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Abnormal phenomena will occur during the analysis of many samples, the most common one is the analysis of solvent samples, and a special case is the analysis of water samples. From a gas chromatography perspective. It is well known that water is not an ideal solvent, mainly due to the following reasons:: 1 It has a large evaporative expansion volume ； 2 Water has poor wettability and solubility in many stationary phases ； 3. Water will affect the normal detection of some detectors and cause chemical damage to the stationary phase of the chromatographic column. Among commonly used chromatographic solvents, water has the largest vaporization expansion volume. Usually the liner volume of the injector of a chromatograph is about 200 to 900 μl. When 1 μl of water sample is used, the vapor volume (about 1010 μl) after vaporization will expand and overflow the liner, which is called backflow. This will cause the vaporized sample to return to the carrier gas and purge gas circuit. Since the temperature of the carrier gas purge gas circuit is much lower than that of the vaporization chamber, the sample will condense here and be blown into the analysis system by the gas in subsequent analysis to form ghost peaks. Methods to avoid ghost peaks can be to increase the liner volume, reduce the injection volume, lower the injector temperature, increase the injector pressure and increase the carrier gas flow rate to reduce the backflow phenomenon. 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 very high, and the surface energy of most capillary column stationary phases is low, this results in poor wettability of water to the stationary phase. It cannot form a smooth solvent film on the chromatographic column wall and flow evenly through the chromatographic column, and forms droplets, resulting in poor column performance. Due to the poor wettability of water and its high boiling point relative to other solvents, a part of the water usually flows through the chromatographic column in a liquid state at a lower column temperature, so that solutes with good solubility in water will also show band broadening, and in extreme cases, chromatographic peak splitting. When injecting samples onto the column, non-volatile compounds, such as water-soluble salts, will also be brought into the column by liquid water, contaminating the column and analysis system. Water can also cause detector problems: For example water will put out fid and fpd ； When injecting larger water samples, in order to avoid detector fire extinguishing, the hydrogen flow rate can be increased to help stabilize the flame at the expense of sensitivity. ； Water will also reduce the sensitivity of ECD. To avoid the influence of water, a thick liquid film column can be used to retain the analyzed components for a long enough time to ensure that when the peak is emitted, the ECD performance may be restored after the water flows through the detector. A more serious problem is that water can cause the degradation of many stationary phases, directly damaging the performance of the chromatographic column. During chromatographic analysis, it is reflected that the separation performance of chromatographic peaks is reduced, the base flow is unstable, and the noise is increased. Therefore, you must be very careful when injecting water samples for analysis and samples with large water content. This also occurs in the case of solvent analysis. A typical example is the analysis of trace organic matter extracts. Whether methylene chloride or carbon disulfide is used as the solvent, when 1 μl of sample is injected, the volume expansion is approximately 3001 μl. When the volume of the injection cannula is less than 300 μl, it is easy to cause backflow. Therefore, no matter what sample is used, the injection volume must be adapted to the volume of the injector in the injector. In this regard, various types of instruments are equipped with a variety of different forms of injection intubations for selection. ； Adding a large amount of solvent at the same time will also cause a washing effect on the stationary phase, directly destroying the performance of the chromatographic column. During chromatographic analysis, it is reflected that the retention time is advanced, the separation performance of the chromatographic peaks is reduced, the base flow is unstable, and the noise is increased. Therefore, when analyzing dilute solution samples, attention must be paid to the selection of solvent and injection volume.