Research and development background and detection principle of new heavy metal detector
Research and development background and detection principle of new heavy metal detector R&D background Food, soil and water quality are gradually polluted by industrial waste gas, waste water and waste slag. Some people even directly use industrial waste water to irrigate crops, causing cadmium, copper, arsenic, chromium, mercury, nickel, iron, aluminum and zinc in the soil cultivation layer. Heavy metals such as manganese and copper are enriched and accumulated in large quantities, especially in urban suburbs. In addition, the use of inorganic chemical pesticides and other heavy metals in vegetables and fish seriously exceeds the standard, and continues to accumulate in the human body, leading to consumption. Chronic poisoning of heavy metals has occurred. There have been many cases of collective poisoning of heavy metals in China, which have attracted great attention from the government and wide attention from all walks of life. However, the current methods for measuring heavy metals are slow, complicated, and expensive. Based on this situation, we have developed a rapid determination method for heavy metals, which can quickly and jointly determine lead, arsenic, chromium, cadmium and mercury in food samples. Detection principle (1) After the sample is digested, all forms of heavy metals (including arsenic, lead, cadmium, chromium, mercury, nickel, iron, aluminum, zinc, manganese, copper, etc.) are converted into ionic forms, and the relevant detection reagents are added. Color development, the color depth of the solution is proportional to the content of heavy metals in a certain concentration range, obey the Lambert-Beer law, and then the content is determined by the instrument, and the safety requirements of the national standard agricultural product safety quality pollution-free vegetables are allowed. Limit the standard to compare the heavy metal content of vegetable samples. Wet digestion method: In the heavy metal inspection of food, sample pretreatment is the most important step of food inspection, which directly affects the precision and accuracy of the analysis results. Choosing the appropriate pretreatment method and shortening the pretreatment time of the sample is to ensure the inspection. An important method to improve the efficiency of inspection at the same time. The wet digestion method is to add an oxidizing strong acid to an appropriate amount of the food sample, heat and destroy the organic substance, and release the inorganic component to be tested to form a non-volatile inorganic compound for analysis and determination. Wet digestion is a widely used food sample pretreatment method. The method is practical and almost all foods can be digested by this method. (II) The detection principle and standard of use of various heavy metals 1. Detection principle and standard of heavy metal arsenic The national standard borohydride reduction colorimetric method is adopted, that is, after the sample is digested, potassium iodide-thiourea is added and heated to reduce the pentavalent arsenic to trivalent arsenic, and under the acidic condition, the potassium borohydride reduces the trivalent arsenic to the negative three. The price, the formation of arsine into the absorption liquid is yellow, and the arsenic content is obtained by instrumental detection. 2. Detection principle and standard of heavy metal lead The national standard dithizone colorimetric method is adopted, that is, after the sample is digested, the lead ion and the dithizone form a red complex under weak alkaline conditions, and after being dissolved in chloroform, the colorimetric determination is performed. 3. Detection principle and standard of heavy metal chromium After the sample is digested, in the presence of divalent manganese, the chromium ion reacts with diphenylcarbazide to form a purple-red complex. The color of the complex is proportional to the hexavalent chromium content. The colorimetric determination can be obtained. Chromium content. 4. Detection principle and standard of heavy metal cadmium The national standard colorimetric method is adopted, that is, after the sample is digested, the cadmium ion forms a red complex with 6-bromophenylthiazole azo-naphthol under alkaline conditions, and is dissolved in chloroform and then determined by colorimetry. 5. Detection principle and standard of heavy metal mercury The national standard dithizone colorimetric method is adopted, that is, after the sample is digested, under the acidic condition, the mercury ion and the dithizone form an orange-red complex, and after being dissolved in chloroform, the colorimetric determination is performed. 6. Detection principle and standard of heavy metal nickel Using the national standard dimethylglyoxime colorimetric method, after the sample is digested, under a strong alkaline condition, a peroxidizer is added, and nickel and dimethylglyoxime form a reddish brown complex, and the color of the complex is dark and The nickel content is proportional, and the colorimetric measurement gives the nickel content. 7. Detection principle and standard of heavy metal iron After the sample is digested, the iron is reduced to divalent iron with a reducing agent. In the range of PH2-9, the ferrous iron reacts with the o-morpholine to form an orange-red complex. The color of the complex is positive and the iron content is positive. Ratio, colorimetric determination gives iron content. 8. Detection principle and standard of heavy metal aluminum Using the national standard chrome azurol S colorimetric method, after the sample is digested, the trivalent aluminum ion reacts with chrome azurol S and cetyl ammonium bromide to form a blue ternary complex in a buffer solution medium. The color of the complex is proportional to the aluminum content, and the colorimetric measurement gives the aluminum content. 9. Detection principle and standard of heavy metal zinc Using the national standard dithizone colorimetric method, after the sample is digested, the zinc ion forms a purple-red complex with dithizone under the suitable pH condition. The color depth of the complex is proportional to the zinc content. The color measurement gives the zinc content. 10. Detection principle and standard of heavy metal manganese After the sample is digested, the divalent manganese ions in the liquid to be tested are oxidized to a purple-red permanganate under an acidic condition under an acidic condition, and then subjected to colorimetric determination, and the manganese content can be obtained by colorimetric determination. 11. Detection principle and standard of heavy metal copper Test items The heavy metal detector can detect total chromium (Cr), hexavalent chromium (Cr6+), lead (Pb), mercury (Hg), cadmium (Cd), trivalent arsenic (As3+), copper (Cu), zinc (Zn), Nickel (Ni), etc. Application field Heavy metal detectors are widely used in waterworks, food factories, factories and enterprises, as well as environmental, industrial and commercial departments at all levels. The test medium covers water quality, food, medicine, aquatic products, soil, cosmetics, urine, and the like. Innovative Technology 1, heavy metal detector can test up to 8 kinds of items: chromium, nickel, mercury, arsenic, zinc, lead, copper, cadmium, can achieve simultaneous detection of various elements, improve detection efficiency; 2. The heavy metal detector is equipped with a microwave digestion instrument to more accurately measure the heavy metal content in the solid sample and greatly reduce the harm to the health of the operator; 3, heavy metal detector built-in multiple sets of test parameters, improve detection capabilities and reduce user operation difficulty; 4. The heavy metal detector adopts mercury-free electrode, which will not cause secondary pollution and is more environmentally friendly; 5. The heavy metal detector is equipped with a vehicle power interface to realize rapid flow detection; 6, exclusive use of built-in magnetic stirring, software control, no manual operation, improve enrichment efficiency, reduce the complexity of operation. Testing plan 1 Scope of application It is used for qualitative or semi-quantitative detection of free lead and lead content in fruits and vegetables. 2 Detection principle After the sample is processed, the lead and the reagent are colored, and compared with the rapid detection color scale card of the lead and fruit content of the fruit and vegetable, the reference concentration of the lead content in the sample to be tested can be read. 3 main instruments Scissors, electronic scales, plastic test tubes. 4 reagents 1 reagent A concentrated acid solution. 2 Reagent B O. 2 mol / L solution of trishydroxymethylaminomethane. 3 reagent C 20mL l% o-phenanthroline and 50mL 2.8% ammonium acetate mixed solution. 4 reagent D o. lOg lead reagent (dithizone) was placed in 100 mL of 2% Tween-20 solution and heated in a constant temperature water bath at 70 ° C for 30 min. 5 distilled water, etc. 5 steps 1 Rinse the sample to be tested with distilled or purified water (wash off the surface soil to avoid interference detection), dry it, cut the sample into small pieces of about 1 cm with a knife or scissors, and weigh 1 kg of the treated sample. Add 20 mL of water to a 20 mL plastic sampling tube. 2 Add 4 drops of reagent A, press the sample under the liquid surface with a stirring needle, cover the sampling tube cover, shake it up and down 10 times, place it for 1 min, then shake it up and down 10 times, take out the fruit and vegetable samples, and use the solution as the test solution. 3 Pipette 1 mL of the sample solution into a blank sample tube. Add 3 drops of reagent B, cover the sample tube cap, shake it up and down 5 times, then add 2 drops of reagent C and 2 drops of reagent D, shake up and down 5 times, and develop color for 5 min at room temperature. 6 result determination By comparing the sample tube with the rapid detection of the lead content of the lead and fruit of the fruit and vegetable, the reference concentration of the lead content in the sample to be tested can be read. 7 Precautions 1 When the sample contains metal ions such as iron ions, calcium ions, magnesium ions, etc., it may cause false positives in the color development of the solution. 2 This method is suitable for the determination of free lead. For the determination of organic lead, it needs to be digested according to the routine laboratory method. 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The earliest commercially available lip gloss was Max Factor's X-Rated4, which was launched in 1932. The original formula was sold until 2003.
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