Beijing Tiandi and introduces VOCs detection methods
Most of the volatile organic compounds (VOCs) are easy-to-explode products, some of which are toxic or extremely toxic, and can generate atmospheric pollutants such as PM2.5 and ozone through reaction. The timely detection of the concentration of VOCs can effectively reduce the occurrence of explosion events. Reduce the degree of pollution to its atmosphere
The main domestic VOCs detection methods are:
1: Gas chromatographic flame ionization detection method (GC-FID): The ion flux is formed by chemical ionization of an organic substance under the action of a hydrogen flame, and the ion current intensity is measured for detection. The sample is destroyed during the test, and generally only those organic compounds that burn a large amount of carbon cations in a hydrogen flame can be detected. The advantage of the FID detector is that it has high precision and can analyze the components. The disadvantage is that the procurement cost and maintenance cost are high, it is not convenient to carry, and the data cannot be met on site.
2: Thermal Conductivity Detector (TCD): Based on different materials with different thermal conductivity, it responds to almost all VOCs, can detect various VOCs, and the sample is not destroyed, but the sensitivity and accuracy are relatively low.
3: PID sensor: consists of a main part such as an ultraviolet light source and an ion chamber. The positive and negative electrodes in the ion chamber form an electric field. The organic volatile molecules are excited by a high-energy ultraviolet light source to generate negative electrons and positive ions. These ionized particles are A current is formed between the electrodes, and the current signal is output after being amplified and processed by the detector, and finally the concentration of the ppm level is detected.
The PID sensor can detect the VOC of the ppm level very accurately and sensitively, but it can not be used to distinguish different compounds qualitatively. That is to say, if there are gases such as styrene, benzene and toluene in the same environment, the styrene and benzene are measured. The comprehensive concentration value of toluene, etc., that is, the VOCs value, also called the non-methane total hydrocarbon value. If the environment is a single component of benzene, then the concentration of benzene is measured. When using PID, pay special attention to the correction factor (CF, also called response coefficient), which represents the sensitivity of measuring the VOCs in a specific certain frequency by PID. It is used to directly obtain the PID after correcting the PID with a gas. The concentration of another gas, which reduces the hassle of preparing a variety of gas standards. The advantages are: fast data, low procurement cost and maintenance cost, small size, easy to carry, the disadvantage is that it can not analyze the on-site components, only the comprehensive concentration can be detected.
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