JP4305849B2 - Organic substance analysis pretreatment method, heavy metal analysis method in organic substance, reaction vessel and batch hydrothermal decomposition apparatus - Google Patents

Description

  The present invention relates to a pretreatment method for analyzing heavy metal components in organic substances such as plastics, biological samples, environmental samples, etc., a heavy metal analysis method in organic substances, a reaction vessel used for the organic substance analysis pretreatment method, and batch hydrothermal decomposition It relates to the device.

  With the recent increase in awareness of environmental conservation, regulations on toxic substances contained in industrial products, industrial materials, waste electronic and electrical equipment, etc. are being strengthened. Specifically, a directive on the restriction of heavy metals such as cadmium and lead came into effect in the European Official Gazette, and the use and disposal of hazardous substances worldwide, including the enforcement of the Soil Contamination Countermeasures Law in January 2003. Regulations on are being strengthened.

  Under such circumstances, demand for the analysis of harmful heavy metals is rapidly increasing, and public testing research institutions and measurement certification establishments are inundated with requests for tests regarding the analysis of heavy metals in products and materials.

As a conventional method for decomposing organic compounds in heavy metal analysis,
(1) Dry disassembly described in the Japanese Pharmacy Law-Plastic Drug Container Test Method, Living Goods Test Method-Equipment / Container Packaging and Toy Test Method, Food Hygiene Inspection Guidelines-Synthetic Resin and Rubber Product Material Test, etc. Law,
(2) Described in ministerial ordinances (see Non-Patent Document 1) and Plastics-Determination of cadmium-Wet decomposition method (see Non-Patent Document 2), which determine the method of cadmium testing according to the designated requirements for agricultural land and soil control areas Wet decomposition method.
(3) There is a microwave heat decomposition method for shortening the decomposition time by performing a heating operation in wet decomposition with a closed microwave.

Incidentally, the ion product of water (Kw) is at normal temperature is 10 ^-14, a critical point 374.1 ° C., supercritical water exceeds 22.1 MPa, or, in the high pressure and high temperature in the vicinity thereof proceeds dissociation of water, It has long been known to function as an acid or alkali, and in the early 1980s, Model of MIT proposed an oxidative decomposition process using supercritical water.

  In Japan, since the beginning of the 1990s, patents using supercritical water characteristics began to be published, focusing on the detoxification and recycling of organic waste. Adaptive supercritical water utilization technology is being developed and put into practical use.

Ministerial Ordinance (Ministry of Agriculture, Forestry and Fisheries Ordinance No. 47 of 1971) that stipulates the method of examination of the amount of cadmium pertaining to designated requirements for agricultural land and soil countermeasure areas Plastics-Determination of cadmium-Wet decomposition method (European Standard EN1122: 2001)

However, each of the conventional decomposition methods described above has advantages and disadvantages.
First, the dry decomposition method has the advantage of being easy to operate, such as being able to decompose a large number of samples at a time and using a small amount of reagent for the decomposition operation. On the other hand, there is a disadvantage that low boiling point elements are likely to be volatilized during the thermal decomposition treatment, and in order to suppress this, a decomposition time represented by a low temperature ashing method or the like requires a relatively long time. It is necessary to adopt analytical methods.

  Secondly, the wet decomposition method has the advantage that it can perform an analytical operation with a low recovery rate and low volatility of low boiling point elements. On the other hand, there are disadvantages in that the types and amounts of reagents used in the decomposition operation are relatively large, and in the case of difficult-to-decompose samples, a long decomposition time is required.

  The technology developed to shorten the decomposition time of the above-described wet decomposition method is the microwave heating decomposition method, but many of the decomposition apparatuses have a relatively small number of samples that can be simultaneously decomposed, and before and after the decomposition treatment. Since the operability is complicated, the number of samples that can be processed per unit time has not shown a significant effect even though the time required for sample decomposition can be shortened.

  In addition, as a pretreatment of samples in the qualitative / quantitative analysis of heavy metal components, a technique for decomposing organic substances using supercritical water has not been developed.

  The present invention has been made by paying attention to such a conventional problem. When analyzing a heavy metal component in an organic substance capable of easily and rapidly decomposing the organic substance using high-temperature high-pressure water or supercritical water. An object of the present invention is to provide a pretreatment method, a heavy metal analysis method in organic matter, a reaction vessel and a batch hydrothermal decomposition apparatus used in the organic matter analysis pretreatment method.

  With regard to the decomposition of organic compounds, there is a need for a rapid processing technique that can process a large number of samples at the same time to prevent the volatilization of elements. A method for decomposing an organic compound and analyzing heavy metal substances contained in the decomposition product was found, and the present invention was completed.

That is, the organic matter analysis pretreatment method according to the present invention is a pretreatment method for analyzing heavy metal components in an organic matter, and decomposes the organic matter with high-temperature high-pressure water or supercritical water at 200 ° C. or higher and 10 MPa or higher. It is characterized by.
When analyzing heavy metal components in organic matter, the organic matter should be supercritical water at 374.1 ° C or higher and 22.1MPa or high-temperature high-pressure water at 200 ° C or higher and 10MPa or higher, especially at high temperatures near the critical point (374.1 ° C · 22.1MPa). By applying the method of decomposing with high-pressure water, it becomes possible to perform the decomposing process quickly. In addition, the qualitative / quantitative analysis operation of the heavy metal component after the organic substance is decomposed can be performed by chemical analysis, instrumental analysis, and the like that are generally performed conventionally.

In the organic matter analysis pretreatment method according to the present invention, the high-temperature high-pressure water or supercritical water may contain an oxidizing agent.
If the sample is an organic compound that does not easily decompose in high-temperature and high-pressure water such as an addition polymerization type polymer (for example, polyethylene), add an oxidizing agent such as hydrogen peroxide in addition to pure water. The processing time can be shortened.

In the organic matter analysis pretreatment method according to the present invention, the decomposition residue generated after the decomposition treatment may be decomposed with an acid or an alkali agent.
When undecomposed residue is generated in the decomposition solution after hydrothermal decomposition, first transfer the decomposition solution together with the residue to another container such as a beaker, and use acid such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, hydrofluoric acid alone. Alternatively, it is possible to perform more accurate quantitative analysis by adding a mixture or adding an alkali agent such as sodium hydroxide alone or in combination to dissolve the undegraded residue and then diluting and measuring the volume. it can.

The method for analyzing heavy metals in organic matter according to the present invention is characterized in that after the organic matter is decomposed by the organic matter analysis pretreatment method described above, the heavy metal component in the organic matter is analyzed.
FIG. 1 is an analysis flow of a typical example of the method for analyzing heavy metals in organic substances according to the present invention. In the method shown in FIG. 1, first, a sample 1 to be analyzed and pure water 2 as a solvent are taken in a pressure-resistant reaction vessel 3 in an arbitrary amount, and a decomposition treatment operation is performed by a hydrothermal decomposition apparatus 4. When an undecomposed residue is generated in the decomposed sample 5, a dissolution treatment is performed by adding an acid or the like (step 6), and after the undecomposed residue is dissolved, a dilution / volumetric operation is performed (step 7).

  In the case of using high-pressure hot water, the temperature and pressure during the decomposition treatment are preferably in the temperature range of 200 to 300 ° C. at which the ionic product (Kw) of water shows a maximum value. When supercritical water is used, the temperature is 374.1 ° C. or higher and 22.1 MPa or higher, which is the critical point of water.

The pressure in the container at this time may be measured using a pressure gauge, but the pressure is determined by the amount of the solvent (g) introduced into the container and the decomposition temperature (° C.). You may adjust with the quantity of the solvent to carry out. This is because the operation can be performed relatively easily without using a pressure gauge or the like. Table 1 shows the amount of water (g) necessary to set a predetermined pressure when the internal volume of the reaction vessel is 10 cm ³ .

  The reaction container according to the present invention is a reaction container used in the organic matter analysis pretreatment method described above, and is characterized in that the inner wall surface of the container for containing the organic matter and water is made of a nickel alloy or a gold alloy.

The material of the reaction vessel in the decomposition treatment step can be used even if it is generally made of SUS316. However, the reaction vessel may gradually corrode with high-temperature and high-pressure water or a halogen-containing organic compound during operation, and safety may be impaired. The problem is small if the container material component does not contain the element for analysis or if the element for analysis does not overlap with the analysis peak position of the component in the container. Contamination of the components in the decomposed sample may impair the quantitativeness of the analysis value.
For example, when analyzing cadmium in an organic compound, if the equipment material is composed of SUS316 material, if a large amount of iron in the equipment material is eluted in the hydrolyzed organic compound decomposition solution, the presence of iron Can be a major hindrance to the accurate determination of cadmium.

  Therefore, in the reaction vessel that performs the above-described decomposition treatment, the inner wall surface of the vessel that contains the organic matter and water is preferably made of a nickel alloy or a gold alloy. In this case, the material of the container may be made of a nickel alloy or a gold alloy, or a corrosion resistant layer such as a nickel plating layer or a gold plating layer may be provided on the inner wall surface of the container that contains the organic matter and water. Thereby, it can suppress that it contaminates with a container material.

  After completion of hydrothermal decomposition, the treatment solution 6 is transferred to a constant volume container such as a volumetric flask, diluted to a constant volume (step 8), and then subjected to heavy metals by conventional chemical analysis, instrumental analysis, etc. Qualitative / quantitative analysis may be performed (steps 9 and 10).

  A batch-type hydrothermal decomposition apparatus according to the present invention is a batch-type hydrothermal decomposition apparatus used in a pretreatment method for analyzing heavy metal components in organic matter, and includes the above-described reaction vessel and the inside of the reaction vessel at 200. It has a heating part which can be heated above ° C, and a temperature control part of the heating part.

  It is preferable to implement the organic substance analysis pretreatment method and the heavy metal analysis method in the organic substance using the batch hydrothermal decomposition apparatus according to the present invention. By making it a batch type, the contact part with the high-temperature high-pressure water becomes only the inner wall surface of the reaction vessel, and further, by using the above-mentioned reaction vessel, it is possible to suppress contamination of the container material substance in the decomposition solution. It becomes possible.

According to the present invention, various organic compound materials and products can be easily and quickly decomposed by a hydrothermal reaction. Therefore, the qualitative properties of heavy metals such as cadmium and lead contained in materials and products can be reduced.・ Quantitative analysis can be performed quickly and accurately.
In addition, according to the reaction container of the present invention, it becomes possible to suppress the contamination of the container material into the decomposition solution, and therefore, qualitative / quantitative analysis can be performed more accurately.

Hereinafter, embodiments of the present invention will be described specifically and in detail with reference to the accompanying drawings.
FIG. 2 is a diagram showing the configuration of the hydrothermal decomposition apparatus of this embodiment.
The hydrothermal decomposition apparatus 4 includes a reaction container 3 and a heating source 13 inside a container storage unit 12 of the container main body 11, and the container storage unit 12 can be closed by an upper lid 14. The hydrothermal decomposition apparatus 4 further includes a thermocouple 15, a temperature control unit 16, and a control communication unit 17.

  A sample and a predetermined amount of ultrapure water are introduced into the reaction container 3, and the reaction container 3 is set in the container storage unit 12 of the decomposition apparatus 4. The container storage unit 12 is covered with an apparatus exterior equipped with a heating source 13. The upper cover 14 of the decomposition apparatus 4 is tightened, and the preparation for the hydrothermal decomposition operation is completed.

  Next, while measuring the temperature of the container storage unit 12 with the thermocouple 15, the temperature control unit 16 heats the heating source through the control communication unit 17 to control the temperature of the container storage unit 12.

  FIG. 3 is a cross-sectional view showing details of the reaction vessel of this embodiment. The reaction vessel 3 has a vessel body 21, a vessel upper lid 22, and a vessel lower lid 23, and can be sealed. After the container lower lid 23 is attached to the container body 21, a predetermined amount of sample and ultrapure water are sealed. A container upper lid 22 made of a different diameter union is attached, and after purging the inside of the container with an inert gas, the container upper lid 22 is closed and sealed.

  In this embodiment, the temperature of the reaction vessel is controlled from room temperature to 600 ° C. by the temperature control device, and the organic compound such as plastic in the reaction vessel is decomposed by supercritical water or high-pressure hot water near the supercritical point. After decomposition, if necessary, the decomposition solution is adjusted by an acid dissolution method, and heavy metals are quantified using a conventional high-frequency plasma emission spectrometer or atomic absorption spectrometer.

Take 100 mg of polyethylene terephthalate (PET: [CAS # 29154-49-2]) pellets and 7.43 g of ultrapure water in a 10 cm ³ SUS-316TP container, purge and seal the interior with Ar gas, and then 300 ° C The hydrothermal reaction was carried out for 10 minutes.
Next, the decomposition treatment liquid and decomposition residue in the reaction vessel were transferred to a beaker, and after adding 1.0 g of sodium hydroxide, the volume was adjusted to 50 ml, and the decomposition residue was dissolved at room temperature.
As a control, 100 mg of PET not subjected to hydrothermal treatment was also dissolved at room temperature in 50 ml of 2% sodium hydroxide solution.
Each dissolved solution was filtered with filter paper No. 5C, and the weight of the dissolved residue remaining on the filter paper was compared.

  Table 2 shows the results of the residual weight of each solution in Example 1. PET subjected to hydrothermal treatment was easily dissolved at room temperature, whereas PET not subjected to hydrothermal reaction hardly dissolved. It was.

Contents (nickel plating the inner wall surface) SUS-316TP steel container of the product 10 cm ³ into two respectively, taking 100mg crushed samples of cadmium (Cd) polyethylene containing (PE), on one ultrapure water 4.75 g, other Was added with 4.75 g of hydrogen peroxide solution for atomic absorption analysis prepared with ultrapure water to a concentration of 20 wt%, and each container was purged with Ar gas and sealed, followed by hydrothermal reaction at 400 ° C. for 10 minutes. . Next, the decomposition treatment liquid and decomposition residue in the reaction vessel are transferred to a separate beaker for each reaction vessel, 1 ml of mixed acid (hydrochloric acid: nitric acid = 1: 1, for each atomic absorption analysis) is added, and about 10 on a hot plate. The solution was gently warmed for 5 minutes and then each lysate was made up to 50 ml in a volumetric flask. The residue (solid matter) in each solution was filtered with filter paper No. 5C, the cadmium concentration in each filtrate was measured with an inductively coupled plasma emission spectrometer, and the cadmium concentration in PE was calculated from the measured values.

Table 3 shows the results of Example 2. The measurement results of cadmium in PE obtained from the decomposition treatment method by addition of hydrogen peroxide were consistent with the guaranteed values attached to the product.
On the other hand, the result of the decomposition process using supercritical water alone was slightly lower than the guaranteed component value, but a quantitative value almost similar to this was obtained.

For comparison between the present invention and the conventional decomposition method, the quantitative accuracy of the decomposition solution and the total sample processing time required for quantitative analysis, a conventional wet decomposition using the PE sample shown in Example 2 is used. The cadmium in samples was quantitatively analyzed by the method and the dry decomposition method.
Wet decomposition method is European Standard EN1122: 2001, dry decomposition method is sanitary test method comment-life goods test method-material test method-decomposition treatment with reference to metals, and the decomposition treatment liquid obtained by each treatment method The cadmium concentration in the sample was measured by an inductively coupled plasma optical emission spectrometer, and the cadmium concentration in the sample was calculated from the measured value.
Regarding the ashing temperature of the sample by the electric furnace in the dry decomposition method, the treatment was performed under two conditions of 450 ° C. and 600 ° C.

  Table 4 shows the results of quantitative analysis of cadmium in each decomposition method and the total time required for sample processing. The supercritical decomposition treatment method according to the present invention has a shorter decomposition treatment time than the dry ashing method in which ashing is performed at 600 ° C. In addition, it was confirmed that heavy metals can be quantitatively analyzed with the same analytical accuracy as the conventional wet decomposition method.

  In order to compare the lower limit of determination of cadmium according to the present invention and the conventional method, the measurement of the operation blank solution in the hydrothermal decomposition method shown in Example 2 and the wet decomposition method shown in Example 3 was performed 10 times, The lower limit of cadmium quantification in each method was determined from a value 10 times the standard deviation.

  Table 5 shows the results of the lower limit of determination of cadmium in each decomposition method. It was confirmed that the hydrothermal decomposition method according to the present invention has a lower limit of quantification than the conventional wet decomposition method.

SUS-316TP steel container having an inner volume of 10 cm ³ without the container wall is plated, and SUS-316TP steel container with gold-plated at the same volume, as well as providing a SUS-316TP steel container with nickel plating, commercially available respectively 100 mg of vinyl chloride polymer (Kanto Chemical Co., Inc./44038-02) and 3.58 g of ultrapure water were introduced and subjected to a supercritical water reaction treatment at 400 ° C. for 10 minutes. Next, the decomposition solution containing insolubles is transferred to the beaker with the washing solution, and 1 ml of mixed acid (hydrochloric acid: nitric acid = 1: 1 for each atomic absorption analysis) is added to the beaker and gently added for about 10 minutes on a hot plate. After warming, the dissolved solution is made up to a volume of 50 ml with ultrapure water, the insoluble residue is filtered, the iron content in each filtrate is measured with an inductively coupled plasma emission spectrometer, and the corrosion condition of the inner wall in each container is measured. Compared.

  Table 6 shows the results of elemental analysis of Example 5, in which iron in the order of ppm was detected from the decomposition solution treated in the reaction vessel not subjected to the plating treatment, whereas the reaction vessel subjected to the plating treatment. In some cases, the iron concentration was less than the lower limit of quantification.

2 is a flow sheet for analysis of heavy metal substances in an organic compound according to the present invention. It is the schematic which shows the structure of the hydrothermal decomposition apparatus of this embodiment. It is sectional drawing which shows the embodiment example of a reaction container.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample 2 Pure water 3 Reaction container 4 Hydrothermal decomposition apparatus 5 Decomposition sample 11 Container main body 12 Container storage part 13 Heating source 14 Upper cover 15 Thermocouple 16 Temperature control part 17 Control communication part 21 Container main body 22 Container upper cover 23 Container lower cover

Claims (6)

A pretreatment method for analyzing heavy metal components in an organic substance, the organic substance being decomposed with high-temperature high-pressure water or supercritical water at 200 ° C. or higher and 10 MPa or higher. 2. The organic matter analysis pretreatment method according to claim 1, wherein the high-temperature high-pressure water or supercritical water contains an oxidizing agent. The organic residue analysis pretreatment method according to claim 1 or 2, wherein a decomposition residue generated after the decomposition treatment is decomposed with an acid or an alkali agent. A method for analyzing a heavy metal in an organic material, comprising analyzing the heavy metal component in the organic material after decomposing the organic material by the organic material analysis pretreatment method according to claim 1, 2 or 3. 4. A reaction vessel used in the organic matter analysis pretreatment method according to claim 1, 2, or 3, wherein the inner wall surface of the vessel containing the organic matter and water is made of a nickel alloy or a gold alloy. A batch-type hydrothermal decomposition apparatus used in a pretreatment method for analyzing a heavy metal component in an organic substance, comprising: a reaction vessel according to claim 5; and a heating unit capable of heating the inside of the reaction vessel to 200 ° C or higher. And a batch-type hydrothermal decomposition apparatus comprising a temperature control unit of the heating unit.

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