At present, heavy metal pollution is one of the main factors affecting crops in China. The arable land area contaminated by heavy metals such as cadmium and lead mercury in China is nearly 20 million hectares, accounting for about 1/5 of the total arable land area. Therefore, rapid and accurate food testing of heavy metals is a basic task that we can ensure food safety. The existing heavy metal analysis methods mainly include atomic absorption spectroscopy (flame and graphite furnace), atomic fluorescence spectroscopy, and TCP emission spectroscopy

1. Basic principle:

1.1 Principles of atomic absorption spectroscopy

Atomic absorption spectroscopy is a method in which the light source emits characteristic spectral radiation. After passing through the atomizer, the monochromatic light obtained by the spectroscopic system is photomultiplied and reaches the detector. The terminal computer obtains the signal from the detector, which is further converted into data for processing. When the atomic converter is not injected, the light is not absorbed when passing through the atomizer, and the transmittance is 100%, When the atomizer injects the sample, a portion of the light is absorbed when passing through the atomizer, resulting in a decrease in transmittance. According to Lambert Beer's law, absorbance is directly proportional to the concentration of the sample, so referring to the standard, the concentration of the sample can be determined based on absorbance

1.2; Principles of Atomic Fluorescence Spectroscopy

 &Nbsp; Atomic fluorescence spectroscopy is an analytical method developed after 1964. The principle is that after the characteristic radiation of the gas free atom absorbs the light source, the outer electrons of the atom transition to a higher energy level, and then return to the ground state or lower energy level. The emission of the same or different wavelengths from the original excitation is called atomic fluorescence. Atomic fluorescence is emitted in all directions of space, making it possible to make multi-channel instruments

1.3; Principles of TPC Emission Spectroscopy

 &Nbsp&Nbsp; The full name of IPC/OES is inductively coupled plasma atomic emission spectroscopy. Its working principle is to apply high-frequency energy provided by an RF generator to the induction coupling coil, and ionize the argon gas in the plasma torch tube, generating electrons and ions to conduct electricity. The conductive gas is subjected to high-frequency electromagnetic fields, forming a vortex zone concentric with the coupling coil. The strong current generates high heat, forming a torch shaped and self-sustaining plasma. After being atomized by the carrier gas (argon) into the atomization system, the sample enters the axial channel of the plasma in the form of an aerosol and is fully evaporated, atomized, ionized, and excited in a high temperature and inert atmosphere, emitting characteristic spectral lines of the contained elements. Identify whether a certain element is present in the sample based on the presence or absence of characteristic spectral lines (qualitative analysis); Confirm the content of corresponding elements in the sample based on the intensity of characteristic spectral lines (quantitative analysis)

2. Comparison of Several Analysis Techniques

 &Nbsp; Among the above food detection methods, ICP-MS has the best detection limit, with most of the elements being PPT grade. However, the instrument itself is expensive, has high environmental requirements, and the types of reaction gases are also complex. Therefore, it is now commonly used for standard measurements; Graphite furnace atomic absorption spectrometry has the second highest detection limit, which is sub ppb level and has a lower usage cost than ICP-MS. It is now widely used for heavy metal detection in water and food. The detection limit of flame atomic absorption is mostly 10

~100ppb, with mature technology, low instrument price and usage cost, and widely used in environmental and food detection. Atomic fluorescence photometers are more commonly used for the analysis and determination of elements such as mercury, arsenic, and selenium in the environment and food

3  Summary: In short, food safety is an important component of the development of the food industry. It is not only related to the healthy development of food industry enterprises, but also to the health and nutrition of the people, and even the quality of the entire nation, To this end, we should earnestly attach importance to and strengthen the supervision of food safety management from the height of "the interests of the people are above everything, and food safety is more important than Taishan". Food safety supervision departments should establish effective supervision mechanisms, adhere to in-depth inspection and testing of primary agricultural products, and control the source of supervision

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