KR20090054347A - A method of pre-treatment for analysis of heavy metals that is contained a sample for analysis of icp - Google Patents

Abstract

The present invention relates to a pretreatment method and analysis for the analysis of heavy metals contained in plastic materials, in particular polypropylenes containing halogen elements, and more particularly, trace amounts contained in polypropylene (Poly-Propylene) materials added with halogen elements. The present invention relates to a pretreatment method for heavy metal analysis by simultaneously using acid decomposition and microwave decomposition for heavy metal analysis such as lead (Pb) and cadmium (Cd) elements of the metals, and using ICP (Inductively Coupled Plasma) In case of analysis, the pretreatment is performed to accurately analyze the amount of heavy metals contained in the sample.

Microwave digestion, ICP (Inductively Coupled Plasma), heavy metals, acid decomposition

Description

A method of pre-treatment for analysis of heavy metals that is contained a sample for analysis of ICP

The present invention relates to a pretreatment method for the analysis of heavy metals such as lead (Pb), cadmium (Cd), etc. contained in a plastic containing a halogen element, and more particularly contained in poly-propylene (Poly-Propylene) For the analysis of heavy metals such as lead, cadmium, etc., the process of pre-treatment of analytical samples to obtain reliable ICP (Inductively Coupled Plasma) analysis results by repeating the process of decomposing with microwaves followed by microwave decomposition will be.

In general, heavy metals refer to heavy metal elements having a specific gravity of 4 or more mainly located below the periodic table such as arsenic, lead, antimony, mercury, cadmium, chromium, tin, zinc, barium, bismuth, nickel, cobalt, manganese, vanadium, and selenium. . When heavy metals are discharged into the environment, humans also belong to the biosphere while circulating the biosphere, and much effort is required to prevent environmental pollution by heavy metals. Heavy metals are very dangerous because even if they accumulate in the body, they do not excrete well and accumulate in the protein in our body and cause side effects over a long period of time. In order to prevent this risk, food, beverages, air, etc., most of the heavy metal content standards are provided, and representative examples of the damage caused by heavy metal contamination are as follows.

People with Itai Thai disease caused by cadmium contamination cause disorders of calcium metabolism, a major component of bone, and cartilage bone, causing many people to suffer pain and death by methyl mercury mixed in factory wastewater. Minamata disease also causes great damage, and many people have been killed by two diseases caused by the heavy metal contamination in Japan in the past, and many people who suffer from sequelae still survive.

Recently, governments around the world have determined that heavy metals, including cadmium, mercury, and lead, are harmful to ecosystems including humans and can cause environmental pollution. Lead and hexavalent chromium are often leaked to the outside when they contain more than a certain amount of waste, contaminating the surrounding ecosystem. Therefore, the European Parliament has identified cadmium, lead, 6 in all vehicles sold in Europe since July 1, 2003. Passed recycling laws (regulations 2000/53 / EC and 2002/525 / EC) prohibiting the inclusion of hazardous heavy metals such as chromium and mercury. This applies to all parts and coating materials of automobiles. Due to technical limitations, we have made exceptions for parts that cannot produce parts or materials that do not contain harmful heavy metals. However, even in such exceptional cases, the amount of use and disposal method are strictly regulated. The amount of consumption required by the European Union is 100 ppm or less for cadmium, and for hexavalent chromium (Cr ⁺⁶ ) and lead (Pb). It must meet 1000 ppm or less.

In addition, in China, which is rapidly developing in the automobile field, Chinese law RoHs has been applied since 2007.3.1 {Pb, Cd, Hg, Cr ⁺⁶ , Brominated Flame Retardant (Restrictions on PBBs, PBDEs)} In Korea, it has been analyzed that the components of lead (Pb), cadmium (Cd), etc. contained in PP (Poly-Propylene) among automotive plastic materials, and accurately quantitate the amount to prevent environmental pollution and emerge globally In order to actively respond to various heavy metal-related regulations, research on how to effectively analyze trace heavy metals is urgently needed.

By the way, the analysis method of the trace amount of heavy metals may be improved by using analytical equipment having high performance, but may improve the analysis performance by controlling the pretreatment process for analysis. Improving the pretreatment process for heavy metal analysis in situations is an important step in improving the precision of the analysis.

Conventionally, in the pretreatment for heavy metal analysis using microwave, even when halogen element is added to polypropylene (Poly-Propylene) of automotive plastic materials, nitric acid (HNO ₃ ) and hydrogen peroxide (H ₂ O ₂₎ Pretreatment method is used to analyze the heavy metal content of metal elements with specific gravity of 4 or more such as lead (Pb), cadmium (Cd), mercury (Hg), and hexavalent chromium (Cr ⁺⁶ ) contained in plastic samples. However, because the analysis technique was not properly established, errors occurred in the analysis, which caused problems in the reliability of the analysis results.

In addition, ICP (Inductively Coupled Plasma) is frequently used for heavy metal analysis.However, even if the analyzer is excellent in ICP, accurate analysis results may not be obtained unless the pre-treatment of the analytical sample or the sample is not sufficiently decomposed, as well as precision. There was an unexpected problem.

Accordingly, the present inventors have tried to improve the conventional analytical sample pretreatment method, and as a result, the analytical sample was analyzed in order to analyze the trace metals such as lead, cadmium, etc. contained in the polypropylene (Poly-Propylene) containing halogen element using ICP. It is a pretreatment method that decomposes analytical samples using acid and microwave. In the pretreatment method, the problem of incomplete dissolution of the halogen element contained in the analyte sample was improved by adding and improving the process of adding a small amount of sulfuric acid for complete dissolution and volatilization of the remaining halogen element after addition of nitric acid and hydrogen peroxide. Due to the presence of the halogen element to reduce the mattress effect that is higher than the actual results in the lead, cadmium analysis, to complete the present invention to provide more accurate and accurate ICP analysis data.

The present invention to solve the above problems

After adding 2-4 ml of nitric acid (HNO ₃ ) per 0.35 g of analyte to a vessel for analytical sample of ICP (Inductively Coupled Plasma), the vessel is charged into the microanalyzer. Stage 1;

A second step of heating for 3 to 6 minutes with a microwave having an energy of 200 to 400 W in a microwave cracker and again for 8 to 12 minutes at 500 to 700 W, and then cooling the heated vessel;

A third step of adding a mixture of sulfuric acid (H ₂ SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ) to the cooled vessel of the _second step;

The vessel of the third stage is heated in a microwave cracking apparatus with a microwave having an energy of 200 to 400 W for 2 to 4 minutes, then heated at 500 to 700 W for 4 to 7 minutes, then cooled and released from the vessel. Fourth step; And

And a fifth step of diluting the cooled analysis sample solution of the fourth step with distilled water.

In the analysis using heavy metal ICP such as lead and cadmium in halogen-added plastics, accurate analysis results could not be obtained due to the problem of analytical data due to incomplete dissolution due to halogen elements. By adding a process step of adding a small amount of sulfuric acid to the pretreatment method by the microwave decomposition method, it is possible to obtain accurate and reliable ICP analysis result data. In addition, since it is a closed system like microwave acidification using microwaves, there is no acid evaporation, no loss of volatile elements, and no vapor from the acid stream flows out. In addition, by using microwaves, the process of repeating and heating is further reduced by two to three times, which greatly reduces the pretreatment time.

Through the pretreatment method of the present invention as described above, it is possible to completely decompose heavy metals contained in plastics and to completely dissolve halogen elements and volatilize halogen elements from the sample to be analyzed, thereby leading lead (Pb), cadmium (Cd), When measuring the heavy metal content of metal elements with specific gravity 4 or higher such as mercury (Hg) and hexavalent chromium (Cr ⁺⁶ ), it is possible to minimize the mattress effect caused by halogen elements and obtain highly reliable analytical data. will be.

In particular, there is an effect that can be precisely analyzed for heavy metal content, such as household articles made of plastics containing halogen elements without using expensive analyzers.

This invention will be described in more detail. However, the present invention is not limited to the description of the structure of the following invention.

The present invention provides a specific gravity such as a trace amount of lead (Pb), cadmium (Cd), mercury (Hg), hexavalent chromium (Cr ⁺⁶ ), etc., contained in a plastic material, particularly a plastic containing halogen elements. The present invention relates to a pretreatment method and analysis for the analysis of heavy metals above. More specifically, a method of pretreatment for analyzing heavy metals of lead (Pb) and cadmium (Cd) elements in polypropylene containing halogen elements, The sample to be analyzed is decomposed by repeating digestion and digestion using microwave. This will be described in more detail below.

The sample to be analyzed is placed in a vessel for a microanalyzer, and 2-5 ml of nitric acid (HNO ₃ ), more preferably 2-4 ml, is added to 0.35 g of the sample to be analyzed. first step of charging the vessel;

Here, if the first step is more than 5 ml of nitric acid, there is a problem that the vessel is exploded due to a violent reaction with the sample, if less than 2 ml there is a problem that the sample is not completely dissolved .

In a microwave cracker it is heated for 3 to 6 minutes with a microwave having an energy of 200 to 400 W, more preferably 250 to 300 W and again 8 to 12 at 500 to 700 W, more preferably 550 to 600 W A second step of heating for minutes and cooling the heated vessel;

Here, the reason for heating the energy of 200 to 400 W, more preferably 250 to 300 W for 3 to 6 minutes is to decompose the carbon bond ring forming the polypropylene structure, which is again 500 to 700 W More preferably, the reason for heating for 8 to 12 minutes at 55 to 600 W is to completely decompose and dissolve the elements except for the halogen element, and the reason for not proceeding to a high energy of 600 W or more from the beginning is that This is to prevent the sample solution from boiling over or exploding.

A third step of adding sulfuric acid (H ₂ SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ) to the vessel at a mixing volume ratio of sulfuric acid: hydrogen peroxide = 0.25 to 0.5: 1 in a vessel;

Conventionally, in the analysis of heavy metals of halogen-containing plastic samples, pretreatment is performed only with nitric acid or sulfuric acid.In the conventional pretreatment method, the halogen element is incompletely processed, and the halogen element remaining in the measurement sample causes the matrix effect. Was low. In order to solve this problem, the present invention devised and applied a method of mixing and adding sulfuric acid and hydrogen peroxide at an appropriate ratio.

Here, hydrogen peroxide is added to oxidize the sample to be dissolved, so as to dissolve the matrix of the remaining sample without being completely dissolved in nitric acid, and sulfuric acid is used to completely dissolve and volatilize the halogen element remaining in the sample. To be added.

In addition, when the amount of sulfuric acid added is less than 0.25 ratio to the amount of hydrogen peroxide added, there is a problem that complete dissolution of the halogen element and volatilization of the halogen element does not volatilize from the sample to be analyzed, and when sulfuric acid is added in excess of 0.5 ratio, sulfuric acid and hydrogen peroxide Rapid reactivity causes the vessel to explode.

In a microwave cracker it is heated for 2 to 4 minutes with a microwave having an energy of 200 to 400 W, more preferably 250 to 300 W and again 4 to 7 at 500 to 700 W, more preferably 550 to 600 W A fourth step of heating for minutes, then cooling and releasing the vessel; And

Here, the reason for initially heating the sample to be analyzed at low energy for 2 to 4 minutes is for the complete decomposition of the polypropylene remaining in the sample to be analyzed. For complete dissolution of remaining metals and halogen elements and complete volatilization of halogen elements from the sample to be analyzed. At this time, the reason for not heating with high energy from the beginning is to prevent the problem of the vessel exploding due to the boiling of the sample solution in the vessel during the heating or the rapid reaction of the analyte and the added sulfuric acid and hydrogen peroxide.

A fifth step of diluting with the cooled distilled water of the fourth step;

After the pretreatment process, the ICP sample is processed in a state suitable for analysis.

Conventionally, by only adding hydrogen peroxide in the third step, sulfuric acid is added to further reduce the process of repeating and heating the sample by using microwave for complete dissolution, volatilization, and discharge of analyte sample and halogen element. In this process, lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As), chromium (Cr), tin (Sn), and zinc (Zn) Heavy metal analysis, which is a metal element having a specific gravity of 4 or more such as) and nickel (Ni), enables the precise measurement even at the ppb level.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to the following examples and the like.

Example  One

As shown in schematic diagrams an embodiment according to the invention in FIG.

350 mg of halogen-added automotive plastic material (Poly-Propylene) was placed in a vessel for microanalyzer, ₃ ml of nitric acid (HNO ₃ , 65%) was added, and the vessel was charged into the microanalyzer. (Step 1) After that, the vessel was heated for 5 minutes with a microwave of 300 W in a microwave cracker, followed by heating at 600 W for 10 minutes, and after cooling the heated vessel at room temperature for 30 minutes (second Open the vessel lid, add 0.5 ml of sulfuric acid (H ₂ SO ₄ , 96%) and 1.5 ml of hydrogen peroxide (H ₂ O ₂ , 30%) to the reaction vessel (step 3). In a microwave digester, a 300 W microwave was heated for 2 minutes and again at 600 W for 5 minutes and the heated vessel was air cooled at room temperature for 30 minutes and the vessel was released. )

The air-cooled analytical sample solution was quantitatively transferred to a 100 mL volumetric flask, filled with distilled water and diluted up to 100 divisions, and pretreated as an analytical sample for ICP analysis.

Example  2

The procedure was carried out under the same conditions and methods as in Example 1, but in the first step of Example 1, the sample was diluted to one tenth before the vessel was charged into the microanalyzer.

Comparative example  One

Halogen-containing plastic plastics (PP, Poly-Propylene) 350 mg was prepared and the samples were pretreated by a pretreatment method for conventional ICP analysis.

According to the conventional pretreatment method,

350 mg of halogen-added automotive plastic material (Poly-Propylene) was placed in a vessel for microanalyzer, ₃ ml of nitric acid (HNO ₃ , 65%) was added, and the vessel was charged into the microanalyzer. The vessel was then heated in a microwave digester for 5 minutes with 300 W microwave, again at 600 W for 10 minutes and the heated vessel was air cooled at room temperature for 30 minutes, then the vessel lid was opened and 2 ml of hydrogen peroxide Only (H ₂ O ₂ , 30%) was added to the reaction vessel, heated for 2 minutes with a 300 W microwave in a microwave digester, then heated at 600 W for 5 minutes, and the heated vessel was kept at room temperature for 30 minutes. The procedure of air cooling the sample solution and releasing the vessel was repeated three to four times.

The air-cooled analytical sample solution was transferred quantitatively into a 100 mL volumetric flask, filled with distilled water to 100 scale, and diluted, and pretreated as an analytical sample for ICP analysis.

Comparative example  2

An analytical sample was pretreated for ICP analysis in the same manner as in Example 1 using the same automotive plastic material as Example 1 (Poly-propylene). However, in the third step, 0.4 ml of sulfuric acid (H ₂ SO ₄ , 96%) and 1.65 ml of hydrogen peroxide (H ₂ O ₂ , 30%) were added to the reaction vessel. (H ₂ SO ₄ : H ₂ O ₂ = 0.24: 1)

Comparative example  3

An analytical sample was pretreated for ICP analysis in the same manner as in Example 1 using the same automotive plastic material as Example 1 (Poly-propylene). However, in the third step, 0.9 ml of sulfuric acid (H ₂ SO ₄ , 96%) and 1.65 ml of hydrogen peroxide (H ₂ O ₂ , 30%) were added to the reaction vessel. (H ₂ SO ₄ : H ₂ O ₂ = 0.54: 1)

Comparative example  4

The same vehicle plastic material and pretreatment method as in Comparative Example 1 were carried out, but the sample was diluted to one tenth before the vessel was charged into the microanalyzer in the first step.

Experimental Example  One

Total within analytical sample Pb  Heavy metals

Using the ICP (model ULTIMA 2, Horiba JoVin.) Analyzer, the lead (Pb) analysis of the Examples 1 to 2 and Comparative Examples 1 to 3 was carried out under the condition that the wavelength of the microwave was Pb 283.306 nm and Cd 228.802 nm. After that, the analytical data results thereof are shown in Table 1 below.

division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 1 time 122.00 11.3 142.00 133.00 123.00 Episode 2 121.00 13.4 146.00 136.00 120.00 3rd time 118.00 12.5 144.00 129.00 119.00 4 times 119.00 11.3 143.00 132.00 119.00 Average 120.00 12.13 144.00 132.50 120.25

(Unit: ppm of Pb heavy metal in the analytical sample of Table 1)

Experimental Example  2

Total within analytical sample CD  Heavy metals

Cadmium (Cd) analysis of the Examples 1 to 2 and Comparative Examples 1 to 3 were carried out using an ICP (model ULTIMA 2, Horiba JoVin.) Analyzer under the condition that the wavelength of the microwave was Pb 283.306 nm and Cd 228.802 nm. After that, the analytical data results thereof are shown in Table 2 below.

division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 1 time 529.00 50.00 585.00 556.00 528.00 Not measurable Episode 2 587.00 54.00 672.00 608.00 588.00 109.00 3rd time 603.00 52.00 723.00 617.00 597.00 Not measurable 4 times 599.00 54.00 649.00 607.50 604.00 Not measurable Average 579.50 52.75 657.25 608.50 579.25 Almost no measurement

(Unit of Pb heavy metal in the analytical sample of Table 1 above: ppb)

Through the analysis results of Example 1 and Comparative Example 1 of Table 1, 2, the pretreatment method according to the present invention can reliably remove the halogen element in the sample to be analyzed, thereby preventing the mattress effect As a result, it can be confirmed that the analysis results are more accurate and reliable than the conventional pretreatment methods.

In addition, through the analysis results of Example 1 and Comparative Example 2 of Table 1, in the third step of the pretreatment method of the present invention, if the sulfuric acid is not added in sufficient amount to the amount of hydrogen peroxide added, the halogen element in the sample to be analyzed is sufficiently It was found that it could not provide accurate analytical results because it could not be dissolved and volatilized. In Comparative Example 3, a large change in the measurement result was obtained even when the mixing volume ratio of hydrogen peroxide to sulfuric acid exceeded 0.5: 1 in the third step. It can be seen that there is no. In other words, it can be seen from the measurement results of Comparative Examples 2 and 3 that the mixing volume ratio of hydrogen peroxide to sulfuric acid is preferably sulfuric acid: hydrogen peroxide = 0.25 to 0.5: 1.

In addition, in Experimental Example 2, through the results of Example 2 and Comparative Example 4 through the pre-treatment method of the analyte sample of the present invention ICP can be confirmed that it is possible to analyze up to ppb unit that is difficult to measure in general ICP analysis. Furthermore, the excellent effect of this invention was confirmed.

When analyzing heavy metal content in plastics containing halogen elements using ICP, pretreatment of analytical samples using the present invention results in more reliable measurement results than conventional ICP analysis. Since it can be provided, it is expected to be able to perform accurate heavy metal analysis using the present invention in the environmental field, analytical chemistry field, and the like.

1 is a schematic diagram of a pretreatment method of an ICP sample according to Example 1.

Claims (4)

After adding 2-4 ml of nitric acid (HNO ₃ ) per 0.35 g of analyte to a vessel for analytical sample of ICP (Inductively Coupled Plasma), the vessel is charged into the microanalyzer. Stage 1; A second step of heating for 3 to 6 minutes with a microwave having an energy of 200 to 400 W in a microwave cracker and again for 8 to 12 minutes at 500 to 700 W, and then cooling the heated vessel; A third step of adding a mixture of sulfuric acid (H ₂ SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ) to the cooled vessel of the _second step; The vessel of the third stage is heated in a microwave cracking apparatus with a microwave having an energy of 200 to 400 W for 2 to 4 minutes, then heated at 500 to 700 W for 4 to 7 minutes, then cooled and released from the vessel. Fourth step; And And a fifth step of diluting the cooled analysis sample solution of the fourth step with distilled water. The method of claim 1, wherein the mixing volume ratio of sulfuric acid and hydrogen peroxide added to the vessel in the third step is sulfuric acid: hydrogen peroxide = 0.25 ~ 0.5: 1. The method of claim 1 or 2, wherein the sample to be analyzed for ICP in the first step is halogen-containing polypropylene (Poly-Propylene). The sample to be analyzed is lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As), chromium (Cr), tin (Sn), zinc (Zn) and nickel (Ni). A pretreatment method for an ICP analysis sample, characterized in that it comprises one or more heavy metals selected from.

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