Ultrasonic auxiliary headspace liquid-phase microextraction method

Abstract

A method of ultrasound-assisted headspace liquid-phase micro-extraction is: getting a clean ultrasonic cleaning machine (1), an insulation board (2), a PCR tube (6) of 0.2mL, a sample bottle (7), a bottle stopper (8) and an ice bath (4); fixing the sample bottle (7) at the center of the insulation board, and the sample is contained in the sample bottle, of which the lower is immersed in the water bath of the ultrasonic cleaning machine (1) where the insulation board is covered; cutting off the cap of the PCR tube (6) of 0.2mL where 10 to 40 mu L extract is contained; inserting the PCR tube with the nozzle upwards into the small hole of the bottle stopper which is put into the sample bottle with sample and the bottom of the PCR tube upwards, and sealed; the upper of the sample bottle together with the PCR tube is put in to the ice bath; ultrasonic extraction. The method for utilizing the PCR tube increases the liquid extraction quantity and extends the extraction time effectively, and the method adapts to extraction and enrichment of trace volatile and semi-volatile components in complex water sample because of having a high efficiency, a high sensitivity and a simple operation.

Description

technical field [0001] The invention relates to a sample pretreatment method for headspace liquid-phase microextraction, in particular to an ultrasonic-assisted headspace liquid-phase microextraction method. Background technique [0002] The sample pretreatment technology has an important impact on the analysis results and has been paid much attention. Currently widely used pretreatment techniques include liquid-liquid extraction (LLE), solid-phase extraction (SPE), solid-phase microextraction (SPME), and membrane extraction. Classical liquid-liquid extraction is cumbersome to operate, uses a large amount of organic solvents that are toxic or harmful to humans and the environment, and is not easy to automate. SPE technology has been rapidly developed in many fields due to its advantages of high efficiency, reliability, and low solvent consumption, but it needs to elute and purify substances to meet the requirements of instrumental analysis such as gas chromatography (GC) or...

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Problems solved by technology

[0005] (2) The liquid droplets suspended on the needle tip will drop due to slight vibrations, so the experiment has very high requirements on the experimental environment, and requires the operator to be extremely careful, and the stirring speed of the sample pool must also be adjusted very low

[0006] (3) Due to the decrease of the droplet volume, its vapor pressure rises, causing the extraction agent to be extremely volatile, and the extraction time is limited. Generally speaking, the extraction of the analyte has stopped before the equilibrium between the two phases is reached, and the equilibrium cannot be achieved. If it is really realized, the enrichment effect is relatively poor and the sensitivity is relatively low; for polar extractants, because the water vapor in the headspace phase enters the extractant, the volume of the extractant droplet increases, and it is easy to cause the extractant to leak from the needle tip. Shedding, leading to experimental failure (Yadollah Y., Mohammad H., Majid H.-H., Mojtaba S., Talanta, 2004, 62:265-270)

[0007] (4) In addition, since the dissolution process of the analyte in the extraction solvent is an exothermic process, low temperature is conducive to accelerating the dissolution of the analyte in the solvent and shortening the equilibrium arrival time, while high temperature can promote the release of the analyte from the sample matrix, In turn, the time to reach equilibrium can be shortened, and the solubility of the analyte in the extraction solvent can be increased to a certain extent, and the sensitivity can be improved. However, in actual operation, it is difficult to achieve a relatively high temperature of the sample matrix and a relatively low temperature of the extraction solvent at the same time.

[0008] Due to the existence of the above problems, the conventional headspace liquid phase microextraction method requires high operation requirements, and the sensitivity is not satisfactory.

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