KR20030086490A - Assay method of heavy metals - Google Patents

Abstract

PURPOSE: An analysis method of heavy metals is provided, thereby easily and cheaply analyzing heavy metals, such as lead, cadmium or the like included in a food vessel, food packing paper and the like, in the field. CONSTITUTION: An analysis method of heavy metals comprises the steps of: (a) heating a testing sample to carbonize and ash it; (b) dissolving the ashed sample in acid, filtering the dissolved solution, and neutralizing the filtered solution with alkali; (c) adding sodium sulfate into the neutralized solution and reacting them; and (d) measuring and analyzing the reaction product, wherein the testing sample is a food vessel or food packaging paper; the acid is nitric acid; and the heavy metal is lead or cadmium or the mixture thereof.

Description

{Assay method of heavy metals}

The present invention relates to a heavy metal test method, and more particularly, to a method for testing lead or cadmium contained in food containers, food packaging, etc. using sodium sulfide.

Heavy metals are generic names of metals having a specific gravity of 4 or more and include mercury, cadmium, lead, copper, chromium, manganese, vanadium, gold, silver, platinum, and iron. Among them, lead and cadmium are representative environmental hormone substances, which have a high accumulation in target organs, and are widely exposed in everyday environments such as drinking water, tobacco smoke, and food containers, and are easily exposed.

Lead is the most widely polluting environment among heavy metals, which can come directly into the body in the form of dust or steam, but lead, which is attached to skin, clothing, and food, can also enter through the mouth and respiratory system. Symptoms of acute toxicity include vomiting and stomach cramps. Chronic toxicity results in decreased intelligence, hearing loss, liver dysfunction, kidney dysfunction, weight loss, diarrhea, muscle pain, weakness, and immune system disorders. Lead poisoning often occurs in environments such as lead manufacturing, pigments, paints, pesticides, compounds, or lead acid batteries.

Cadmium is a more dangerous heavy metal than lead. The symptoms of acute toxicity include dyspnea, chest compressions, anorexia, and vomiting. The chronic toxicity symptoms include emphysema, kidney disease, and three major symptoms of protein and hypopigmentation. , Osteomyelitis, cadmium yellow ring of abnormal teeth, high blood pressure, reduced immune function, prostate cancer, etc. may appear. In addition, cadmium is a substance that causes Itai Thai disease, which is well absorbed from the soil by plants, and the absorbed cadmium accumulates inside plant cells and is not removed even when washed.

In particular, since food containers or food wrapping papers come into contact with foods when they are manufactured, stored, distributed, and stored, they become toxic and accumulate in the body through foods when contaminated with lead and cadmium. In addition, a large amount of heavy metals are present on the outer surface or printed matter of the packaging that does not come in direct contact with food, and sometimes enters the human body during the use, landfill or incineration.

In addition, the detection of hazardous substances in food containers or food packaging is often reported. Lead was detected in beverage cans in the 1970s and DOP was detected in vinyl chloride wraps in 1986. In 1998, styrene dimers and styrene trimers were detected in cup noodle containers, bisphenol A was detected in polycarbonate bottles, and in 2002, benzophenone was detected in food containers. It can be seen that the possibility of poisoning due to heavy metals is very high.

Heavy metal contamination, especially lead and cadmium contamination, in food containers or food packaging is caused by the use of industrial pigments to give color to plastics.In order to prevent such contamination, Article 19 (1) of the Food Sanitation Act states, The person who conducts business shall comply with the standards and standards under Article 7 (1) and (2) or 9 (1) and (2) as prescribed by Ordinance of the Ministry of Health and Welfare. Should be inspected. " However, the existing heavy metal inspection method requires expensive foreign devices and specialized knowledge and skills, so it is practical to inspect the contamination of heavy metals in food containers or food wrapping papers in small food containers or food packaging manufacturers with insufficient capital and no human resources. There is an impossible problem.

The present invention has been made in order to solve the above problems, it is composed of the steps of pre-treatment of the sample and the preparation of the test solution and the measurement and analysis by the addition of sodium sulfide solution, the site inspection is possible and cost-effective heavy metal inspection method The purpose is to provide.

In order to achieve the above object, the present invention comprises the steps of heating the carbonized sample and then ingesting; Dissolving with acid, filtering and neutralizing; Reacting by adding sodium sulfide solution; It provides a heavy metal test method comprising the step of measuring and analyzing the reactants.

Heavy metal inspection method according to the present invention can be used for food containers, food packaging, plastic containers and the like.

In addition, the heavy metal test method according to the present invention can be used to detect heavy metals such as lead, cadmium, etc. from the sample, it can be economically and efficiently qualitatively and quantitatively analyze the heavy metal content of the sample.

Hereinafter, the configuration of the present invention will be described in detail.

Heavy metal test method according to the present invention comprises a pre-treatment step of the sample, the preparation of the test solution, the precipitation step of the heavy metal component, the qualitative test or quantitative test step of the heavy metal component.

In the pretreatment step of the specimen of the heavy metal inspection method according to the present invention, the specimen is heated and carbonized, followed by incineration. A certain amount of sample is attached to a quartz or porcelain crucible, loosely capped and carbonized by mild heating at 300 to 400 ° C, followed by intense heating at 500 to 600 ° C, and cooling to room temperature. The pretreatment step of the sample is a process for heating the sample to carbonize and decompose the organic matter contained in the sample, and not to decompose the heavy metal material to be examined.

In the preparation step of the test solution of the heavy metal inspection method according to the present invention, the sample pretreated in the above step is dissolved with acid, filtered and neutralized. Most of the heavy metals are dissolved in acid, but other carbonized components are not dissolved in acid, so that the samples are dissolved with acid and filtered to remove the carbonized components that are not necessary for the inspection, leaving only the heavy metals to be subjected to the heavy metal inspection of the present invention. As an acid for dissolving the heavy metal of the sample, sulfuric acid, hydrochloric acid and nitric acid may be used, but preferably 0.3-0.8 N nitric acid may be used, and most preferably 0.5 N nitric acid is used. . The process of dissolving heavy metals in acid is shown in Scheme 1 below.

Pb ²⁺ + Cd ²⁺ + 4HNO ₃ → Pb (NO ₃ ) ₂ + Cd (NO ₃ ) ₂ + 2H ₂ ↑

In addition, the heavy metal test method according to the present invention uses the principle that precipitation occurs when sodium sulfide solution is added to a solution containing heavy metal as described below. However, if the concentration of acid in the solution is high, the solubility constant increases, so that precipitation does not occur well, so that accurate heavy metal test results of the sample cannot be obtained. Therefore, in order to neutralize the test solution which has been acidified by adding acid, it is preferable to add phenolphthalein indicator, neutralize with ammonia solution, and then add acetic acid solution to adjust the acid concentration of the test solution to an appropriate level. The appropriate level of acid concentration is preferably adjusted to pH 3 to 5, which is an advantageous range in which heavy metal precipitates are generated.

In the heavy metal component precipitation step of the heavy metal inspection method according to the present invention, sodium sulfide solution is added to the test solution treated as described above, and reacted by mixing. The reaction of heavy metal ions with sodium sulfide produces sulfides that are insoluble in water. In particular, lead or cadmium ions react with sodium sulfide to give a yellowish brown precipitate. Sodium sulfide solution is added to the test solution for 5 minutes. The process of producing a yellowish brown precipitate from the lead or cadmium and sodium sulfide solution is shown in the following schemes 2 and 3.

Pb (NO ₃ ) ₂ + H ₂ S → PbS ↓ + 2HNO ₃

Cd (NO ₃ ) ₂ + H ₂ S → CdS ↓ + 2HNO ₃

Qualitative analysis of heavy metal components in the heavy metal inspection method according to the present invention can be carried out by placing the test solution treated as above on a white paper and observing from above. In addition, the quantitative test of heavy metal components can determine the concentration of lead or cadmium in a sample by comparing the standard solution of lead or cadmium with sodium sulfide solution.

The concentration of lead that can be detected from the test solution according to the heavy metal inspection method according to the present invention is 0.1 to 250ppm, preferably 5ppm to 100ppm can be detected.

In addition, the concentration of cadmium which can be detected from the test solution according to the heavy metal inspection method according to the present invention is 0.3 to 250ppm, preferably 25 to 100ppm can be detected.

Hereinafter, preferred examples are provided to aid in understanding the present invention. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited by the following examples.

Example 1

Sample pretreatment

1 g of a food container was used as a sample, and 1 to 2 drops of sulfuric acid were added thereto, and the mixture was carbonized by mild heating at 300 to 400 ° C, and then heated at 450 to 550 ° C for incineration and then cooled.

Example 2

Preparation of Test Solution

0.5N nitric acid was added to the sample prepared in the above step, and 10-20 ml of nitric acid was filtered to dissolve the heavy metal in the sample and to remove other carbonized components. Adjust the filtrate to 50 ml with 0.5 N nitric acid, take 20 ml of the solution, place it in a Nessler tube, add 1 drop of phenolphthalein indicator, and add 10 ml of ammonia (28%) to water until the solution becomes pale red. The solution was neutralized by dropwise addition of the ammonia solution prepared by adding ml, and then the acid concentration was adjusted to pH 3-4 by adding 4 g of acetic acid to 100 ml of water. Water was added to the solution prepared as described above to make 50 mL to obtain a test solution.

In the lead standard solution, 159.8 mg of lead nitrate was dissolved in 0.1 N nitric acid to make 1,000 ml, and 5 ml of the solution was added thereto to make 100 ml (5 µg / ml). In addition, the cadmium standard solution was dissolved 100 mg of metal cadmium in 50 ml of 10% nitric acid and evaporated to dryness in a water bath. 0.1 N nitric acid was added to the residue to make 1,000 ml, and 0.1 N nitric acid was added to 5 ml of the solution to make 100 ml (5 µg / ml).

The lead standard solution or cadmium standard solution prepared by the above method was prepared in 1 ml, 2 ml, 4 ml and 8 ml, respectively, in a Nessler tube, and 20 ml of 4% acetic acid solution and water were added to make 50 ml.

Example 3

Precipitation Step of Heavy Metal Components

1 to 2 drops of sodium sulfide solution were added to each Nessler tube containing the test solution and the comparative standard solution, mixed well, and left for 5 minutes, and then placed on a white paper and observed from above. When a yellowish brown precipitate is formed, it can be seen that the test solution contains lead or cadmium.

The sodium sulfide solution was prepared by dissolving 5 g of sodium sulfide in a mixed solution of 10 ml of water and 30 ml of glycerin.

Example 4

Determination and Analysis of Heavy Metal Components

As a result of reacting the test solution with sodium sulfide solution in Example 3, a tan precipitate was formed, indicating that the test solution contained lead or cadmium. In addition, the concentration of the test solution could be determined by comparing the color of the reactant of the test solution with the color of the reactant of the comparative standard solution. This is shown in Table 1, Table 2, Table 3 and Table 4. Table 1 and Table 2 show the results of measuring the sensitivity of the lead in the standard solution and test solution, Table 3 and Table 4 shows the results of measuring the sensitivity of cadmium in the cadmium standard solution and test solution.

Sensitivity Measurement of Lead Standard Solution Standard concentration Intake Absolute quantity Result (visual identification) Unreacted Pb 5 ppm 20 ml 100 µg ○ none 2 ppm 20 ml 40 µg ○ none 1 ppm 20 ml 20 µg ○ none 0.5 ppm 20 ml 15 µg ○ none 0.2ppm 20 ml 10 µg ○ none 0.1 ppm 20 ml 4 µg ○ none 0.05ppm 20 ml 2 µg × none

As shown in Table 1, the range in which the content of lead can be visually identified by sodium sulfate solution is possible when the content is 0.1 ppm or more.

Determination of Lead Content and Concentration in Test Solution density Dilution ratio (times) Intake Absolute quantity Result (visual identification) Unreacted Pb 1.36 ppm One 20 ml 27.2 μg ○ none 0.68 ppm 2 20 ml 13.6 µg ○ none 0.34 ppm 4 20 ml 6.8 µg ○ none 0.272 ppm 5 20 ml 5.44 µg ○ none 0.136ppm 10 20 ml 2.72 μg ○ none 0.068 ppm 20 20 ml 1.36 µg × none

As shown in Table 2, when compared with the lead standard solution sensitivity of Table 1, it was impossible to detect lead in a test solution having a lead concentration of 0.068 ppm, but was identified when the lead concentration was 0.136 ppm or more.

Sensitivity Measurement of Cadmium Standard Solution Standard concentration Intake Absolute quantity Result (visual identification) Unreacted Cd 5 ppm 20 ml 100 µg ○ none 2 ppm 20 ml 40 µg ○ none 1 ppm 20 ml 20 µg ○ none 0.5 ppm 20 ml 15 µg ○ none 0.2ppm 20 ml 10 µg ○ none 0.1 ppm 20 ml 4 µg × none 0.05ppm 20 ml 2 µg × none

As shown in Table 2, the range in which the cadmium content was visually identified by the sodium sulfate solution was possible when 0.2 ppm or more.

Determination of Cadmium Content and Concentration in Test Solution density Dilution ratio (times) Intake Absolute quantity Result (visual identification) Unreacted Cd 1.24 ppm One 20 ml 24.8 μg ○ none 0.62 ppm 2 20 ml 12.4 μg ○ none 0.31 ppm 4 20 ml 6.2 µg ○ none 0.208ppm 5 20 ml 4.16 μg × none 0.124ppm 10 20 ml 2.48 µg × none 0.062ppm 20 20 ml 1.24 µg × none

As shown in Table 4, lead was not detected in the test solution having a cadmium concentration of 0.208 ppm compared to the sensitivity of the cadmium standard solution of Table 2, but was identified when the cadmium concentration was 0.31 ppm or more.

Comparative example

Heavy Metal Inspection Method by Food Code

The following method was performed based on the heavy metal inspection method according to the Food Code. 1 g of the food container used in Example 1 was taken as a sample, taken into a crucible, 10 drops of sulfuric acid was added thereto, and heated to evaporate sulfuric acid, followed by drying on a direct burn. The mixture was cooled by heating at 450 DEG C and cooled, and 20 ml of 0.1 N nitric acid was added to the residue to prepare a test solution. 0.1 N nitric acid was added to 2 mL of the prepared sample to make 20 mL, and then measured using an atomic absorption spectrophotometer. The results of measuring the concentration of lead in the test solution are shown in Table 5, and the results of measuring the concentration of cadmium are shown in Table 6.

Determination of Lead Concentration in Test Solution density Dilution ratio (times) Measured value (ppm) Relative standard deviation (RSD%) % Error 1.36 ppm One 1.36 0.6 - 0.68 ppm 2 0.65 0.4 4.4 0.34 ppm 4 0.37 1.0 8.8 0.272 ppm 5 0.25 1.9 8.8 0.136ppm 10 0.104 5.8 26.4 0.068 ppm 20 0.045 20.2 33.8

As shown in Table 5, as a result of measuring the concentration of lead using an atomic absorption spectrometer, it is possible to measure the concentration even in a test solution containing a small amount of lead. It is not suitable as the measured value that the value of (RSD) is more than 2%. Therefore, accurate measurement value was obtained when lead concentration was 0.272 ppm or more. It was found that the lead concentration measurement by sodium sulfide (see Table 2) was superior to the analysis using an atomic absorbance in terms of sensitivity.

Determination of Cadmium Concentration in Test Solution density Dilution ratio (times) Measured value (ppm) Relative standard deviation (RSD%) % Error 1.24 ppm One 1.24 0.4 - 0.62 ppm 2 0.63 0.2 1.6 0.31 ppm 4 0.29 0.3 6.5 0.208ppm 5 0.21 0.3 0.9 0.124ppm 10 0.13 0.3 4.8 0.062ppm 20 0.058 1.2 6.9

As shown in Table 6, as a result of measuring the concentration of cadmium by using an atomic absorption spectrometer, it is possible to measure the concentration even in a test solution containing a small amount of cadmium, and the relative standard deviation (RSD) indicating the reproducibility and precision of the measured value. The value was less than 2% over the entire range, so the accuracy and reproducibility were good.

The heavy metal concentration of the sample measured by the method of Examples 1 to 4 of the present invention and the heavy metal concentration of the sample according to the comparative example were almost the same.

However, in order to implement the heavy metal inspection method according to the present invention, relatively simple facilities such as incinerators, reagents and consumables are required, but in order to perform the heavy metal inspection method according to the comparative example, an atomic absorber, a hood facility, a gas, an incineration furnace Since reagents and consumables are required, it can be seen that the use of the heavy metal inspection method according to the present invention is much simpler and lower in cost than the conventional method.

That is, the heavy metal inspection method according to the comparative example requires the expensive facility cost, equipment experts and high proficiency as described above, so the manufacturer's own quality inspection is practically impossible, but the heavy metal inspection method according to the present invention has a low facility cost It is understood that the manufacturer's own quality inspection is possible because no device expert or high level of skill is required.

On the other hand, in terms of economics, when the heavy metal inspection using the present invention, such as food containers or food packaging manufacturers, the cost can be reduced by 90% or more than when the heavy metal inspection using the method of the comparative example.

As described above, according to the heavy metal inspection method according to the present invention, it is possible to simply check the heavy metal without expensive equipment and specialized personnel, thereby reducing the cost, and also useful for on-site inspection, which is useful for the manufacturer's own quality control. Can be used.

Claims (4)

(a) heating and carbonizing the sample and incubating the sample; (b) dissolving with acid, filtering and neutralizing; (c) adding sodium sulfide solution to react; And (d) measuring and analyzing the reactants produced in step (c). 2. The method of claim 1, wherein the sample is a food container or a food wrapper. The method of claim 1, wherein the acid is nitric acid. The method of claim 1, wherein the heavy metal is lead or cadmium alone or in a mixture.