JP4758708B2 - Cadmium measurement method - Google Patents

Description

The present invention also relates to cadmium measured how. In more detail, the present invention relates agricultural, marine, cadmium measuring how the cadmium contained in animal products detected by immunoassay.

  In recent years, attention has been paid to the trend of accumulation of environmental pollutants in various scenes associated with industry and daily life due to the growing concern about social environmental awareness and health effects such as environmental conservation. Among environmental pollutants, heavy metals, especially cadmium, have caused serious problems due to their toxicity in the past, and the amount of cadmium contained in food is an important problem.

  Therefore, in general, for agricultural products, marine products, and livestock products, the amount of cadmium contained therein is measured using an analytical instrument such as an ICP emission spectrophotometer or an atomic absorption photometer. For example, for analysis of cadmium contained in agricultural products, marine products, and livestock products by the Ministry of Agriculture, Forestry and Fisheries, the sample is pretreated by the procedure shown in FIGS. 8 to 10 and then measured by an atomic absorption photometer or ICP. The quantification by the emission spectroscopic analysis method is performed (nonpatent literature 1).

JP 2004-323508 A MAFF website: Information on cadmium in foods, 48 Cd (http://www.maff.go.jp/cd/index.html)

  However, according to cadmium analysis using ICP emission analysis, atomic absorption method, etc., not only a very expensive analytical instrument is required, but also instrumental analysis requiring time, cost and labor, it takes time to measure. Furthermore, since the inspection cost is high, the amount of cadmium contained in grains and the like cannot be easily measured. For this reason, when inspecting cadmium contamination such as grain, it is not practical to reduce the inspection lot in a small amount, and there is a problem that damage when contamination exceeding the regulation value is detected becomes large. In addition, measurement cannot be performed on site, and it is necessary to perform it at a facility where measurement equipment is installed. For this reason, there is a need for a quick and simple determination method that is inexpensive and can be performed in the field.

  By the way, the present applicants have previously developed a method capable of immunologically detecting and quantifying cadmium and mercury, and a monoclonal antibody specifically recognizing cadmium used therefor (Patent Document 1). This anti-cadmium monoclonal antibody is a monoclonal antibody that specifically recognizes cadmium in a complex, and examples thereof include So25A1, So21D5, and So26G8. The hybridoma producing the monoclonal antibody So26G8 has been deposited with the Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology, under the accession number FERM P-19240 on February 27, 2003. Moreover, the monoclonal antibody Nx22C3 produced from the hybridoma deposited on February 26, 2004 as the deposit number FERM P-19703 at the Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology. They exhibit the property that they react primarily with cadmium and have little or no cross-reactivity with other metals such as calcium, magnesium, copper, iron, nickel, lead, zinc.

  In an immunological method (immunoassay) for quantitatively measuring cadmium using such a monoclonal antibody, cadmium is coordinated to a chelating agent, and the formed complex is detected and measured by the monoclonal antibody. Therefore, in this method, (i) a chelating agent is added to a test sample to form a complex, and (ii) cadmium is quantitatively measured by an immunological technique using an antibody that specifically recognizes the complex. be able to. As described above, since this monoclonal antibody has a high affinity for cadmium and a low cross-reactivity with other metals, cadmium in a test sample can be measured more accurately. In view of this, the present inventors considered that cadmium contained in agricultural products, marine products, and livestock products can be easily and quickly detected at low cost by an immunoassay method using an antibody having specificity for cadmium.

  According to this immunoassay method, cadmium can be expected to be detected very easily. However, although the above monoclonal antibody has high specificity to cadmium, it also reacts with other metals, so if the test sample contains a large amount of other metals such as manganese, zinc, magnesium, etc. There is a problem that cadmium cannot be detected due to interference. That is, although the above monoclonal antibody has high specificity for cadmium, it also reacts with other metals. For example, as shown in Table 1, the cross-reactivity of monoclonal antibody Nx22C3 is 1.47% for manganese, 0.974% for zinc, and 0.025% for magnesium. Thus, even if the cross-reactivity is small, if a large amount of these metals are present, they are hindered by these metals and cadmium cannot be detected.

  However, in the case of agricultural products, marine products, and livestock products, manganese, zinc, magnesium, iron, which are much higher in concentration (about 50-5500 times) than the cadmium regulation value (for example, 0.4 ppm for brown rice) Metals such as copper are included. For example, when Koshihikari (brown rice: 27 locality 34 samples) in various parts of Japan was investigated, as shown in FIG. 11, 28.5 ppm of manganese, 1400 ppm of magnesium, 24 ppm of zinc, 4 ppm of copper, and 11 ppm of iron were detected. Table 2 shows the amounts of magnesium, zinc, copper and manganese contained in typical agricultural products, marine products and livestock products.

Compared to the regulated value of the cadmium content of 0.4 ppm, these metals are contained in almost two orders of magnitude in the case of Mn and Zn and nearly three orders of magnitude in the case of Mg. Therefore, although the above monoclonal antibodies have a higher specificity for cadmium than metals such as manganese, zinc, magnesium, iron, copper, etc., the value of the concentration of each metal contained in brown rice is relative to the specificity for cadmium. Will be lost. That is, as it is, it has been found that it is impossible to detect cadmium because it is obstructed by the metal contained more than these cadmium.

An object of this invention is to provide the cadmium measuring method which can measure cadmium contained in agricultural products, marine products, and livestock products, without using analytical instruments, such as an ICP emission spectrophotometer and an atomic absorption photometer. Another object of the present invention is to provide a cadmium measurement method that can quickly and easily determine that cadmium contained in agricultural products, marine products, and livestock products is below a certain value .

In order to achieve this object, the cadmium measurement method according to claim 1 extracts a cadmium by adding a 0.002 M to 2 M hydrochloric acid solution to a measurement object, and the resulting solution is adjusted to a pH of 1.5 to 2.5. The solution is brought into contact with a carrier having tri-n-octylmethylammonium chloride immobilized on the surface thereof, and then the carrier is brought into contact with nitric acid having a concentration of more than 0.01 and not more than 0.5M. A pretreatment step of neutralizing the obtained solution to obtain a measurement sample, and a measurement step of analyzing the cadmium content by subjecting the measurement sample to an immunoassay for measuring cadmium using an antigen-antibody reaction. .

According to the method for measuring cadmium according to claim 1 , the hydrochloric acid solution obtained by extracting cadmium and other metals from the measurement object by hydrochloric acid solution treatment is adjusted to pH 1.5 to 2.5, and then tri-n- By bringing octylmethylammonium chloride into contact with the carrier immobilized on the surface, cadmium dissolved in the hydrochloric acid solution is selectively adsorbed on the carrier surface. Then, by bringing the carrier into contact with nitric acid having a concentration of more than 0.01 and not more than 0.5M, cadmium adsorbed on the carrier is eluted into nitric acid, and a solution in which cadmium is selectively extracted is obtained. Is possible. The nitric acid solution is neutralized and subjected to immunoassay as a measurement sample to analyze the cadmium content. At this time, metals other than cadmium that interfere with the measurement, such as zinc, magnesium, manganese, and organic substances, are removed or reduced in the measurement sample, so that the cadmium content is relatively concentrated and the cadmium content is determined by immunoassay. The content can be easily measured.

When the hydrochloric acid solution is brought into contact with a carrier having tri-n-octylmethylammonium chloride immobilized on the surface, it is preferable to employ the column method as described in claim 2 . By using a column with a carrier on which tri-n-octylmethylammonium chloride is immobilized on the surface, a hydrochloric acid solution in which cadmium and other metals are extracted from the measurement object by the hydrochloric acid solution treatment is passed through the column. Cadmium can be selectively adsorbed to the column simply and efficiently.

According to the cadmium measurement method according to claim 1, an anti-cadmium antibody is used for a measurement object containing a larger amount of metal such as manganese, zinc, magnesium, or copper than cadmium, such as agricultural products, fishery products, and livestock products. The presence or absence of cadmium contamination can be easily detected in a short time by the immunochromatography apparatus, and the determination of whether or not the cadmium content exceeds a certain value (for example, a regulation value) can be made very simple objectively. In addition, the immunochromatography device has a simple structure in which an antigen that reacts with an anti-cadmium antibody or an anti-cadmium antibody is fixed, so the inspection cost is much lower than that of instrumental analysis, and it is used to inspect cadmium contamination such as grains. In this case, the inspection lot can be made small, and damage when contamination exceeding the regulation value is detected can be reduced. Furthermore, unlike instrument analysis, it enables on-site inspection and measurement.

Also, it is detrimental to the human body when the extraction operation of cadmium, it is not necessary to use an organic solvent that can not be treated as general waste. Furthermore, it is possible to easily separate cadmium selectively and provide a measurement sample without performing complicated operations such as aqueous phase recovery and organic phase recovery as in the case of solvent extraction. For this reason, even an inexperienced person or an inexperienced person who is not familiar with this type of analyzer can easily obtain a sample for cadmium content measurement, and simple cadmium measurement by immunoassay is more reliable. I can do it.

Next, as described in claim 2 , a hydrochloric acid solution in which cadmium and other metals are extracted from an object to be measured is contacted by a column method with a carrier on which tri-n-octylmethylammonium chloride is immobilized. By doing so, cadmium can be selectively adsorbed to the column very easily and efficiently.

Hereinafter, the configuration of the present invention will be described in detail based on the best mode shown in the drawings.
The cadmium measurement method according to the present invention includes a pretreatment step of extracting cadmium by reducing or removing metals other than cadmium, such as manganese, zinc, magnesium, copper, and the like, and cadmium using an antigen-antibody reaction. The method comprises a measurement step of analyzing the cadmium content by subjecting the measurement sample to the immunoassay to be measured.

As the implementation of the invention will be described pretreatment step hydrochloric acid treatment and Capri coat extract cadmium from the object to be measured by the immobilized carrier.

First, cadmium is extracted from an object by hydrochloric acid treatment. The concentration of the hydrochloric acid solution is about 0.002 to 2M, preferably about 0.02 to 1M, and more preferably about 0.02 to 0.1M. When the concentration of the hydrochloric acid solution is less than 0.002M, cadmium is not sufficiently extracted. On the other hand, when the concentration exceeds 2M, it is neutralized when the pH is adjusted to 1.5 to 2.5 in a later step. A large amount of neutralizing agent is required, and as a result, cadmium is diluted, which is not preferable. For this reason, it is preferable to adjust the hydrochloric acid solution concentration so that the pH is 1.5 to 2.5 because it is not necessary to adjust the pH in the subsequent steps. The cadmium is efficiently extracted by shaking or stirring the hydrochloric acid solution having such a concentration and the object. When shaking or stirring, the amount of the object is preferably 5 to 20% by volume, more preferably 10 to 20% by volume. If the amount of the hydrochloric acid solution is too large, the cadmium concentration becomes too thin and concentration is necessary for measurement. On the other hand, if the amount of the hydrochloric acid solution is small, impurities are generated, which is not preferable. Moreover, it is preferable that the sample is made into fine pieces before shaking for cadmium extraction or before stirring. Shaking time can be shortened by using fine pieces. For example, taking an example of manually pulverizing grain like brown rice, brown rice is very hard to pulverize manually. For example, soak rice grains in a hydrochloric acid solution with a concentration of about 0.02 to 1M and leave it overnight. Soften in advance, then grind the grain, add 0.02-1M hydrochloric acid solution to 10-20% capacity, shake for 2-8 hours, usually about 4 hours. In the case of mechanical pulverization, it is not necessary to soak brown rice in a hydrochloric acid solution and soften it beforehand, so that it is possible to save time and effort. In the case of this mechanical pulverization, the brown rice is finely pulverized, so that the treatment time of the hydrochloric acid solution can be shortened to at least about half that of manual pulverization, usually about 1 hour.

By the above hydrochloric acid treatment, to extract the cadmium in the solution, At this time, zinc, manganese, and other metals such as magnesium are extracted together. Therefore, the hydrochloric acid treatment solution obtained above also contains zinc, manganese, magnesium and the like, which hinders accurate measurement of cadmium. Therefore, the hydrochloric acid treatment solution is filtered through a cadmium separation column apparatus packed with a capricoat-immobilized carrier to adjust the pH to 1.5 to 2.5, and then poured to flow, thereby cadmium contained in the hydrochloric acid solution. Is selectively adsorbed on the capricoat-immobilized carrier. Here, when the pH of the hydrochloric acid treatment solution is less than 1.5, cadmium is not sufficiently adsorbed on the capricoat-immobilized support, whereas when it exceeds 2.5, zinc and manganese exceed the allowable range and are adsorbed together with cadmium. It will be. The capricoat immobilization carrier can be used, for example, by immersing the capricoat immobilization carrier in a hydrochloric acid treatment solution to adsorb cadmium without filling the column.

  Next, a 0.01 to 1M hydrochloric acid solution containing no or almost no cadmium or other metal is poured to wash the inside of the cadmium separation column container and the capricoat immobilization support. As a result, cadmium that has adhered to the column container and did not reach the capricoat-immobilized carrier is not only adsorbed to the capricoat-immobilized carrier, but also metal other than cadmium remaining on the surface of the carrier and in the gap between the carriers. As a result, it is possible to reduce the amount of metal other than cadmium and to perform measurement more accurately. If the hydrochloric acid concentration is less than 0.01M, the pH becomes high, and metals other than cadmium may be adsorbed on the column. On the other hand, if it exceeds 0.1 M, the cadmium adhering to the container is not preferable because the pH does not increase to the extent that the column is adsorbed on the column. Therefore, it is effective that the concentration of the hydrochloric acid solution when washing the inside of the cadmium separation column container and the capricoat immobilization carrier is 0.01 to 1M.

  The cadmium adsorbed on the capricoat immobilization carrier is eluted by flowing a nitric acid solution having a concentration of more than 0.01 and not more than 0.5M through the column. Then, immunoassay is performed with the pH of the cadmium-eluting nitric acid at 6.5 to 8.5. As for the nitric acid concentration, cadmium is not sufficiently eluted when it is 0.01M or less, and if it exceeds 0.5M, a large amount of neutralizing agent is required to adjust the pH to 6.5 to 8.5. As a result, cadmium is diluted, which is not preferable.

  By the above operation, cadmium is dissociated from the capricoat immobilization carrier and eluted into the nitric acid solution. The nitric acid solution thus extracted is neutralized to obtain an immunoassay sample. Neutralization may be performed by a normal method.

  The cadmium adsorbed on the capricoat immobilization carrier can be eluted using an EDTA solution adjusted to a concentration of about 0.1M. In this case, although the elution efficiency is slightly lower than in the case of using a nitric acid solution, there is an advantage that it is not necessary to add EDTA when performing an immunoassay. Further, by mixing and using a nitric acid solution and an EDTA solution, it is not necessary to add EDTA at the time of immunoassay without lowering the cadmium elution efficiency.

  Here, the optimum flow rate when flowing the solution through the cadmium separation column will be described. If the flow rate is increased, the cadmium separation processing time can be shortened, but the cadmium recovery rate decreases. Therefore, it is necessary to set the flow rate so that the recovery rate of cadmium does not decrease. In this embodiment, the column apparatus has a diameter of 20 mm, and the solution is caused to flow through a cadmium separation column packed with a 0.3 g column at a flow rate of 3 ml / min or less. However, the present invention is not limited to this example. The optimum flow rate is appropriately determined depending on the amount of the carrier, the nature of the carrier (size, pore diameter, etc.) and the like.

Next, the capricoat immobilization carrier used in this embodiment will be described. The capricoat immobilization carrier has a function of selectively adsorbing cadmium. For example, when a capricoat-immobilized support is brought into contact with a solution containing a metal other than cadmium, it has a function of selectively adsorbing cadmium, that is, separating cadmium. Capricoat (tri-n-octylmethylammonium chloride) has three n-octyl groups and one methyl group that bind to N ⁺ , but if it has selective adsorption performance for cadmium. A capricoat-like compound in which these functional groups are substituted with another functional group may be used. For example, a methyl group substituted with an ethyl group or a propyl group may be used.

  As a carrier for immobilizing the capricoat, for example, porous particles having a large surface area can be employed. Examples of specific materials include ODS silica gel, silica gel, alumina, magnesium sulfate, porous polymer, etc. Among them, ODS silica gel (silica gel having an octadecylsilyl group) is particularly preferred from the viewpoint of increasing the number of theoretical plates. Although it is preferable to use, it is not limited to these.

  For example, the capricoat is immobilized on the carrier as follows. First, the carrier is washed with, for example, a hydrochloric acid solution (6M), the hydrochloric acid solution adhering to the carrier is washed away with distilled water, dried, and then dissolved in an organic solvent capable of dissolving the capricoat (eg, hexane). The capricoat solution containing 0.5% by weight or more of the capricoat is prepared. Next, after the solution and the carrier are brought into contact with each other and shaken or stirred for about 1 hour to adsorb the capricoat to the carrier, the carrier and the capricoat solution are separated by filtration, and the carrier is dried. The capricoat is immobilized on the carrier by the above procedure.

  The capricoat-immobilized support thus obtained is packed into a column container having a sample liquid inlet and a sample liquid outlet.

  Incidentally, if the average particle size of the capricoat immobilization carrier is too large, the number of theoretical plates will decrease, so the desired performance will not be exhibited, and if it is too small, the pressure loss will increase and the liquid passing speed will decrease. It is preferable to use a 5-500-micrometer thing, and it is more preferable to use a 150-425-micrometer thing.

  Here, the cadmium separation column apparatus 6 shown in FIGS. 15 and 16 will be described. The cadmium separation column device 6 includes a container 7 having a sample liquid inlet 8 and a sample liquid outlet 9, and a filler 12 accommodated between the sample liquid inlet 8 and the sample liquid outlet 9. The filler 12 is a carrier having a capricoat immobilized on the surface.

  The column container 7 is provided with a sample liquid inlet 8 and a sample liquid outlet 9. As a material of the container 7, for example, plastic or the like can be used, but is not limited thereto. The shape of the container 7 may be other than the cylindrical shape shown in the figure. In this embodiment, a plastic transparent syringe container having a commercially available volume of 5 ml and an inner diameter of 13 mm is used. Further, when passing the sample liquid through the filler 12, the sample liquid may be dropped by gravity (natural drop), or pressurized by a piston or the like from the sample liquid inlet 8 side to pass the sample liquid. You may do it.

  In addition, it is preferable to provide the filter 10 so as to hold the filler 12 on the sample liquid inlet 8 side. By providing the filter 10, it is possible to prevent the filler 12 from being clogged by a suspension or the like present in the sample liquid, and the filler 12 can be diffused into the liquid and cannot maintain a good filling state. Can be prevented. The filter 10 preferably has a pore size smaller than the particle size of the filler 12 and further small enough to prevent the intrusion of a suspension or the like present in the sample liquid. Moreover, since the liquid permeate | transmits the whole filter 10 and it spreads uniformly to the filler 12 by making the filter 10 hydrophilic, it is preferable that the filter 10 has hydrophilicity. Furthermore, it is also necessary to have resistance to the liquid to be used, and for example, a quantitative filter paper for analysis (advancetech high-purity filter paper, No. 5B, etc.) can be employed, but it is not limited to this. Absent.

  Moreover, it is preferable to provide the filter holder 13 inside the column container 7. If the filter 10 on the side of the sample liquid inlet 8 is not fixed, the filter 10 may float when the sample liquid is added, and the filler 12 may diffuse into the liquid and a good filling state may not be maintained. However, by providing the filter holder 13, not only can the filter 10 float and the filler 12 can be prevented from dispersing, but also the filling state of the filler 12 can be stably maintained.

  Further, it is preferable to provide a filter 11 on the sample liquid outlet 9 side to prevent the filler 12 from flowing out of the sample liquid outlet 9. As the filter 11, it is preferable to use a filter having a pore size smaller than the particle size of the filler 12 and having a minimum pressure loss due to liquid passage during use. By doing so, it is possible to prevent the filler 12 from flowing out through the filter 11. Further, in order to efficiently discharge the liquid that has passed through the filler 12 from the sample liquid outlet 9, it is preferable that the filter 11 has hydrophilicity. Furthermore, it is also necessary to have resistance to the liquid to be used, and in this case as well as the filter 10, for example, an analytical quantitative filter paper (advancetech high-purity filter paper, No. 5B, etc.) should be employed. However, it is not limited to this.

  Next, when filling the container with the filler 12, for example, the following is performed. First, the filter 11 is put in the container 7. Next, an appropriate amount (for example, 0.3 g in this embodiment) of the filler 12 is put, and the filter 10 is placed thereon. Then, the entire filter 10 is lightly compressed with a piston or the like. For example, when the filler 12 is of a solid type that fits the size of the column container 7, it is not necessary to fill as described above. Further, if such a solid type filler is used, it is possible to prevent the filler from being prevented from the sample liquid outlet 9, so that it is not necessary to use the filter 11, and when there is no suspension in the sample liquid. It is not necessary to use the filter 10.

  Capricoat is a compound that may cause photodegradation, although it does not cause a problem as long as the time is sufficient to separate cadmium. Therefore, it is preferable to store the cadmium separation column apparatus in a dark place or to make the container 7 have light shielding properties.

The upper you facilities embodiment, the use of the sample obtained by extracting cadmium from the object, using immunoassay methods, such as immunochromatography using anti cadmium antibodies (immunochemistry assay), simply cadmium You can know the content.

  The sample preparation method of the present invention can be applied to those containing a large amount of zinc, magnesium, manganese, etc. so as to interfere with the measurement of cadmium, and includes grains such as rice and wheat, beans such as soybeans, and potatoes such as potatoes. It can be used for seafood such as seafood, meat, squid, firefly squid, scallops, scallops, oysters, and tobacco.

An immunoassay method using an anti-cadmium antibody that provides such a sample will be described below.
Examples of the anti-cadmium monoclonal antibody used in this immunoassay method include monoclonal antibodies that specifically recognize cadmium in a complex form, such as So25A1, So21D5, and So26G8. The hybridoma producing the monoclonal antibody So26G8 has been deposited with the Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology, under the accession number FERM P-19240 on February 27, 2003. Moreover, monoclonal antibody Nx22C3 is also mentioned. The hybridoma producing the monoclonal antibody Nx22C3 has been deposited at the National Institute of Advanced Industrial Science and Technology Patent Biological Deposit Center under the accession number FERM P-19703 on February 26, 2004. They exhibit the property that they react primarily with cadmium and have little or no cross-reactivity with other metals such as calcium, magnesium, copper, iron, nickel, lead, zinc. The antibody having specificity for cadmium used in the immunoassay method is not particularly limited to the monoclonal antibody described above, and other antibodies can be used.

  In the immunological method of measuring cadmium using the monoclonal antibody as described above, cadmium is coordinated to a chelating agent, and this formed complex is detected and measured by the monoclonal antibody. Therefore, in this method, (i) a chelating agent is added to a test sample to form a complex, and (ii) cadmium is quantitatively measured by an immunological technique using an antibody that specifically recognizes the complex. . Since the monoclonal antibody used in the immunoassay that provides the sample according to the preparation method of the present invention has high affinity for cadmium and low cross-reactivity with other metals as described above, cadmium in the test sample is more accurately detected. Can be measured.

  In the immunoassay method to which the sample obtained in the present invention is applied, cadmium ion alone does not have antigenicity. Therefore, cadmium is coordinated to a chelating agent to produce an anti-cadmium antibody, and the formed metal complex is used as an antigen. . Any chelating agent can be used as long as it can coordinate cadmium. For example, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), tetraethylenetriamine (TET), ethylenediamine ( EDA), diethylenetriamine (DETA), citric acid, oxalic acid, crown ether, nitrilotetraacetic acid, disodium edetate, sodium edetate, trisodium edetate, penicillamine, trisodium pentetate calcium, pentetate, succil and edetate Although trientine can be mentioned, EDTA is preferable.

  In addition, a cadmium complex such as a cadmium and EDTA complex (hereinafter abbreviated as Cd-EDTA) is too small as a molecule to induce an immune response. Use as a source. Examples of the high molecular weight substance that can be used as the carrier include polysaccharides and proteins, and proteins are preferred. Examples include, but are not limited to albumin, ovalbumin, hemocyanin, globulin, gelatin, collagen and the like.

  In order to produce a complex of these metal complex and protein, a chelating agent having a functional group capable of binding to the protein or a chelating agent into which the functional group is introduced is used, or the protein and the chelating agent are bound via a linker. be able to. Such chelating agents are commercially available, and examples include isothiocyanobenzyl-EDTA (Dojindo Laboratories). The formation of the complex can be performed by a conventional method.

  For the production of a series of monoclonal antibodies such as mouse immunization, hybridoma production and culture thereof, for example, monoclonal antibody production manual, published by Tada et al., Interdisciplinary Planning, 1995 (ISBN 4-906514-19-7) Reference can be made as appropriate, and the strain of mouse to be immunized, myeloma fused with spleen cells, etc. are not particularly limited.

  As the immunological technique to be used, any of the above monoclonal antibodies may be used. For example, immunochromatography, radioimmunoassay (RIA), fluorescent immunoassay (FIA), immunoluminescence assay, enzyme immunoassay (EIA or ELISA), Examples include CLEIA (chemiluminescence enzyme immunoassay), immunoturbidimetry (TIA), latex immunoturbidimetry (LTIA), fluorescence sensor method, surface plasmon analysis and the like.

  A kit for quantitatively measuring cadmium used in an immunoassay method may be composed of only the above-mentioned anti-cadmium monoclonal antibody, but other reagents such as a chelating agent, a chelating agent-protein complex, and a positive control sample. , Negative control samples and the like may be included. In addition, either the monoclonal antibody, the chelating agent-protein complex, or both may be labeled.

<Fluorescence immunoassay (FIA)>
A fluorescence immunoassay using a flow-type fluorescence sensor will be described as an example of an immunological measurement method using a monoclonal antibody. FIG. 1 illustrates the measurement principle.
In the apparatus, for example, a bead-like insoluble carrier on which an antigen is immobilized is installed. As the insoluble carrier for immobilization, for example, immobilization beads made of polymethylmethacrylic acid, glass or the like, fine particles such as calcium alginate particles can be used, but are not particularly limited thereto, Various shapes and materials can be used. Of these, beads or fine particles are preferred, particularly those having an average particle size of about 50 to 100 μm.

  The antigen, that is, the cadmium EDTA complex can be indirectly bound via a spacer such as a protein. Here, it is fixed with ovalbumin. Immobilization can be performed by directly binding a cadmium EDTA complex protein complex to a carrier using a natural adsorption method, an ionic bond method, a covalent bond method, or the like. In addition to a direct immobilization method, an appropriate chemical substance such as glutaraldehyde is used. It is also possible to fix it via a spacer such as a crosslink.

  First, (1) a certain concentration of anti-cadmium monoclonal antibody (primary antibody) is allowed to flow and bind to the immobilized antigen (cadmium EDTA complex). Next, (2) a fluorescently labeled antibody that specifically binds to the primary antibody, that is, a secondary antibody, is allowed to flow and bind to the primary antibody. Thereafter, (3) washing is performed, and the fluorescence intensity after washing is measured. The fluorescence intensity at this time is defined as a detection value F0. Next, (1) the sample to be tested is contacted with the same concentration of anti-cadmium monoclonal antibody as above, and then the contact mixture is run and allowed to bind to the immobilized antigen (cadmium EDTA complex). Similarly, the fluorescence intensity of the anti-hormone antibody bound by the secondary antibody is measured in the same manner (this value is set as a detection value F1).

  Here, if cadmium (antigen) is present in the sample, a part of the anti-cadmium monoclonal antibody (primary antibody) binds to cadmium in the first contact with the sample, and the anti-cadmium bound to the cadmium. The cadmium monoclonal antibody (primary antibody) no longer tries to bind to the immobilized antigen in subsequent contact with the immobilized antigen (cadmium EDTA complex). Then, since the secondary antibody cannot be bound and remains in the reaction mixture in a free state, the result is shown as a decrease in the fluorescence intensity at the detection value F1. Therefore, when the detection value F1 is smaller than the detection value F0 (F1 <F0), it can be determined that cadmium is present in the sample to be tested. Since the rate of decrease of F1 compared to F0 is proportional to the amount of cadmium contained in the test sample, the F1 decrease can be achieved by creating a calibration curve in advance using a known concentration of cadmium. The cadmium contained in the test sample can be quantified according to the ratio.

<Immunochromatography>
An immunochromatography will be described as an example of an immunological measurement method using an antibody. This method is excellent in simplicity because it can determine the presence or absence of cadmium within a few minutes to several tens of minutes simply by dropping a sample onto a test paper, and is very inexpensive because it does not require a special mechanical device. Immunochromatography effectively detects a desired metal ion by using a chelating agent-protein complex. In the immunochromatography apparatus, either the monoclonal antibody or the chelating agent-protein complex may be fixed, and the other may be supplied in a flowable manner. FIG. 2 shows an example of the embodiment. When the membrane 2 and the absorption pad 3 are arranged so as to partially overlap on the plastic backing sheet 1 and the sample is dropped on the sample dropping position 4 at the tip of the membrane 2, the sample moves on the membrane 2 toward the absorption pad 3. When flowing and passing through the region 5 where the anti-metal EDTA monoclonal antibody or the EDTA-protein complex is immobilized, the labeled metal EDTA complex is captured by the antibody or the labeled anti-metal EDTA monoclonal antibody becomes EDTA- By forming a complex with EDTA of the protein complex, the antimetal EDTA is captured by the complex, and the immobilization region B can be visually observed, so that the presence or absence of the detection target can be easily detected. Since it is difficult to directly label a chelating agent such as EDTA, it is preferable to indirectly label the chelating agent by adding pigment particles to the protein before or after adding the protein to the chelating agent. Alternatively, the monoclonal antibody itself can be labeled. These proteins can be labeled by a commonly used technique.

(1) Test method 1
The monoclonal antibody is immobilized on a part of the test paper in a strip shape so as to cross the sample flow. Next, a chelating agent-protein-dye particle (chelating agent-labeled protein) complex is added to the test sample, combined with cadmium ions, and dropped onto the test paper. When the desired metal ion is present, a metal-chelator complex is formed, and the metal complex and the labeled protein complex are captured by the monoclonal antibody immobilized on the test strip in the form of a strip, resulting in the strip of pigment particles. The metal ions in the sample are visualized densely. In the absence of metal ions in the sample, the chelator-protein-dye particle complex is not captured by the dye particles because it is not captured by the monoclonal antibody immobilized on the test paper.

(2) Test method 2
There are the following methods as immunochromatography for detecting metal ions using a chelator-protein complex. First, instead of the antibody in Test Method 1, a chelating agent-protein is immobilized in a strip shape on a test paper (see FIG. 3B). Dye particles are added to the monoclonal antibody. When this labeled antibody and the test sample are mixed and dropped onto the test paper (see FIGS. 3A and 3B), the metal ions are captured by the chelating agent-protein complex on the test paper and the metal-chelating agent. As a result, the labeled monoclonal antibody is captured on the test paper via the metal-chelator complex, and the metal ions in the sample are visualized by the densely packed pigment particles (FIG. 3C). (See (D)).

  The advantage of these two test methods is that it is easy to fix the chelating agent on the test strip through the protein, and multiple chelating agents can be added per protein molecule. Compared to the case where a chelating agent is fixed on the test paper, it is possible to increase the surface area, and as a result, the detection sensitivity can be increased. In addition, if a control line is applied to the absorption pad side from the cadmium detection line, an antibody that binds all monoclonal antibodies is applied, and when cadmium is not detected, this line detects the monoclonal antibody, It can be seen that the monoclonal antibody has passed through the cadmium detection line and can prove that the test was successful.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[ Reference Example 1]
In order to investigate the recovery rate of cadmium from the object by hydrochloric acid treatment, the recovery rate was investigated by the following procedure using the object as brown rice. To 2 g of each of 8 types of brown rice having different cadmium contents whose cadmium concentration is known in advance, a hydrochloric acid solution having a concentration of 0.02M was added so that all the rice grains were immersed, and left overnight. The brown rice was crushed with a glass rod, 0.02M hydrochloric acid solution was added to a volume of 10% (total amount 20 ml), and the mixture was shaken for 4 hours. The cadmium concentration in the hydrochloric acid solution obtained from these 8 types of brown rice was analyzed by an ICP emission spectroscopic analyzer. The results are shown in FIG. From this result, it was confirmed that the cadmium concentration (measured concentration after hydrochloric acid treatment) in the hydrochloric acid solution was almost equal to the cadmium concentration (attached concentration) known in advance. In addition, the cadmium concentration of the extract obtained by the hydrochloric acid-nitric acid method according to the official method was also analyzed by an ICP emission spectrophotometer, and the recovery rate = (cadmium concentration of the extract of the present method / cadmium concentration of the official method extract). As a result, 95% of the cadmium contained in the brown rice on average could be recovered in the solution. From the above results, it was confirmed that cadmium can be sufficiently recovered from the object by hydrochloric acid treatment.

  FIG. 5 shows the results of examining the concentrations of Mg, Mn, and Zn in the hydrochloric acid solution obtained as described above using an ICP emission spectroscopic analyzer. It was revealed that magnesium, zinc, manganese, and the like were contained in the hydrochloric acid treatment solution obtained above to such an extent that accurate measurement of cadmium was hindered.

  Next, DDTC (dibenzyldithiocarbanoic acid) -capricoat (tri-n-octyl) for selectively extracting cadmium by removing magnesium, zinc, manganese, etc., which hinder accurate measurement of cadmium, from the hydrochloric acid solution. (Methylammonium chloride: Dojindo Chemical) solution was prepared as follows. First, an equal amount of 1% DDTC aqueous solution and 0.05% capricoat / chloroform solution were combined and shaken for 60 minutes. When it was allowed to stand for a while, it separated into an aqueous phase and an organic phase, and the organic phase was used as a DDTC-capricoat solution.

  Next, the cadmium recovery rate by DDTC-capricoat treatment was investigated. Prepare an aqueous solution containing cadmium, zinc, manganese, copper, iron (each 1 ppm), magnesium (50 ppm) assuming cadmium-contaminated rice as a sample, and adjust the pH of this aqueous solution to 1.0, 2.0, 3.0, It adjusted to 4.0, 7 ml of said DDTC-capricoat solutions were added to 7 ml of each solution, and it left still after shaking. When left standing for a while, it separated into an aqueous phase and an organic phase. Therefore, only the organic phase was separated, 7 ml of 2M hydrochloric acid solution was added thereto, and cadmium was extracted from the organic phase into the aqueous phase (back extraction).

  The aqueous phase extracted by the above (hydrochloric acid extraction solution after DDTC-capricoat treatment) and the cadmium, manganese, magnesium, iron, zinc, and copper concentrations of the hydrochloric acid solution before DDTC-capricoat treatment were respectively measured by an ICP emission spectrophotometer. Based on the measured values, the recovery rate was determined as (recovery rate = (cadmium concentration of solution after DDTC-capricoat treatment / cadmium concentration of solution before DDTC-capricoat treatment)). The results are shown in FIG.

  From the results shown in FIG. 6 (A), when the pH of the hydrochloric acid treatment solution before DDTC-capricoat treatment is 1.0 and 2.0, cadmium is selectively extracted compared to other metals. I found out. In particular, when pH was 2.0, cadmium was more selectively extracted. On the other hand, when pH was set to 3.0, zinc was extracted to the same extent as cadmium, indicating that cadmium could not be selectively extracted. Further, it was found that when pH is 4.0, iron and manganese are also extracted, and cadmium cannot be extracted selectively at all. Therefore, it was found that the pH of the hydrochloric acid treatment solution before DDTC-capricoat treatment is preferably less than 3.0, more preferably around 2.

  Next, an extract obtained by treating brown rice previously known to contain about 1 ppm of cadmium by ICP emission spectroscopic analysis with a 2M hydrochloric acid solution as described above is adjusted to pH 2.0. Comparison of recovery rates when extraction with DDTC-capricoat solution and back extraction with 7 ml of 2M hydrochloric acid was performed compared with extraction with 2 ml of DDTC-capricoat solution and back extraction with 2 ml of 2M hydrochloric acid . The results are shown in FIG. From this result, it was confirmed that selective extraction of cadmium can be sufficiently performed even if the DDTC-capricoat solution is reduced from 7 ml to 2 ml.

  From the above, it was found that cadmium can be selectively separated from an object by adjusting a solution obtained by treating the object with hydrochloric acid to around pH 2 and then treating the solution with DDTC-capricoat solution.

[Example 1 ]
A column for selectively separating cadmium was prepared by the following procedure. As a carrier, 10 g of octadecylsiloxane-based silica gel resin (Wakogel C-100, Wako Pure Chemical Industries) was adopted, washed with hydrochloric acid (50 ml, 6M), further washed with distilled water and dried. Next, an organic solvent (hexane) was prepared so as to contain 3% by weight of capricoat (tri-n-octylmethylammonium chloride: Dojindo Chemical). 50 ml of this 3 wt% capricoat-containing hexane and 10 g of the above octadecylsiloxane-based silica gel resin were put in a light-shielding Erlenmeyer flask and shaken for 1 hour. After fully adsorbing the capricoat to the resin, the resin is transferred to a filtration device while washing the Erlenmeyer flask with hexane, the resin and hexane are separated by filtration, and the resin is dried in an oven set at 80 ° C., The capricoat was fixed to the resin surface. 0.3 g of resin with the capricoat immobilized thereon was packed into a light-shielding glass tube (diameter 20 mm x height 300 mm) for chromatography to obtain a cadmium separation column.

  Next, DDTC was mixed with the sample solution, and it was examined whether cadmium could be selectively extracted with a hydrochloric acid solution or a nitric acid solution using a cadmium separation column. 0.1 ml hydrochloric acid solution containing Cd, Mn, Zn, Mg, Fe, Cu, and Pb (the content of each metal element is known) was adjusted to pH 1.8, 5 ml of 1.3 mM DDTC was added, The solution was allowed to flow at 2-3 ml / min through a cadmium separation column using the above-mentioned capricoat immobilization resin. Next, 5 ml of 0.01M hydrochloric acid solution was passed through the cadmium separation column at 2-3 ml / min to wash the column, and then 5 ml of 0.5M hydrochloric acid solution was passed through the cadmium separation column at 2 to 3 ml / min to elute cadmium. I let you. Further, 5 ml of 0.1 M hydrochloric acid solution was passed through the cadmium separation column at 2-3 ml / min to wash the column, and 5 ml of 0.5 M nitric acid solution was passed through the column at 2 to 3 ml / min to elute cadmium. Then, the cadmium and other metal concentrations in the liquid obtained by passing the sample solution, column washing hydrochloric acid solution, and cadmium elution solution used in each of the above steps through the column were all measured with an ICP emission spectrometer, and cadmium And the recovery situation of other metals was investigated. The results are shown in Table 3. In Table 3, the solution after passing through the column is the solution obtained by passing the sample solution through the column, the solution after washing is the solution obtained by passing the column cleaning hydrochloric acid solution through the column, and the solution after elution is the solution for cadmium elution Is a solution obtained by passing through the column. The cadmium recovery rate was determined as recovery rate = (cadmium concentration of each solution / cadmium concentration of the sample solution). Since the cadmium recovery rate calculated from the cadmium concentration of the solution after passing through the column was 2.4%, it was confirmed that the column of the present invention has sufficient cadmium adsorption ability. The cadmium recovery calculated from the cadmium concentration in the solution after washing was 4.4% when washed with 0.01M hydrochloric acid solution and 0.4% when washed with 0.1M hydrochloric acid solution. From this, it was confirmed that cadmium adsorbed on the column hardly eluted in the column washing with the hydrochloric acid solution having these concentrations. Furthermore, cadmium could not be recovered with 0.5M hydrochloric acid solution, but about 90% of cadmium could be recovered with 0.5M nitric acid solution. The recovery rate of metals other than cadmium was higher than that of cadmium. And very low. From the above, cadmium adsorbed on the column does not elute even when the column is washed with 0.01 to 0.1M hydrochloric acid solution, and cadmium can be selectively recovered with 0.5M nitric acid solution. Was confirmed.

  Next, it was examined whether cadmium can be selectively extracted without using DDTC. In addition, regarding the concentration of nitric acid solution at the time of cadmium elution, it was further examined whether cadmium can be eluted with an EDTA solution. As a sample, a 0.1M hydrochloric acid solution containing Cd, Mn, Zn, Mg, Fe, Cu, and Pb (content of each metal element is known) is adjusted to pH 1.8, and 5 ml of the solution is added to the above-mentioned capri. After flowing through a cadmium separation column using a coat immobilization resin at 2 to 3 ml / min, 5 ml of 0.1 M hydrochloric acid solution was flowed through the cadmium separation column at 2 to 3 ml / min to wash the column. Then, 5 ml of 0.01 M, 0.05 M, 0.1 M, and 0.5 M nitric acid solutions or 5 ml of 0.1 M and 0.01 M EDTA solutions were applied to the column at 2-3 ml / min to elute cadmium. . Then, the cadmium and other metal concentrations in the liquid obtained by passing the sample solution, column washing hydrochloric acid solution, and cadmium elution solution used in each of the above steps through the column were all measured with an ICP emission spectrometer, and cadmium And the recovery situation of other metals was investigated. The results are shown in Table 4. In Table 4, the solution after passing through the column is the solution obtained by passing the sample solution through the column, the solution after washing is the solution obtained by passing the column cleaning hydrochloric acid solution through the column, and the solution after elution is cadmium. This is a solution obtained by passing the elution solution through a column. The cadmium recovery rate calculated from the cadmium concentration in the solution after passing through the column and the cadmium recovery rate calculated from the cadmium concentration in the solution after washing were almost the same as those obtained by experiments using DDTC. Therefore, it was confirmed that the adsorption of cadmium to the column and the washing of the column were not affected even without using DDTC. When nitric acid solution was used, almost 100% of cadmium was recovered at concentrations of 0.05M, 0.1M, and 0.5M, but the recovery rate of cadmium was greatly reduced at 0.01M. (5.6%). In the case of the EDTA solution, about 70% of cadmium was recovered at 0.1M, but the recovery rate of cadmium was greatly reduced (6.9%) at 0.01M. In any condition, it was confirmed that the recovery rate of metals other than cadmium was very low compared to the recovery rate of cadmium. As described above, it is possible to selectively extract cadmium without using DDTC, and selective recovery of cadmium from the column is a nitric acid solution having a concentration of more than 0.01 and not more than 0.5M, about 0.1M. It was confirmed that it is preferable to use a 0.05 to 0.5 M nitric acid solution.

  Next, separation of cadmium contained in rice was attempted using a cadmium separation column. Three gram samples of 11 kinds of brown rice having different cadmium contents were each shaken with 30 ml of 0.05 M hydrochloric acid for 1 hour, and then insolubles were removed from the extract by filtration. Pour 5 ml of this hydrochloric acid extract into a cadmium separation column using the above-mentioned capricoat-immobilized resin at 2 ml / min, adsorb cadmium on the resin, and then flush the column with 5 ml of 0.1 M hydrochloric acid at 2 ml / min. did. Next, 5 ml of 0.05 M nitric acid was passed through the column at 2 ml / min to collect cadmium. The concentrations of cadmium and other metals in the liquid obtained by passing the rice sample extract, column washing hydrochloric acid solution, and cadmium elution solution used in each of the above steps through the column were all measured using an ICP emission spectrometer. The status of cadmium and other metals recovered was investigated. The results are shown in Table 5. In Table 5, as in Tables 3 and 4, the solution after passing through the column is a solution obtained by passing the sample solution through the column, and the solution after washing is a solution obtained by passing the column cleaning hydrochloric acid solution through the column. The post-elution solution is a solution obtained by passing a cadmium elution solution through a column. The recovery rate was calculated using the known cadmium concentration in each brown rice (Akita attached concentration). In this experiment, the concentration of cadmium and other metals in the rice sample extract (before passing through the column) was also measured using an ICP emission spectrometer. From the measurement results of the cadmium concentration in the solution after passing through the column and in the solution after washing, it was confirmed that the cadmium was adsorbed on the column and the column was washed without problems even in the sample where cadmium was actually extracted from brown rice. . Next, the results of plotting the cadmium concentration in the nitric acid extract (the solution from which the cadmium adsorbed on the column by nitric acid was eluted) and the cadmium concentration in the hydrochloric acid extract before the column treatment for nine samples out of the above are plotted in FIG. Shown in From this result, the cadmium concentration is 0.04 ppm (the precious amount of rice has been increased 10 times by the pretreatment, which is 0.4 ppm when converted to the concentration in the rice). It was found that almost all amounts of cadmium were recoverable (average recovery rate was 99%), whether low, high or nearly equal. Next, the average of the recovery rate was determined for the concentrations of manganese, zinc, magnesium, and copper. The results are shown in FIG. Note that the recovery rate in FIG. 13 was determined by recovery rate = (metal concentration of nitric acid extract (solution in which cadmium adsorbed to the column was eluted by nitric acid) / metal concentration of rice sample extract (before passing through the column)). The recovery rates were 99% for cadmium, 1% for manganese, 5% for zinc, 1% for magnesium, and 9% for copper. Thus, it was confirmed that the recovery rate of manganese, zinc, magnesium and copper, which might interfere with the cadmium immunoassay, was very low compared to the recovery rate of cadmium. From the above, it was found that cadmium can be selectively separated from rice using a cadmium separation column using a capricoat-immobilized resin.

[Example 2 ]
For several types of brown rice with different cadmium contents, the results of analysis by instrumental analysis by ICP emission analysis and immunoassay (kinexa method and immunochromatography method by fluorometer), which are conventional methods, were compared.

As in Reference Example 1, a measurement sample was obtained by treating a solution obtained by treating brown rice with hydrochloric acid with DDTC-capricoat solution and collecting (back-extracting) it in a water phase with a 2M hydrochloric acid solution.

  In conducting the immunoassay, it was deposited as a monoclonal antibody specifically recognizing Cd-EDTA as cadmium and deposited with the Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology as accession number FERM P-19703 on February 26, 2004. Nx22C3 produced from the hybridoma being used was used.

  As the ICP emission spectroscopic analyzer, SPECTRO CIROS-120 (EOP) manufactured by Rigaku Corporation was used. The measured elements and the wavelengths used are Cd (214.438 nm), Zn (213.856 nm), Mn (257.610 nm), Mg (279.553 nm), Fe (259.940 nm), Cu (324.754 nm). Plasma conditions are RF power 1.4 kW, plasma gas 13.0 L / min, auxiliary gas, and nebulizer gas 0.9 L / min. A standard metal solution for preparing a calibration curve was prepared using atomic absorption analysis (manufactured by Wako Pure Chemical Industries). The hydrochloric acid treatment solution was introduced into the apparatus as it was. The sample introduction time is 25 seconds, and the analysis time is 24 seconds. The measurement was repeated three times, and the average was taken as the measured value.

  The Kinexa method using a fluorometer was performed using a flow-type fluorescence sensor (Sapidyne Instruments Inc., trade name KinExA3000). In addition, agarose beads (Pharmacia) were used as a carrier for immobilizing the antigen. To 1 ml of the agarose bead suspension, 100 μl of Cd-EDTA-OVA solution (1 mg / ml) was added to immobilize the antigen on the beads. A secondary antibody (anti-mouse IgG antibody) labeled with the fluorescent substance Cy5 was indirectly fluorescently labeled, and the binding between the antibody and the immobilized antigen was detected with a fluorescent sensor. The procedure is as follows.

  In the measurement operation, a sample mixed with a known amount of primary antibody in advance is brought into contact with antigen-immobilized beads (step 1). Here, surplus unreacted primary antibody that has not reacted with cadmium contained in the sample reacts with the immobilized antigen on the beads and is captured. After washing liquid is poured into the cell and the sample is removed from the cell, a sufficient amount of fluorescently labeled secondary antibody is flowed into the cell (step 2). In this operation, the fluorescently labeled secondary antibody reacts specifically with the primary antibody captured by the immobilized antigen, and only an amount corresponding to the amount of the bound primary antibody binds to the immobilized beads. Finally, when the washing solution is flowed to remove unbound fluorescently labeled secondary antibody from the cell (step 3), only the labeled fluorescent substance bound to the primary antibody bound to the antigen-immobilized beads via the secondary antibody is contained in the cell. The amount of the primary antibody bound to the antigen-immobilized beads can be detected by measuring the fluorescence intensity that remains inside, and the amount of free antigen present in the sample can be known.

  When cadmium is added to a fixed concentration of fluorescently labeled antibody at various concentrations, the decrease rate of the detected fluorescence intensity is defined as the binding inhibition rate to cadmium, and a calibration curve showing the relationship with the cadmium addition concentration at that time is shown in the figure 7 (A). The measurement sample was measured with this apparatus, and the cadmium concentration contained in the rice was determined from the calibration curve.

  Moreover, it compared with the value measured by the ICP emission spectrometry currently performed using the same measurement sample. The results are shown in FIG. As can be seen from FIG. 7B, the measurement value obtained by the immunoassay method using the flow type fluorescence sensor showed almost the same value as the measurement obtained by the ICP emission spectroscopic analysis method. Therefore, it was found that this immunoassay can be used in the same manner as conventional instrumental analysis to determine whether the rice contains cadmium that exceeds the standard value (0.4 ppm in rice, that is, 40 ppb in the processing solution) according to the notification of the Food Agency.

[Example 3 ]
An immunoassay of cadmium separated by a cadmium separation column was studied. The brown rice-derived cadmium solution (brown rice extract) 75 μl eluted with nitric acid in Example 1 was diluted and neutralized with 925 μl of Tris-hydrochloric acid buffer (pH 8.0, 50 mM) containing 1 μM EDTA.

  Next, to prepare a calibration curve, a cadmium solution containing 50 mM nitric acid was prepared in the laboratory, diluted and neutralized in the same manner as the brown rice extract, and then slowly added with 500 μl of about 2 nM Nx22C3 antibody solution. Mixed. Further, about 2 nM Nx22C3 antibody solution (500 μl) was added to the above brown rice sample and mixed slowly, and then measured using a flow-type fluorometer KinExA3000 (Sapidyne). Each measurement was performed twice.

The measured value of the brown rice sample by immunoassay was converted into the cadmium concentration by the calibration curve. Further, a sample pretreated by a conventional method (decomposing rice with nitric acid to elute cadmium) was prepared, and the cadmium concentration was measured with an ICP emission spectroscopic analyzer. These results are shown in FIG. In addition, since both the immunoassay and the ICP emission spectroscopic analysis have increased the volume of the rice 10 times by the pretreatment, the value obtained by multiplying the measured value of FIG. 14 by 10 corresponds to the concentration in the rice. In FIG. 14, the correlation coefficient (R ² ) between the immunoassay and the ICP emission analysis for the sample (7 points) for which the measurement value of the cadmium concentration was 65 ppm or less was obtained in both the immunoassay and the ICP emission analysis was 0.97, It was a good match. Further, none of the samples (4 points) determined to be 60 ppb or more by ICP emission analysis were determined to be 40 ppb or less by immunoassay. Therefore, it was found that the present immunoassay can be used in the same manner as in conventional instrumental analysis to determine whether the rice contains cadmium exceeding the standard value (0.4 ppm in rice, that is, 40 ppb in the processing solution) according to the notification of the Food Agency. This also revealed that a cadmium separation column using capricoat can be applied to the immunoassay of cadmium in rice.

  The present invention can be used for easily measuring the amount of cadmium contained in food such as rice, agricultural products, marine products, livestock products, or other agricultural products, marine products, livestock products by immunoassay.

It is a figure which shows the measurement principle of a fluorescence immunoassay. It is a block diagram of an example of an immunochromatography apparatus. It is a principle figure of the 2nd detection method of cadmium using the anti-cadmium monoclonal antibody by immunochromatography. It is a graph which shows the collection | recovery rate of cadmium from the brown rice by a hydrochloric acid solution. It is a graph which shows the density | concentration of Mg, Mn, and Zn extracted from the brown rice with the hydrochloric acid solution. (A) is a graph which shows the relationship between the pH of the aqueous solution of the simulation sample containing the multiple types of metal supposing cadmium contamination rice, and the recovery rate of each metal. (B) is a graph showing the recovery rate of each metal at pH 2 using an actual sample known to contain cadmium by ICP emission spectroscopic analysis. (A) is a calibration curve showing the relationship between cadmium concentration and fluorescence intensity, and (B) is a diagram showing the correlation between the concentration measured by ICP emission analysis and the concentration measured by Kinexa method. It is a flowchart which shows the procedure of the cadmium analysis of the brown rice attached to the information (48Cd) regarding the cadmium in the foodstuff currently disclosed on the website of the Ministry of Agriculture, Forestry and Fisheries. It is a flowchart which shows the procedure of cadmium analysis of cereals other than brown rice, beans, vegetables collected by pre-harvest survey, and fruit trees. It is a flowchart which similarly shows the procedure which analyzes the cadmium in salty spice. It is a graph which shows the measured value of metal content about 27 localities 34 samples of brown rice (Koshihikari). It is a figure which shows the cadmium density | concentration contained in hydrochloric acid extract and nitric acid extract (after column elution). It is a figure which shows the ratio of the various metals collect | recovered by nitric acid elution. It is a comparison figure of the measurement result of an immunoassay and ICP analysis. It is a perspective view of the cadmium separation column apparatus of this invention. It is sectional drawing of the cadmium separation column apparatus of this invention.

Explanation of symbols

6). 6. Cadmium separation column device Container 8. Sample liquid inlet 9. Sample liquid outlet 12. filler

Claims (3)

  0.002M to 2M hydrochloric acid solution is added to the measurement object to extract cadmium, the resulting solution is adjusted to pH 1.5 to 2.5, and tri-n-octylmethylammonium chloride is applied to the surface. A pretreatment step for obtaining a measurement sample by neutralizing a solution obtained by bringing the carrier into contact with nitric acid having a concentration of greater than 0.01 and 0.5 M or less after contacting the carrier with the immobilized carrier; A cadmium measurement method comprising a measurement step of analyzing the cadmium content by subjecting the measurement sample to an immunoassay for measuring cadmium using an antigen-antibody reaction.   The method for measuring cadmium according to claim 1, wherein the hydrochloric acid solution is contacted with the carrier by a column method.   The cadmium measurement method according to claim 1 or 2, wherein the measurement object is a grain.