Solvent sample analysis It is well known that water is not an ideal solvent, mainly due to the following reasons: 1 it has a large evaporation expansion volume; 2 the wettability and solubility of water in many stationary phases is poor; 3 water will affect a certain The normal detection of these detectors can cause chemical damage to the stationary phase of the column. Among the commonly used chromatography solvents, water has the largest vaporization expansion volume. Introduction of solvent sample analysis (water) Normally, when the volume of the liner of the sampler of the chromatograph is about 200-900 μl when the water sample is 1 μl, the vaporized vapor volume (about 1010 μl) will expand and overflow the liner, which is called backfilling. It will cause the vaporized sample to return to the carrier gas and the purge gas path. Because the temperature of the purge gas path of the carrier gas is much lower than that of the gasification chamber, the sample will condense here and be blown into the analysis system by the gas in later analysis The formation of ghost peaks can be avoided by increasing the volume of the liner, reducing the injection volume, lowering the injector temperature, increasing the injector pressure, and increasing the carrier gas flow rate to reduce backflushing. Water enters the column, and the form of water is destructive to the stationary phase of the column. Because the surface energy of water is high, and the surface energy of most capillary column stationary phases is low, this leads to poor wettability of the stationary phase by water, and a smooth solvent film cannot be formed on the column wall to flow uniformly through the chromatography Column, and the formation of droplets, resulting in poor performance of the column. Due to this poor wettability of water and higher boiling point relative to other solvents, usually at a lower column temperature, a part of the water flows through the column in a liquid state, so that solutes with good solubility in water are also It will show band broadening, and in extreme cases, chromatographic peak splitting. When injecting on the column, non-volatile compounds, such as water-soluble salts, are also carried into the column by liquid water, contaminating the column and the analytical system. Application of Gas Chromatograph in Analysis of Solvent Samples Water can also cause detector problems: for example, water can extinguish FID and FPD; when entering a larger water sample, in order to avoid the detector extinguishing fire, the hydrogen flow can be increased to help stabilize the flame at the expense of sensitivity; water will also To reduce the sensitivity of ECD, in order to avoid the influence of water, a thick liquid membrane column can be used to keep the analyzed components long enough to ensure that the performance of ECD may be restored after the water flows through the detector when the peak is out. A more serious problem is that water can cause the degradation of many stationary phases, directly destroying the performance of the column. In the chromatographic analysis, it reflects the decrease of chromatographic peak separation performance, unstable base flow, and increased noise. Therefore, you must be very careful when analyzing incoming water samples and samples with large water content. This also occurs in the case of solvent analysis. Typical is the analysis of trace organic extracts. Regardless of whether dichloromethane or carbon disulfide is used as a solvent, the volume expansion is about 3001μl when the injection volume is 1μl. When the injection cannula volume is less than 300μl, it is easy to form backfill. So no matter what kind of sample, the size of the injection volume must be compatible with the volume of the cannula in the injector. In this regard, various types of instruments are equipped with a variety of different types of injection cannula for selection; A large amount of solvent will also form a washing effect on the stationary phase, directly destroying the performance of the chromatographic column. In the chromatographic analysis, it reflects the earlier retention time, the lowered peak separation performance, the unstable base flow, and the increased noise. Therefore, it is necessary to pay attention to the choice of solvent and injection volume when analyzing dilute solution samples. The original intention of the smart water dispenser is to allow cats to drink more water. Two water outlet modes, simulating natural springs, waterfalls and flowing water, arouse the curiosity of pets. Smart Water Fountain For Pets,Water Fountain For Pets,Fountain For Pets,Smart Fountain For Pets DongGuan Lucky Pet Products Co., Ltd. , https://www.dgpetproduct.com
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