New purpose of miniature-needle trapping device

Abstract

The invention relates to a new purpose of a miniature-needle trapping device. The new purpose is characterized in that the miniature-needle trapping device is connected with an injector; water containing semi-volatile and non-volatile organic matter is injected into the injector and the injector is pushed to enable the semi-volatile and non-volatile organic matter to be adsorbed by the miniature needle trapping device; water in an adsorbing agent is removed and dried by using nitrogen gas; and the miniature-needle trapping device is inserted into a gas-chromatographic high-temperature sample inlet for thermal-desorption sample injection, and finishes integrated operation of sampling, extraction, concentration and on-computer testing. The new purpose has the advantages that the extraction and enrichment multiple of SVOC is high, the sensitivity of chromatographic analysis is improved, the actual sample-injection amount of SVOC is 10 times of the sample-injection amount of extraction liquid, and the sensitivity of chromatographic analysis is obviously improved; taking a 5mL water sample as an example, the extraction flow speed is 2mL / min by virtue of needle trapping, nitrogen gas is dried for 2 minutes, the extraction process before chromatographic sample injection only needs about 5 minutes, headspace gas-liquid phase equilibrium is established without liquid-liquid extraction, a solvent or a water sample, and the unexpected effect is achieved. The new purpose is a solvent-free extraction technology with simplicity and fastness in operation and low cost.

Description

Technical field: [0001] The invention relates to a pretreatment method of an environmental analysis chemical method, especially a direct solvent-free extraction and enrichment of a volatile semi-volatile organic compound sample in water coupled with a gas chromatograph to form an integration of sampling, extraction and enrichment, and direct chromatographic sampling. analysis techniques. Background technique: [0002] At present, the analysis of pollutants in water samples, especially semi-volatile and refractory organic pollutants (VOC and SVOC), is usually analyzed by gas-liquid chromatography, of which gas chromatography is the most commonly used. However, since the development of gas chromatography technology, due to the structural design of the injection port and the fixation of the chromatographic column, it does not support direct injection of water samples. Because if water is directly fed in, firstly, due to the extremely high vaporization expansion coefficient of ...

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Problems solved by technology

[0008] ①. The liquid-liquid extraction process usually needs to go through shaking flasks, demulsification, standing, phase separation, drying, concentration, phase inversion, constant volume, etc. The operation is complex and cumbersome, the work intensity is high, and it takes a long time (usually 1-2 hours / Sample);

[0009] ②. Organic solvents such as dichloromethane, chloroform, n-hexane, and benzene are highly toxic, consume a large amount, cause serious secondary pollution, and cause harm to operators and the environment;

[0010] ③. The extraction operation needs to use a variety of instruments and equipment, and the investment cost is high, such as separating funnel, rotary evaporator (or KD concentrator), nitrogen blowing instrument (nitrogen cylinder) and supporting facilities, etc.

[0011] ④, commercially available automatic liquid-liquid extraction instrument, equipment investment is large;

[0012] ⑤. Limited by the characteristics of liquid phase extraction technology, it is difficult to achieve the needs of rapid and emergency detection

[0020] ①. Solid-phase extraction needs to go through operations such as activation, sample loading, rinsing, elution, drying of the extract, concentration (phase inversion), etc. Although the amount of solvent is small, the steps are also very cumbersome; and in order to ensure the recovery of the target The rate, sample loading and elution must be controlled at a low flow rate of 2-4mL / L, which increases the time cost of solid phase extraction; the harm of a small amount of solvent cannot be ignored

[0021] ②. The solid-phase column is affected by the manufacturer's production batch number, filling specifications and product quality, and the extraction results may be quite different;

[0028] ① Solid-phase microextraction relies on static adsorption extraction, and the target substance is adsorbed by free diffusion in the sample matrix. Therefore, the extraction capacity of the target substance is small and the analysis sensitivity is low.

[0029] ② The stationary phase of the extraction head of solid-phase microextraction and the adsorbent captured by the needle are mostly polymer polymers, such as Tenax-TA, Porapak-P, Porapak-Q, Carbopack, Carboxen, etc., which can withstand high temperature during thermal desorption Poor performance, and the solid-phase microextraction head is fragile, which affects the service life

If it is directly inserted into water for extraction, the high molecular polymer will decompose or fall off due to the strong displacement ability of water on the stationary phase and adsorbent, reducing the service life

[0031] ④ For water samples, to establish headspace-liquid phase equilibrium, it is necessary to keep the water sample system under pressure, keep warm, and prevent leakage, which is difficult to control

The method of this invention is only used for collecting the gas samples of volatile and semi-volatile organic compounds in the air, but not for collecting the volatile and semi-volatile organic compounds in water

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