Pretreatment device and pretreatment method for online monitoring of underwater volatile organic compounds

Abstract

The invention relates to a pretreatment device for online monitoring of underwater volatile organic compounds. The pretreatment device comprises a sweeping container, a feeding pipeline, a sweeping pipeline and a gas collecting pipeline. The feeding pipeline, the sweeping pipeline and the gas collecting pipeline are connected with the sweeping container. The pretreatment device further comprises a preheating device, a dewatering device and a cover. A to-be-detected water sample is heated by the preheating device to a preset temperature and then enters the sweeping container. The dewatering device is arranged on the gas collecting pipeline. A gas inlet of the dewatering device is lower than a gas outlet. A water storage container is arranged below the joint between the gas inlet and the gas outlet, and is communicated with the gas inlet and the gas outlet. The cover covers the sweeping container to seal the sweeping container. The sweeping pipeline and the gas collecting pipeline penetrate the cover to be respectively connected with first gas and a chromatographic instrument. The invention further provides a pretreatment method for online monitoring of the underwater volatile organic compounds. The pretreatment device has the advantages of simple structure, high sweeping efficiency, low maintenance cost, accuracy of detection results and the like.

Description

technical field [0001] The invention relates to the field of water quality monitoring, in particular to a pretreatment device and method for on-line monitoring of volatile organic compounds in water. Background technique [0002] The purge and trap method is a dynamic headspace technology. This method does not require the use of organic solvents, does not cause secondary pollution to the environment, has a small amount of sampling, high enrichment efficiency, and simple operation. It can be used in combination with gas chromatography to realize the concentration of volatile organic compounds in water. online monitoring. However, the combination of purge and trap and gas chromatography has the following shortcomings in the online monitoring of water quality: [0003] 1. The influence of different temperatures on the stripping efficiency of organic matter; [0004] The solubility of organic matter in the solution and the equilibrium pressure ratio of the solute above the liq...

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Problems solved by technology

[0005] 2. Organic matter is easily adsorbed in the pipeline, which will affect the next measurement;

[0006] 3. The water vapor contained in the blown-off mixed gas will cause the stationary phase of the chromatographic column to expand rapidly, change the polarity of the stationary phase of the chromatographic column, and cause the chromatographic peak to drift, and the system cannot identify the target

[0007] In order to reduce the influence of ambient temperature, the method of prolonging the purging time is usually adopted at present, but after increasing the purging time, the water content of the stripped gas will be greatly increased, and the pressure of water removal will be increased.

The blow-off gas is dried and moisture is removed through the NAFION drying tube, but there are also problems: 1. Halogenated hydrocarbons will permeate out through the NAFION tube, which affects the detection limit of halogenated hydrocarbons; 2. The NAFION tube needs to be removed during the water removal process. A large amount of dry zero gas is introduced. In order to ensure the effect of water removal, new NAFION tubes need to be replaced frequently, which not only makes the system complex, but also increases maintenance costs and limits the application of purge and trap method-gas chromatography on water quality online analyzers.

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