Effervescence assisted extraction of semivolatile substances

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  • Published: Sep 13, 2016
  • Author: Rafael Lucena
  • Channels: Detectors / Gas Chromatography / Laboratory Informatics / Proteomics & Genomics / HPLC / Ion Chromatography / Electrophoresis / Sample Preparation / X-ray Spectrometry / UV/Vis Spectroscopy / Raman / Infrared Spectroscopy / Base Peak / MRI Spectroscopy / Atomic / Chemometrics & Informatics / Proteomics / NMR Knowledge Base

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The effective isolation of volatile, and especially semivolatile, substances contained in liquids samples is a challenging task. Although several techniques involving isolation/preconcentration of the analytes are available, direct headspace analysis is particularly applied in routine laboratories due to its simplicity and its potential for automation. Despite these positive features, the partition of the analytes between the sample and its headspace is usually controlled by the proper selection of the temperature and/or time of incubation. This aspect, which is not limiting when volatile analytes are intended to be analysed, becomes critical for semivolatile compounds. In these cases, high temperatures that may produce analyte decomposition, are required. In addition, incubation temperature is usually restricted by the liquid sample boiling point in order to avoid vial overpressure. Therefore new procedures that enhance the transference of semivolatile substances from the liquid sample to its headspace are really welcome as they will improve the sensitivity of these determinations.

Researchers from Taiwan, our colleagues Chang and Urban, have recently proposed effervescence to assist this analyte transference. This simple and great idea, published in Analytical Chemistry, exploits the reversible dissolution of carbon dioxide in water as the driving force for purging the analytes from the samples. Moreover, carbon dioxide acts a carrier gas of the analytes to the instrument (mass spectrometry in this case). In short, the extraction vessel (see Figure) is a headspace vial (covered by a protective chamber) with two entrances: (i) an inlet orifice used to introduce carbon dioxide into the vial and (ii) an outlet orifice that is coupled to the instrument. In addition, a motor connected to a spindle is also employed to agitate the solution at defined times.

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The extraction procedure consist of several steps, the main ones being described in the following table.

The results, acquired for different analytes with boiling points between 170-208ºC, showed a better performance of the effervescence-assisted procedure compared to the classical headspace process. The original article, given below, is highly recommended and the reader will find also interesting supplementary material uploaded to the journal webpage.

I also recommend these other resources just in case you wish to read more about in the potential of effervescence in microextraction.

Main reference:

  1. Anal. Chem. 2016, 88, 8735. C.-H. Chang and P. L. Urban. Fizzy Extraction of Volatile and Semivolatile Compounds into the Gas Phase.

Other effervescence techniques sources:

  1. Steve Down, Fizzy function: Effervescent tablet for dispersive extraction, separationsNOW, November 28, 2011.
  2. Guilermo Lasarte, Effervescence-assisted dispersive micro-solid phase extraction, Microextraction Tech blog.

Blog post by: Rafael Lucena

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