticides (the same pesticides as used in Experimental Example A) and 9 mL of the solvent shown in Table 7, and shake by hand for 1 minute. Then, the test tube is centrifuged, the supernatant is separated, and it is analyzed by GC-MS to study the removal rate of each impurity compound in the supernatant and the recovery rate of each pesticide. In addition, the silica gel I of the carbon-containing material is changed to silica gel of the carbon-containing material modified with ion exchange groups, and the same operation is performed to study the removal rate of each impurity compound and the recovery rate of each pesticide. The results are shown in Table 7 (the results of the pesticide recovery rate when 35 pesticides were added) and Figure 4 (Results of removal rates of various inclusion compounds when using silica gel I containing carbon and adding 9 inclusion compounds) and Figure 5 (Results of removal rates of various inclusion compounds when using silica gel containing carbon materials modified with ion exchange groups and adding 9 types of inclusion compounds).

[0115]

[0116] <Experimental Example F>

[0117] 500 mg of powdered carbonaceous silica gel Ib was placed in a test tube, and 1 mL of an acetonitrile solution containing 10 μg of caffeine, 1 μg of each of 6 pesticides (the same pesticides used in Experimental Example C), and 9 mL of a mixed solvent of acetone and hexane shown in Table 8 were added thereto, and the mixture was shaken by hand for 1 minute. Then, the test tube was centrifuged, and the supernatant was separated and analyzed by GC-MS to study the removal rate of caffeine in the supernatant and the recovery rate of each pesticide. The results are shown in Table 8.

[0118] [Table 8]

[0119] Table 8

[0120]

[0121] <Experimental Example G>

[0122] 200 mg of silica gel containing carbonaceous materials modified with ion exchange groups was placed in a test tube, and 1 mL of acetonitrile solution containing 1 μg of each of 6 pesticides (the same pesticides used in Experimental Example C) and 1 mL of acetonitrile solution containing 10 μg of each of 9 impurities considered as impurities in food (the same impurities as those used in Experimental Example A) and 9 mL of a mixed solvent of toluene and acetonitrile shown in Table 9 were added thereto, and the mixture was shaken by hand for 1 minute. The test tube was then centrifuged, and the supernatant was separated and analyzed by GC-MS to study the removal rate of impurity compounds in the supernatant and the recovery rate of each pesticide. The results are shown in Table 9. Figure 6 and Table 9.

[0123] [Table 9]

[0124] Table 9

[0125]

Claims

1. A method for preparing samples for analysis of residual pesticides, which is a method for preparing samples for simultaneous analysis of residual pesticides in food using a mass spectrometer, comprising the following steps: A step of extracting the above-mentioned residual pesticide from the above-mentioned food using an organic water-soluble extraction solvent to obtain an extract; A step of obtaining a mixture of a treating agent for silica gel containing a powdered ion exchange group-modified carbonaceous material, the extract and an organic purification solvent capable of dissolving the residual pesticide; and The step of separating a portion of the liquid component from the above mixture, The ion exchange groups of the silica gel of the powdery ion exchange group-modified carbonaceous material are amine functional groups having anion exchange capacity.

2. The method for preparing a sample for analysis of residual pesticides according to claim 1, wherein: The above-mentioned amine functional group is 3-(2-aminoethylamino)propyl or 3-aminopropyl.

3. The method for preparing a sample for analysis of residual pesticides according to claim 1, wherein: The above-mentioned powdered ion exchange group-modified carbonaceous material silica gel is prepared by a method including the step of further treating the carbonaceous material silica gel with a silane coupling agent having an amine functional group with anion exchange capacity, and the carbonaceous material silica gel is prepared by a method including the steps of adding hydrochloric acid to a sodium silicate aqueous solution added with carbon material to gelate it and further adding hydrochloric acid until the pH of the gelled reaction system is less than 2.

4. The method for preparing a sample for analysis of residual pesticides according to claim 1, wherein: The powdered ion exchange group-modified carbonaceous silica gel contains a specific surface area of ​​700 to 1,700 m 2 / g of the first carbon material, and a specific surface area of ​​100 to 300 m 2 / g, and when 1g of the carbonaceous material is added to 5mL of pure water, the pH of the pure water changes to the alkaline region.

5. The method for preparing a sample for analysis of residual pesticides according to claim 4, wherein: The content ratio of the first carbon material in the powdery ion-exchange group-modified carbon-containing silica gel is 5 to 50% by mass.

6. The method for preparing a sample for analysis of residual pesticides according to claim 1, wherein: The above-mentioned treatment agent further contains silica gel which is a powdery carbonaceous material.

7. The method for preparing a sample for analysis of residual pesticides according to claim 6, wherein: The silica gel of the powdered carbon-containing material is prepared by a method comprising the following steps: adding hydrochloric acid to an aqueous sodium silicate solution to which carbon material is added to gelate the solution; and further adding hydrochloric acid until the pH of the gelled reaction system is less than 2.

8. The method for preparing a sample for analysis of residual pesticides according to claim 6, wherein: The powdered carbonaceous material is silica gel containing a specific surface area of ​​700 to 1,700 m 2 / g of the second carbon material, and a specific surface area of ​​700 to 900 m 2 / g, and when 1 g of the silica gel is added to 5 mL of pure water, the pH of the pure water changes to an acidic region.

9. The method for preparing a sample for analysis of residual pesticides according to claim 8, wherein: The content ratio of the second carbon material in the silica gel of the powdery carbon-containing material is 0.5 to 10% by mass.

10. The method for preparing a sample for analysis of residual pesticides according to any one of claims 1 to 5, wherein: When the food is a food other than a caffeine-containing food, acetonitrile is used as the water-soluble extraction solvent, and a mixed solvent of toluene and acetonitrile or acetonitrile is used as the purification solvent.

11. The method for preparing a sample for analysis of residual pesticides according to any one of claims 6 to 9, wherein: When the food is a caffeine-containing food, acetonitrile is used as the water-soluble extraction solvent, and a mixed solvent of acetone and hexane is used as the purification solvent.

12. A purification agent for an organic solvent containing residual pesticides, which is a treatment agent for purifying an organic water-soluble solvent containing residual pesticides extracted from food. Silica gel comprising a powdered ion exchange group-modified carbonaceous material, The ion exchange groups of the silica gel of the powdery ion exchange group-modified carbonaceous material are amine functional groups having anion exchange capacity.

13. The purification treatment agent for an organic solvent containing residual pesticides according to claim 12, wherein: The above-mentioned amine functional group is 3-(2-aminoethylamino)propyl or 3-aminopropyl.

14. The purification treatment agent for an organic solvent containing residual pesticides according to claim 12, wherein: The powdered ion exchange group-modified carbonaceous silica gel contains a specific surface area of ​​700 to 1,700 m 2 / g of the first carbon material, and a specific surface area of ​​100 to 300 m 2 / g, and when 1 g of the carbonaceous material is added to 5 mL of pure water, the pH of the pure water changes to an alkaline region.

15. The purification treatment agent for an organic solvent containing residual pesticides according to claim 14, wherein: The content ratio of the first carbon material in the powdery ion-exchange group-modified carbon-containing silica gel is 5 to 50% by mass.

16. The purification treatment agent for an organic solvent containing residual pesticides according to any one of claims 12 to 15, further comprising silica gel which is a powdery carbonaceous material.

17. The purification treatment agent for an organic solvent containing residual pesticides according to claim 16, wherein: The powdered carbonaceous material is silica gel containing a specific surface area of ​​700 to 1,700 m 2 / g of the second carbon material, and a specific surface area of ​​700 to 900 m 2 / g, and when 1 g of the silica gel is added to 5 mL of pure water, the pH of the pure water changes to an acidic region.

18. The purification treatment agent for an organic solvent containing residual pesticides according to claim 17, wherein: The content ratio of the second carbon material in the silica gel of the powdery carbon-containing material is 0.5 to 10% by mass.

Images