If it is ICP-MS multi-element analysis technology (ICP-MS instrument takes plasma (ICP) as the ion source, and mass spectrometry (MS) analyzer detects the generated ions, hence the name), then its principle of measuring heavy metals is to atomize the solution to be measured, then dissociate it with argon atom high-energy plasma, and finally analyze it with mass spectrometer. This method can simultaneously measure most elements in the periodic table, and the analyte concentration can be as low as per liter 1 nanogram (ng/l) or parts per trillion (ppt).
Detailed explanation of principle:
Plasma ion source
Generally, a liquid sample is introduced into an atomizer through a peristaltic pump to generate an aerosol. The double-channel fog chamber ensures the aerosol to be transported into the plasma. Argon (Ar) is introduced into a set of concentric quartz tubes for plasma formation. The welding torch is placed in the center of the radio frequency (RF) coil, and the RF energy line passes through the coil. The strong RF field leads to the collision between argon atoms and produces high-energy plasma. The sample aerosol instantly dissociates in the plasma (the plasma temperature is about 6000- 10000 K), forming the analyzed atoms and being ionized at the same time. Ions generated in the plasma are extracted into the mass spectrometer by high vacuum (generally 10-4 Pa). The vacuum is maintained by a differential vacuum pump system: the analyzed ions are extracted through a pair of interfaces (called sampling cone and extraction cone).
Quadrupole mass spectrometer
The analyzed ions are focused by a set of ion lenses into a quadrupole mass analyzer and separated according to their mass-to-charge ratio. It is called quadrupole because the mass analyzer is actually composed of four parallel stainless steel rods, on which RF and DC voltages are applied. The combination of RF and DC voltage allows the analyzer to transmit only ions with a specific mass-to-charge ratio.
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Finally, the ions are measured by an electron multiplier, and the count of each mass is collected by a counter.
mass spectrum
Mass spectrometry is simple. The isotope of each element appears with its different mass (for example, 27Al will appear at 27 amu), and its peak intensity is directly proportional to the initial concentration of the isotope in the sample solution. 1-3 minutes can simultaneously analyze a large number of elements from low-quality lithium to high-quality uranium. Using ICP-MS, various elements with concentration levels ranging from ppt to ppm can be measured in one analysis.
App application
ICP-MS is widely used in many industrial fields, including semiconductor industry, environmental field, geological field, chemical industry, nuclear industry, clinical and various research laboratories, and is a key analytical tool for the determination of trace elements.
Supplement: Yes.
Quantitative analysis of inductively coupled plasma mass spectrometry
Similar to other quantitative methods, ICP-MS quantitative analysis usually adopts standard curve method. Prepare a series of standard solutions, and calculate the content of the components to be measured from the obtained standard curve. In order to make quantitative analysis accurate and reliable, we should try our best to eliminate the interference factors in quantitative analysis, including the influence of acids, oxides and hydroxides, isotopes, complex ions and doubly charged ions.
Under the influence of acid in the sample, when the sample solution contains nitric acid, phosphoric acid and sulfuric acid, N2+, ArN+, PO+, P2+, ArP+, SO+, S2+, SO2+, ArS+, ClO+, ArCl+ and plasma may be generated, and these ions will affect silicon, iron, titanium, nickel, gallium and zinc. In this case, the interference can be eliminated by selecting another isotope ion of the analyte, and at the same time, high-concentration acid should be avoided as much as possible, and nitric acid should be used as much as possible to reduce the influence of acid.
Influence of oxides and hydroxides: In ICP, oxides of metal elements can be completely dissociated, but near the sampling cone, the temperature is slightly lower and the residence time is longer, which provides an opportunity for re-oxidation. The existence of oxides will reduce atomic ions, so the measured value is low. The influence of oxides can be estimated by the intensity ratio of Ce+ to CeO+, and the influence of oxides can be reduced by adjusting the position of sampling cone. At the same time, the existence of oxides and hydroxides will also interfere with the determination of other ions, such as 40ArO and 40CaO will interfere with 56Fe, 46CaOH will interfere with 63Cu, and 42CaO will interfere with 58Ni. Therefore, isotopes that do not interfere with * * * should be selected for quantitative analysis.
Isotope interference: Common interferences include 40Ar+ interference 40Ca+, 58Fe interference 58Ni, 1 13In interference 1 13Cd+ and so on. When choosing isotopes, we should try to avoid the interference of isotopes.
Other aspects of interference: mainly complex ion interference and double charge ion interference. Complex ions include: 40ArH+, 40ArO+ and so on. For elements with low secondary ionization potential, the existence of double charge ions will also affect the reliability of the measured values, and the level of double charge ions can be reduced by adjusting the flow rates of carrier gas and auxiliary gas.
ICP-MS has relatively uniform sensitivity to the elements in the whole periodic table, so the detection limits of most elements are relatively consistent. The random background of the instrument is about 10-20 count /s, and the detection limit is expressed by the concentration corresponding to the signal with three times blank response, and the detection limit of most elements is about 0.03ng/ml.
ICP-MS has the advantages of high sensitivity and simultaneous qualitative and quantitative analysis of multiple elements, and is widely used in water analysis, trace element analysis in blood, food analysis, isotope ratio determination and other fields.
There are many hazards to the human body from the food discharged with heavy metals, and each heavy metal has different hazards to the human body. Generally speaking, the common heavy metals are lead, mercury, chromium, arsenic and aluminum. Lead is toxic in heavy metal pollution, so it is difficult to metabolize after entering the body, accumulate in the human body, damage brain cells, easily lead to fetal congenital mental retardation, and lead to dementia for middle-aged and elderly people.
If heavy metals enter the human body and stay on the panel, it will cause pigmentation of the panel and abnormal cuticle. However, heavy metals are mainly metabolized in the liver and kidney, which will cause visceral poisoning after entering the viscera. For example, mercury can cause liver poisoning, and arsenic can cause renal insufficiency.
Foods that discharge heavy metals are:
1, kelp
Kelp is a kind of seaweed, which has many health-care functions, such as losing weight, relaxing bowels, regulating the three highs, and supplementing iodine and calcium. Here, we focus on its role in heavy money.
First of all, seaweed gum in kelp has the function of regulating arteriosclerosis and preventing human body from absorbing heavy metals. It can form gel in human intestines, adsorb toxins such as heavy metals, and help the human body detoxify. Therefore, kelp is also known as the scavenger of gastrointestinal tract.
Secondly, kelp has anti-oxidation and anti-cancer effects, and its sodium alginate will combine with heavy metals strontium and cadmium and be excreted, thus avoiding the carcinogenicity of these metals.
Step 2: carrots
Carrots are also one of the essential foods for discharging heavy metals. In daily life, we all know that carrots can supplement vitamin A, beautify the skin and protect the eyes, but the pectin in carrots has been ignored by everyone.
First of all, carrots contain a lot of pectin, which belongs to a kind of soluble dietary fiber. After entering the human body, it can combine with mercury, reduce the content of mercury ions in the blood and excrete them. Therefore, if you want to have healthy liver and kidney, then carrots are essential substances.
Secondly, carrots are also beneficial to the health of human intestines, which is the largest gathering place for bacteria and toxins. Eating carrots regularly can proliferate intestinal beneficial bacteria, protect intestinal mucosa and reduce the harm of heavy metals and free radicals to human body.
In addition, if you want to use β -carotene in carrots, you need to cook it, because β -carotene mainly exists in the cell wall of carrots, and the cell wall of carrots is mainly composed of wood fibers, and carotene can be absorbed and utilized by the human body after cooking.
3. Milk
With the development of industrial level, there are more and more children with lead poisoning in China, and about 40% of urban children have lead exceeding the standard. Lead removal is not a one-off event, and it needs long-term persistence to be effective.
Protein and iron can combine with organic substances in human tissues to form soluble substances instead of lead, and accelerate the metabolism of lead, so supplementing high-quality protein can play a role in expelling lead. Although protein in milk is not the highest, protein in milk is more easily absorbed and utilized by human body, thus playing a role in discharging lead.
In addition, iron supplementation is also a necessary work to discharge lead, so iron supplementation is also a method to discharge lead. It is best to choose vegetables containing iron, such as spinach and fungus.
4. Auricularia auricula
Auricularia auricula can detoxify, but Auricularia auricula can not expel the dust from the lungs, but can absorb the dust from the gastrointestinal tract. The colloidal substance in Auricularia auricula can adsorb the dust in the intestine, and the intestine peristalsis, which can remove dust and discharge heavy metals.
In addition, the plasma protein in pig blood has a similar effect after digestion, so pig blood and fungus can discharge heavy metals and dust, but not the lungs, but the stomach.
The principle and method of atomic absorption determination of heavy metals How to atomic absorption spectrometry (AAS), namely atomic absorption spectrometry, is an analytical method to quantify the content of elements to be measured based on the absorption intensity of electrons in the outer layer of gaseous ground state atoms to the vibration radiation of corresponding atoms in the ultraviolet and visible light ranges, and it is a method to measure the absorption of light radiation by specific gaseous atoms. This method appeared in the mid-1950s, and gradually developed into a new instrumental analysis method. Widely used in geology, metallurgy, machinery, chemical industry, agriculture, food, light industry, biomedicine, environmental protection, material science and other fields. This method is mainly suitable for the analysis of micro and trace components in samples.
Principle of detecting heavy metals by atomic absorption spectrometry
Basic principle: The instrument radiates the light with characteristic spectral lines of the elements to be measured from the light source, and when it passes through the sample vapor, it is absorbed by the atoms in the ground state of the elements to be measured in the vapor, and the content of the elements to be measured in the sample is determined by the degree of attenuation of the characteristic spectral lines.
Use:
Many elements can be determined by atomic absorption spectrometry, with flame atomic absorption spectrometry reaching the order of 10-9g/ml and graphite furnace atomic absorption spectrometry reaching the order of 10- 13g/ml. Its hydride generator can detect the trace of eight volatile elements, such as mercury, arsenic, lead, selenium, tin, tellurium, antimony and germanium.
Because of its sensitivity, accuracy and simplicity, atomic absorption spectrometer has been widely used in the analysis of major and trace elements in metallurgy, geology, mining, petroleum, light industry, agriculture, medicine, health, food and environmental monitoring.
What is the definition of heavy metals? Heavy metals, especially mercury, cadmium, lead and chromium, have significant biological toxicity. They can not be degraded by microorganisms in water, but can only be transformed, dispersed and enriched (that is, migrated) in various forms. The characteristics of heavy metal pollution are as follows: (1) In addition to being carried away by suspended solids, it will be enriched in the sediment near the sewage outlet due to adsorption and precipitation, which will become a long-term secondary pollution source; (2) Various inorganic ligands (chloride ion, sulfate ion, hydroxide ion, etc. ) and organic ligands (corrosive substances, etc. ) will form complexes or chelates with it in water, which will lead to greater water solubility of heavy metals and may re-release heavy metals that have entered the sediments; (3) Heavy metals with different valence states have different activities and toxicity. Its morphology changes with pH value and redox conditions. (4) As far as its harm to the environment is concerned, it shows toxicity (generally 1 ~ 10 mg/L, and mercury and cadmium are 0.01~ 0.001mg/L); Under the action of microorganisms, it will be transformed into more toxic organometallic compounds (such as marine-methylmercury); It can be enriched by organisms and enter the human body through the food chain, resulting in a chronic pathway. Sulfur-loving heavy metal elements (mercury, cadmium, lead, zinc, selenium, copper, arsenic, etc. ) has a particularly strong affinity with sulfhydryl groups (-SH) of some enzymes in human tissues, and can inhibit the activity of enzymes. Ferrophiles (iron, nickel) can accumulate in the kidney, spleen and liver of human body and inhibit the activity of arginase. Hexavalent chromium may be a precipitant for protein and nucleic acid, which can inhibit intracellular glutathione reductase and lead to methemoglobin, which may cause cancer. Excessive vanadium and manganese (pro-MagmaElemental) will damage the function of nervous system.
The difference between metals and heavy metals The definition of heavy metals is as follows:' Metals with a density above 5 are collectively referred to as heavy metals, such as 45 kinds of gold, silver, copper, lead, zinc, cobalt, cadmium, chromium and mercury. In terms of environmental pollution, heavy metals actually mainly refer to heavy metals with obvious biological toxicity such as mercury, cadmium, lead, chromium and metalloid arsenic, and also refer to general heavy metals with certain toxicity such as zinc, copper, cobalt, nickel and tin. According to scientific classification, the biological toxicity of heavy metals such as mercury, cadmium, lead and chromium is the most significant. Zinc, copper, nickel and tin are general heavy metals, but the article "Countermeasures for PVC Products after Lead Prohibition" lists lead and organotin in the list of heavy metals, but strongly recommends calcium/zinc stabilizer, which is somewhat confusing. As we all know, many foods used to be packed in tin foil.
What is the principle of heavy metal poisoning? The mechanism of heavy metal poisoning is protein degeneration.
The degeneration of protein means that protein is influenced by the outside world (such as radiation, heavy metals, acid and alkali, high temperature, etc.). ), destroyed the original morphological structure of protein and lost its normal physiological function.
What is the standard for heavy metals? Heavy metals refer to metals with specific gravity greater than 4 or 5, and there are about 45 kinds, such as copper, lead, zinc, iron, cobalt, nickel, vanadium, niobium, tantalum, titanium, manganese, cadmium, mercury, tungsten, molybdenum, gold and silver. Although heavy metals such as manganese, copper and zinc are trace elements needed for life activities, most heavy metals such as mercury, lead and cadmium are not necessary for life activities, and all heavy metals are toxic to human body if they exceed a certain concentration.
Density of heavy metals? The original meaning of heavy metals refers to metals with a specific gravity greater than 5 (generally speaking, metals with a density greater than 4.5 grams per cubic centimeter), including gold, silver, copper, iron and lead. When heavy metals accumulate in the human body to a certain extent, it will cause chronic poisoning. In fact, there is no strict and unified definition of what heavy metals are. As far as environmental pollution is concerned, heavy metals mainly refer to heavy metal elements with obvious biological toxicity such as mercury, cadmium, lead, chromium and metalloid arsenic. Heavy metals can't be biodegraded. On the contrary, they can be enriched thousands of times under the biomagnification of the food chain and eventually enter the human body. Heavy metals can interact strongly with protein and enzymes in human body, making them inactive, and may accumulate in some organs of human body, leading to chronic poisoning.
The harm of heavy metals? The heavy metals mentioned in environmental pollution refer to heavy metals with obvious biological toxicity such as mercury, cadmium, lead, chromium and metalloid arsenic. There are five most toxic substances to human body: lead, mercury, chromium, arsenic and cadmium. These heavy metals can't be decomposed in water, and their toxicity is amplified after drinking, and they combine with other toxins in water to produce more toxic organic substances. The benefits of Lemmon Medical Heavy Metal Detoxification Course to human body: It can be used not only for healthy people, but also for the prevention and intervention of various chronic diseases, taking away toxic substances deep in cells, expelling heavy metals and various toxins from the body, and laying a good foundation for health and beauty.