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Anonymous users2024-02-06The MERTS800D VOC** monitoring system in water adopts purge and trap extraction and gas chromatography detection, collects and heats the water sample and sends it into the purge device, blows out the VOCs component in the water sample to be measured, removes the water in the blow-off mixture through the water removal device, and then enriches the VOCs component after water removal in the trap trap, and finally starts heating desorption, and brings the desorbed VOCs component into the chromatography through the carrier gas for separation and analysis of the concentration of each component. It is used for continuous monitoring of trace volatile organic compounds in water, and is suitable for the determination of 57 kinds of volatile organic compounds in seawater, groundwater, surface water, domestic sewage and industrial wastewater specified in the national environmental protection standard HJ 639-2012 for the monitoring needs of volatile organic compounds (VOCs) in surface water and drinking water sources. Minimum detection limit l for the compound of interest.
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Anonymous users2024-02-05VOCs that may be present in water
The American ASTM D3960-98 standard defines VOCs as any organic compound that can participate in atmospheric photochemical reactions.
The U.S. Environmental Protection Agency (EPA) defines volatile organic compounds as any carbon compound that participates in atmospheric photochemical reactions, except carbon monoxide, carbon dioxide, carbonic acid, metal carbides, metal carbonates, and ammonium carbonate.
The World Health Organization (WHO, 1989) defines total volatile organic compounds (TVOC) as a general term for volatile organic compounds with a melting point below room temperature and a boiling point between 50-260.
The international standards ISO 4618 1-1998 and the German DIN 55649-2000 on the general terminology of basecoats and varnishes define any organic liquid and/or solid that can emit spontaneously at room temperature and pressure. At the same time, the German standard makes a limit for the determination of VOC content, that is, any organic compound with a boiling point or initial distillation point lower than or equal to 250 at atmospheric pressure.
The most convenient and common way to define which substances are VOCs based on their boiling points, while the most common consensus is that VOCs are those chemicals that have a boiling point of 250 or less. Therefore, those substances with a boiling point higher than 250 are not classified as VOCs and are often referred to as plasticizers.
In the Chinese National Standard GB T 18883-2002 "Indoor Air Quality Standard", the definition of total volatile organic compounds (TVOC) is: volatile organic compounds with a retention time between n-hexane and n-hexadecane using Tenax GC and Tenax Ta sampling, non-polar chromatography column (polarity index less than 10) for analysis.
Hehe, well, it's rare to see such a high score.
This question is very interesting, if only ions are measured, the above methods have many limitations, for example, liquid chromatography is indeed suitable for liquid detection, but the commonly used ultraviolet detector is not high, and calcium ions have no ultraviolet absorption, and the fluorescence detector with higher sensitivity in high-performance liquid phase needs to coordinate calcium ions, which is not good. Not to mention nuclear magnetic resonance, I have never heard of liquid nuclear magnetic resonance (NMR) with nuclear magnetic calcium spectroscopy, as for doing hydrogen spectroscopy in water, does it make sense? >>>More
When a laser is used as the light source and the light is monochromatic light of a certain wavelength, the spatial (angle) distribution of diffracted and scattered light energy is only related to the particle size. >>>More
Causes of loss of inductor cores:
The loss of the chip inductor core is mainly in the core loss and the coil loss, and the size of the loss in these two aspects needs to be judged according to its different circuit modes. Among them, the core loss is mainly caused by the alternating magnetic field in the core material, and the loss generated by it is a function of the operating frequency and the total magnetic flux swing (δb), which will greatly reduce the effective conduction loss. Coil loss is due to the energy loss caused by the change in magnetic energy, which reduces the strength of the magnetic field when the power inductor current drops. >>>More
1. In the Windows desktop, open the Internet Explorer browser. >>>More
Hello friend, it's a pleasure to be able to help you. The nicotine and tar in cigarettes have a great impact on human health, reduce the harm of smoking, you can try to choose low-tar cigarettes, the less additives smoke, the less harm to the body, smokers at least one banana a day, help clear the lungs, and can also help quit smoking through e-cigarettes or drugs. If you don't quit smoking, it is difficult to reduce the harm, you can use some filtered cigarette holders, but the effect is only to minimize the function, there is no way to filter thoroughly, the most important thing is to quit smoking in time is the king. >>>More